Petrous Apex Cephaloceles: Radiology Features and Surgical Management of a Rare Entity

Introduction: Petrous apex cephalocele (PAC) is an uncommon condition resulting from the herniation of the posterolateral wall of Meckel’s cave into the petrous apex. These lesions are usually asymptomatic and diagnosed as an incidental finding on adult brain imaging. However, PAC may be a cause of spontaneous CSF leak. In the present study, we outline radiologic features of this rare lesion and describe the surgical management of three spontaneous CSF leak cases secondary to PAC.

Methods: A retrospective review of all cranial imaging archived at an academic center between 2008 and 2019 identified 32 patients with PAC (27 females and 5 males; age range: 7–87; mean: 57 years). All imaging was reviewed by a neuroradiologist to characterize the identified lesions including associated radiographic anomalies. Patients who were radiographically diagnosed with a PAC were further characterized by demographics, further workup, and surgical intervention. In addition, three patients were clinically identified as having been treated for CSF leak in the presence of PAC.

Results: Radiological assessment showed the following characteristics of PAC: 9 (25.7%) bilateral and 26 (74.2%) unilateral. There was an association with a partially or expanded empty sella in 29 (82.8%) of the cases and arachnoid pits in 5 (14.2%). Enlarged CSF spaces of the optic nerve sheath were seen in 7 (20.0%) with a decreased interpeduncular distance in 3 patients (8.6%). Coexisting pathology included temporal, sphenoid, and bilateral jugular foramen meningocele; as well as cribriform, middle crania fossa, and right temporal defect. Initial presentation, radiographic data, intraoperative findings, significant surgical anatomy, and follow-up will be reviewed of three spontaneous CSF leak cases secondary to PAC that were managed with the middle cranial fossa approach.

Conclusion: The authors provide a comprehensive analysis of the incidence of PAC and associated radiographic abnormalities. PAC is an uncommon condition; furthermore, PAC is an exceedingly unusual cause for CSF leak in the adult and pediatric population. A middle fossa approach may be used to treat CSF as a result of PAC. Both radiologically and clinically diagnosed PAC cases display features of IIH that require vigilance and may warrant future treatment. Typically CSF otorrhea originates from an encephalocele that extends via a bony defect in the tegmen tympani or tegmen mastoideum. However, on occasion the source of the CSF otorrhea is not via the tegmen; in these cases defects in the middle fossa floor medial to the ridge for the gasserian ganglion need to be considered.

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