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Spontaneous Intracranial Hypotension (Spontaneous Cerebrospinal Fluid Leak)
Definition
Spontaneous intracranial hypotension is defined as a
marked reduction of intracranial cerebrospinal fluid (CSF)
volume from a dura tear without any ascertained cause
1,2
such as trauma or lumbar puncture.
Epidemiology
Incidence of spontaneous intracranial hypotension
1
(SIH) is approximate 5 per 100,000 of the population.
Women are affected more frequent than men in a 2:1 ratio.
Incidence of SIH is higher in the fourth and fifth decade of
2
life.
Pathophysiology
The etiology of SIH is not clear. It is believed SIH is
resulted from a leaking of CSF from a tear in the dura
1
mater. Two major contributing factors to CSF leak are
3,4
weakness of the dural sac and mild trauma. The most
common causes of weakness of the dura are connective
tissue disorder, meningeal diverticula, and a weakened
5
thecal sac. Schievink & Louy identified three precipitating
factors for CSF leakage: 1) rapid positional changes such
as sudden arising into the upright position from a bending
position. This sudden position change shift intracranial
CSF down to the spinal canal rapidly, which increases the
spinal CSF pressure and leads to a CSF leak; 2) Valsalva
maneuvers such as coughing, lifting, labor and delivery.
Valsalva maneuvers increase intracranial pressure and
subsequently increase spinal CSF pressure that result in
CSF leak; 3) a trivial nonpenetrating spinal injury such as
cervical manipulation. Cervical manipulation may cause a
tear in the fragile meningeal diverticula or attenuated dura
1,4,6,7,8
and result in CSF leakage.
Most CSF leaks are typically found at either the cervico1,7,9
thoracic junction or the upper thoracic region.
It is
because the meningeal sheaths in these areas are thinner
10
than in other regions The less common sites are lumbar
and sacral regions. In most cases, CSF leakage sites are
8,11,12
unidentifiable.
Complications of SIH include cortical vein thrombosis,
subarachnoid hemorrhage, subdural hematoma, brainstem
1
compression, and cerebellar tonsillar herniation.
According to Kellie-Monroe doctrine, decreases in
volume of one intracranial component will result in
increases in volume of other component. In SIH,
decreases in CSF volume will increase venous blood
volume especially the bridging veins. Due to the downward
displacement of brain when patient is in the upright
position, it increases stretch to the engorged bridging veins
and increases risk of bridging vein rupture and subdural
13
hematoma. Radiographic results may also find venous
sinus engorgement, pachymeningeal enhancement,
14
subdural effusion, and enlargement of the pituitary gland.
Manifestations
Manifestations of SIH are related to the intracranial
hypovolume which leads to the brain shifting towards the
1,12
foramen magnum.
Orthostatic headache is common and occurs in 76% of
patients with SIH. The majority of these patients developed
headache within 15 minutes after a change from supine to
a standing position. This is relieved when patient return to
ra ecumbent position. Other presentations include nausea,
vomiting, neck stiffness, hypacusia (hearing impairment),
2,6,7,15
tinnitus, and photophobia.
Orthostatic headache is related to intracranial
hypovolemia. When a patient is in the upright position, the
brain descents to the bottom of the cranial vault and
creates traction of the pain fibers located on the cerebral
7
blood vessels and meninges resulting in headache.
Dilation of the cerebral venous blood vessels in SIH is
4
another cause of headache. Fifty five percent of patients
15
present with subdural fluid collection.
Descent of the brain may lead to distortion and
compression of the brain stem and some of the cranial
4
nerves and result in various cranial nerve palsies .
Ophthalmoplegia may occur as s result of cranial nerve
palsy. Approximate 30-35% of intracranial hypotension
patients presented with ophthalmoplegia. Eighty percent of
these patients had abducens nerve paresis. Abducens
nerve is more vulnerable due to its long intracranial
course. Occular manifestations include decreased visual
14
acuity, visual field deficits, nystagmus, and photophobia.
Diagnostic Tests
The criteria established by the International
Classification of Headache Disorders (ICHD) for diagnosis
of SIH include: A) orthostatic headache that is associated
with neck stiffness, tinnitus, hypacusia, photophobia, or
nausea; B) Evidence of low CSF pressure or leak by
conventional
myelography,
CT
myelography
or
cisternography, or lumbar puncture CSF opening pressure
<60 mmH2O in sitting position; C) No history of dural
16
puncture or other cause of CSF fistula.
Both magnetic resonance imaging (MRI) and CT scan
have been used to diagnose SIH. Researches have shown
CT scan is not effective in diagnosis for SIH but may be
6,17
helpful to rule out other causes of headache.
Magnetic resonance imaging is the preferred test for
10
SIH. Brain MRIs are able to reveal any anomalies such
as subdural hematomas or hygromas, brain herniation,
descent of cerebella tonsilis, and diverticula. The
compensatory venous vasodilation in SIH causes greater
concentration of gadolinium in the dural vasculature and
6,18
interstitial fluid.
Reference
MRI myelogram shown gadolium leaking from the C1-2 level
Treatment Options
Depending on the severity of symptoms and whether
the CSF leak site can be identified, treatments for SIH
include strict bed rest, epidural blood patch (EBP), and
1,11
surgery.
Conservative treatment includes bed rest, hydration of
patient, caffeine intake, abdominal binder, analgesics,
7
theophylline, and steroid therapy.
If conservative
treatments are ineffective, other treatment options such as
EBP, injection of fibrin sealant, epidural saline infusion, or
7,15
surgery may be required.
Currently, EBP is the most
commonly used treatment modality when conservative
12
management has failed.
Epidural blood patch is to inject 10 to 20mL of
7
autologous blood into the spinal epidural space. The
injected blood increases the intraspinal pressure and
creates a tamponade effect that “plugges” the dural hole
and prevent CSF leak. After EBP, a series of healing
processes occur, they are fibroblastic remodelling,
collagen deposition, and scar formation. The plugged dura
13
hole will be sealed in approximate 3 months. More than
6,19
one EBP may be required to stop the CSF leak.
Intrathecal infusion of saline is usually through a lumbar
catheter. Saline infusion rate is between 10mL/h and
30mL/h. Mechanism of epidural saline injection is similar
to EBP. However, increases in spinal pressure after
infusion is transient, andadditional intervention may be
13
required.
If both conservation and EBP failed, patients are
disabled by their symptoms, and the location of CSF leak
can be identified, surgical treatment is suggested. Surgical
interventions include partial or bilateral laminectomy and/or
facetectomy, ligation of the leaking meningeal diverticulum,
epidural packing with blood soaked Gelfoam, muscle
20
pledgets, or fibrin glue.
Nursing Implications
When patients are on conservative treatment, provide
different types of fluid choices to encourage oral fluid
intake. Administer caffeine and analgesia to alleviate
headache and discomfort.
Patient may be discharged on the day of EBP
procedure. Patient should be adviced to report back if
fever, back or radicular pain, or any abnormal symptoms
21
occurs.
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©2014
Disclaimer: The author neither represents nor guarantees that the
practices described herein, if followed, ensure safe and effective patient
care. The authors further assume no responsibility or liability in
connection with any information or recommendations contained in this
article. The recommendations and instructions in this article are based on
the knowledge and practice in neuroscience as of the date of publication.
These recommendation and instructions are subject to change based on
the availability of new scientific information.