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Postoperative infection in cochlear implant patients CALHOUN D. CUNNINGHAM III, MD, WILLIAM H. SLATTERY III, OBJECTIVE: Recently, the association of meningitis with cochlear implants has raised concern over the safety of these devices. We examined the incidence of all postoperative infections in patients undergoing cochlear implant surgery. STUDY DESIGN AND SETTINGS: A retrospective chart review of all patients undergoing cochlear implants at a private tertiary referral center from 1993 to 2002 was performed. Cochlear implant surgeries in 462 adults and 271 children were reviewed. Patients with evidence of a postoperative infection or infectious complication related to cochlear implantation were identified, and data on patient characteristics, surgery, and treatment outcome were obtained. RESULTS: The overall incidence of postoperative infection in our cochlear implant series was 4.1%. Major infectious complications occurred in 3.0% of cases, and the majority of infections required surgical intervention. A history of chronic ear disease may increase the risk of infectious complications. There were no cases of meningitis. CONCLUSIONS: Cochlear implants remain a safe procedure with a low complication rate. The majority of infections can be managed without removing the implant device. Advances in surgical technique and flap design have decreased the occurrence of wound-related complications. However, identification of risk factors for infection and optimization of treatment regimens will further reduce the complications associated with postoperative infection. (Otolaryngol Head Neck Surg 2004;131:109-14.) I nfectious complications following cochlear implantation are relatively rare and have been reported to occur with an incidence ranging from 1.7% to 3.3%.1-3 These complications frequently involve surgical wound problems such as skin flap necrosis and wound dehiscence, which may result in persistent infection and potential device extrusion. Advances in surgical techniques and From the House Ear Clinic and House Ear Institute. Presented at the Annual Meeting of the American Academy of OtolaryngologyHead and Neck Surgery, Orlando, FL, September 21-24th, 2003. Reprint requests: William H. Slattery III, MD, House Ear Institute, 2100 W. 3rd Street, Los Angeles, CA 90057; e-mail, [email protected]. 0194-5998/$30.00 Copyright © 2004 by the American Academy of Otolaryngology–Head and Neck Surgery Foundation, Inc. doi:10.1016/j.otohns.2004.02.011 MD, and WILLIAM M. LUXFORD, MD, Los Angeles, California flap design have fortunately decreased the occurrence of such complications. Other infectious complications are the direct result of wound infection with abscess formation, potentially resulting from ongoing chronic ear disease or acute otitis media.4,5 Despite aggressive medical and/or revision surgical therapy, eradication of infection may ultimately require removal of the implant. Such an outcome will not only be devastating to the patient who has achieved good speech reception, but may also place the patient at increased risk for possible intracranial complications. Recent reports of meningitis associated with cochlear implants have raised concern over the safety of these devices.6-8 Specifically, devices using an electrode positioner appear to be associated with an increased risk of postoperative meningitis, and have, therefore, been withdrawn from the market by the manufacturer. Removal of the device with the electrode positioner is alone expected to reduce the incidence of postoperative meningitis. However, cases of meningitis have been reported with the use of all current FDAapproved implants. When meningitis occurs in the setting of a cochlear implant, the source can be assumed to be otogenic. Postoperative infections, including acute otitis media, chronic otitis media, and wound infections theoretically carry a risk of meningitis, given the potential for intracranial spread along the electrode through the inner ear. Current recommendations include active immunization against Streptococcus pneumoniae and Haemophilus influenzae type B in all prospective implant candidates as well as patients with an implant already in place. In addition, consideration should be given to prophylactic antibiotic treatment perioperatively. Identification of risk factors for infectious complications is important to prevent the significant consequences of possible device extrusion or meningitis. We reviewed all cochlear implants performed over a 10year period at the House Ear Clinic to assess the incidence of postoperative infectious complications and identify factors that might increase the risk of infection. METHODS A 10-year retrospective chart review of all patients undergoing cochlear implant surgery (N ⫽ 733) at the House Ear Clinic between January 1993 and October 2002 was performed. In October 2002, we instituted the routine use of perioperative antibiotics in all cochlear implant patients because of the risk of meningitis. Prior 109 Otolaryngology– Head and Neck Surgery July 2004 110 CUNNINGHAM et al Table 1. Characteristics of patients with postoperative infections (n ⫽ 29) n Adult Peds Total No. of patients Gender Male Female Age [mean (range)] Follow-up [mean (range)] 14 15 29 9 5 57 y (29–76 y) 43 mo (9–105 mo) 8 7 3.5 y (15 mo–10 y) 42 mo (15–83 mo) 17 12 30 y (15 mo–76 y) 43 mo (9–105 mo) to this time, it had been our custom not to use perioperative antibiotics. There were 271 pediatric implant patients (age ⬍18 yrs) and 462 adult patients. A total of 734 implant procedures were performed on 733 patients. One patient underwent two separate implant surgeries in the same ear. Devices from all 3 major cochlear implant manufacturers (Advanced Bionics, Sylmar, CA; Cochlear Corporation, Sydney, Australia; and Med-El Corporation, Innsbruck, Austria) were reviewed. There were 389 males and 345 females (mean age at implantation, 35 years; age range, 12 months to 90 years). The mean follow-up time was 24 months (range, 9-116 months). Clinic charts were reviewed to identify patients with evidence of a postoperative infection or infectious complication involving the implant ear. Selected data from these patients was obtained from clinic charts and hospital records and entered onto a data collection sheet designed for this study. Variables including patient demographics, device type, surgical time, perioperative antibiotics, flap technique, round window seal, cochlear malformations, surgical complications, time course to infection, infecting organism, history of previous ear disease, and other medical comorbidities were analyzed. Infection type, treatment course, and final outcome were also reviewed. Postoperative infections were classified as early if they occurred less than 30 days from the time of surgery, or delayed if occurring after 30 days. Infections were categorized as being a wound infection, complicated otitis media, or meningitis. Cases of complicated otitis media were infections resulting in adverse sequelae such as tympanic membrane perforation or subperiosteal abcesses. Complications from infection were classified as major if they resulted in device explantation, surgical wound revision, hospitalization and intravenous (IV) antibiotics, or meningitis. Minor complications were identified as those requiring local wound care and/or oral antibiotics. RESULTS Of the 733 patients, 29 were identified with postoperative infections. The demographics of these patients and causes of hearing loss are shown in Tables 1 and 2, respectively. There were 14 adult and 15 pediatric patients. The mean patient age at implantation was 30 years. The mean length of follow-up was 43 months, and similar between adult and pediatric groups. Thirty postoperative infections were identified in the 29 study patients, for an overall incidence of 4.1%. One patient underwent two separate cochlear implant surgeries on the same ear and both were complicated by post-implant infection. Fourteen adult and 16 pediatric infections occurred. The overall incidence of infection in the pediatric patients (5.9%) was higher than the adult patients (3.0%), although the pediatric group had a higher number of minor infections (Table 3). The majority of infections (n ⫽ 22) were delayed (occurring ⬎30 days postoperatively), with 8 occurring in the early postoperative period (⬍30 days). The mean time to infection was 338 days (11.3 mo) with a range of 7 days to 6 years, and a median of 202.5 days (6.75 mo). Postoperative infections were classified as wound infections in 26 cases and complicated acute otitis media in 4 cases (Table 4). There were no cases of meningitis identified in the entire series. Wound infections were further categorized according to whether or not device exposure was present. There were 9 cases of infection with device exposure. Eight of these 9 cases ultimately required removal of the implant for resolution of the infection. One case was successfully treated with revision of the surgical wound. Seventeen cases of wound infection without device exposure were identified. Successful treatment of the infection required device removal in 3 patients, surgical wound revision in 5 patients, IV antibiotics in 3 patients, and oral antibiotics/local wound care in 6 patients. In 8 of the 11 infections requiring device explantation, a prolonged course of treatment consisting of oral and/or IV antibiotics preceded device removal. Six of these patients additionally underwent unsuccessful irrigation and debridement of the wound in an attempt to preserve the implant. In 3 cases, device extrusion was already present at the time of presentation. In all but Otolaryngology– Head and Neck Surgery Volume 131 Number 1 CUNNINGHAM et al 111 Table 2. Etiology of hearing loss in patients with infection (n ⫽ 29) Cause No. Congenital Hereditary Meningitis Chronic otitis media Congenital rubella Congenital syphilis Measles Autoimmune Vicodin abuse Menière’s disease Cochlear otosclerosis Unknown 13 3 3 2 1 1 1 1 1 1 1 1 one case of device removal, the intracochlear electrode was left in place to serve as a stent for revision implant surgery. The electrode was removed in 1 case because of extensive involvement with cholesteatoma. In the complicated otitis media group (n ⫽ 4), surgical therapy was required in 1 case. This patient developed acute otitis media 6 years after cochlear implant placement and presented to another institution with a pneumocephalus which required a middle fossa craniotomy for repair of a tegmen defect. In the remaining cases, hospitalization and IV antibiotics were required in 1 patient who developed a subperiosteal ABCs, and oral antibiotics and local wound care were used to treat the other 2 patients. One of these patients developed a draining ear following an episode of acute otitis media and the other developed an early subperiosteal ABCs. Cultures from infected wounds were obtained from 15 patients. The most common organism isolated was Staphylococcus aureus (Table 5). The overall rate of major infectious complications in this study was 3.0% (Table 6). Device explantation to control infection was required in 11 patients, for an overall incidence of 1.5%. An additional seven patients underwent surgical wound revision combined with IV (n ⫽ 2) and oral (n ⫽ 5) antibiotics to eradicate infection. The implant was saved in these 7 cases. Of the 30 postoperative infections identified, 26.7% were successfully managed with oral antibiotic therapy or local wound care alone. The remaining 73.3% required more aggressive treatment consisting of device explantation (36.7%), surgical wound revision (23.3%), or IV antibiotics (13.3%). Preoperative and intraoperative variables were reviewed to determine whether there was an association with postoperative infections (Table 7). Although adult patients had a greater number of medical comorbidities than pediatric patients, no specific condition was found to predispose to infection. Two of the 30 patients with postoperative infections received perioperative antibiotics for endocarditis prophylaxis. A history of ear disease was identified in 15 out of 29 patients. Nine patients had a history of chronic ear disease with 3 patients undergoing a previous tympanoplasty with intact canal wall mastoidectomy in the ipsilateral ear and 1 patient with a history of a canal wall down mastoidectomy in the contralateral ear. The other 5 patients with a history of chronic otitis media had previously undergone myringotomy and tube placement in the ipsilateral ear. Only one of these patients had a tube in place at the time of cochlear implantation. This patient developed otitis media postoperatively and was treated with ear drops and oral antibiotics. A history of acute otitis media treated medically was identified in 6 additional patients. Of the 4 patients who developed otitis media postoperatively, 2 patients had a prior history of acute otitis media and 2 had a history of chronic otitis media. Review of the remaining variables revealed no additional risk factors for postoperative infection. DISCUSSION Complications associated with cochlear implants are relatively rare and usually involve flap problems such as skin necrosis and wound dehiscence. Wound complications have a reported incidence of 4.5% to 11.2%.1-3 The incidence of infection following cochlear implant surgery ranges from 1.7% to 3.3%.1,2 Significant overlap exists between these two groups, however, because of the fact that flap problems often become secondarily infected and vice versa. Our review of 734 cochlear implant procedures revealed an overall incidence of infection of 4.1%. Excluding minor complications treated with local wound care and/or oral antibiotics, the incidence of major infectious complications was 3.0%. These results are consistent with the previously published literature. Only 27% of infections in this series occurred in the early postoperative period, with the majority (73%) occurring at a mean time of 11.2 months after implantation. Early postoperative complications are usually a result of flap technique or contamination at the time of implantation. In our review, 2 of 8 early infections were due to mild wound dehiscence successfully treated with oral antibiotics and local wound care. Since the early 1990s we have used a “lazy-S” incision whereby a standard post-auricular incision is gently curved superiorly and posteriorly over the temporal squamosa. We believe a smaller incision using this technique has decreased the occurrence of flap related problems as is Otolaryngology– Head and Neck Surgery July 2004 112 CUNNINGHAM et al Table 3. Classification of postoperative infection (n ⫽ 30) n (no. of cochlear implant procedures) No. of infections Early (⬍30 d) Delayed (⬎30 d) Time to infection [mean (range)] (median) Adults (n ⴝ 462) Peds (n ⴝ 272) Total (n ⴝ 734) 14 (3.0%) 4 (.86%) 10 (2.2%) 11.2 mo (15 d–6 y) (4.25 mo) 16 (5.9%) 4 (1.5%) 12 (4.4%) 11.3 mo (7–820 d) (12.5 mo) 30 (4.1%) 8 (1.1%) 22 (3.0%) 11.3 mo (7 d–6 y) (6.75 mo) Table 4. Categories of postoperative infection (n ⫽ 30) n (no. of cochlear implant procedures) Infection type Wound infection Device exposed Device explantation Surgical wound revision Device not exposed Device explantation Surgical wound revision IV antibiotic therapy PO antibiotics/local wound care Otitis media Surgical wound revision IV antibiotic therapy PO antibiotics/local wound care Meningitis Table 5. Pathogens isolated from wound culture (n ⫽ 30) Pathogen Staphylococcus aureus Escherichia coli Group A beta-hemolytic Streptococcus Klebsiella pneumoniae Pseudomonas aeruginosa No. 11 1 1 1 1 reflected in the low occurrence of early postoperative infection. The remaining 6 patients with early infections presented with overt wound fluctuance possibly related to contamination at the time of implantation. Bacterial colonization of a surgical implant is a prelude to clinical infection. Most cases of implantrelated infection that clinically manifest within 1 year of surgical placement are thought to result from perioperative inoculation of pathogens.9 Systemic and local antibiotics are therefore used to prevent colonization of the implant or contamination of adjacent tissues. The clinical efficacy of antimicrobial prophylaxis, however, remains largely unconfirmed. A previous review of antibiotic prophylaxis in cochlear implant surgery by Adults (n ⴝ 462) Peds (n ⴝ 272) Total (n ⴝ 734) 12 5 5 0 7 1 2 2 2 2 1 1 0 0 14 4 3 1 10 2 3 1 4 2 0 0 2 0 26 9 8 1 17 3 5 3 6 4 1 1 2 0 Robinson and Chopra revealed no significant difference in the incidence of infection with or without the use of perioperative antibiotics.10 Since the early history of cochlear implants, we have not used perioperative antibiotics during cochlear implant surgery; the exception being endocarditis prophylaxis. Our rate of postoperative infection (4.1%) is comparable to the 4.5% infection rate reported with the use of antibiotic prophylaxis.10 Although 73% of our infectious complications were delayed, colonization of the implant at the time of surgery must be considered as an etiologic factor. The majority of wound cultures obtained in our series revealed Staphylococcus aureus, which is the most common pathogen found in surgical implant infections and may represent a skin contaminant at the time of surgery.9 Despite uncertainty regarding the clinical efficacy of antibiotic prophylaxis, the serious medical consequences and economic sequelae of surgical implant infections lend support to its use. Although we had no cases of meningitis in this series, recent reports of meningitis associated with cochlear implants have further increased awareness of the potential complications of implant infections. This has led to more formal recommendations regarding the use of perioperative antibiotics.6 Since October 2002, we have started using Otolaryngology– Head and Neck Surgery Volume 131 Number 1 CUNNINGHAM et al 113 Table 6. Complications of postoperative infection (n ⫽ 30) n (No. of cochlear implant procedures) Major complications (total) Device explantation Surgical wound revision IV antibiotic therapy Meningitis Minor complications Oral antibiotics/local wound care Adults (n ⴝ 462) Peds (n ⴝ 272) Total (n ⴝ 734) 12 (2.5%) 6 (1.3%) 3 (.65%) 3 (.65%) 0 10 (3.7%) 5 (1.8%) 4 (1.5%) 1 (.37%) 0 22 (3.0%) 11 (1.5%) 7 (.95%) 4 (.54%) 0 2 (.43%) 6 (2.2%) 8 (1.1%) Table 7. Variables related to postoperative infection (n ⫽ 30) n No. of infections Ear (R:L) Device type Nucleus 22 Clarion Hi F/positioner Surgery time (mean hr:min) Perioperative antibiotics Flap technique Post-auricular lazy-S Electrode insertion Full Ossification present Round window soft tissue seal Surgical complications Inner ear malformation Medical comorbidities History of ear disease (total) Chronic otitis media n 30 13:17 7 8 1:53 2 Nucleus 24 Clarion 10 5 29 Inferiorly based 1 30 4 30 0 2 16 15 9 Partial 0 Acute otitis media 6 perioperative antibiotics in all cases. We plan to monitor our infection rate in this new series to determine whether there is a difference in the incidence of infections. We searched for additional factors that may have contributed to an increased risk of postoperative infection. Of all the factors reviewed, only a history of previous ear disease appeared significant. Fifteen of 29 patients with postoperative infections had a prior history of chronic (n ⫽ 9) or acute otitis media (n ⫽ 6). One patient with a prior history of tympanomastoid surgery for cholesteatoma was found to have recurrent cholesteatoma at the time of implantation. A canal wall down mastoidectomy was performed and the ear canal was closed. A wound infection developed 2 years later secondary to recurrent cholesteatoma and required explantation of the device. In 4 patients with a history of chronic (n ⫽ 2) and acute (n ⫽ 2) otitis media, postoperative wound infections developed following recurrent episodes of acute otitis media. Two of these patients were successfully treated with oral antibiotics and wound care, 1 patient required IV antibiotics to treat a subperiosteal abscess, and 1 patient underwent a middle fossa craniotomy to repair a tegmen dehiscence. We now recommend that all patients with a significant history of previous ear disease be counseled regarding the possible risk of problems postoperatively. Patients should seek care immediately if signs or symptoms of an ear infection develop. Aggressive antibiotic treatment is required for these individuals. Few reports exist in the literature regarding management of postoperative infections following cochlear implantation. Although previous studies have recommended removal of the infected implant to allow healing of the wound,11,12 current recommendations call for conservative measures. Postoperative infections must be assessed for the severity of infection to determine how aggressive treatment should be. Treatment may involve oral antibiotics and local wound care, IV antibiotics, and/or surgery. Oral antibiotics and local wound care were sufficient in one fourth of our cases. This treatment is appropriate for minor infections. However, the majority of our cases (60%) required surgical intervention, and the rate of device explanta- Otolaryngology– Head and Neck Surgery July 2004 114 CUNNINGHAM et al tion was high (37%). Wound infections with device exposure carried a poor prognosis, requiring removal in the majority of cases (8 of 9). Only one case of device exposure with infection was salvaged through surgical wound revision and medical therapy. When device removal is necessary, we recommend leaving the electrode in the cochlea. The electrode is cut at the facial recess and the intracochlear portion is left in place to act as a stent. Failure to leave the electrode stent will most likely result in cochlear ossification in the setting of an infection and may compromise future attempts at re-implanting the same ear. When device exposure was not present, successful treatment was achieved in 14 out of 17 cases without explantation. Although infectious complications are rare, they assume greater importance in the setting of a cochlear implant given the increased potential for wound breakdown and contamination of the device. Removal of an infected implant can have significant emotional and economic consequences for the patient who has achieved good speech reception. Furthermore, placement of an intracochlear electrode provides a potential pathway for intracranial extension of pathogens and an increased risk of meningitis in the setting of an infection. Advances in surgical technique and flap design have decreased the occurrence of wound-related complications. However, identification of risk factors for infection and optimization of treatment regimens will further reduce the complications associated with postoperative infection. CONCLUSION This series demonstrates that the postoperative infection rate in patients undergoing cochlear implant surgery without the use of perioperative antibiotics is similar to previously published reports, with major infectious complications occurring in 3.0%. Although antibiotic therapy was required in all cases of postoperative infection, surgical intervention was also required in the majority of cases. The rate of device explantation was high (37%). A prior history of signif- icant ear disease is a possible risk factor for postoperative infection. With recent awareness of meningitis, we now recommend prophylactic antibiotics in all cochlear implant patients.11,12,13 We wish to thank Karen I. Berliner, Ph.D. for her critical review of this manuscript and Stephanie Moody, M.D. for her invaluable assistance in collecting data on these patients. REFERENCES 1. Hoffman RA, Cohen NL. Complications of cochlear implant surgery. Ann Oto Rhinol Laryngol 1995;104(Suppl 166):420-2. 2. Yu KCY, Hegarty JL, Gantz BJ, Lalwani AK. Conservative management of infections in cochlear implant recipients. Otolaryngol Head Neck Surg 2001;125:66-70. 3. Telian SA, El-Kashlan HK, Arts HA. Minimizing wound complications in cochlear implant surgery. Am J Otol 1999;20:331-4. 4. Donnelly MJ, Pyman BC, Clark GM. Chronic middle ear disease and cochlear implantation. Ann Oto Rhinol Larygol 1995; 104(Suppl 166):406-8. 5. Kempf HG, Stover T, Lenarz T. Mastoiditis and acute otitis media in children with cochlear implants: recommendations for medical management. Ann Otol Rhinol Laryngol 2000;(Suppl 185):25-27. 6. FDA public health web notification: risk of bacterial meningitis in children with cochlear implants. October 17, 20002. http:// www.fda.gov/cdrh/safety/cochlear.html. 7. Reefhuis J, Honein MA, Whitney CG, et al. Risk of bacterial meningitis in children with cochlear implants. New Eng J Med 2003;349:435-45. 8. Arnold W, Bredberg G, Gstottner W, et al. Meningitis following cochlear implantation: pathomechanisms, clinical symptoms, conservative and surgical treatments. ORL J Otorhinolaryngol Relat Spec 2002;64:382-89. 9. Darouiche RO. Antimicrobial approaches for preventing infections associated with surgical implants. Clin Infec Dis 2003;36: 1284-89. 10. Robinson PJ, Chopra S. Antibiotic prophylaxis in cochlear implantation: current practice. J Laryngol Otol 1989;18(Suppl):2021. 11. Cohen NL, Hoffman RA. Complications of cochlear implant surgery in adults and children. Ann Oto Rhinol Laryngol 1991; 100:708-11. 12. Kempf HG, Johann K, Lenarz T. Complications in pediatric cochlear implant surgery. Eur Arch Otorhinolaryngol 1999;256: 128-32. 13. Rubinstein JT, Gantz BJ, Parkinson WS. Management of cochlear implant infections. Am J Otol 1999;20:46-9.