A Durable Repair of Middle Fossa Defects

Middle fossa defects are becoming increasingly common in the setting of rising rates of obesity and associated chronic diseases. Two variants that are most frequently seen are spontaneous temporal encephaloceles (TEs) and superior semicircular canal dehiscences (SSCDs). Symptoms of SSCDs can present with a constellation of auditory and vestibular symptoms. TE symptomatology can range from chronic otitis media and CSF otorrhea to life threatening diagnoses such as meningitis, epidural or intracranial abscesses. Surgical repair is necessary to alleviate symptoms and prevent progression to more serious intracranial pathology. Methods of repair have varied with mixed results. The purpose of this study was to describe a durable repair of such defects.

We performed a retrospective chart review of those patients undergoing open middle fossa craniotomy for the repair of either TEs or SSCDs at our institution between January 2010 and December 2017. Inclusion criteria were the diagnosis of TE or SSCD at the time of surgery and 30-day postoperative follow-up. There were no excluding factors. Age, gender, symptoms, past medical history, and surgical procedure were recorded for each patient. All patients with neuroimaging-documented middle fossa defect underwent a middle fossa craniotomy. Once the defect was identified and packed with a mixture of bone wax and ofloxacin, the middle fossa floor was reconstructed with hydroxyapatite cement to cover the defect ([Figs. 1] and [2]). This was then followed by a layer of collagen-based dural substitute matrix as an onlay graft.

Sixteen patients met criteria to be included in the retrospective review ([Table 1]). Ten patients presented with TEs and six presented with SSCDs. In both clinical entities, there was a predominance of men presenting with these defects. The mean follow-up period was 7.75 months. One patient developed a recurrent CSF leak with concomitant wound dehiscence requiring return to the OR for repair. Another patient developed a superficial wound infection that was managed conservatively, and another patient developed facial droop on the side of the repair.

The middle fossa approach with the utilization of a combination of hydroxyapatite cement and collagen-based dural substitute matrix provides a safe and durable method of repairing middle fossa defects. Synthetic materials can provide an alternative to the current materials available to the skull base surgeon.

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No conflict of interest has been declared by the author(s).