Reconstruction of Temporal Bone Encephaloceles and Associated Cerebrospinal Fluid Leaks: Operative Technique, Nuances, and Results in 17 Patients

Objective: Temporal bone encephaloceles are associated with skull base defects and cerebrospinal (CSF) fistulas that often require surgical intervention. We describe our surgical technique and report our incidence of postoperative CSF leak and complications.

Methods: We retrospectively reviewed 17 patients with temporal bone encephaloceles that were treated between November 2009 and September 2014. The average age at surgical repair was 58.3 years old. There were 13 females and 4 males. Presenting symptoms included otorrhea in 11 (61.1%) patients, hearing loss in 6 (33.3%), rhinorrhea in 3 (16.7%), and dizziness in 2 (11.1%). Ten patients (58.8%) presented with a defect of unknown cause, 6 (35.3%) had associated chronic otitis media, and 1(5.9%) patient had a history of recent trauma. Fifteen patients (88.2%) underwent surgical repair via a combined middle fossa and transmatoid approach, while two (11.8%) underwent surgical repair with the middle fossa approach only. The defect involved the tegmen tympani in 3 (17.6%) cases, tegmen mastoideum in 8 (47.2%) cases, both tegmen tympani and mastoideum in 4 (23.5%) cases, and other location in the petrous skull base in 2 cases (11.7%). Our surgical technique involved exposing the middle fossa floor extradurally from the foramen ovale and V3 anteriorly, the petrous ridge medially, and the tegmen mastoideum posteriorly. After resection of the temporal encephaloceles, the bony defects were repaired using a self-setting calcium phosphate cement to surface the floor of the middle fossa. If a defect was overlying the ossicular chain, an autologous split thickness bone graft was used to create a “roof” to prevent the cement from adhering to the ossicles. Multi-layer dural reconstruction was performed using a two-layer method with acellular dermal allograft (AlloDerm). The first layer of AlloDerm was placed directly over the reconstructed middle fossa floor and the second layer was placed against the temporal lobe dura. In combined cases that involved a mastoidectomy, the bony defects that could be accessible from the mastoidectomy view were supplemented with additional calcium phosphate cement, as long as the defect was not associated with the ossicular chain.

Results: Successful repair without recurrent or postoperative CSF leak was achieved in 100% of cases. For the patients who had audiologic data available, there was no significant change in audible thresholds before and after surgery for both air conduction (N = 10) and bone conduction (N = 9) at all tested frequencies. Postoperative complications included a myocardial infarction and a wound infection. All other patients had an uneventful postoperative course. Mean time of follow-up was 30 months (range: 11 to 69 months).

Conclusions: Temporal lobe encephaloceles can be successfully treated using a combined middle fossa and transmastoid approach or a middle fossa approach alone to eliminate the CSF fistula. Our repair technique using calcium phosphate and multi-layered AlloDerm reconstruction provides a safe and effective method to reconstruct the middle fossa skull base defects.