Download The Appropriate Use of Neurostimulation: Avoidance and Treatment

Neuromodulation: Technology at the Neural Interface
(onlinelibrary.wiley.com) DOI: 10.1111/ner.12206
The Appropriate Use of Neurostimulation:
Avoidance and Treatment of Complications of
Neurostimulation Therapies for the Treatment
of Chronic Pain
Timothy R. Deer, MD1; Nagy Mekhail, MD, PhD2; David Provenzano, MD3;
Jason Pope, MD1; Elliot Krames, MD4; Simon Thomson, MD5; Lou Raso, MD6;
Allen Burton, MD7; Jose DeAndres, MD, PhD8; Eric Buchser, MD9;
Asokumar Buvanendran, MD10; Liong Liem, MD11; Krishna Kumar, MD12;
Syed Rizvi, MD12; Claudio Feler, MD13,14; David Abejon, MD15; Jack Anderson,
MD16; Sam Eldabe, MD17; Philip Kim, MD18,19; Michael Leong, MD20;
Salim Hayek, MD, PhD21; Gladstone McDowell II, MD22; Lawrence Poree, MD,
PhD23,24; Elizabeth S. Brooks, PhD24; Tory McJunkin, MD25; Paul Lynch, MD25;
Leo Kapural, MD, PhD26; Robert D. Foreman, PhD27; David Caraway, MD,
PhD28; Ken Alo, MD29,30; Samer Narouze, MD, PhD31; Robert M. Levy, MD,
PhD32; Richard North, MD33,34*
21
Address correspondence to: Timothy Deer, MD, Center for Pain Relief, 400 Court
St, Ste 100, Charleston, WV 25301, USA. Email: [email protected]
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26
27
28
29
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31
32
33
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For more information on author guidelines, an explanation of our peer review
process, and conflict of interest informed consent policies, please go to http://
www.wiley.com/bw/submit.asp?ref=1094-7159&site=1
*
Now retired from Johns Hopkins University.
Sources of financial support: This project was supported by the International
Neuromodulation Society and was partially funded by a series of unrestricted
educational grants from Medtronic, Inc., St. Jude Medical, Inc., Boston Scientific
Corp., Nevro Corp., and Spinal Modulation, Inc. No corporate entities had any direct
input into the contents of this manuscript or the conclusions of the collaborators.
© 2014 International Neuromodulation Society
Neuromodulation 2014; 17: 571–598
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Center for Pain Relief, Charleston, WV, USA;
2
Cleveland Clinic, Cleveland, OH, USA;
3
Institute for Pain Diagnostics and Care, Ohio Valley General Hospital, Pittsburgh,
PA, USA;
4
Pacific Pain Treatment Center, San Francisco, CA, USA;
5
Basildon and Thurrock University Hospitals, NHS Foundation Trust, Basildon,
Essex, UK;
6
Jupiter Interventional Pain Management Corp., Jupiter, Florida, USA;
7
Houston Pain Associates, Houston, TX, USA;
8
Department of Anesthesiology, Critical Care, and Pain Management, General
University Hospital, Valencia University Medical School, Valencia, Spain;
9
Anaesthesia and Pain Management Department, EHC-Hospital, Morges and
CHUV University Hospital, Lausanne, Switzerland;
10
Department of Anesthesia, Rush University Medical Center, Chicago, IL, USA;
11
St. Antonius Hospital, Nieuwegein, The Netherlands;
12
University of Saskatchewan, Regina General Hospital, Regina, SK, Canada;
13
University of Tennessee, Memphis, TN, USA;
14
Valley View Hospital, Glenwood Springs, CO, USA;
15
Hospital Universitario Quiron Madrid, Madrid, Spain;
16
Arizona Pain Specialists, Scottsdale, AZ, USA;
17
The James Cook University Hospital, Middlesbrough, UK;
18
Christiana Hospital, Newark, DE, USA;
19
Bryn Mawr Hospital, Bryn Mawr, PA, USA;
20
Stanford University, Palo Alto, CA, USA;
Department of Anesthesiology, Case Western Reserve University, Division of
Pain Medicine, University Hospitals Case Medical Center, Cleveland, OH, USA;
Integrated Pain Solutions, Columbus, OH, USA;
University of California at San Francisco, San Francisco, California, USA
Pain Clinic of Monterey Bay, Aptos, CA, USA;
Arizona Pain Clinic, Scottsdale, AZ, USA;
Carolinas Pain Institute at Brookstown, Wake Forest Baptist Health, WinstonSalem, NC, USA;
College of Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA;
Center for Pain Relief, Tri-State, LLC, Huntington, WV, USA;
The Methodist Hospital Research Institute, Houston, TX, USA;
Monterey Technical Institute, Monterey, Mexico;
Center for Pain Medicine, Summa Western Reserve Hospital, Cuyahoga Falls,
OH, USA;
University of Florida College of Medicine, Jacksonville, FL, USA;
School of Medicine, Johns Hopkins University, Baltimore, MD, USA; and
The Neuromodulation Foundation, Inc., Baltimore, MD, USA
DEER ET AL.
Introduction: The International Neuromodulation Society (INS) has determined that there is a need for guidance regarding safety
and risk reduction for implantable neurostimulation devices. The INS convened an international committee of experts in the field
to explore the evidence and clinical experience regarding safety, risks, and steps to risk reduction to improve outcomes.
Methods: The Neuromodulation Appropriateness Consensus Committee (NACC) reviewed the world literature in English by
searching MEDLINE, PubMed, and Google Scholar to evaluate the evidence for ways to reduce risks of neurostimulation therapies.
This evidence, obtained from the relevant literature, and clinical experience obtained from the convened consensus panel were
used to make final recommendations on improving safety and reducing risks.
Results: The NACC determined that the ability to reduce risk associated with the use of neurostimulation devices is a valuable
goal and possible with best practice. The NACC has recommended several practice modifications that will lead to improved care.
The NACC also sets out the minimum training standards necessary to become an implanting physician.
Conclusions: The NACC has identified the possibility of improving patient care and safety through practice modification. We
recommend that all implanting physicians review this guidance and consider adapting their practice accordingly.
Keywords: Chronic pain, complications, guidance, neurostimulation, peripheral nerve stimulation, risk reduction, spinal cord
stimulation
Conflict of Interest: Dr. Deer holds minor stock options in Bioness, Inc., Spinal Modulation, Inc., and Nevro Corp. He is a paid
consultant for St. Jude Medical, Inc., Spinal Modulation, Inc., Bioness, Inc., Nevro Corp. and Medtronic, Inc. He has patent relationships
with Bioness, Inc., and Nevro Corp. He is an advisor for St. Jude Medical, Inc., Medtronic, Inc., Spinal Modulation, Inc., Bioness, Inc.,
Nevro Corp., Flowonix Medical, Inc., and Jazz Pharmaceuticals PLC. Dr. Provenzano is a paid consultant for Medtronic, Inc. and St. Jude
Medical, Inc. Dr. Pope is a paid consultant for Medtronic, Inc., St. Jude Medical, Inc., and Spinal Modulation, Inc. He is a speaker for Jazz
Pharmaceuticals PLC. Dr. Krames holds stock options with Nevro Corp. and Spinal Modulation, Inc. He is a minor stockholder with
Medtronic, Inc. Dr. Thomson is a paid consultant for Boston Scientific Corp., British Standards of Industry, and Alcimed (on behalf of
Johnson & Johnson). Dr. Raso is a paid consultant for St. Jude Medical, Inc., Boston Scientific Corp., and Medtronic, Inc. Dr. Burton is
a paid consultant for Medtronic, Inc. Dr. De Andres has no conflicts of interest to report. Dr. Buchser is a paid consultant for Medtronic,
Switzerland. His employer, EHC Hospital, Morges, Switzerland, has received fees for expert testimony that he provided for Medtronic.
He has been reimbursed for travel costs by Medtronic, Switzerland. Dr. Buvanendran consults for Medtronic, Inc. Dr. Liem is a
consultant for Spinal Modulation, Inc. He is a medical advisor for Boston Scientific Corp. and has received a research grant from Spinal
Modulation, Inc. Dr. Kumar is a paid consultant for Medtronic, Inc., and serves on an advisory committee for them. He is also a
consultant for Boston Scientific Corp. Dr. Rizvi has no conflicts of interest to report. Dr. Feler has no conflicts of interest to report. Dr.
Abejon is a speaker for St. Jude Medical, Inc., Boston Scientific Corp., Medtronic, Inc., Nevro Corp., Cardiva Medical, Inc., and Prim SA.
Dr. Anderson has no conflicts of interest to report. Dr. Eldabe is a paid consultant for Medtronic, Inc., Spinal Modulation, Inc. and
Mainstay Medical Ltd. Dr. Kim has management/advisory relationships with Medtronic. Inc., Jazz Pharmaceuticals PLC, and Biotronik.
He is also a paid consultant for these same companies. Dr. Leong has a management/advisory relationship with Jazz Pharmaceuticals
PLC and Covidien Ltd. Dr. Hayek is an advisor for Boston Scientific Corp. and Medtronic. Inc. He is a paid consultant for Boston
Scientific Corp., Globus Medical. Inc., Medtronic. Inc., and QiG Group LLC. Dr. McDowell is a paid consultant with Medtronic. Inc., and
St. Jude Medical. Inc. Dr. Poree holds stock options in Spinal Modulation, Inc. He was a consultant for Medtronic, Inc. Dr. Brooks has
no conflicts of interest to report. Dr. McJunkin has no conflicts of interest to report. Dr. Lynch has no conflicts of interest to report. Dr.
Kapural is a paid consultant for Medtronic, Inc., St. Jude Medical, Inc., and Boston Scientific Corp. Dr. Foreman has received research
funding from St. Jude Medical, Inc., and Boston Scientific Corp. He is a paid consultant for Boston Scientific Corp., St. Jude Medical,
Inc., and Respicardia, Inc. Dr. Caraway owns stock options in Spinal Modulation, Inc. He has a management/advisory role with
Medtronic, Inc., Spinal Modulation, Inc., Nevro Corp., Bioness, Inc. and Jazz Pharmaceuticals PLC. He has a paid consulting
relationship with Medtronic, Inc., Spinal Modulation, Inc., Jazz Pharmaceuticals PLC, Nevro Corp., and St. Jude Medical, Inc. Dr. Alo is
a paid consultant for St. Jude Medical, Inc. Dr. Narouze has no conflicts of interest to report. Dr. Levy holds stock options with Spinal
Modulation, Inc. and Bioness, Inc. He is a paid consultant for St. Jude Medical, Inc., Medtronic, Inc., Spinal Modulation, Inc., Vertos
Medical, Inc., Bioness, Inc., and Boston Scientific Corp. Dr. North’s former employers (the Johns Hopkins University and Sinai Hospital
of Baltimore) received funding from industry (Boston Scientific, Inc.; Medtronic, Inc.; St. Jude Medical, Inc.), as does the nonprofit
Neuromodulation Foundation, of which he is an unpaid officer. He has a consulting/equity interest in Algostim LLC. He has multiple
patents in the field of spinal cord stimulation.
INTRODUCTION
572
Spinal cord stimulation (SCS) and peripheral nerve stimulation
(PNS) have become important tools in the medical algorithm of
therapies to resolve symptoms from disease processes that involve
the central or peripheral nervous systems. The need to better
define the appropriateness of the use of these advanced tools has
been identified by the International Neuromodulation Society
(INS) and has led to the formation of the Neuromodulation Approwww.neuromodulationjournal.com
priateness Consensus Committee (NACC) to evaluate the current
literature and best practices to form expert opinions on the topic.
The purpose is to give guidance to physicians and other healthcare providers on the appropriateness of these advanced treatments, with the goal of improving care for those afflicted with
chronic diseases and pain.
Spinal cord and peripheral neurostimulation techniques for the
relief of pain and improvement in organ function have been practiced since 1967 (1). These neurostimulation techniques are safe,
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RISK REDUCTION IN NEUROSTIMULATION
reversible, and effective at relieving pain and improving function
and overall quality of life. However, patient selection is of utmost
importance to outcomes, and neuromodulation does have recognized risks and complications, although very rarely do complications result in long-term morbidity or mortality. Extensive published
reviews suggest that approximately 30% to 40% of patients treated
with SCS will have a complication requiring a revision (2–6). The
majority of the complications resulting from SCS and PNS are minor
and easily reversible with minor surgery and rarely affect patient
morbidity or mortality significantly. Hardware-related complications are more common than biologic complications, with leadrelated complications, including migration and fracture, most
frequent. Biological complications most commonly include superficial infection and pain over the implant. Devastating technical and
biologic complications have both been reported, although these
are becoming increasingly rare.
The INS reviewed the initial development of medical-based consensus when forming the NACC. Using the template of the consensus
and evidence synthesis as described by the Polyanalgesic Consensus
Conference for intrathecal therapy, this model was employed for
assimilating the evidence and consensus for neuromodulation strategies (7–9). The conference was formulated in association with INS
and funded by unrestricted educational grants from Medtronic, Inc.,
St. Jude Medical, Inc., Nevro Corp., Spinal Modulation, Inc., and
Boston Scientific Corp. No corporate entities had any direct input into
the contents of the manuscript or the conclusions of the collaborators. Meetings were held throughout the development of the guideline both in round-table fashion and via teleconference. The
literature was critiqued using the United States Preventive Services
Task Force (USPSTF) criteria for evidence synthesis and level of certainty of net benefit on evidence strength (10) or the Centers for
Disease Control and Prevention (CDC) evidence rankings (11). The
Steering Committee for the NACC was appointed by the Board of the
INS, and all expert participants for the research and formulation of
opinion were appointed by the Steering Committee.
This is the third of four companion articles addressing a wider
analysis of the literature and the practice of neuromodulation for
chronic pain. The INS also convened working groups to address the
appropriate use of neuromodulation for the treatment of chronic
pain and ischemic diseases (7), the treatment of pain of the head
and face (8), and the future development and use of new technology, devices, and neural circuitry (9).
Overuse, Underuse, and Misuse of Spinal Cord Stimulation
The concepts of overuse, underuse, and misuse are increasingly
used in discussions of health-care quality, safety, and value-based
purchasing. The Institute of Medicine National Roundtable on
Health Care Quality defined these terms in 1998 (12).
• Overuse occurs when “a health care service is provided under
circumstances in which its potential for harm exceeds the possible
benefit.” Reducing overuse “improves quality (by sparing patients
the unnecessary risk that attends to inappropriate health services)
and reduces costs at the same time.”
• Underuse is defined as “failure to provide a service that would
have produced a favorable outcome for the patient.”
• Misuse occurs when“an appropriate service has been selected but
a preventable complication occurs and the patient does not
receive the full potential benefit of the service.”
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573
Quantifying the overuse of neurostimulation is difficult. Since
the initial introduction of SCS, there have been wide variations of
its use in clinical practice. In the 1980s, SCS was limited to paddletype leads inserted through a laminotomy. In the late 1980s
through the 1990s, increasing numbers of minimally invasive trials
using percutaneous cylindrical leads were conducted in outpatient
settings, either in hospital operating rooms or in outpatient
surgery centers. Over the next decade, many, but certainly not all,
percutaneous trials with cylindrical leads occurred outside of operating rooms in physicians’ offices (this is still the case today). Once
these trials were moved out of operating-room settings, the procedures went unsupervised, and it is believed that some
untrained, unqualified physicians started placing these leads
strictly for monetary gain, a prime example of overuse. It is important to state that successful outcome for SCS, peripheral nerve
field stimulation (PNfS), or combined SCS/PNfS is directly related
to how the procedure is performed and on whom. As stated previously, patient selection is foundational to success. Poorly trained
physicians have poor outcomes.
Whether well trained or not, physicians have been reimbursed
per contact on the lead, not by numbers of leads used. With PNfS or
combined PNfS/SCS techniques (so-called hybrid SCS), untrained
and unskilled physicians were able to collect large fees for low-risk
and poor-outcome office procedures. In many cases, abuse
occurred, leading to implants being placed regardless of medical
need or physician training, and in many cases, physicians in the
office setting would place four- or eight-contact leads epidurally or
subcutaneously and bill up to $400 per contact for a brief procedure. This practice by the poorly trained and poorly skilled physician
who does not understand appropriate patient selection can and
does produce an unacceptably low trial-to-permanent-implant ratio
and a high explant rate in those who are permanently implanted.
Some of these physicians, who have no privileges at a surgical
center or hospital for permanent implantation, have no interest in
whether or not the patient proceeds to implant. The NACC supports
the appropriate training of physicians who are implanters of
neurostimulation devices and the use of neurostimulation by practitioners committed to the continuity of care through trial, implantation, and long-term management of patients.
There are numerous examples of the underuse of neurostimulation devices. Not using neurostimulation early enough in
severe, progressing complex regional pain syndrome (CRPS) exemplifies underuse. A number of authors suggest greater benefit and
better functional outcomes with greater economic value if the
application of neurostimulation occurs earlier rather than later (13–
16). Additionally, it has been well established that SCS may currently
be underused for postlaminectomy syndrome (failed back surgery
syndrome or FBSS) when compared with repeat spine surgery
(5,16). Many interventional pain physicians are not trained to
perform neurostimulation procedures or choose not to perform
them, and many do not refer to those who do. This, together with
the fact that many physicians other than pain physicians do not
know about the benefits of stimulation procedures for pain or feel
that the procedure is too costly and invasive for their patients, leads
to underuse for patients who need neurostimulation. There also
exists the notion in the pain management community that SCS is a
procedure of last resort after all other treatments have failed (17).
This mindset lingers despite many recent articles touting a change
in the treatment algorithm of SCS for pain control and moving it to
earlier consideration. The SAFE principles have been in the literature
for years and have become the accepted algorithm (16).
Pain is the transmission of a series of signals carrying data over a
system of nerve synapses to and from the peripheral and central
nervous systems. We lack a universally recognized objective
DEER ET AL.
Table 1. Recommendations of the Neuromodulation Appropriateness Consensus Committee (NACC) of the International Neuromodulation Society (INS) to
Mitigate the Risks of, Improve the Safety of, and Improve Outcomes of Neuromodulation Procedures.
1. The NACC recommends that implanters of neuromodulation devices be properly trained and credentialed by either an accredited interventional pain
medicine training program or an accredited surgical training program.
2. The NACC recommends that implanters be specially trained in the community standards for the management of preoperative, intraoperative, and
postoperative care of the patient undergoing surgical procedures.
3. The NACC recommends that, when possible, neuromodulation surgical procedures performed in operating room theaters be staffed by personnel
specially trained in the understanding of the procedure and technologies used.
4. The NACC recommends that neuromodulation therapies be performed for neuropathic pain conditions prior to commencing long-term long-acting
opioid maintenance.
5. The NACC recommends that patients being considered for neuromodulation procedures be treated in an interdisciplinary fashion with special attention
paid to patients’ pain reduction and emotional and functional restoration.
6. The NACC recommends the use of selection criteria for neuromodulation procedures be based on pain characteristics, including pain location and
intensity.
7. The NACC recommends that a psychological evaluation by credentialed psychologists or psychiatrists be performed prior to a trial of neuromodulation
therapies to select psychologically appropiate candidates for the procedure.
8. The NACC recommends that patients’ wishes regarding cosmesis, choice of implant, and timing of surgery be considered as part of the preoperative
and intraoperative planning.
9. The NACC recommends that prior to the day of trial or permanent implant, the implanter should fully explain to the patient the entire intended
procedure, the risks attendant to the procedure, the benefits of the procedure, and the alternatives to the procedure, and receive consent to proceed
with the procedure.
10. The NACC recommends that before trialing patients for neuromodulation procedures, the implanting physician discuss plans of the intended procedure
with the patient’s non-pain-treating physicians.
11. The NACC recommends the use of an appropriate preoperative assessment checklist and laboratory testing prior to either a trial or permanent implant.
12. The NACC recommends that before implanting a permanent device, a trial for tolerability and efficacy be performed.
13. The NACC recommends that prior to implanting an epidural lead, whether percutaneously or surgically, the patient should be evaluated for risks of
anticoagulation and steps be taken to mitigate those risks appropriately before attempting placement of the lead.
14. When placing epidural and subcutaneous leads, the NACC recommends that the procedure be performed in an accredited sterile environment, such
as a hospital surgical suite or ambulatory surgery center, using meticulous sterile techniques. If an office setting is used, the facility should meet the
same standards as an accredited hospital facility.
15. The ideal anesthesia strategy enables real-time interaction between implanter and patient, thereby allowing the patient to describe the area and
intensity of intraoperative paresthesia. If this is not possible, general anesthesia may be considered with somatosensory evoked potential monitoring.
16. The NACC recommends that all patients undergoing either a spinal cord stimulation trial or implantation of a permanent device should receive
perioperative antibiotics less than one hour before incision.
17. The NACC recommends that the implanting physician be involved in the preoperative and postoperative care of the patient when possible.
18. The NACC recommends that programming of the neuromodulation device be performed by trained health-care professionals or device company
representatives with appropriate patient monitoring and vigilance.
19. The NACC recommends that physicians who offer neuromodulation therapies within their scope of practice employ quality control and quality
improvement through monitoring of outcomes, success indicators, and complications of their practice.
diagnostic or measurement tool for any type of pain, and the gold
standard is the description of pain by the person experiencing it.
This reality creates challenges in choosing the right type of therapy
and applying it. Neurostimulation is valuable and effective, but for it
to be a sustainable clinical tool, we must continue to generate data
on quality, safety, and efficacy. Neuromodulation applied responsibly in properly chosen patients should have a low complication rate.
Institutional educational requirements and interventional society
and consensus guidelines, when followed, should protect patients
against the misuse of the technology (16).
574
Analysis, Evidence, and Recommendations
The concept of evidence-based medicine is defined as “the conscious, explicit and judicious use of the best current evidence in
making decisions about individual patients” (18,19), which means
that it is necessary to have credible scientific information available
to apply appropriate treatment in clinical practice. Scientific evidence is achieved by analyzing the scientific rigor of available published studies. In today’s clinical practice, it is vital that our use of
treatments and existing devices be based on medical evidence and,
in cases where deficiency in the evidence exists, that clinical practice be improved by consensus opinion of experts in the field. The
NACC recommendations suggested here represent the best availwww.neuromodulationjournal.com
able evidence and consensus among the expert authors of this
article. Table 1 lists the recommendations of the NACC regarding
methods for mitigating risk, improving safety, and improving outcomes of neuromodulation.
SAFETY OF NEUROSTIMULATION
SCS is generally believed to be a safe procedure, primarily
because it is considered minimally invasive and reversible. Unlike
long-acting, high-dose, long-term opioid use, SCS is not associated
with hormonal and immune system dysfunction, depression,
weight gain, hyperalgesia, or the potential for dependence and/or
addiction (20–24). Compared with spine surgery, SCS is intuitively
safer, but data comparing the two modalities are not available in a
synthesized form (5). Permanent neurological deficits and serious
spinal cord lesions due to epidural hematoma have been associated
with epidural electrode implantation (25–29), although this
problem can occur with any epidural intervention.
Older criteria for placement of an implantable neurostimulation
device required failure or inadequate response to conservative
medical management (CMM); thus, the data on comparative therapies are limited (17). The present accepted algorithm for the use of
implantable neurostimulation devices for pain control, and the one
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RISK REDUCTION IN NEUROSTIMULATION
recommended by the NACC, has moved consideration of neurostimulation therapies from after to before that of the use of longacting opioid pain management or reoperation (5), though still after
CMM failure (15,16). The best two examples of comparing neurostimulation therapies with CMM are the PROCESS study for patients
with FBSS by Kumar et al. (30) and the CRPS analysis by Kemler et al.
(31), both of which suggest superiority for neuromodulation therapies for pain control compared with CMM. Kumar et al. (32) have
reported that long-term success is dependent on the underlying
pain pathology being treated, with best outcomes reported in cases
of refractory angina pectoris, CRPS, and FBSS, and worst results seen
with postherpetic/intercostal neuralgia. Pain medicine physicians
who are starting their neuromodulation practice would optimize
their outcomes by restricting the patients who are trialed for SCS by
disease states, with the strongest efficacy data existing for FBSS with
predominant leg pain, CRPS, and peripheral vascular disease.
FACTORS ASSOCIATED WITH FAILURE
OR SUCCESS
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The complications of SCS are numerous, and their incidence has
been reported at 30% to 40% in multiple studies (40,41) (Table 2).
Hardware-related problems such as lead failure and migration are
more common than biological complications such as infection, pain,
and wound breakdown (54,55). Infection is one of the major complications of SCS, with an incidence of 4% to 10%, and is a common
cause for removal of the device and failure of therapy (56). A recent
review has recommended an average 18% budgetary allocation per
patient per annum for the maintenance of the therapy, including
complication management (57). It is important to note that in
device-based therapies, the experience of the implanter significantly
affects the rate of complications. This has been successfully demonstrated in the case of cardioverter–defibrillator implantation and
total hip replacement (58).
In their Health Technology Assessment of the therapy, the UK
National Institute of Clinical Excellence (NICE) concluded that among
the total of 403 permanently implanted patients across all trials
examined, four device removals were required (1%), all as the result
of infection. Across trials, the percentage of implantations requiring
surgery to resolve a device-related complication, including device
removals, ranged from 0% to 38%, which may be due to differences
in follow-up periods, populations, or clinical settings (59).
SCS-related complications have been stratified using various categories. We will first examine patient-related complications that are
associated with inappropriate diagnosis or anatomic targeting, the
psychological status of the patient, the ability of the patient to
comply with device use, and continuing maintenance. Next, we will
examine device-related complications, the most common being
lead-related complications, such as lead migration or fracture,
extension-related complications, disconnection or misconnection,
and implantable pulse generator-related complications such as
battery depletion,“flipping,” and recharging difficulties. Technique or
therapy-related complications include loss of paresthesia or painful
or unpleasant paresthesia. These complications are less threatening
and can usually be addressed by reprogramming, although, on rare
occasions, they can result in therapy failure and device removal.
Finally, we will address common biological complications such as
deep and superficial infections, the development of hematoma or
seroma over the device, and the more common complaint of pain
over the implanted hardware. Less frequent biologic complications
include dural puncture-related headaches and, more seriously, nerve
damage, including spinal cord injury and paralysis (see Table 2).
REDUCING THE RISKS OF COMPLICATIONS
Rigorous preimplantation screening usually dictates the longterm success rate of SCS therapy. The NACC recommends institution
of the following selection criteria for implantation of neurostimulation devices for pain control:
• a well-defined, noncancer, physiologic (nonpsychiatric) cause of
pain; if the pain is related to cancer treatment or surgical morbidity from tumor resection and the patient is stable, the use of
neurostimulation may be considered
• after failure of CMM for at least three to six months, but before a
reoperation for back surgery, if the patient is neurologically stable
• after failure of CMM in patients with mixed or neuropathic pain for
at least three to six months, but before consideration of longacting opioid maintenance therapy
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575
SCS is successful for the treatment of many chronically painful
conditions, such as FBSS, chronic back pain, chronic neck pain,
chronic radicular pain, chronic neuropathic pain, CRPS, and chronic
pain from peripheral ischemia (7). SCS is also used for phantom limb
pain, but the results have been mixed. Some authors have found
that SCS provides minimal relief, with improvement for only 25% of
patients (33,34). When treating chronic pain with neuromodulation
devices, such as spinal cord stimulators, it is important to select the
appropriate patients to achieve the best outcomes. Multiple indicators can help determine the effectiveness of neuromodulation with
SCS; these include the experience of the implanter, the etiology of
the patient’s pain, early treatment, the existence of comorbidities
that might cause failure or lead to complications, and a wellperformed psychologic evaluation to rule out neuromodulation
therapy for patients with psychologic cause for pain, underlying
psychoemotional distress, or schizophrenia. Concurrent psychiatric
illness negatively impacts success rates of interventional pain
therapy (35). An estimated 20% to 45% of patients with chronic pain
concurrently suffer from psychiatric illness (36). Specifically, individuals with significantly depressed mood and those with low
energy levels were at higher risk of failing their SCS trial (37). In
addition, somatization, anxiety, and poor coping were important
predictors of poor outcome, according to a recent systematic review
of 25 studies (38). However, negative outcomes with these psychiatric illnesses and SCS are no different from those with other surgeries, such as spine surgery or knee replacement.
In addition, research has identified other factors that can determine treatment success or failure with SCS. A study involving 410
patients over a 22-year period determined that age, sex, laterality of
pain, and number of surgeries before implant did not play a role in
predicting the treatment outcome (32). However, the percentage of
pain relief was inversely related to the time interval between pain
onset and time of implantation, stressing the importance of early
consideration of neuromodulation when using a treatment algorithm for pain control. Another study found SCS efficacy to be
related to the time between patients’ first surgery in the region of
their chronic pain and time of SCS implantation (39). If the patient
had less than a three-year delay to implant, success was obtained
93% of the time compared with 9% when there was more than a
12-year delay. Expectation of therapy sustainability needs to be
stressed to the patient.
NATURE OF COMPLICATIONS
DEER ET AL.
Table 2. Management of Complications Related to Spinal Cord Stimulation.
Complication
Occurrence rate
Diagnosis
Management
Prevention
Mechanical
complications
Lead fracture or
disconnect
5.9% (32)
9.1% (3)
Stimulation pattern has changed.
Compare current x-rays to hard
x-ray copies of initial implant
procedure. Macrofractures of the
lead or lead disconnect from the
IPG can often be seen on x-ray.
Microfractures of the lead (i.e.,
internal fibers) cannot be seen on
x-ray, but impedance testing is
often indicative of a fracture.
Impedance testing of electrodes
should be performed for suspected
macro- or microfractures.
Stimulation pattern has changed.
Compare current x-rays with hard
copies of x-rays performed at time
of implant.
Likely requires disuse of lead
and/or replacement of
fractured lead; however,
sometimes the lead can be
preserved by programming
“around” the microfracture.
Lead fracture frequency can be reduced by using stress
loops and appropriate anchoring techniques, by
avoiding mobile structures such as joints, and by
placing the IPG close to the permanent leads (35,42).
Leads may have to be
replaced or a paddle lead
considered.
The probability of lead migration can be reduced by
using strain-relief loops near the anchor and
generator site, as well as placing the tip of the
anchor into the supraspinous ligament. The angle of
lead entry, the placement of the battery, and
suturing techniques can also affect lead migration
(35). Mechanical locking anchors have been shown
to secure the leads with a higher tensile strength,
and adhesives have been reported to improve
anchor clinical performance. The IPG should be
placed near the permanent leads. Paddle leads have
a lower incidence of lead migration than
percutaneous leads. Limiting the patient’s
movements (i.e., twisting, bending, lifting) in the
postoperative period to allow for scarring of the lead
in the epidural space will decrease the incidence of
lead migration.
Proper testing of device connections can reduce the
chances of failure of the battery or IPG. Suture
ligature can be placed around lead as it enters the
silicone boot of the IPG. This complication can also
be mitigated by following the device manufacturer’s
recommendations, such as placing the IPG at the
recommended depth (35).
Lead migration
0–1.37% (43)
13.6% (3)
Battery/IPG failure
1.7% (3)
Battery failing to hold a charge or
work properly. Compare current
x-rays with those taken at time of
implant. Ask patient about direct
trauma to the battery.
Battery/IPG failure may require
device replacement. Check
with manufacturer to rule
out known problem with
battery.
3.4% (3,32)
10% (44)
Patient may complain of nausea,
vomiting, fever, chills, and/or
malaise, or may not. Physical
examination may reveal redness
(rubor), warmth (calor), swelling
(tumor), pain (dolor), and purulent
drainage from IPG site or other
incisions. If infection is advanced,
the patient may exhibit neurological
changes.
Consider CT scan with contrast.
Consider CBC, blood cultures,
wound cultures, ESR, and CRP. May
also consider infectious disease
consultation or appropriate surgical
consultation as warranted.
If infection is diagnosed or
highly suspected,
management usually
includes opening the
device pocket and
removing the device.
Cultures of fluid and tissue,
along with the IPG, should
be sent to microbiology
and or pathology for
identification of the
responsible microbe.
Treatment with antibiotics
should be directed by the
microbial report from
culture. Many will consult
infectious disease experts
for further
recommendations.
Case reports (46)
Patient may complain of itching,
malaise, and/or pain. May assess
with skin patch test, which can be
obtained from device manufacturer.
Allergic reactions can be
misdiagnosed as infection. Blood
work to rule out infection and
allergy consult may be helpful.
Device removal may be
required.
Biologic
complications
Infection
Allergic reaction
The risk of infection is elevated by immunosuppressive
therapy or conditions (e.g., taking steroids, HIV,
diabetes), prolonged hospital stay, undergoing
multiple surgeries, perioperative transfusions,
inappropriate or inadequate antibiotic therapy, poor
ventilation of the operative suite, and improper skin
preparation at the surgical site (35,42,45). Various
patient comorbidities or characteristics also increase
the probability of infection and might include, but
are not limited to, the comorbid existence of
diabetes, rheumatoid arthritis, malnutrition, obesity,
and the use of alcohol or tobacco. Antibiotics
preoperatively and postoperatively should be given
as recommended by the operating facility’s
infectious disease standards based on local bacteria
and prevalent infections. Neuromodulation implants
should be considered high risk for infection similar to
a joint implant, and similar precautions should be
taken (i.e., limit traffic through OR, thorough
scrubbing of area, administer preop antibiotics, use
copious irrigation).
Administer skin patch test prior to implantation if high
preoperative suspicion for allergic reaction exists.
Patients can also have allergic reactions to any
materials used in surgery (i.e., scrub solutions,
sutures, medications, IPG, silicone, latex, other
materials) and these sources should all be
considered.
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Table 2. Continued.
Complication
Occurrence rate
Diagnosis
Management
Prevention
IPG seroma
2.5% (47)
Pain, swelling, redness, and/or pain at
IPG site. CT scan with contrast.
Some will order blood work to rule
out infection.
Risk of seroma can be mitigated by limiting the
amount of aggressive blunt dissection, avoiding
excessive cautery, creating a smaller IPG pocket,
limiting dead space with a layered closure, and
careful hemostasis (48). Also, based on expert
opinion, the risk of seroma can be mitigated by
preemption using an abdominal binder
postoperatively for approximately 2 months.
Epidural fibrosis
Case reports (35)
Stimulation pattern changes.
Epidural
hematoma
0.3% (35)
New neurologic changes that might
include paresthesias (with the
device turned off), weakness,
paralysis, or bowel or bladder
changes. More subtle changes
might include pain in a new area or
worsening of existing pain.
Emergency CT scan with contrast
and appropriate emergent
neurosurgical/spine surgeon
consultation.
When seromas develop, they
can often be treated with
abdominal binder and
drainage in a sterile
environment. Wound
cultures can be sent for
pathological analysis if
infection is suspected.
Though scarring is expected
around SCS leads, it can
alter electrical impedance,
preventing therapeutic
effect of the device despite
otherwise intact hardware
and continued coverage
(41). Reprogramming of the
device can often overcome
the effects of epidural
fibrosis.
Though rare, epidural
hematoma formation can
result from an SCS trial or
implantation. Effective
treatment requires
evacuation of the
hematoma within eight
hours of neurologic deficit
(49). This is a true
neurosurgical emergency
and should be managed as
one!
See above
(lead migration,
epidural fibrosis,
etc.)
Changes in stimulation pattern. If not
resolved by reprogramming, x-rays
should be taken and compared
with ones taken at time of implant.
May require device
replacement, lead revision,
or removal.
May be related to preexisting or new neurological
abnormalities in patient.
2% (51) 0.3% (42)
Presence of spinal fluid within the
operative field during the procedure
or leaking from closed incision after
the procedure. Postoperatively,
patient may complain of headache
(positional headache is the classic
presentation); however, some
patients, especially the elderly, may
not complain of headache in spite
of the presence of CSF leak.
Dural puncture is more likely in uncooperative
patients, those who have previously had surgery
at the site, those with spinal stenosis, and patients
with a calcified ligamentum flavum (42).
Suspected nerve or
cord injury
Case report (52)
Compressive
phenomena
from leads along
nerves or the
spinal cord
Case reports (53)
Patient may complain of worsening
pain, paresthesias, weakness,
paralysis, or bowel or bladder
changes. Complete a thorough
neurological examination and
emergent CT scan with contrast.
Seek emergency neurosurgical and
neurology consult.
Patient may complain of worsening
pain, paresthesias, weakness,
paralysis, or bowel or bladder
changes. Thorough neurological
examination and emergent CT scan
with contrast. Seek emergency
neurosurgical and neurology
consult.
Conservative measures for
dural puncture may be
considered postoperatively
(e.g., supine position,
caffeine, IV fluids). Some
implanters will abandon
intraoperative procedure,
while others will proceed
(continuing at the same
level or changing the level
of entry). An epidural blood
patch is controversial as it
may become a nidus for
infection (42).
Some cases of mechanical
damage to the spinal nerve
or spinal cord from SCS
implantation have been
reported (52). Seek
emergent neurosurgical
and neurology
consultation.
Decompressive procedures
that may include removal
of the device leads and/or
lamina, other bony
structures, or disk may be
required. An emergency
neurosurgical or spine
surgical consult should be
obtained.
Physiologic
complications
Stimulation
change in
coverage
pattern or
patchy
stimulation
Dural puncture
Patients receiving anticoagulation therapy should be
treated according to American Society of Regional
Anesthesia 2010 guidelines (50).
The use of general anesthesia during lead placement
can increase the risk of this type of injury. Multiple
attempts at placing needles, passing electrodes, or
passing paddle leads increase risk of neurotrauma.
Thorough review of preoperative imaging should be
performed before SCS trial is initiated. Particular
attention should be paid in patients with spinal
stenosis. Patients with lumbar spinal stenosis
might also have nonclinical thoracic spinal stenosis.
CSF visualized 360° around spinal cord at the level
of implant should be noted and, if not, consider
spinal stenosis as a cause.
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IPG, implantable pulse generator; CBC, complete blood count; ESR, erythrocyte sedimentation rate; CRP, C-reactive protein; OR, operating room; CSF, cerebrospinal fluid; SCS, spinal
cord stimulation.
DEER ET AL.
Table 3. Procedure Checklist.
Preoperative medical issues
Check for evidence of active dermal, dental, or urologic infections and treat.
Order urinalysis before procedure.
Address prior history of infection and make a plan for prophylaxis.
Review MRI imaging of cervical, thoracic, or lumbar spine in past 12 months, depending on diagnosis and planned placement of stimulator tip.
Discontinue anticoagulation with approval of treating physician for a length of time prior to procedure that is appropriate for the specific anticoagulant and
surgical bleeding risk. The appropriate timing for discontinuation should be based on the medication half-life and whether the patient is taking the
medication for primary or secondary prevention.
Off nonsteroidal anti-inflammatory drugs for 1 week if desired
Off acetylsalicylic acid for 7 days
Off warfarin or fondaparinux for 5 days, clopidogrel for 7 to 10 days, ticlopidine for 10 to 14 days
If patient was on warfarin, order prothrombin time testing for morning of the procedure.
Review psychological evaluation.
Obtain cardiac clearance in patients at risk for cardiac disease.
Review trial films and operative notes in preparation for permanent implant.
Evaluate the potential sites of implantation and battery pocket for infection or inflammatory process.
If there are any potential technical or patient-specific concerns, communicate with the treating physician and/or the anesthesiologist prior to implant.
Educate the patient/caregiver(s).
Obtain insurance coverage and document medical necessity.
Surgical considerations
Assess health status the day of surgery.
Have patient empty bladder preoperatively.
Obtain baseline pain score.
Review postoperative instruction sheet with patient/caregiver preoperatively.
Check that adult driver has been arranged to take patient home.
Order preoperative antibiotics and administer 30 to 60 min before incision or within 2 hours for vancomycin. Antibiotic doses should be based on the
patient’s weight.
Arrange for family to stay in postoperative area to observe programming and learn about recharging.
Confirm follow-up appointment before discharge.
• remedial surgical procedures not feasible or advisable or preferred
• any major untreated or unstable psychiatric disorder as determined by a well-performed psychological screening; patients who
are found to have significant somatization complaints should be
excluded
• discussion of therapy expectations
• elimination of inappropriate drug use before implantation
• absence of unresolved issues of secondary gain or litigation that
could potentially be central to the propagation of the pain
complaint
• capacity to give informed consent for the procedure
• possession of the cognitive ability to operate SCS equipment
• preoperative MRI or CT myelogram of the spine (within 12
months) to rule out pathology that might confound diagnosis
and/or compromise outcomes of SCS
• life expectancy greater than 12 months
• patient willingness and agreement to follow institutional protocol
for follow-up visits.
For patients selected for SCS, Table 3 presents a procedure
checklist.
PATIENT-RELATED COMPLICATIONS
578
In the properly selected patient, the result of neurostimulation is
very promising. There are several common and preventable pitfalls
the implanter should consider before the final step of implanting a
permanent device.
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• The type of pain should be considered; for example, the use of SCS
to treat osteoarthritis is likely to fail.
• The patient’s cognitive ability should be considered when choosing the device; for example, the implanter may choose a
nonrechargeable implant if the patient has difficulty understanding the charging process.
• The placement of the generator should be based on the patient’s
ability to rotate the shoulder in order to access the site of implant.
Other factors to be considered include bony landmarks, skin
pathology, and garment preferences.
• The patient, and caretakers when applicable, should be willing to
participate in both preoperative and postoperative educational
programs as recommended by the implanting doctor.
DEVICE-RELATED COMPLICATIONS
System Malfunction
Despite recent improvements in SCS systems, complications from
system malfunction have been a significant historical concern. In
2004, Cameron reviewed SCS complications over 20 years (1981–
2003) in 51 papers that totaled 2972 patients (3). Complications
were categorized as either technical (lead migration, lead breakage,
over- or understimulation, intermittent stimulation, hardware
malfunction, loose connection, and battery failure) or biologic
(infection, epidural hemorrhage, seroma, hematoma, paralysis,
cerebrospinal fluid [CSF] leakage, pain over the implant site, allergic
reaction, skin erosion, and other reaction specific to an implantable
pulse generator [IPG]). The most common of these were lead migration (13.2%), lead breakage (9.1%), infection (3.4%), hardware
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malfunction (2.9%), unwanted stimulation (2.4%), and battery
failure (1.6%) (3).
In 2012, Medtronic Neurologic Inc. (Minneapolis, MN, USA) published a similar review from their Implantable Systems Performance
Registry (ISPR). This product report prospectively enrolled 1983 SCS
patients from 43 domestic centers over seven years (June 2004
through July 2011). An adverse SCS event was defined as any related
to a device, implant procedure, and/or therapy. A total of 973
events were reported, 30% (295) of which were categorized as
product-performance-related and the remaining 70% (656) as
not product-performance-related (60). The majority (96.3%) of
product performance-related events involved the lead or extension (migration/dislodgment/fracture/high impedance), with the
remainder (3.7%) primarily involving the IPG (undesirable stimulation change, difficulty charging or programming, and issues with the
tract or pocket). The majority (90.2%) of non-product-performancerelated events involved the IPG and included expected battery
depletion, ineffective therapeutic response, pocket site pain, infection and wound dysfunction, and undesirable changes in stimulation
(60). Despite three decades of investment in electrode materials,
anchoring systems, education, training, and platform technologies,
the Cameron and ISPR reviews underscore the fact that SCS system
malfunction remains a significant clinical challenge. SCS system malfunctions can now be generally classified as hardware failures (electrode breakage/migration and loose anchoring or connections) and
battery failures (primarily programming issues and depletion).
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Battery Failures
Depending on the type of SCS system, power consumption of the
battery or “battery depletion” is dependent on the model of the IPG,
electrode location, hours of active therapy/use, and programmed
parameters. The current types of implantable devices include external battery-powered radiofrequency (RF)-coupled devices; totally
implantable, nonrechargeable IPGs; and totally implantable,
rechargeable IPGs.
The longest-lasting implants should theoretically be RF-coupled
devices, as they couple a 9-V battery-driven external transmitter
telemetrically to a subcutaneous receiver. Unfortunately, the
therapy burden to the patient is often high because the external
belt and frequent battery changes are cumbersome and limit the
hours/day of active therapy/use. Painful subcutaneous receivers
leading to complete system explantation have also been reported in
47% of 80 systems within three years (72). In the Alo series, chest
wall hyperesthesia from electrode fracture and/or broken connection led to an inability to couple transmitter with receiver. This same
phenomenon was also described by Heidecke et al. in 2000 (73).
In contrast, fully implantable IPGs have no external belts, do not
require battery changes, and have improved connections and a
much lower rate of pain at the implant site—0.1% in the ISPR of
Medtronic and 2.9% combined in the Matrix and Itrel 3 prospective
studies (53). As such, IPGs have the potential for significantly more
hours/day of active therapy and overall less therapy burden compared with RF. Nonetheless, all rechargeable and nonrechargeable
IPGs ultimately require battery explantation and/or replacement.
As most nonrechargeable IPG platforms were just being introduced when the ISPR began its enrollment, it is one of the first reports
to track depletion rates of both rechargeable and nonrechargeable
IPGs. Interestingly, the 35% expected battery depletion rate for the
combined ISPR (234/656 non-product-performance, ISPR events)
compares favorably with the 43.7% battery-depletion rate described
by Abejon et al. in a study of nonrechargeable IPGs only, which
terminated just before the ISPR began (74).
Finally, when a battery requires replacement before the expected
date (determined by the use parameters), it is considered an unexpected battery failure. Unexpected battery failure of a fully implantable IPG occurred in 32 (1.7%) of the 900 cases reviewed by
Cameron through 2004, although 22 of 32 of those occurred after
more than the expected three-year battery duration (3). The ISPR
did not specifically report on the rate of premature depletion for
either rechargeable or nonrechargeable fully implantable IPGs.
The remainder of the SCS system malfunctions described in the
literature are numerous but much less frequent than the hardware
and battery failures just outlined. Reported complications include
bacterial infection (including methicillin-resistant Staphylococcus
aureus or MRSA), subcutaneous or epidural hematoma, skin erosion,
aseptic meningitis, headache, asthenia, dizziness, muscle spasms,
postdural puncture headache (related to the needle, guide wire,
leads, or surgery), electromagnetic interference (external or deviceto-device), neurologic injury, device-tissue reaction, erythema,
erosion, and allergy (3).
Despite recent improvements in SCS platforms, complications
from system malfunction remain an evolving concern. While lead
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Hardware Failures
Lead and/or extension migration (or breakage) may result in a loss
of paresthesia and pain relief. If reprogramming cannot recapture
paresthesia/pain overlap, then reoperation to replace the lead over
the spinal target/level that produces paresthesia/pain overlap may
be needed. On the topic of reprogramming, North et al. and Alo et al.,
in separate articles, have described the improved paresthesia recapture of multichannel systems and reduction in reoperation rates
(61–63). Specifically, North’s group noted that surgical revisions were
required for 16% of single-electrode multichannel devices and 23%
of single-electrode bipolar systems, while Alo’s group reported even
fewer revisions when dual-electrode multichannel systems were
applied (3.7%). Subsequently, others have published similar dualelectrode findings (64). Andersen also reported a lesser reoperation
rate for single-electrode quadripolar (11%) vs. single-electrode
monopolar (23%) systems when treating angina (65).
Changes in stimulation paresthesia (e.g., uncomfortable intensity,
character, or pattern) may occur as the result of postural changes
that alter electrode position within the epidural space relative to the
spinal cord or because of changes in tissue impedance around
the electrodes (66–69). These changes in electrode position within
the epidural space relative to the spinal cord can cause patientperceived painful stimulation, ineffective stimulation, or loss of
stimulation over time and may contribute to therapy failure.
Cameron and Alo reported on the postural effects in patients in
whom a percutaneous SCS electrode was implanted (67). They
described differences in perceived stimulation thresholds between
the cervical and thoracic spine when lying, sitting, or standing.
These statistically significant changes were the result of spinal cord
movement and the thickness of the CSF layer at the level of the
implant. Lower described thresholds were due to both smaller CSF
layers and the electrode being close to the spinal cord (67). The
further contributions of tissue impedance to changes in perceived
intensity were in part detailed by Alo et al. (69). If changes in posture
or tissue impedance produce significant increases in intensity or
intolerable dysesthetic or motor sensations, therapy failure rates
may increase (70). In an attempt to offset spinal cord movement in
real time, an adaptive electrode position-sensing system has
recently been introduced (71).
DEER ET AL.
Table 4. Troubleshooting Implantable Pulse Generator Problems.
Problem
Possible solution
Generator depth too deep
Generator upside down or flipped
Surgical revision
Surgical revision; consider
anchoring at time of implant
Replacement of external
generator
Patient education
External programmer
malfunctioning
Patient inability to understand or
maintain the device
Loss of communication leads
Impedance measurement;
probable surgical revision
fractures and migrations have benefitted from improved anchoring
and implant advances, the longevity of rechargeable batteries and
new electrode geometries remain significant unknowns. In an era of
evidence-based medicine, increasing pressure from regulators and
third-party administrators will focus on the historical and future
costs associated with SCS system malfunction (56,75).
Communication and Generator Problems
The placement of an IPG is an essential part of the procedure to
create a neurostimulation system. Unfortunately, in some cases
external telemetry devices cannot communicate with the
implanted programmable IPG, leading to treatment failure of the
system. Table 4 lists some common causes of IPG problems and
potential solutions.
Percutaneous vs. Paddle Electrodes
A percutaneous electrode offers relatively easy access to multiple
spinal levels and thus facilitates paresthesia mapping. A surgical
plate/paddle electrode, however, might be required for screening if
a percutaneous catheter electrode cannot access the epidural space
satisfactorily, for example in a patient who has undergone a previous laminectomy or posterior fusion at the level of insertion. There
is no inherent difference in the fracture rates for these two types of
electrodes (7).
Device–MRI Compatibility
580
Background
The clinical use of MRI for anatomic diagnosis and, therefore,
management of various disease states is well established and is the
standard of care worldwide for imaging in many medical conditions.
Not surprisingly, utilization of MRI has increased tremendously in
the past 10 years, although often inappropriately (76). Thus, when
considering the use of SCS to treat chronic pain or other indications,
a potential limitation for neuromodulation is the lack of sanctioned
MRI compatibility with these devices. All neurostimulator manufacturers have labels warning that exposing a patient with an
implanted neurostimulation system or component to MRI may
potentially injure the patient or damage the system.
The intrinsic hazards of MRI exposure to patients with an SCS
system result from one or more of the main components of the MRI
environment (77,78): the static magnetic field, the static magnetic
field spatial gradient, the gradient magnetic field, and RF energy
produced by the MRI. The absorption of RF radiation constitutes the
specific absorption rate (SAR), typically indicated in units of watts per
kilogram (W/kg). When interacting with an implanted medical
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device, these magnetic fields can induce a rotational force (torque)
upon the device, which may result in tearing of the surrounding
tissues. Moreover, rotation to align the object with the field, translational force exerted upon the device, and acceleration of the object
into the bore of the magnet (the so-called “missile effect”) may also
cause tissue damage. Additionally, current induction due to the rate
of change of the magnetic flux density over time (tesla [T]/sec) may
result in device malfunction or failure, and RF-induced currents may
cause device heating and thermal or electrical burns to the patient.
Less concerning, but still important, are the effects of the medical
device on the operation of the MRI scanner, which may result in
poor-quality images due to excessive electromagnetic emission. In
the presence of an IPG or lead in or near the imaging field of view,
image degradation is to be expected (distortion, artifacts, etc.).
Although ex vivo (79–81) and in vivo (77) MRI compatibility of SCS
systems have been tested on 1.5-T and 3-T MRI scans, according to
the most recent Food and Drug Administration (FDA)-recognized
terminology (82), an implantable SCS system cannot be considered
as “MRI safe” because some of its parts cannot be classified as nonconducting, non-metallic, and non-magnetic. However, prior to the
recent FDA approval of an MRI-compatible SCS system, the FDA had
only approved safety language for Medtronic SCS systems for MRI
examinations of the head only, using an RF transmit/receive head
coil, under very specific conditions with MRI parameter adjustments.
Recently, Medtronic received approval in Europe and the USA for
the first implantable neurostimulation system for use for the treatment of leg and/or chronic back pain designed to be compatible
with full-body MRI scans under specific conditions. With this new
system, unwanted movement of the entire device is reduced by the
minimal presence of ferrous material. The lead is shielded, reducing
the risk of thermal tissue damage by dispersing RF energy along its
entire length, and a filter in the IPG shunts RF energy from the lead
to the outside of the neurostimulator, protecting internal circuitry
from damage (83).
Discussion
Safety is paramount when using MRI in patients with implanted
SCS systems because the interaction of MRI and SCS is complex.
Evaluating the potential risk of exposing a patient with conventional SCS systems to the MRI environment must include consideration of magnetic field interactions, heating, induced electrical
currents, implant damage, and functional/operational disruption.
Many factors affect the heating profile for a given device, including
• the electrical characteristics of the particular neurostimulation
system
• the field strength of the MR system
• the orientation of the IPG
• the presence of an extension cable
• the location of the leads in relation to the site of imaging
• the type of RF coil used (transmit/receive body coil, transmit body
coil with receive-only head coil, transmit/receive head coil)
• the anatomic region being scanned
• the amount of RF energy delivered
• how the SAR is calculated for a given MRI system
MRI safety criteria, defined by using a particular neurostimulation
system and/or utilizing a given MRI system configuration, may not
be readily applied to other neurostimulation systems (84). Currently,
more universal and appropriate measures are required in order to
guide MRI safety recommendations for neurostimulation across different systems and platforms (85).
The interaction between the MRI system and configuration used
and the SCS system is not only a safety issue, it may also cause MR
image quality corruption. The size of the artifact for an implant or
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device may affect the diagnostic utility of MRI. Information is typically provided in the SCS device label that characterizes the size and
shape of the artifacts associated with certain pulse sequences.
Therefore, it may be necessary to optimize MRI imaging parameters
for the presence of an SCS implant.
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Device Removal
There are many reasons for device removal, including persistent
or overwhelming infection, therapy failure, persistent pain over
hardware, skin erosion, and necessity of an MRI. Device removal is
not reported in all SCS studies. The review by Turner et al. reported
a device removal incidence of 11% with a median figure of 6% and
a range of 0% to 47% (54). The authors did not elaborate on the
causes for device removals. Brazzelli et al. noted a device-removal
incidence of 9% for sacral neuromodulation (SNS) (94). Verrills et al.
described two cases (2%) of hardware failure and removal in PNfS
(95).
TECHNIQUE-RELATED COMPLICATIONS
Appropriate Training and Mentorship
The NACC recommends that improvement of outcomes for
implanted neurostimulation devices must include setting higher
standards for the training and quality of potential implanters.
Implanters should have undergone training in a recognized, highvolume center with proper credentialing. During formal training
the implanter should ideally perform a minimum of 10 cases as the
primary implanter and under supervision. Appropriate training
should include patient selection and contraindications to intended
procedures, the anatomy of the intended implant area, complication identification and management, and collaboration with
colleagues. The implanter should be comfortable with troubleshooting during the implantation procedure and with the
methods and techniques used to achieve proper stimulation, while
maintaining patient and implanter safety. The implanter should be
able to recognize and treat hardware-related and biological complications and should be able to recognize the benefits and pitfalls
of various commercial leads and lead types and their specific
indications.
It is obvious that only neurosurgeons should perform intracranial
procedures and only trained surgeons should perform surgical laminectomies for implantation of SCS systems. High cervical SCS should
be performed only by those with extensive experience with SCS
system implantation via a percutaneous or open surgical approach.
Although implanters may choose to implant trial extracranial
systems in an office setting, they must obtain privileges to perform
implantation in an accredited hospital setting, properly certified
surgical center, or similar facility. This recommendation varies from
country to country, but the NACC recommends that any physician
who cannot receive privileges to do these implants in a hospital of
good standing should cease from implanting. The NACC does not
recommend performing permanent implantation of any of these
devices in the office setting.
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Recommendations
MRI should not be considered for patients with neurostimulation
systems that are not MRI-compatible if other potentially safer
diagnostic methods, such as CT, radiography, or ultrasound, will
provide adequate diagnostic information. It should be noted that
the risk of developing cancer from CT scan radiation is rare,
although important public health implications in the future may
exist (86–88). However, given that radiation-induced cancer is
greatly reduced among those requiring CT after age 60, this may not
be clinically significant. In light of the relatively high lifetime risk of
requiring advanced imaging and of concerns related to the risk of
CT scanning, all patients, and especially those with multiple medical
risk factors that would lead to use of such imaging (e.g., those at
increased risk for stroke), should be informed about the MRIcompatible alternative SCS system.
Several authors have designed strategies to offer a measure of
safety for MRI explorations in patients with conventional SCS
systems when MRI is required. These strategies involve the patient
(information, capacity to report complications), the MRI system
(tesla and SAR specifications), the neurostimulation system (programming and pre- and postradiological exploration adjustments)
(77), and the presence of a health-care provider with expertise in
programming the system during the examination (89). Patients who
require MRI over other imaging modalities (e.g., those with malignancy that requires MRI monitoring, demyelination diseases, or specific biliary problems) should be told by the implanting physician
that there exists an MRI-compatible alternative system.
If MRI imaging is essential in patients with MRI-incompatible SCS
systems, the amplitude should be set to 0 V/mA and output turned
off. The approach to the MRI bore and activation of the MRI magnet
should be done slowly and under careful supervision. The SAR
rating must be the lowest possible value and never more than
0.9 W/kg. Perhaps the most feared physical risk associated with MRI
exploration in patients with an SCS is heating of the generator
and/or tip of the lead and the electrodes due to the variable magnetic fields and pulsed RF fields elicited by MRI signals (90). This
generated heat may result in heat-induced lesions, such as burns at
the site of implanted components. A burn from magnetic- induced
currents to the lead tip could result in neurologic disaster.
In general, scientific guidelines provided either by radiologists or
implanting physicians consider the use of MRI in patients with an
implanted SCS system to be a relative contraindication. Besides
injury to the patient, a second major problem with MRI utilization in
patients with an SCS device is direct damage to the device itself.
While there have been series of cases reported without problems,
concerns remain. Field strengths as low as 10 G may be sufficient to
cause deflection, programming changes, or closing of switches.
Therefore, in a patient with an SCS system, the initial recommendation is to utilize other imaging modalities if at all possible. If MRI is
required, the advice of a radiologist should be sought and, depending on imaging site and sequencing, imaging may be possible.
Nevertheless, MRI compatibility of implantable SCS devices has
been examined previously in vitro, and the devices were shown to
be safe and therefore were labeled as MRI-conditional (82). The
application of a strict protocol, based on safety criteria previously
established in relation both to the MRI technique (91) and to programming of the neurostimulation system (90,92), results in low
patient morbidity. For several years, various centers have performed
a variety of MRI examinations with few reported complications (93).
With the elimination of ferromagnetic components and new specific designs and structures, SCS systems will become increasingly
safe. At the same time, the power of the magnets of the MRI will be
increasing and technologies evolving. (Current MRI-compatible
systems were tested using 1.5-T scanners, not the commonly
employed 3-T scanners.) Therefore, the NACC proposes an evolutionary strategy, adapted to the evolution of the technology itself. In
conclusion, current recommendations for safety and quality
imaging in the performance of MRI are summarized in Table 5. If an
MRI is attempted, the ordering physician and radiologists should
carefully weigh the risk-to-benefit ratio and discuss it with the
patient and the family. Careful and deliberate education is a critical
part of this decision.
DEER ET AL.
Table 5. Neuromodulation Appropriateness Consensus Committee Recommendations for Quality Magnetic Resonance Imaging (MRI) in a Patient With a
Neurostimulator That Is Not MRI-Compatible.
In some settings, implanting physicians have opted to order MRI in patients with entire systems or components that have not been labeled as compatible
(these include most currently implanted systems). The NACC does not endorse this decision, but is providing guidance to those who choose that path.
Patient
• If possible, do not sedate the patient and monitor so that the patient can provide feedback of any problems during the MRI examination.
• The implantable pulse generator side of patient’s skin should not be in contact with the inner bore of the magnet.
• Carefully position the body part relative to the transmit coil.
• Report to the radiologist the specific type of neuromodulation system implanted.
• The patient should be responsible and educated about the spinal cord stimulation system and able to communicate any problems to a health-care
professional. Problems may include “heating,” paresthesias, or pain.
Radiologist
• Monitor the patient both visually and audibly.
• Follow manufacturer/device-specific protocols for the following:
o Field strength and radiofrequency wavelength
o Type of transmit radiofrequency coil
o Amount of radiofrequency field pulsed during imaging (= energy delivered)
o Amount of specific absorption rate and technique to calculate
o Gradient magnetic field (pulsed during imaging) induced currents due to dB/dt
Implanting physicians
• Patients should be told that an MRI-compatible SCS system alternative exists, and the physician should comment on the benefits and limitations of
acceptable, existing systems and weigh the MRI issue compared with other factors that may impact outcomes.
• Inform the patient of all of the risks of undergoing an MRI examination with conventional spinal cord stimulation systems. This should include the fact that
many implanting doctors do not perform MRI in these patients.
• Test for possible open circuits that might exist by measuring impedance on all electrodes. If a broken lead wire is suspected, do not perform an MRI
examination as higher-than-normal heating may occur.
• Implanted system leads or wires should not form large-radius wire loops.
• Specify when ordering an MRI the type and electrical characteristics of neuromodulation system complications.
• Personnel experienced in programming must be available before, after, and preferably during the MRI.
Perioperative Preparation
Before implanting a device, the physician should consider the
amount of anatomical space within the epidural space required for
the lead or leads. Patients with lumbar or cervical spinal stenosis
may have asymptomatic thoracic spinal stenosis as well.
In awake patients for whom a percutaneous lead placement is
planned, the ability to access the patient’s response during the
implant procedure is essential. In cases where the clinician is unable
to converse with the patient or where concerns about spinal stenosis exist, the clinician should order an appropriate imaging study to
assess spinal diameter before implantation of either the trial or permanent lead. Imaging options include MRI, CT, and CT myelogram.
If at reading the MRI or CT no CSF can be seen around the cord, an
implant should not be done without prior surgical decompression
of the stenosis.
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Surgical Technique: Insertion, Anchoring, and Suturing
Hardware failures due to anchoring or tunneling technique have
been an issue since SCS systems were introduced in the 1960s.
Despite the application of many different tunneling and anchoring
tools, lead migration and fracture rates remained high into early
2006 (6). At that time, multiple soft silicone or hard plastic devices
were still in use, none of which was consistently reliable over the
preceding four decades.
Out of frustration and necessity in early 2000, Alo et al. began
using a figure-eight silk suture“drain stitch”strain-relief loop directly
between the electrode and the subcutaneous tissue (96,97). That
simple technique unexpectedly eliminated lead fractures and
migrations from the authors’ clinical practice, which had previously
exceeded 20%. This experience led to a bench evaluation by Kreis
et al., who studied the integrity of the electrode–suture interface
under high-power microscopy (98). Specifically, a total of 56
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surgeon’s knots or “drain stitches” were tied around 28 electrodes
under tension and then evaluated for evidence of microscopic insulation or contact disruption. With none of the electrodes showing
disruption and the initial concern of iatrogenic fracture mitigated,
Kreis et al. began uniformly applying and monitoring the technique
clinically with similar results to Alo et al. Anatomic variations of this
technique were subsequently developed by Mironer et al. and more
recently by Bowman et al. (99,100).
A key factor for decreasing lead migration is choice of suture.
Many implanters use a nonabsorbable braided polyethylene terephthalate suture (i.e., Ethibond, Ethicon Inc., Johnson & Johnson,
Somerville, NJ, USA) rather than silk for both strength and visibility
(because of its blue color). Greenwald et al. demonstrated that all
sutures decreased in strength, strain, and toughness over time
except for Ethibond, with silk losing the greatest strength and
toughness (101). Although silk is often classified as a nonabsorbable
suture, it nonetheless degrades in tissue at a variable rate.
In concert with the aforementioned, a formal clinical evaluation of
specific electrode failure modes was carried out by Rosenow et al. in
577 systems (6). The breadth of this study subsequently led to a
modeling evaluation of electrode insertion angles (skin and
sublaminar), tunneling tools, and anchor engineering assessments
(102). This evaluation by Henderson et al. emphasized the need for
implanters to apply a shallow needle insertion angle at the skin and
sublaminar entry points, as well avoiding electrode kinking at the
fascial plane. This insertion and suturing strategy, which was not
previously addressed by the soft silicone or hard plastic anchors,
seemingly abated fracture, migration, and subsequent failure.
Shortly thereafter, “slip lock” anchoring devices with improved
holding forces were introduced, which minimize electrode fatigue
and markedly reduce migration and fracture rates (103–105). Lead
migration and anchoring techniques will be addressed later in this
article.
© 2014 International Neuromodulation Society
Neuromodulation 2014; 17: 571–598
RISK REDUCTION IN NEUROSTIMULATION
Anesthesia
Local anesthesia supplemented by conscious sedation is used for
the majority of cases involving SCS cylindrical lead implantation.
The use of local anesthesia at the time of implant enables the
implanter to interrogate the patient about the location of
stimulation-induced paresthesia coverage. This is important to
ensure an accurate overlap between the dermatomal distribution of
pain and the paresthesia. Failure to check paresthesia coverage
results in less than satisfactory pain relief. Where the cooperation of
the patient is lacking, general anesthesia may be considered. In such
a case, the implanter may use somatosensory evoked potentials
(SSEPs) to verify if stimulation-induced paresthesia will cover the
distribution of pain upon patient awakening.
Placement of surgical leads can be accomplished using local analgesia with conscious sedation but has the drawback of patient discomfort during the laminotomy procedure. As a result, some
implanters prefer to place laminotomy leads using epidural anesthesia (106,107). Other surgeons use general anesthesia, which may
require the use of SSEPs. Kumar et al. have demonstrated that spinal
anesthesia for lead implantation overcomes the problem of painproducing laminotomies in the awake patient, yet does not block
the perception of stimulation-induced paresthesias. These authors
have performed more than 200 cases successfully using spinal anesthesia in the last three years without adverse outcomes. It should be
noted that spinal anesthesia will inhibit the perception of painful
stimuli but not the paresthesia felt on stimulation of the dorsal
columns. The threshold amplitude for spinal anesthesia is 2 mA
higher than that required for local anesthesia (108).
Preoperative Education and Postoperative Care
Patient education helps set realistic expectations for SCS therapy
and helps engage the patient, family, and caregivers in the therapy.
A discussion of the intended procedure should address the patient’s
cosmetic concerns. Preoperative instruction may include a description of neurostimulator components, the goals of therapy, the
purpose of the trial, the implant procedure, the possible risks and
complications, and the importance of follow-up care. A written list
of preoperative patient responsibilities can reinforce verbal instructions. This list may cover the date, time, and location for the procedure and reminders to obtain previous imaging studies, to require
the patient to stop specific medications before trial and implant, to
call to cancel the procedure should the patient become ill or choose
not to undergo the procedure, to bathe with appropriate prep
material before surgery, and to arrange for transportation to and
from the surgical suite. Postoperative care/discharge instructions
can be distributed on the day of the trial or implant. The patient/
caregivers should know how to contact the physician or clinic if
questions arise or complications occur.
SPECIFIC COMPLICATIONS
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© 2014 International Neuromodulation Society
Neuromodulation 2014; 17: 571–598
583
Lead Migration
Lead migration is by far the most common complication of spinal
and peripheral nerve stimulation (Table 6). The majority of the
instances of lead migration require minor reoperation to relocate
the lead to its original position, and most will incur the cost of a new
lead. Lead migration rates vary greatly between studies, with some
quoting figures as high as 60% to 100% but the majority quoting
figures of 10% to 25% for SCS. This variation can be explained by
varying implanter experience, differing clinical context of the
therapy, and varying clinical practices. It has been suggested that
lead migration following surgical paddle lead implantation is less
common than with percutaneous cylindrical leads and that location
of the lead in the spine may influence the rate of migration, with
higher rates occurring where the lead is implanted in a highly
mobile area of the spine (3). However, evidence to the contrary also
exists (5,116). Most reviews do not differentiate between vertical
(craniocaudal) and lateral (horizontal) lead migration.
In a 20-year literature review of SCS, Cameron (3) reported 361
lead migrations in 2753 patients, an overall migration rate of 13.2%.
In two systematic reviews of 18 studies of SCS for FBSS and eight
studies of SCS for CRPS, Taylor et al. (109,113) reported lead-related
complications to be 27% and 20%, respectively. There was no breakdown of these numbers as to lead fractures or lead migrations. In a
retrospective review of 410 patients over a 22-year period, Kumar
et al. (32) reported lead migrations in 88 patients (21.4%), of which
40 leads were repositioned and 48 replaced. In a more recent retrospective review of 707 patients, Mekhail et al. (56) reported an initial
lead-migration rate of 0.7% during the trial period, but a subsequent 22.6% eventually developing lead migration. Turner et al. (54)
systematically reviewed 22 studies of SCS; they did not report a rate
of lead migration but instead reported a 23.1% mean rate of stimulator revision for reasons other than battery change (median value
21.5% and a range of 0% to 80%). In their discussion, the authors
acknowledged that the majority of these occurrences were related
to lead migration; however, it is not possible to estimate how many
of these events were related to lead malfunction instead of migration. The authors did not elaborate on the numbers of patients
requiring revisions. In the PROCESS study (44) at 24 months, nine
lead migrations had occurred in six of 42 (14%) patients. All six
patients required surgery to reposition the leads. In a further randomized controlled trial (RCT) comparing SCS to reoperation, North
et al. (5) reported three of 33 (9%) patients requiring lead revision
due to migration or malposition. It is important to note that some of
the patients in this study received surgical plate leads. These are
reported to be associated with lower migration rates compared with
the more commonly used cylindrical percutaneous leads (110,116),
although work by Rosenow et al. suggested the converse (6).
In a systematic review of seven RCTs and 47 case reports of SNS
for functional urinary bladder stimulation, Brazzelli et al. (94) concluded that the rate of lead migration in this therapy was 16%
despite the use of tined leads.
In the largest of case series reporting on the use of PNfS for pain
relief, Sator-Katzenschlager et al. (114) and Verrills et al. (95) reported
rates of lead migration of 13% and 2%, respectively. The large difference in lead migration between these two studies may well relate to
the multicenter nature of the first study compared with the second,
which reports on the results of a single-center practice.
A lead migration rate as high as 100% was reported in a case series
of occipital nerve stimulation (ONS) at three years, with the rate being
60% at the end of one year (117). Lead migration occurred in 12 of 51
subjects (24%) in the ONSTIM study of ONS (112). The high percentage of lead migration for ONS may be due to anatomic location (head
vs. thoracic placement), neck mobility, or poor anchoring technique.
For conventional thoracic placement of SCS leads in the hands of
experienced implanters, a lower incidence is accepted as standard.
Lead migration can occur due to poor anchoring technique
and/or failure of the anchor. SCS leads can migrate longitudinally
(cephalocaudad in an axial direction) or transversely (laterally) in the
epidural space. Lead migration occurs most commonly in the
cephalocaudad plane. Lateral or transverse migration is believed to
be relatively less common than vertical migration, and the mechanism is less well understood (32,102).
DEER ET AL.
Table 6. Reported Rates for Complications of Spinal Cord Stimulation.
Publication
Therapy type
N
Lead migration (%)
Cameron 2004 (3)
Review
Taylor et al. 2006 (113)
Systematic review
Taylor et al. 2005 (109)
Systematic review
Kumar et al. 2006 (32)
Retrospective analysis
Mekhail et al. 2011 (56)
Retrospective analysis
Turner et al. 2004 (54)
Systematic review
Kumar et al. 2008 (44)
Randomized controlled trial
North et al. 2005 (5)
Randomized controlled trial
Total SCS
SCS
2753
13.6
Lead fracture (%)
Brazzelli et al. 2006 (94)
Systematic review
Saper et al. 2011 (112)
RCT
Schwedt et al. 2007 (117)
Retrospective analysis
Paemeleire et al. 2010 (111)
Retrospective analysis
Sator-Katzenschlager et al. 2010 (114)
Retrospective analysis
Verrills et al. 2011 (95)
Retrospective analysis
SNS
?
ONS
75
24
2
ONS
15
60–100
0
Not reported
ONS
44
30
0
Not reported
4.5
PNfS
111
13
5
Not reported
6
PNfS
100
2
2
Not reported
1
9.1
Pain over implant (%)
0.9
Infection (%)
3.4
SCS (CRPS)
554
20
Not reported
Not reported
4
SCS (FBSS)
3427
27
Not reported
Not reported
6
SCS
410
21.4
5.9
None reported
3.4
SCS
527
22.6
6
None reported
4.5
SCS
830
23.1
10.2
SCS
42
14
7
12
SCS
45
9
0
None reported
5308
Range 9–27
Mean 17.5
CI 14.5–20.49
16
Range 0–10.2
Mean 4.775
CI 3.55–5.97
0
5.8
4.6
10
Range 0.9–12
Mean 6.233
CI −0.871–13.2
24
6
6
Range 3.4–10
Mean 5.23
CI 4–6.4
5
4
Not reported
SCS, spinal cord stimulation; CRPS, complex regional pain syndrome; FBSS, failed back surgery syndrome; SNS, sacral neurostimulation; ONS, occipital nerve
stimulation; PNfS, peripheral nerve field stimulation; RCT, randomized controlled trial.
During SCS implantation, percutaneous leads are typically secured
at the lead-exit site, either the deep fascia or the supraspinous ligament. Contrary to the aforementioned evidence, concern should still
be exercised before placing a suture or a ligature directly around the
lead, as it may damage the internal components of the leads and is
not recommended by manufacturers, although a small short-term in
vitro study suggested minimal if any damage (98). Lead anchors have
been developed to protect the lead components while securing the
percutaneous leads to paraspinal structures such as deep fascia or
the supraspinous ligament. However, the implanter needs to keep in
mind a number of factors that can result in lead migration.
584
Needle Placement
The introducing needle for percutaneous SCS leads should be
placed using a paraspinous approach and a shallow entry angle.
This places the exiting lead body away from the anatomic midline
between the spinous processes and helps avoid friction or damage
to the leads by the moving spinous processes. The needle tip,
although entering the fascia from a paramedian position, should
enter the epidural space in the midline. Along with a shallow entry
angle, this ensures appropriate midline lead placement in the posterior epidural space and minimizes lateral lead migration while
optimizing current delivery to the dorsal columns. A shallow entry
angle also maximizes the bend radius on the lead as it enters the
deeper paraspinal structures, thereby decreasing the risk of lead
migration (98).
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Anchoring Technique
A number of anchors have been developed to secure the leads
safely. Silicone anchors with suture sleeves are supplied by all manufacturers in their SCS lead kits. These anchors are low-profile and
soft, which makes them advantageous in thin patients. Although
they may provide robust anchoring, the strength/durability of the
anchored lead is totally dependent on the surgical technique and
skills of the implanting physician. Enhanced silicone anchors with
titanium sleeves have been developed. These anchors are radiopaque, facilitating their identification should a lead revision be
needed. However, the holding strength of the anchor on the lead is
still highly dependent on the implanter’s skills. Both types of silicone anchors require placement of retention ties around the anchor
sleeve in order to secure the lead to the anchor, creating a single
unit; the lead and the anchor become one.
Mechanical anchors have been developed to bypass the necessity of tying the anchor to the lead, but they are touted to also
provide superior holding force. There are no studies that have validated the claim that these mechanical anchors lead to a decreased
rate of migration.
The sequence of securing the anchor to the fascia and then the
lead to the anchor is largely implanter-dependent. It is recommended that the “system” be anchored to the supraspinous ligament or to deep fascia using nonabsorbable braided nylon sutures
through the suture sleeves of/or just around the anchor. Alternatively, some surgeons secure the lead and anchor to the patient with
the first stitch, all at once, so as not to cause the electrode to migrate
© 2014 International Neuromodulation Society
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RISK REDUCTION IN NEUROSTIMULATION
Table 7. Commercially Available Anchoring Mechanisms.
Clik
Swift Lock
Twist Lock
Injex
Boston Scientific
2011
Silicone
Hex wrench
Not known
$375 a pair
St. Jude Medical
2010
Hard plastic
Twist apart
Not known
$350 a pair
Medtronic
1998
Hard plastic
Untwist
Shown by Kumar 2006 (55)
Included in lead kit
Medtronic
2012
Silicone
Cut with special tool
Not known
Not known
Appearance
Company
Year of FDA approval
Material
Release mechanism
Damages lead
Cost
even before implantation. Surgical paddle leads are typically
anchored either to the dura or to the ligamentum flavum. Using an
anchor for surgical paddle leads placed at the fascial layer has been
shown to result in lead fracture upon thoracolumbar spine flexion,
as the lead is taut between two fixed rigid points (102). Should an
extension be needed, anchoring the connector next to the lead
anchor is recommended.
Strain-Relief Loop
A strain-relief loop placed at the epifascial level distal to the
anchor for both percutaneous and paddle leads has been recommended to provide slack and decrease the risk of lead migration
(4,102).
Implantable Pulse Generator Position
The distance between the midline anchor and an IPG implanted
in the gluteal region elongates by 9 cm upon thoracolumbar spine
flexion (4). Placing the IPG in the abdominal wall results in a minimal
excursion of 0.2 cm upon walking and 1.7 cm with twisting (4). Alternatively, the IPG may be placed just to the side of the midline incision, except in thin patients or those with increased paraspinal
muscle bulk (118,119). In an abstract presented at the 2006 North
American Neuromodulation Society meeting, Pyles and Khodavirdi
describe this technique being used in six patients (119). Moreover,
these authors mention one of the major advantages of the technique as being decreased probability of lead migration due to elimination of lead traction that might have resulted from placement of
the IPG at a site distant from the anchoring point (119). No lead
migration occurred with off-midline placement of the IPG in a series
of 26 implanted patients described in an abstract from the INS
annual meeting in 2011 (118). However, the IPG moved toward
midline in one patient, necessitating revision.
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Aberrant Stimulation
Aberrant stimulation can be defined as painful, unhelpful, or otherwise unwanted stimulation, often a change from the expected
stimulation. Aberrant stimulation results from multiple causes, with
three mechanical or physiologic events explaining most situations.
The first is lead migration, a mechanical event, and thus recruitment
of additional and unhelpful neural tissues, often with the loss of
© 2014 International Neuromodulation Society
Neuromodulation 2014; 17: 571–598
585
Anchoring Mechanisms
The anchors that have been used to secure percutaneous leads
have historically been constructed of materials such as silicone or
hard plastic (Table 7). Silicone anchors are secured to leads by nonabsorbable ties and then to deep fascia with similar sutures. Hard
plastic anchors, on the other hand, are secured to leads by using a
twist-locking mechanism and are then secured to deep fascia with
nonabsorbable sutures. Kumar et al., in a combination literature
review and expert panel consensus statement in 2007, showed that
silicone anchors attached to deep fascia, with the nose of the
anchor pushed through the fascia, were superior in preventing lead
breakage compared with the only hard plastic anchor available then
(4). Moreover, this hard plastic mechanical anchor, FDA-approved
for use since 1998 (120), has been associated with lead breakage as
well as localized pain (102).
A Swift-Lock mechanical anchor (St. Jude Medical, Plano, TX, USA)
has been in use since February 2010. This anchor is unidirectional,
with a longer, nozzle-like soft end intended to be the proximal end
of the anchor pointing toward the spine. This anchor has a mechanical twist-locking mechanism.
The Clik anchor is a mechanical anchor released in March 2011
(Boston Scientific Neuromodulation, Valencia, CA, USA). This lead
anchor combines the advantages of the silicone anchor with the
locking feature of hard plastic anchors. It consists of a set screw that
can be tightened with a hex wrench, resulting in an audible and
tactile click to confirm the lock. The same wrench/screw-locking
mechanism is used to connect leads to the generator. The Clik is
bidirectional and the titanium set screw anchor housing makes it
radiopaque, facilitating localization should a lead revision be necessary. A Pellethane (Lubrizol Corp., Cleveland, OH, USA) sleeve covers
the inner lumen of the anchor and distributes the force from the
engaged set screw over a larger area, protecting the lead. A silicone
overmold encases the screw system to enhance patient comfort.
Additionally, the set screw can easily be unscrewed to manipulate
the lead if necessary, unlike other locking anchors that are difficult
to unlock once locked.
The Injex anchoring system (Medtronic Neurological, Minneapolis, MN, USA) is the latest mechanical anchor to enter the market. It
uses a unique compression-fit anchor design that maintains lead
integrity by allowing the lead wires to float without undue restraint.
A handheld dispenser propels the silicone rubber anchor over the
lead while the tool is pushed against fascia at the lead-exit site. The
lead is then anchored to the fascia or supraspinous ligament using
ties (the manufacturer recommends against using polypropylene
suture material on silicone). A special anchor-removal tool with a
stainless steel slitting blade is required once the anchor is deployed
to free the lead or replace the anchor, if desired.
To date, there are no studies that support the notion that the
newer mechanical anchors cause less lead breakage or localized
pain. Prospective studies on lead migration would be useful to
determine the utility of such products. However, lead migration may
be dependent on the surgeon’s skills and experience more than the
anchor itself. Thus, aggregate studies would be more useful than
analysis of a single implanter’s results with the newer anchors.
DEER ET AL.
stimulation of effective neurons. The second situation occurs as a
function of costimulation of intended and unintended neurons, a
physiologic event. The third situation results from the momentary
migration of an electrode relative to its intended target, a mechanical event, as seen with rotation of the neck in cervical stimulation, or
when the patient changes position and the spinal cord moves relative to the fixed position of the electrode (67,68,121).
Significant literature exists regarding lead migration and is
covered elsewhere in this paper. Costimulation of targeted and
untargeted neurons can often be mitigated or improved upon with
programming changes, such as narrowing of pulse width and or
reduction of amplitude to reduce the chronaxie–rheobase
strength–duration curve (122,123). Programming of the electrodes
to produce relative hyperpolarization of collateral nerves (guarding)
can also confer benefit. If programming cannot reduce unwanted
neural recruitment, then improvements in the proximity of the electrode to the intended neural target may help. This may require electrode repositioning or revision, based on the circumstances.
Improvements in hardware and the ability to more discretely depolarize or more adequately anodally guard unwanted nerves will
improve this side effect (124,125).
Changes in stimulation conferred by changes in position occur
because the anatomic location of the electrode changes in relation
to the neural substrate, often secondary to the thickness of dorsal
CSF (68,126,127). Remedies include choosing a different location for
stimulation, such as moving proximally in the cervical cord from
mid-cervical to high cervical position or changing from a cylindrical
lead to a thicker and wider paddle lead. Because paddle leads are
typically thicker, solutions to positioning with thoracically placed
cylindrical leads may also include use of a paddle lead. Use of specialized position-sensing accelerometers has also been beneficial
(128,129).
586
Pain Related to Device Components
Patients implanted with neuromodulation devices often report
pain related to the site of device components, such as pain around
the IPG site or pain over the lead-anchor site or lead-extension
junctions. In SCS studies the incidence of component pain is variable (Table 6); for example, Kumar et al. (44) reported an incidence
of 12% (5 of 42 patients) in the PROCESS study, with one patient
requiring reoperation. This high incidence, however, may be related
to the large size of the IPG used in the study (Synergy, Medtronic,
Inc.). By contrast, North et al., Kumar et al., and Mekhail et al.
(5,32,56) reported no cases of device-related discomfort. Cameron
et al. (3) reported 24 cases of device-related discomfort from a total
of 2753 (0.9%). Turner et al. found a higher incidence, with a mean
5.8% of patients across 20 studies reporting pain over the implant, a
median value of 0%, and a range of 0% to 40% (54).
Regarding ONS, Saper et al. (112) reported two cases of pain over
the IPG site and one case of burning pain over the lead/extension
site (6%). By contrast, Paemeleire et al. (111) reported no cases of
pain over the implant site.
Device-related discomfort appears to be far more common in
SNS. Brazzelli et al. (94) reported a 24% incidence of pain over the
lead or IPG site. This may well relate to the location of the lead and
IPG implant in the presacral and buttock area, where subcutaneous
fat may be less dense than in the anterior abdominal wall, where
many SCS devices are implanted.
In cases considered for revision, including placement of paddle
electrode in cases of lead migration, the clinician may consider
another percutaneous trial to guide the revision surgery. This is an
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especially important consideration when doubt exists about the best
location for the paddle. Best practice mandates careful communication between the trialing clinician and the surgeon performing the
paddle placement. The stimulator company representative can also
assist in transmitting images and facilitating this communication.
BIOLOGIC COMPLICATIONS
Infection
Background
Approximately 22% of all health-care-associated infections are
surgical-site infections (SSIs), and the majority of SSIs are thought to
be acquired during surgery (130,131). In addition, most SSIs originate from the patient’s own bacterial flora (11,45,132). For example,
>80% of health-care-associated Staphylococcus aureus infections
are endogenous (133). SSIs associated with implantable pain
devices may result in high levels of morbidity and devastating clinical consequences, including the costly (to the patient and to
society) removal of equipment. There have been reports of MRSA
cultured from the CSF of patients who underwent the placement of
a stimulator lead and paralysis from an epidural abscess following
SCS infections (134,135). In general, direct expenses attributed to an
SSI may result in a doubling of total medical inpatient costs. Significant policy and treatment measures have been advocated for the
reduction of SSIs.
Infection rates associated with SCS systems vary (Table 6) and
have been reported in the range of 3.4% to 4.6% from two large
systematic reviews (3,54). Kumar et al. (41), in a multicenter RCT
comparing SCS with CMM for neuropathic pain, reported an 8%
infection/wound breakdown rate. Biological complications are most
prevalent within the first three months postimplantation.
The three major types of infection related to SCS implantation
include superficial infections, deep infections, and epidural
abscesses. Superficial SSIs involve the skin and subcutaneous tissue
surrounding an incision and are defined as infections occurring
within 30 days after the operation (11). A deep incisional infection
related to surgery involves the deep soft tissue, including muscle and
fascia. When an implant is involved, the responsible timeframe for a
deep infection is up to one year postsurgery (11). Turner et al. (54)
reported that a majority of infections associated with SCS systems
are superficial infections (4.5% superficial SSIs and 0.1% deep SSIs).
Follett et al. (136) reported that a majority of infections occur at the
generator site (54%) and that infection rates are lower at the SCS
electrode implant site (17%) and with lumbar incision (8%). The most
commonly reported organisms were Staphylococcus species at 48%.
Preoperative Practices
During the preoperative stage, focus should be placed on the
recognition of known risk factors for the development of SSIs and
ways to modify these factors. Patient risk factors associated with a
higher level of infection include altered immune response (e.g., HIV/
AIDS and corticosteroid use), diabetes, obesity, remote infection,
tobacco use, and carriers of staphylococci (131,132). Prior to surgery,
all remote infections should be treated. In addition, glucose control
should be optimized (CDC Recommendation Category IB) and
patients should be encouraged to discontinue tobacco use (CDC
Recommendation Category IB). When hair removal is required at the
surgical site, it should be done with electrical clippers immediately
before surgery (CDC Recommendation Category 1A). Preoperative
screening and decolonization for S. aureus nasal carriers (both
methicillin-sensitive S. aureus and MRSA) with mupirocin nasal ointment and chlorhexidine soap has been reported to reduce the risk
of hospital-associated S. aureus infection (11,133).
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Prophylactic antibiotic therapy (CDC Recommendation Category
IA) should be utilized and has been shown, in both animal and
clinical studies, to reduce the risk of SSIs (47,55,137). Furthermore,
antibiotic prophylaxis has been shown to be an effective intervention for preventing postoperative wound infection, independent of
surgery type, resulting in an approximately 50% reduction in the
incidence of wound infections (138). Multiple factors are involved in
optimal antimicrobial prophylaxis, such as agent selection, timing
and route of administration, duration, renal function, and appropriate dosing. Failure to optimize antimicrobial therapy has been
shown to increase the risk of infection by two- to six-fold (139).
Intravenous antibiotics should be administered within one hour
before surgical incision or within two hours before surgical incision
with vancomycin. Although great emphasis has been placed on the
appropriate timing of the administration of antibiotic prophylaxis
prior to incision, weight-based dosing is another factor that plays a
role in the efficacy of therapy. In order for antimicrobial prophylaxis
to be effective in the prevention of SSIs, serum and tissue levels
must exceed the minimum inhibitory concentration (MIC) for the
organisms likely to be encountered during the operation (140,141).
For antimicrobial prophylaxis for SCS cases, a single dose of a
cephalosporin is recommended. The current preoperative dosing of
cefazolin, based on weight, is 1 g for individuals weighing less than
80 kg, 2 g for individuals 81 to 160 kg, and 3 g for individuals
>160 kg (140). For individuals with a beta-lactam allergy,
clindamycin (600 to 900 mg based on weight) or vancomycin (1 g)
may be used. Vancomycin should not be used routinely (CDC Recommendation Category IB). Indications for vancomycin use include
a beta-lactam allergy, MRSA colonization, institutionalized patients
(nursing home, long-term care facilities, etc.), or if a surgical procedure is being performed in a facility with a recent outbreak of MRSA
(142). No advantages have been documented for post-SCS implantation antibiotic use (143). In addition, in other surgical specialties,
prolonged antibiotic use in the postoperative period has not been
shown to improve outcomes and in some studies resulted in poor
outcomes (144,145).
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IA
IB
II
No recommendation/
unresolved issue
Strongly recommended for implementation and
supported by well-designed experimental,
clinical, or epidemiological studies.
Strongly recommended for implementation and
supported by some experimental, clinical, or
epidemiological studies and strong theoretical
rationale.
Suggested for implementation and supported
by suggestive clinical or epidemiological
studies or theoretical rationale.
Practices for which insufficient evidence or no
consensus regarding efficacy exists.
fibroblasts and keratinocytes (45). Some empirical recommendations might also include using pop-off sutures, so that skin is not
reentered for multiple stitches, and silver-impregnated sutures that
have some antiseptic properties (149).
Postoperative Practices
Surgical incisions should be protected with an occlusive sterile
dressing for 24 to 48 hours (CDC Recommendation Category IB)
(48,150,151). Although dressings are often left in place for longer
periods of time, extended dressing use has not been shown to limit
SSI rates (48). If dressing changes are required, handwashing (CDC
Recommendation Category IB) and sterile technique are recommended (CDC Recommendation Category II) (11).
Discussion
SSIs are associated with significant morbidity and costs; therefore,
appropriate steps should be taken to limit SSIs when performing
SCS implants. If an infection is suspected, then a diagnostic workup
should be initiated. Superficial infections often present with erythema, tenderness, and possible purulent drainage (42). Laboratory
tests, including white blood count, C-reactive protein, and erythrocyte sedimentation rate, may help define an SSI. In certain cases,
infections isolated to the superficial tissues can be treated effectively with antibiotics. During conservative treatment, it is important to monitor for any signs of infection spreading to deeper
structures. If the infection has spread to deeper structures, surgical
incision and drainage, often with the removal of the device, is the
recommended treatment (42). Cultures should be obtained to
define antibiotic treatment. In addition, a consultation should occur
with an infectious disease specialist. Radiographic imaging assists in
determining whether the infection has spread to the neuraxis. The
MRI is performed following device removal. Reimplantation with a
new device should not occur until the infection has been effectively
treated and the infectious disease specialist has provided medical
clearance.
Recommendations and Evidence for Prevention and Treatment
Studies examining infection-control policies specifically for SCS
systems are limited; therefore, extrapolation of best practices often
occurs from other surgical fields (140,152). The CDC has published
evidence-ranked recommendations for the prevention of SSIs
(Tables 8 and 9) (11).
Skin Erosion
Skin erosions are typically a consequence of superficial lead
placement and are more a consequence of PNS or PNfS, usually
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587
Intraoperative Practices
Appropriate preparation technique and agent selection for skin
antisepsis is an important measure for the prevention of an SSI
(CDC Recommendation Category IB). Povidone–iodine- and
chlorhexidine-based solutions are two agents commonly utilized
for skin preparation (146). These products are often combined with
isopropyl alcohol, which is an effective bactericidal agent that disorganizes cell membrane lipids and denatures cellular proteins. Isopropyl alcohol has been shown to increase the antimicrobial activity
of both products. In clinical studies chlorhexidine-based products
were superior to povidone–iodine-based products (147,148).
Darouiche et al. (147) examined the SSI rates of patients who underwent surgery in six hospitals and were assigned either to
chlorhexidine–alcohol or povidone–iodine skin preparation. The
overall rate of SSIs was significantly lower in the chlorhexidine–
alcohol group than the povidone–iodine group (9.5% vs. 16.1%),
respectively.
Other intraoperative steps that should be taken include maintaining positive pressure ventilation in the operating room (CDC Recommendation Category IB), keeping the operating room doors
closed (CDC Recommendation Category IB), and limiting traffic
(CDC Recommendation Category II) (11). Tissue should be handled
gently, and efforts should be made to minimize devitalized tissue
and eradicate dead space at the surgical site (CDC Recommendation
Category IB) (11). Wound irrigation assists in the removal of foreign
material, debris, and blood clots. The addition of antibiotics to the
irrigation solution has not been shown to positively influence infection rates (45,142). In addition, added antibiotics may be toxic to
Table 8. Evidence Rankings From the Centers for Disease Control and
Prevention (11).
DEER ET AL.
Table 9. Infection Control Measures Recommended by the Centers for
Disease Control and Prevention (11).
Recommendations
Evidence
rankings
Preoperative measures
Optimize glucose control
Discontinue tobacco use
If hair is removed, use electric clippers immediately
before surgery
Use prophylactic antibiotic therapy
Vancomycin should not be used routinely
Intraoperative measures
Use appropriate preparation technique and agent
selection for skin antisepsis
Maintain positive pressure ventilation in the operating
room (OR)
Keep the OR doors closed during procedure
Limit OR traffic
Handle tissue gently and eradicate dead space
Postoperative measures
Use occlusive sterile dressing for 24–48 hours
postoperatively
If a dressing change is required, use:
Handwashing
Sterile technique
IB
IB
IA
IA
IB
IB
IB
IB
II
IB
IB
IB
II
centering on the distal end of the lead (4). Skin erosion of leads or
hardware is an uncommon complication of SCS; overall, Cameron
reported a 0.2% incidence of skin erosion (3). This is in contrast to
PNfS, where Verrills reported an incidence of 7% for hardware
erosion in 100 cases (95). IPG battery erosion or dehiscence can be
reduced by appropriate placement away from mobile or osteal locations and by careful layered closure with avoidance of suture lines
over the implanted device.
Management of skin erosion complications differs for SCS and
PNS/PNfS systems, concerns being stratified by the development of
the surgical emergent epidural abscess, a serious infection of septic
joints, or the easily treatable superficial cellulitis. The NACC recommends the following regarding skin erosions as a result of device
implant: If a deep infection occurs that involves the device pocket,
the SCS device must be removed, regardless of whether there
are systemic infection symptoms or not, and salvage attempts are
discouraged. After removal of an infected device, whether symptoms of epidural infection exist or not, radiographic diagnostic tests
such as MRI or CT should be performed to rule epidural abscess in or
out. After wound cultures are taken, immediate treatment for infections must be employed. If reimplantation is planned, appropriate
measures to ensure adequate risk reduction and repeat dehiscence
are suggested.
Peripheral systems may be explanted and reimplanted as
described, or salvage of the existing system may be attempted.
Commonly, peripheral systems have been adopted because of CMM
failure, and in the case of headache, many patients elect to trial
salvaging methods (153). Introduction of equipment designed specifically for the periphery may aid in reducing complications (154).
588
Seroma
A seroma is a collection of serosanguinous fluid within a developing pocket or a surgically created pocket that is likely due to
frictional forces of two tissue planes and excessive surgical trauma,
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with an overall surgical risk of 2.5% (47). Seromas can form when
dead space is not adequately closed, and they are common after
breast surgery and reconstruction, as well as abdominoplasty. Furthermore, populations with poor wound healing, such as patients
with diabetes or small-vessel diseases and smokers, are certainly at
a higher risk for the development of seroma.
Seroma risk reduction includes preoperative patient preparation,
such as treating comorbidities like diabetes by optimizing glucose
control. Intraoperative risk management procedures should include
limiting aggressive blunt dissection, reducing excessive electrocautery, maintaining and achieving careful hemostasis, and performing
a layered closure to limit dead space. Gentle pressure, such as the
utilization of an abdominal binder overlying the surgical site, is
advocated to minimize seroma formation. See recommendations
for seroma in Table 2.
Treatment of seroma as a complication of implantable technologies is largely anecdotal. Treatment centers on fluid removal, either
episodic or with indwelling postoperative drains. The fear of pathogen introduction is critical and should govern the algorithmic risk–
benefit assessment for invasive treatment. Caustic agents may be
introduced to promote scarring, although graded evidence for this
practice is lacking. If a seroma persists over a length of time in spite
of all good intentions to treat, it may be advisable to reoperate and
reduce dead space that exists by paying attention to appropriate
closure techniques.
Neurologic Injury
Neurologic injury is by far the most serious complication of SCS
implantation. Such injury can result from direct trauma to nerves
and spinal cord caused primarily by complications of the procedure,
whether during the placement of a needle or of a percutaneous lead
or paddle leads. Meyer et al. reported a case of quadriplegia following inadvertent intramedullary percutaneous lead placement in a
patient under general anesthesia (52). In a MAUDE (FDA Manufacture and User Facility Device Experience) database review, Levy et al.
recently investigated neurologic injury following traditional paddle
lead placement (155). During a three-year period, 44,587 paddles
were implanted in as many patients. Neurologic complications
occurred in 260 patients, for a rate of 0.58%. Motor dysfunction
without epidural hematoma occurred at a rate of 0.13% for paddle
leads introduced by laminotomy (43).
Neuraxial Hematoma
Epidural hematoma formation following the placement of SCS
leads, whether percutaneous or surgical, is a rare occurrence. In a
series of 509 plate electrodes, Barolat (156) reported one case of
epidural hematoma resulting in paraplegia. In a 20-year review of
the literature, Cameron estimated the risk of epidural hematoma
development at 0.3% and paralysis at 0.03% (3). Levy and colleagues
reported on a sample of 44,587 cases, among whom 0.25% had
major neurologic deficit (155). Sixty-one of the 111 cases (0.14%)
had limited motor deficit, six had autonomic changes (0.013%), 46
had sensory deficits (0.10%), and 21 had CSF leakage due to dural
puncture. Sixteen epidural hematomas with limited motor deficit,
15 hematomas without motor deficit (0.034%), and 52 hematomas
with major motor deficits (0.12%) were reported in the same series
(155). Franzini et al. suggested increased postoperative vigilance in
high-risk patients for epidural hematoma following spinal surgery.
High-risk patients included those of male gender, with a male-tofemale risk ratio of 4:1, and patients in the fifth or sixth decade of life
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Figure 1. Epidural hematoma in a patient who took aspirin before or during
SCS trial and Excedrin the morning after his leads were removed. A T5 to L1–2
hematoma (a [white arrows] in the sagittal view, b in the axial view) was evacuated. but the patient suffered permanent weakness in one leg. Case courtesy of
Dr. Poree. Used with permission.
evaluating the other published guidance already noted and determining which guides best serve the implanting physician and
neurostimulation patient.
Safety for patients who are anticoagulated requires that the
patient safely tolerate anticoagulation cessation. The recommendation to abstain from reinitiating anticoagulants during the duration
of the trial is the fear of the inadvertent removal of the leads while
anticoagulated. This concern must be balanced against the risk of
thrombotic events and may influence the length of the trial. Deer
and Pope retrospectively reviewed continuation or initiation of anticoagulation for the permanent implant and found no neuraxial
bleeding complications, although, formally, the question of safety
still remains (166).
Warfarin inhibits vitamin K-dependent coagulation factors, and
cessation within the first one to three days often does not result in
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589
(25). Neurologic deficits presented more commonly with progressive motor and sensory deficit than with severe radicular pain and
back pain.
More recent case reports describe hematomas with implantation of either paddle or percutaneous leads in patients taking
anticoagulant/antiplatelet medications or not and as the potential
result of lead migration (27,29,155,157–159). For example,
Giberson and colleagues recently published two cases of patients
who developed spinal epidural hematomas following removal of
percutaneous SCS trial leads (159). Both of these patients took
aspirin either before or during their trial period. In the first case,
upon removal of the patient’s trial leads, the patient reported
taking Excedrin (acetaminophen, aspirin, and caffeine) that
morning, despite instructions to avoid any nonsteroidal antiinflammatory drugs (NSAIDs). The patient almost immediately
developed severe back pain and lower extremity weakness and
was transported to the nearest emergency department. An MRI
revealed an epidural hematoma from T5 to L1–2 that required a
multilevel laminectomy for evacuation (Fig. 1). The patient,
however, was reluctant to have this surgery, and it was not performed for two days after his admission. The patient suffered from
permanent weakness in one leg. The second patient ceased lowdose aspirin (81 mg) and all other NSAIDs one week before trial
(159). Shortly after the trial leads were removed, this patient developed lower thoracic burning pain as well as paraparesis and
spasms. The patient was directed to the nearest emergency
department, where an emergent MRI revealed a T8-to-L3 epidural
hematoma (Fig. 2a,b). A multilevel laminectomy and hematoma
evacuation was performed the same day with complete resolution
of the patient’s symptoms. The patient went on to have a permanent SCS implant that provided excellent pain relief (Fig. 2c,d).
Obvious concerns exist regarding bleeding into the spinal canal
when patients are anticoagulated and require neuraxial instrumentation for neurostimulation. The fact that there are no published
guidelines regarding anticoagulated patients and SCS has
prompted many implanters to adopt and accept guidelines for the
anticoagulated patient undergoing regional anesthesia. However,
the applicability of these guidelines to anticoagulated patients
undergoing neuraxial implants is being questioned. The American
Society of Regional Anesthesia (ASRA) guidelines (50) for neuraxial
analgesia are commonly followed to reduce the risk of neuraxial
hematoma formation following SCS lead placement. The ASRA
guidelines stratify perioperative thromboembolism with bleeding
in anticoagulated patients as a risk, and despite this, spinal hematomas following neuraxial interventions continue to occur
(25,26,160–164). Recently, Manchikanti et al. published a bestevidence synthesis of anticoagulation management in the setting of
neuraxial chronic pain procedures and largely concurred with the
ASRA guidelines (165).
Bleeding risk is highest during placement and removal of the
device, and it is crucial in the patient who is anticoagulated to
consult with the prescribing provider to determine the patient’s
suitability for anticoagulation cessation and the need for bridging
before the temporary or permanent system placement. Because
most trials are performed on an outpatient basis and because a
controlled inpatient environment to ensure patient compliance and
postoperative surveillance is absent, patients undergoing outpatient procedures may be at greater risk of sequelae to a developing
epidural hematoma than those admitted to a hospital for observation after their implant or trial. Table 10 lists suggested
perioperative anticoagulation management practices for dorsal
column SCS. These recommendations have occurred based on
DEER ET AL.
Figure 2. This patient ceased low-dose aspirin and all other NSAIDs one week
before the trial began. The patient suffered an epidural hematoma, shown
sagittally (a) and axially (b), compressing the spinal cord and extending from T8
to L3. The patient later had permanent implantation of a 2 × 4 paddle lead at T9
(c, black arrow) and two quadripolar subcutaneous leads at L4 (d, white arrows).
Case courtesy of Dr. Poree. Used with permission.
590
normal coagulation. It is the recommendation of the NACC that
warfarin be stopped five to seven days before the intended surgery.
Preoperative international normalized ratio (INR) testing should be
performed, and if the INR is >1.5, the procedure should not be
performed.
Because enoxaparin (Lovenox), a low-molecular-weight heparin,
has a short half-life, it is commonly used as a bridging agent in the
outpatient setting when patients cannot tolerate anticoagulation
cessation for long periods. The use of enoxaparin invariably requires
a therapeutic, not prophylactic, dose. In this setting, stopping warfarin and initiating enoxaparin therapy to “bridge” anticoagulation
until the warfarin is gone and then stopping the enoxaparin for 24
hours before surgery is commonly performed. For the SCS trials,
comparatively, a patient would be off anticoagulants for five days as
opposed to 11 days following a three-day trial.
The antiplatelet thienopyridine derivatives clopidogrel and
ticlopidine inhibit adenosine diphosphate (ADP)-induced platelet
aggregation. As these medications differ in their pharmacokinetics
and require vastly different cessation times prior to platelet and
coagulation normalization, they are listed separately.
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The glycoprotein (Gp) IIb/IIIa receptor antagonists inhibit
platelet–fibrinogen and platelet–VWbF aggregation. Normal platelet activation typically occurs within eight hours (eptifibatide,
tirofiban) to 48 hours (abciximab) following reintroduction. The
NACC’s increased suggested cessation time of three days before
surgery reflects the accommodation for a more invasive procedure
than those presented in the ASRA guidelines.
Direct thrombin inhibitors are becoming more popular for the
treatment of atrial fibrillation. These anticoagulants (dabigatran
etexilate and rivaroxaban) inhibit thrombin and factor Xa. The halflife varies for each but can be up to 17 hours for dabigatran following multiple doses and 12 hours for rivaroxaban. The half-life of each
drug depends on renal function. Since few data currently exist
regarding bleeding risk with dorsal column stimulation, the NACC
recommends a cautious approach to cessation of these agents.
Although historical recommendations suggest there is not a
higher rate of bleeding following perioperative neuraxial interventions with patients continuing aspirin or NSAIDs, there is now a
growing consensus within the neuromodulation community to stop
aspirin and NSAIDs seven days prior to SCS trial and implant. The
NACC believes that further investigation is needed to identify
the appropriate length of the NSAID-free period prior to implant. The
experts of the NACC have suggested that the use of low-dose aspirin
may be reasonable as it has been stated that the risk of bleeding is
less than that with a 325-mg dose. This has not been proven, so no
consensus can be published at this time. It is the recommendation of
the NACC that the implanting doctor should encourage the patient
to discuss the risk-to-benefit ratio of stopping aspirin with the physician who recommended the therapy (cardiologist, neurologist,
primary care).
Commonly, anticoagulant combination therapy is employed and
requires further consideration and discretion prior to neuraxial
surgery. The implanters’ concerns regarding cessation of combination therapy or monotherapy should be communicated to the
patient after consultation with the cardiologist or primary care physician, with thoughtful consideration given to the potential risks
from stopping such medications. Clearly, cardiac thrombotic risk
assessment is important to gauge candidacy for the therapy;
however, as data emerge regarding the use of SCS for angina and
the potential improvement in functional measures, this topic will
need to be revisited.
There is a paucity of data regarding the performance of peripheral neuromodulation therapies such as PNS, SNS, and PNfS when
patients are anticoagulated or when it is appropriate to stop anticoagulation medications prior to performing these procedures. To
date, neurologic complications for these peripheral procedures in
anticoagulated patients have not been reported. Since peripheral
compartments for SNS and PNS are not rigidly contained, and there
are no compartments surrounding peripheral nerve fields as when
PNfS is performed, hematoma formation is less catastrophic than
when neuromodulation procedures are performed within the spinal
space. As previously stated, information can be borrowed from the
regional anesthetic literature. The ASRA guidelines suggest adherence to the neuraxial guidelines written for deep regional peripheral interventions (50).
Dural Puncture
Accidental dural puncture can and occasionally does occur when
performing epidural needle placement for lead positioning, which
can result in postdural puncture headache (PDPH) symptoms as
well as CSF leakage into the wound. The incidence of dural puncture
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Table 10. Anticoagulation Management Practices for Spinal Cord Stimulation as Recommended by the Neuromodulation Appropriateness Consensus
Committee.
Anticoagulant
Recommendation for trial
Recommendation for permanent implant
Warfarin
Discontinue 5–7 days before, INR < 1.5; if bridging
required, refer to bridging medication; continue
cessation during duration of trial, resume 24 hours
following trial lead removal.
Hold therapeutic dose of LMWH 24 hours before
procedure; hold for duration of trial; resume 24 hours
following lead removal.
High-risk patients for cardiac events—discontinue at
least 5 days before; low risk 7–10 days before; hold for
duration of trial; resume 24 hours following lead
removal.
Discontinue 7–10 days prior to procedure, hold for
duration of trial, resume 24 hours following lead
removal.
Discontinue 14 days prior to procedure, hold for
duration of trial, resume 24 hours following lead
removal.
Discontinue for 3 days prior to procedure, hold for
duration of trial, restart 24 hours following lead
removal.‡
Discontinue 7 days prior to procedure, hold for duration
of trial, restart 24 hours following lead removal.§
Discontinue 5–7 days before, INR < 1.5; if bridging
required, refer to bridging medication; resume 24
hours postoperatively.
Enoxaparin (LMWH)
Clopidogrel (ADP receptor
antagonists)
Effient (ADP receptor antagonist)
Ticlopidine (ADP receptor
antagonists)
Abciximab, eptifibatide, tirofiban
(platelet GPIIb/IIIa receptor)
Dipyridamole, aggrenox
(aspirin/dipyridamole)
(phosphodiesterase inhibitors)
Naproxen, ketorolac, ibuprofen,
etodolac, etc. (nonsteroidal
anti-inflammatory drugs)§
Aspirin§
Herbals (ginseng, ginkgo, garlic)
Pradaxa (dabigatran etexilate),
Xarelto (rivaroxaban) (direct
thrombin inhibitors)
Heparin IV*
Heparin SQ†
Discontinue 7 days prior to procedure, hold for duration
of trial, reinitiate 24 hours following lead removal.
Hold therapeutic dose of LMWH 24 hours before
procedure; resume 24 hours following surgery.
High-risk patients for cardiac events-discontinue at least
5 days before; low risk 7–10 days before; resume 24
hours following surgery.
Discontinue 7–10 days prior to procedure, hold for
duration of trial, resume 24 hours following lead
removal.
Discontinue 14 days prior to procedure; resume 24
hours following surgery.
Discontinue for 3 days prior to procedure, hold for
duration of trial, restart 24 hours following the
surgery.‡
Discontinue for 7 days prior to procedure, hold for
duration of trial, restart 24 hours following the
surgery.§
Discontinue 7 days prior to procedure, hold for duration
of trial, reinitiate 24 hours following the surgery.
Discontinue 7 days prior to procedure, hold for duration
of trial, reinitiate 24 hours following lead removal.
Discontinue 7 days prior to the procedure, hold for
duration of trial, reinitiate 24 hours following lead
removal.
Discontinue 5 days prior to procedure, hold for duration
of trial, reinitiate 24 hours following lead removal.
Discontinue 7 days prior to procedure, hold for duration
of trial, reinitiate 24 hours following surgery.
Discontinue 7 days prior to the procedure, reinitiate 24
hours following surgery.
Discontinue 5 days prior to procedure, hold for duration
of trial, reinitiate 24 hours following surgery.
NA
NA
NA
NA
*Requires inpatient hospitalization and monitoring, suggesting a special need or indication for neurostimulation, and should be assessed on case-by-case basis.
†
Peaks at 2–4 hours after administration; typically thrombotic prophylaxis as inpatient and may require platelet assessment if more than 4-day dosing. Please
refer to American Society of Regional Anesthesia guidelines and determine on a case-by-case basis.
‡
Typically contraindicated 4 weeks following surgery. If reinitiated, careful follow-up and vigilance is suggested (50).
§
Current recommendations (50) suggest variable stoppage is necessary based on clinical context and on the specific half-life of the nonsteroidal antiinflammatory drug in question. The half-life determines the time required for discontinuation in order to limit the drug’s effect on platelet function.
INR, international normalized ratio; ADP, adenosine diphosphate; LMWH, low-molecular-weight heparin; NA, not applicable.
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focus of the patient’s complaints. The PDPH may not leave sufficient
time to assess candidacy for the permanent system and efficacy of
the trial (167). Care must be taken when performing the blood patch
to match the volume of autologous blood injected to the level of
puncture, with smaller volumes required for more cephalad punctures in the thoracic and cervical spine (168).
Immunologic Reactions
Contact dermatitis, allergy, and foreign-body reactions to
implanted SCS devices have been described in case reports
(46,53,169). Ochani et al. (46) described a case of suspected allergic
reaction six weeks following cervical and lumbar SCS placement for
CRPS for atypical face pain after facial trauma. The patient presented
with dysesthesia, erythema, and burning overlying the device. An
infection workup was negative. Patch dermatologic allergy testing
revealed sensitization to platinum, silicone, and polyurethane.
Stimulator removal resolved the complaints.
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Neuromodulation 2014; 17: 571–598
591
has been estimated at 0% to 0.3%. The incidence of CSF leak
following traditional paddle lead placement was reported to be
0.05% (3,155). Risk factors for dural puncture include previous
surgery at needle entry into the epidural space, a calcified ligamentum flavum, spinal stenosis at the site of needle entry into the epidural space, and an uncooperative patient.
Patients who develop PDPH after placement or attempted placement of an SCS lead may suffer from a positional headache, diplopia, tinnitus, neck pain, photophobia, and fluid accumulation at the
lead-anchoring site. Although dural puncture headache commonly
resolves within a week in the majority of patients, some may require
more interventional strategies for resolution of the headache.
Autologous epidural blood patch has been utilized both prophylactically and therapeutically in cases where dural puncture occurs.
If the SCS trial is complicated by dural puncture and resultant
PDPH, results of the trial for efficacy of stimulation may be complicated by the headache, as that occurrence may now become the
DEER ET AL.
McKenna et al. reported on a patient with a skin reaction overlying the IPG site one month following the stimulator placement
(169). Although the patient was found to be allergic to nickel, the
authors of this case report described the reaction as an isomorphic
response to the expansion of underlying tissues, rather than nickel
allergy. Lennarson et al. (53) reported on a case of a giant cell mass
as a result of a foreign-body reaction to the lead following explant
that was compressing the spinal canal, necessitating multilevel cervical laminectomy, excision of the giant cell reaction mass, and
fusion. Gadgil and colleagues (170) reported on two cases of
contact dermatitis with implanted SCS IPG units. Successful treatment involved revising the IPG and sealing it in a pouch of
polytetrafluoroethylene.
Urologic Complications
Renal failure, micturition inhibition, and other urologic complications have been reported as complications to SCS (171–173).
Loubser et al. (173) described the case of a patient with partial
T12–L1 spinal cord injury who had an SCS implanted to treat his
neuropathic/central pain. As a result of high therapeutic amplitudes
required to produce desired paresthesias, the patient developed
urethral sphincter spasm, preventing self-catheterization. The
author suggested routine urologic functional testing be incorporated during the trial period.
Larkin et al. reported a case of acute renal failure secondary to a
trial for SCS and related the mechanism of the renal failure to the
secondary sympatholysis effects of SCS, although this conclusion
has been highly debated (172). More recently, a case of micturition
inhibition complicating SCS was reported by Grua et al. (171). Their
patient had cauda equina syndrome from an angioma at T12, and
the percutaneous SCS lead was placed with the tip positioned left of
center at T12. The patient reported complete resolution of his pain,
but urge incontinence occurred and reoccurred with initiation of
stimulation after a 30-day interval. The authors postulated that the
autonomic effects of stimulation may have unbalanced the signals,
altering urinary function.
Gastrointestinal Complications
Sporadic cases of gastrointestinal complications associated with
SCS have been reported (174,175). Kemler et al. (174) described a
case of relapsing colitis caused by SCS. The patient had an SCS
system with the lead placed at C4 and the IPG placed in the left
lower abdominal quadrant for upper-extremity CRPS. The patient’s
ulcerative colitis relapsed and remitted twice as the device was
employed and discontinued, respectively. The authors postulated
that the mechanisms of action of this effect of SCS may have been
an electromagnetic effect on the colon, aberrancy of the GABAergic
system, or an electrical effect on intestinal circulation.
Thakkar et al. (175) described two cases of patients who experienced gastrointestinal challenges exacerbated by SCS, including
nausea, diarrhea, worsened gastrointestinal reflux, and flatulence.
The authors suggested that the sympatholytic effect of SCS leading
to unopposed parasympathetic tone was the cause for this patient’s
gastrointestinal symptoms.
Stimulation Tolerance
592
Background
Neurostimulation therapy has expanded in indications, modalities, and number of implants worldwide; the last now number over
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25,000 per year (176,177). Although SCS systems are safe, the existing literature reveals a high complication rate ranging from 34% to
42% (167), despite system improvements and technological
advances. As stated previously, complications have been divided
into biological and hardware-related, with hardware complications
occurring in between 24.4% and 50% of cases vs. 7.5% of cases for
biological complications (6,55). Other complications cannot be
included in the cited categories, because real incidence and underlying physiopathology are not well known. One of them is the
so-called stimulation tolerance, which, although apparently related
to hardware, cannot be clearly classified. The term stimulation tolerance was coined by Kumar’s group after a retrospective study in 160
patients with nine years between the first and the last implant (55).
Stimulation tolerance to SCS is defined in patients where pulse
amplitude must be increased to achieve the same analgesic level
over time, sometimes even losing the efficacy of the technique
(167). This complication affects the long-term efficacy of the system,
provided that it keeps functioning properly and the lead position is
correct. The onset of this complication cannot be predicted; it
appears in the course of patients’ follow-up, affecting 29% of
patients (55).
Possible causes for stimulation tolerance include neuroplasticity
of pain transmission pathways in either the dorsal root ganglion, the
spinal cord, the thalamus, or the brain cortex. Some authors consider that these losses or changes in stimulation efficacy, and therefore the appearance of systemic tolerance, may be attributed to
cellular or fibrotic changes in the tissues around the stimulating
electrodes (3). None of these explanations could be demonstrated
in postmortem analysis or surgical examinations. A plausible and
possible cause for stimulation tolerance is psychological or psychiatric affective factors (32,178,179).
Evidence
No scientific evidence exists regarding efficacious treatment for
patients developing stimulation tolerance to SCS. Expert opinion
suggests that the most reasonable course is to institute a
neuromodulation holiday and stop stimulation for several weeks.
Only Kumar and colleagues have addressed management of this
complication.
Discussion
Management of stimulation tolerance could be approached by
altering stimulation program parameters, provided that the system
is working properly and achieving an appropriate level of paresthesia coverage. From the very beginnings of the therapy, experts have
advocated adjusting frequency (180). The electric parameters suitable for manipulation are 1) pulse amplitude, which is determined
by the patient’s stimulation thresholds; 2) pulse width, which has
been traditionally used to perform fine adjustments in the stimulation levels, but has recently gained relevance at high values, which
seem to recapture different spinal fibers at different depths; and 3)
pulse frequency (181).
Frequency is the only parameter that affects stimulation quality,
eliciting a pounding feeling at low settings and a tingling sensation
at higher settings (180). On the other hand, frequency is the only
parameter that is kept fixed in some pathologies, such as urinary/
fecal incontinence or deep brain stimulation (DBS).
Because of evidence that frequency matters clinically, stimulation
frequency for the control of pain has garnered more attention
recently. New high-frequency (HF) systems, such as the Senza HF-10
device (Nevro Corp., Menlo Park, CA, USA), approved for clinical use
in Europe and Australia and in clinical trials in the USA, and the
Neuros stimulation device (Neuros, Cleveland, OH, USA) for
postamputation pain, produce similar or even better relief than
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RISK REDUCTION IN NEUROSTIMULATION
traditional devices at kilohertz frequencies, without producing the
paresthesia sensations produced by conventional neurostimulators.
Some authors have experimented with systems that combine standard frequencies with high-rate bursts (182–184) and have demonstrated acceptable clinical results. Nevertheless, although the safety
of HF systems has been confirmed in a follow-up period of more
than one year (181), no conclusions can be drawn regarding systemic tolerance, as this complication was not analyzed in the
studies. As far as burst stimulation is concerned, De Ridder et al.
demonstrated that when compared with tonic stimulation or
placebo, burst stimulation of the spinal cord was more selective in
the activation of the dorsal anterior cingulate and right dorsolateral
prefrontal cortex of the brain (184), which may be beneficial if one of
the causes for the development of stimulation tolerance is thalamic
and cortical neuroplasticity. As in the case of HF (kilohertz) stimulation, burst stimulation also features absence of paresthesia, which
may be useful for avoiding the onset of tolerance (183).
Most transcutaneous electrical neurostimulators (TENSes) are
capable of providing “modulated” stimulation, that is, cyclic and
progressive variation of one or more parameters over time, which
seems to be useful for preventing tolerance (185). The most
common types of TENS modulation include high/low frequency,
combined frequency/pulse width, and combined pulse amplitude/
pulse width cycles. This stimulation modality was incorporated in
TENS more than a decade ago but is not yet available in implantable
systems.
Recommendations
There are no clear recommendations for the prevention or management of stimulation tolerance in the existing literature. Only a
few attempts have been made to improve these patients’ condition.
In their review, Kumar et al. propose two types of treatment for
stimulation tolerance: 1) provide the patient a “stimulation holiday”
by turning the system off during a six-week period or 2) use pharmacological treatment with amitryptyline or L-tryptophan (55).
Neither maneuver was effective—only two of 16 patients recovered
the system’s efficacy after the six-week stimulation holiday.
As we have seen, modulation of frequencies as performed with
TENS may solve the complication of stimulation tolerance. Woods
considered the possibility of using high stimulation frequencies to
overcome systemic tolerance, although no significant improvement
could be documented (167). In patients who lose efficacy from conventional SCS at approximately 50 Hz, a switch to 10 kHz frequency
produces improvement in pain control (181). In the opinion of the
NACC, a future method to prevent the development of
neuromodulation stimulation tolerance will most likely be related to
manipulation of frequencies. Future implantable systems will probably offer the possibility of choosing between paresthesia and
paresthesia-free stimulation and modulation capabilities to prevent
or alleviate this therapy-limiting complication.
FACTORS AFFECTING COMPLICATION RATES
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Hardware Appropriateness for the Procedure
Hardware for peripheral and SCS techniques has evolved significantly over the past four decades. While we continue to await the
introduction of custom-made hardware for particular techniques,
such as ONS and PNfS, such devices already exist for SCS and SNS.
For SCS, the hardware has evolved from monopolar leads through
quadripolar leads to the current state-of-the-art, 16-contact leads.
Early reports of complications, particularly the need for lead
replacement, show a statistically lower rate in patients with
quadripolar leads (11%) than in those with monopolar electrodes
(45%) (p < 0.003) (65,66). As there was no difference in the frequency
of electrode migration between the two types of electrodes, proper
paresthesia coverage was most often recaptured by reprogramming with the multipolar leads (65). North et al. (61) reported SCS
treatment in 62 patients with chronic pain. They found that surgical
revision was necessary in 23% of the cases in which simple bipolar
leads were placed to obtain optimal paresthesia coverage. Surgical
revision, however, was required in only 16% of those cases with
multichannel devices. Finally, the introduction of rechargeable
pulse generators may well reduce the need for battery replacements in a population of neurostimulation patients, particularly for
indications that require high current consumption, such as peripheral arterial disease (190). However, this fact remains to be established over the long term.
IMPROVING OUTCOMES
The high incidence of complications with neurostimulation,
albeit mostly benign, detracts from the value of the therapy, as it
leads to poorer outcomes and increased health-care expenditures.
Minimizing complications would be expected to result in improved
outcomes and more therapeutic successes. Understanding the root
causes of complications constitutes the foundation for preventing
and minimizing untoward events.
Improvements in several variables for neuromodulation procedures would lead to lower complication rates:
1. Patient selection. Perhaps the most critical factor for minimizing
complications is proper patient selection, which entails careful
selection of neurostimulation candidates based on clinical
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593
Lead Location
Different rates of lead migration have been observed when the
use of SCS was examined for differing indications. For example,
locating the lead in the relatively immobile thoracic spine for indications such as refractory angina was associated with low lead
migration rates. In a review, Taylor et al. (186) reported a combined
rate of lead migration or fracture of 7.8% (10 of 128 patients), which
is much lower than the rates the same author observed for CRPS
(20%) and FBSS (27%). We may conclude that the position of the
lead in a nonmobile area of the spine has a limiting effect on the rate
of migration.
Technique Familiarity and Surgeon Experience
Other implant disciplines have demonstrated a clear link
between the level of experience of the operating surgeon and the
rate of complications related to the implant procedure (187,188).
This is clearly the case for neuromodulation procedures as well. Early
work by Schwedt et al. (117) on ONS was associated with a much
higher rate of complications relative to later reports by Paemeleire
et al. and Saper et al. (111,112).
A recent cohort study by Turner et al. (189) utilized inexperienced
implanters and consequently reported higher complication rates, as
well as the occurrence of rare life-threatening complications. Furthermore, early SCS work by Andersen et al. (65) for refractory
angina treatment reported a high incidence of lead migration (23%)
compared with a more recently reported incidence of 7.8% (186).
We can, therefore, conclude that novel techniques in spinal and
peripheral nerve stimulation are usually associated with a higher
rate of complications, particularly lead-related complications, and
that as surgeons gain experience in a particular implant technique,
the complication rate decreases over time.
DEER ET AL.
2.
3.
4.
5.
6.
7.
criteria and thorough psychological screening and judicious
medical optimization of patient comorbidities (38,191–193).
Physician training and credentialing. Currently no mandated
standards of training exist for many procedures in
neuromodulation. There are also gaps in credentialing, with lack
of official credentialing and standardizing bodies (194,195).
Restricting neurostimulation implants to more experienced physicians may limit complications and improve patient outcomes
(152).
Improving equipment. Over the past 40 years, progressive
improvements have occurred in neurostimulation equipment.
Recent advances in anchoring devices and techniques, as well as
improvements in lead technology, have reduced lead fracture
and lead migration rates (30,196).
Better dissemination and application of lessons learned from
studies and registries.
Continuously innovating with new products geared to current
indications as well as emerging applications, such as peripheral
nerve stimulation and field stimulation.
Developing guidelines based on best available evidence and
expert consensus.
Periodically reassessing such practice guidelines and their
effects.
CONCLUSIONS
594
Spinal cord and peripheral nerve stimulation therapies are safe
and reversible therapies. These effective therapeutic techniques
result in a range of minor complications. Hardware-related complications are more common than biological complications, with leadrelated complications most frequent. Biological complications
include the most common complications such as infection and pain
over the implant. Serious adverse events such as neurological
damage are uncommon. The rate of complications is governed by
factors such as the lead position in the spine or periphery, the experience of the surgeon, and the availability of custom-made equipment for the technique. It is clear that novel techniques are
associated with a higher incidence of hardware-related complications than established techniques.
Neurostimulation is a rapidly evolving field where technological
advances may play a critical role in patient outcomes. A limited
number of patients with similar clinical conditions exist for particular neurostimulation applications, and among these patients, significant clinical and technical variabilities also may exist, making
robust studies of neuromodulation therapies difficult. Therefore,
regarding neuromodulation therapies, clinical evidence may often
lag behind clinical experience. Practice guidelines, therefore, are
necessary to help guide physicians regarding their clinical decisionmaking, their assimilation of expanding knowledge, and their
understanding of novel clinical applications.
Evidence-based guidelines follow strict sequential processes in
common clinical entities (197). However, in many clinical settings,
development of such guidelines is significantly limited by evidence; thus, consensus guidelines become necessary to guide
clinical practice (198). Modern EBM incorporates a merger of published evidence and expert clinical opinion in such situations. A
consensus of thought leaders may provide not only a framework
for clinical practice but may also ensure patient access to needed
care. A frequent assessment and reassessment of the adaptation
and implementation of such guidelines will continue to be necessary. There should also be a periodic evaluation of potential effects
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of these guidelines on patient outcomes and risk mitigation to
assess their ultimate utility.
Note
The Boston Scientific Precision Spectra SCS System has received
Food and Drug Administration approval for MRI-conditional head
scans. The ImageReadyTM Guidelines and Patient Eligibility Checklist are available from the company. St. Jude Medical is planning MRI
compatibility submissions in the European Union in 2014.
Authorship Statements
Dr. Deer served as primary author, project organizer, and editor;
Drs. Pope, Krames, Mekhail, Buchser, North, Provenzano, and Leong
served as primary authors and editors. The remaining authors
contributed sections of the manuscript or provided critical
reviews. Opinions expressed herein are not necessarily shared by
all authors.
How to Cite this Article:
Deer T.R., Mekhail N., Provenzano D., Pope J., Krames E.,
Thomson S., Raso L., Burton A., DeAndres J., Buchser E.,
Buvanendran A., Liem L., Kumar K., Rizvi S., Feler C.,
Abejon D., Anderson J., Eldabe S., Kim P., Leong M.,
Hayek S., McDowell G. II, Poree L., Brooks E.S., McJunkin
T., Lynch P., Kapural L., Foreman R.D., Caraway D., Alo K.,
Narouze S., Levy R.M., North R. 2014. The Appropriate
Use of Neurostimulation: Avoidance and Treatment of
Complications of Neurostimulation Therapies for the
Treatment of Chronic Pain.
Neuromodulation 2014; 17: 571–598
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COMMENTS
This is an extraordinary consensus document that will guide best
practice for many years to come.
Paul Verrills, MBBS
Melbourne, Australia
***
The NACC under the leadership of Dr Tim Deer has brought together
both critical literature review and many multiples of lifetime clinical
practice to bear on the issue of avoiding and treating complications in
© 2014 International Neuromodulation Society
Neuromodulation 2014; 17: 571–598
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DEER ET AL.
neurostimulation. I have always felt that the low hanging fruit in medicine is to attempt to bring up the rear rather than push the frontier
forward an inch. By that I mean that improving both median performance and lowest quartile performance in outcomes yields the
biggest improvement for the smallest financial outlay compared to
trying to invent the next biggest breakthrough. I recommend Atul
Gawande’s books Complications, Better and Checklist to truly understand this. This paper aims to do just that not only for the experienced
implanter but also as a “Neurostimulation Primer” for the non-expert
physician. It serves as a template that can be added to or modified as
additional literature or clinical experience evolves.
In the absence of suitable literature to conduct a meta-analysis of
RCTs then this stands as the most appropriate way to reduce both
complications and costs across practices, states and countries. It is not
to say that individual recommendations cannot be adjusted or countermanded but it reasonable to ask that individuals do so by presenting
their own evidence to substantiate that practice. I would encourage
readers to consider doing so via publication of their techniques and
results so that we may add to the canon of published clinical experience and thus all benefit from the broadest data set possible. The
authors are to be commended for this impressive initial report from the
NACC and the International Neuromodulation Society for initiating
discussion in this area.
Marc Russo, MBBS
Newcastle, New South Wales, Australia
***
This NACC paper is an outstanding summary of the current knowledge
surrounding neuromodulation risks and risk mitigation approaches.
The last NACC recommendation should have suggested requisite
familiarity with the suggestions within this very document.
***
We have to laud the authors for their thoughtful recommendations
that are important in many aspects that reflect the actual practice in
neuromodulation. The last ten years neuromodulation therapy has
evolved from an exceptional therapy to a more common and accessible one. Bringing this therapy to a larger volume necessary to serve
the patient population who might benefit from it brings also new
challenges. Quality assurance in health care delivery is certainly one
of them. We must recognize and identify the specific required
neurostimulation training for physicians and their assistants but also
monitor their outcomes and complications. This is an engagement to
be taken by the physicians as well as administrators of the health care
provider. Reviewing and adopting the recommendation will hopefully
strengthen the value of the therapy and will bring a better cost-utility
of what it is already known as effective.
In the context of the rapidly changing advanced technologies it is
not always possible to elaborate definitive (often long and expensive)
randomized-controlled studies (which can be futile as the technology
used can be obsolete by the end of the study). Expert consensus is
therefore greatly needed to identify best practices. Complementary to
their opinions would be to have clinical registries that could relate
strengths and weakness of usual practice and can be analyzed and
adapted to the rhythm of the evolving technologies. Neuromodulation
is certainly here to stay if we can provide an adapted retroaction to
monitor the benefit for the patient and the health care system.
Michel Prudhomme MD, PhD
Quebec, Canada
Comments not included in the Early View version of this paper.
William Porter McRoberts, MD
Fort Lauderdale, FL, USA
598
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© 2014 International Neuromodulation Society
Neuromodulation 2014; 17: 571–598