Cerebrospinal fluid (CSF) leaks traditionally have been classified as traumatic or nontraumatic (1,2). Nontraumatic CSF leaks may be spontaneous in the absence of obvious cause, such as skull base abnormalities or bone erosion related to a mass lesion or hydrocephalus (1–3). Spontaneous CSF leaks sometimes are referred to as high-pressure leaks when increased intracranial pressure (ICP) is a contributing factor (2,3). Idiopathic intracranial hypertension (IIH) is increasingly recognized as a cause of spontaneous CSF leak in the otolaryngological and neurosurgical literature. There are reports suggesting that the so-called primary spontaneous CSF leaks might be due to IIH (2–8). Some of these patients are asymptomatic or only have symptoms attributable to the CSF leak (such as rhinorrhea, CSF hypotension–related headaches, or bacterial meningitis) while the leak is active. The diagnosis of IIH is typically made weeks or months after surgical repair of the leak (9). At times, patients with a known diagnosis of IIH may develop a spontaneous CSF leak, presumably secondary to the chronically raised ICP with skull base erosion and meningoceles (2).
MATERIALS AND METHODS
Medical records and neuroimaging of the illustrative cases were reviewed. PubMed was searched for English-language articles published before January 2013 using the search terms “idiopathic intracranial hypertension,” “encephalocele,” “skull-base defect,” “spontaneous cerebrospinal fluid leak,” “CSF rhinorrhea,” and “CSF otorrhea.” The reference lists of identified articles were searched for further relevant articles.
A 49-year-old obese African American woman developed isolated CSF rhinorrhea, which initially was mistaken for sinusitis. One year later, she developed bacterial meningitis, and computed tomography (CT) demonstrated a skull-base defect in the right cribiform area causing meningocele with CSF leak (Fig. 1A). She underwent endoscopic sinus surgery with repair of the leak. Three months later, she complained of headaches and transient visual obscurations and was found to have bilateral papilledema (Fig. 1B). Automated perimetry showed enlarged blind spots and nasal visual field loss (Fig. 1C). Lumbar puncture revealed increased CSF opening pressure (OP) of 37 cm H2O and resulted in temporary resolution of the headaches. She underwent a ventriculoperitoneal shunt with immediate resolution of her symptoms of raised ICP; papilledema resolved within 1 month. The CSF leak did not recur.
A 32-year-old obese Caucasian woman was found to have isolated CSF rhinorrhea after presenting with postural headaches. Brain imaging showed an empty sella and intrasellar bone erosion (Fig. 2A, B). She underwent endoscopic surgical repair of the CSF leak, and her headaches resolved after the procedure. A few weeks later, persistent headaches developed, and she experienced transient visual obscurations. She was found to have bilateral optic disc edema (Fig. 2C) with enlarged blind spots on visual field examination. Lumbar puncture showed elevated CSF OP of 42 cm H2O and resulted in temporary resolution of headaches. The patient subsequently underwent a CSF shunting procedure with complete resolution of all symptoms of intracranial hypertension; at 6 weeks of follow-up, papilledema had resolved. The CSF leak did not recur.
A 43-year-old mildly overweight Caucasian man was followed for 3 years for symptomatic IIH treated intermittently with acetazolamide. He had moderate bilateral papilledema with enlarged blind spots in his visual fields but only mild headaches, and generally did well without treatment. He was reevaluated for worsening headaches, which were occurring daily and associated with tinnitus and transient visual obscurations. Repeat neuro-ophthalmic examination showed persistent, bilateral papilledema (Fig. 3A) and stable visual fields. Repeat lumbar puncture showed elevated CSF OP of 33.5 cm H2O. His headaches improved, but he developed CSF rhinorrhea. Neuroimaging showed a right cribriform plate defect (Figs. 3B & 3C), an empty sella, and bilateral transverse sinus stenoses (Fig 3D). The patient was placed on prophylactic antibiotics and underwent a ventriculoperitoneal shunt. CSF rhinorrhea markedly decreased, and endoscopic repair of the leak was subsequently performed, with immediate resolution of the leak. However, 6 weeks later, the leak recurred in the setting of recurrent increased ICP secondary to proximal shunt obstruction. The shunt was revised, and the CSF leak resolved. One month later, he remained asymptomatic, with improvement of his papilledema.
Review of the Literature
Table 1 presents a summary of reports in the English literature of spontaneous CSF leaks associated with presumed or diagnosed IIH (2–24).
IIH is increasingly recognized as a cause of primary spontaneous CSF leaks. Over the past 2 decades, several articles on this topic have been published mostly in the otolaryngological and neurosurgical literature (2–25). These reports highlight the similarities between the demographics of patients with IIH and those with spontaneous CSF leaks suggesting a causal relationship between IIH and the so-called spontaneous CSF leak (Table 1).
Similar to IIH patients, reported cases of spontaneous CSF leak are often young or middle-age obese women, with a mean body mass index (BMI) greater than 30 kg/m2 (4,24) (Table 1). Such demographic overlap also is shared by patients with primary empty sella syndrome, an endocrinologic entity in which chronically increased ICP may be a contributing factor (26,27). In a retrospective study of 11 patients with β-2 transferrin–proven spontaneous CSF leaks, 72% of patients met the criteria for the diagnosis of IIH (5). Obesity has been suggested as an independent risk factor for the development of spontaneous CSF leaks and spontaneous encephaloceles, and the BMI of these patients is significantly higher than in those of patients developing CSF leaks for other reasons. In 1 study specifically performed to evaluate the role of obesity (BMI ≥ 30 kg/m2) in spontaneous encephaloceles and CSF leak, the mean BMI of the patients with spontaneous encephaloceles was 33.4 kg/m2 vs 27.0 kg/m2 in the group of nonspontaneous encephaloceles (28).
The presenting symptoms of spontaneous CSF leaks vary greatly depending on multiple factors, including the location and activity of the leak, and the presence of concurrent signs of raised ICP. If the leak is active, symptoms and signs of intracranial hypotension (e.g., orthostatic headaches, neck stiffness) may occur (9). Depending on the location of the leak, CSF otorrhea and conductive hypoacusia may be a presenting sign in patients with bone defects in the posterior fossa (24), whereas CSF rhinorrhea usually develops in patients with defects of the cribiform plate (6,8,29). Bacterial meningitis may be the initial presentation leading to the discovery of the CSF leak. Some patients may have symptoms of increased ICP even when the leak is active (including headache, tinnitus, visual disturbances, and papilledema) (2), but most often, patients develop symptoms and signs of intracranial hypertension only after the CSF leak has been repaired (9,30).
The factors predisposing some IIH patients to develop spontaneous CSF leaks remain unclear, although it is likely that chronically elevated ICP is necessary, as demonstrated by our third patient. Some patients with increased ICP secondary to intracranial tumors (distant from the skull base) or hydrocephalus may also develop CSF leak, confirming that raised ICP in itself can cause CSF leaks, possibly through remodeling of the skull base and resultant encephaloceles (1,2,31,32).
CT and MRI of the brain are required to identify skull base defects. Often, these studies show imaging findings associated with increased ICP (32). A retrospective study showed that 100% of patients with spontaneous CSF leaks had a completely or partially empty sella compared with 11% of patients with nonspontaneous CSF leaks and 5%–6% of the general population (15). Tortuosity of the optic nerves, increased CSF around the optic nerves, arachnoid pits and dural ectasias are other radiological findings often observed in patients with both IIH and spontaneous CSF leaks (31). The most frequent site of skull basal defects includes the ethmoid sinuses and lateral wall of the sphenoid sinus (3). In addition, there are reports that spinal CSF leak might be associated with increased ICP (9). Given the overlapping clinical and neuroimaging profiles, it has been proposed that patients with primary spontaneous CSF leaks may have a variant of IIH (5).
Spontaneous CSF leak patients may develop raised ICP once the leak is repaired (9,25), as did 2 of our patients. In a small prospective study measuring ICP through lumbar catheters after surgical repair of spontaneous CSF leaks, elevated ICP was observed in 7 of 8 patients and in none of 3 patients with traumatic CSF leaks (30).
Although spontaneous resolution of spontaneous CSF leak may occur after treatment of increased ICP, the high risk of bacterial meningitis usually requires endoscopic surgical repair of the skull base defect (33). Interestingly, following skull base surgical repair in patients with spontaneous CSF leak, the leak recurrence rate is high, ranging from 25% to 87% (2,3,20). This high rate of recurrence likely reflects excessive elevation of ICP that occurs after leak repair in those patients with presumed IIH (30). Obesity (common in IIH) is also associated with the failure of the CSF leak repair (21).
Appropriate ICP-lowering management usually is the first step in managing patients with CSF leak. Reh et al (23) proposed monitoring of CSF pressure through a lumbar drain to assess response to a therapeutic trial of acetazolamide before surgical intervention. Once there is appropriate control of ICP, the rate of success of the spontaneous CSF leak repair approaches 95% and is similar to that of repair of CSF leaks due to other causes (2). It has been proposed that interventions to lower the ICP including medical therapy (weight loss, acetazolamide) or a CSF diversion procedure be performed before or at the time of surgical repair of the skull base (20, 25). Our patients underwent CSF shunting procedures as the first-line treatment due to concern that medical management alone might not result in an immediate and dramatic decrease in ICP, necessary to prevent visual loss from papilledema. Indeed, recurrence of the leak occurred in the patient who had shunt malfunction soon after surgery.
Because elevated BMI is a risk factor for patients with primary spontaneous CSF leaks, weight loss likely should be recommended. However, there are only case reports of resolution of spontaneous CSF leaks after bariatric surgery (22,25), so further study is needed to assess the effectiveness of weight loss in the treatment of spontaneous CSF leaks (22,25).
Our cases illustrate the association between IIH and spontaneous CSF leaks and support systematic screening for symptoms and signs of increased ICP within weeks after surgical repair of a spontaneous CSF leak. Identification of these patients is warranted to prevent failure of the CSF leak repair and to prevent potential visual loss from papilledema. Additionally, IIH patients with chronically raised ICP require close follow-up for the development of a CSF leak.
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