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.
Fig. 1
Fig. 2
