Elsevier

World Neurosurgery

Volume 83, Issue 4, April 2015, Pages 560-566
World Neurosurgery

Peer-Review Report
Cerebrospinal Fluid Leaks and Encephaloceles of Temporal Bone Origin: Nuances to Diagnosis and Management

Portions of this work were presented in abstract form and in poster form at the Fifteenth WFNS World Congress of Neurological Surgery, Seoul, Korea, September 8–13, 2013.
https://doi.org/10.1016/j.wneu.2014.12.011Get rights and content

Objective

Temporal bone encephalocele has become less common as the incidence of chronic mastoid infection and surgery for this condition has decreased. As a result, the diagnosis is often delayed, and the encephalocele is often an incidental finding. This situation can result in serious neurologic complications with patients presenting with cerebrospinal fluid leak and meningitis. We review the occurrence of, characteristics of, and repair experience with temporal encephaloceles from 2000–2012.

Methods

We conducted a retrospective review of 32 patients undergoing combined mastoidectomy and middle cranial fossa craniotomy for the treatment of temporal encephalocele.

Results

The diagnosis of temporal encephalocele was made in all patients using high-resolution temporal bone computed tomography and magnetic resonance imaging. At the time of diagnosis, 12 patients had confirmed cerebrospinal fluid leak; other common presenting symptoms included hearing loss and ear fullness. Tegmen defect was most commonly due to chronic otitis media (n = 14). Of these patients, 8 had undergone prior mastoidectomy, suggesting an iatrogenic cause. Other etiologies included radiation exposure, congenital defects, and spontaneous defects. Additionally, 2 patients presented with meningitis; 1 patient had serious neurologic deficits resulting from venous infarction.

Conclusions

The risk of severe neurologic complications after the herniation of intracranial contents through a tegmen defect necessitates prompt recognition and appropriate management. Computed tomography and magnetic resonance imaging aid in definitive diagnosis. A combined mastoid/middle fossa approach allows for sustainable repair with adequate exposure of defects and support of intracranial contents.

Introduction

The herniation of dura mater (meningocele) or brain tissue (encephalocele) into the mastoid or middle ear has become a rare condition. The potential devastating complications, such as meningitis, intracranial abscess, hemorrhage, venous infarction, and seizures, necessitate a high degree of clinical suspicion and prompt surgical evaluation. Before the widespread use of antibiotics, temporal encephaloceles occurred in association with chronic otogenic abscess and sinus thrombophlebitis as well as after surgery for these infections. Antibiotic therapy has greatly reduced the incidence of temporal encephaloceles, and a large series has not been reported in the recent literature.

Meningoceles and meningoencephaloceles of the temporal bone still occur. They may also be seen in congenital defects of the tegmen, after surgery to the skull base, after traumatic fractures, as a result of erosion from intracranial tumors, or after radiation therapy (15). Despite improvements in radiologic imaging of the temporal bone, delayed diagnosis of temporal encephalocele continues to occur. This delay is often due to the nonspecificity of clinical signs and symptoms. The most common presenting symptoms are a conductive or mixed hearing loss with a draining ear or serous otitis media. A retrotympanic pulsating mass occasionally can be found on otologic examination or during surgical drainage of the mastoid. Various surgical techniques have been proposed for the closure of this defect. We review 32 cases of temporal encephalocele at our institution between 2000 and 2012 and discuss some of the nuances of its presentation and management.

Section snippets

Materials and Methods

A retrospective chart review was performed examining 32 patients treated from 2000–2012 by a single neurosurgeon. All patients identified had been treated for encephalocele of the temporal bone. In 12 patients, spontaneous CSF leaks occurred, and encephalocele was discovered during mastoid surgery in 3 patients. Patients who developed temporal bone CSF leaks after acoustic neuroma surgery were excluded from the study.

Demographic data were collected from office and hospital charts, including

Patient Demographics

There were 32 patients who underwent 34 operations for temporal encephalocele; 15 of the patients were male. The median age at diagnosis was 51 years (range, 5–74 years). Of patients, 2 had undergone prior repair—1 patient via a transmastoid repair alone and 1 patient with use of only fascia for skull base repair.

Clinical Presentation

Of the 12 patients with spontaneous CSF leaks, 2 had a history of meningitis or presented with meningitis confirmed by lumbar puncture. Otorrhea was a symptom in 10 patients. In 3

Discussion

Although a bony defect is necessary to allow meningeal or brain tissue to protrude into the temporal bone (24), the dura mater overlying the middle cranial fossa is capable of supporting the intracranial contents over a large defect, making the herniation of brain tissue into the middle ear cavity a rare entity. Anatomic studies have shown that 20%–33% of adult temporal bones have 1 or multiple defects along the middle cranial floor, yet the incidence of encephaloceles is much less (10). An

Conclusions

The severity of sequelae from brain herniation and CSF leak associated with COM emphasizes the necessity for recognition and appropriate management. Because the initial symptoms can be nonspecific, a high degree of suspicion is necessary with prompt referral for high-resolution temporal bone CT and MRI. A combined transmastoid/middle cranial fossa approach with the use of allogeneic bone graft for middle fossa resurfacing and selective use of lumbar drainage allow a sustainable repair to be

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    Conflict of interest statement: The authors declare that the article content was composed in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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