Facial Nerve and Hearing Outcomes after Middle Cranial Fossa Vestibular Schwannoma Surgery

Background: Decision making for patients with small, intracanalicular vestibular schwannomas (VS) remains challenging. These individuals frequently have significant residual hearing and limited other symptoms. For younger patients, surgery through a middle fossa craniotomy (MFC) approach offers a chance for long-term hearing preservation, even for laterally placed tumors, and potentially avoids the need for radiation therapy and/or lifetime surveillance. However, the middle fossa approach has been characterized as one where the facial nerve location and temporal lobe retraction can be problematic.

Objective: The purpose of this study was to determine the outcomes and complications for selected patients with VS resected with the MFC.

Methods: A review of all the VS cases performed at a single institution between 2001 and 2011 yielded 36 cases resected by an MFC approach. Pre- and postoperative audiograms, facial nerve function results, and complications (CSF leak, meningitis, vestibular symptoms, and temporomandibular joint [TMJ] dysfunction, stroke and death) were collected. Operative reports were also reviewed to assess facial nerve stimulation levels and degree of tumor resection. Pre- and postoperative MRIs were reviewed by a senior neuroradiologist for tumor location, size, completeness of resection, and radiographic evidence of recurrence. Hearing outcomes were reported according to the new AAO-HNS recommendations using scatter grams depicting preoperative pure tone averages (PTA) and word recognition scores (WRS) as well as the change seen postoperatively. Statistical analysis was performed using SPSS version 13.

Results: Average tumor size was 0.73 cm (range, 0.2–2.6 cm). Complete resection occurred in 86% of patients. Radiographic residual tumor observed in 14% (follow-up 1–9 years; mean, 3.3). Only 5% of patients had recurrence or growth of residual tumor requiring surgery. All the patients (100%) had HB I or II at 12 months post-op (I:91 and II:9%). Cranial nerve VIII was anatomically preserved in 91% of patients. Where postoperative audiograms were available, 58% of patients had a PTA of better than 50 dB, and 74% had a WRS of 48% or better postoperatively. Overall, 63% of patient had hearing within 20dB and 20%WRS of preoperative scores. A learning curve was evident in the hearing outcomes with later patients having better hearing outcomes than earlier patient. There were no cases of meningitis, stroke, or death. CSF leak occurred in 2.8%, TMJ dysfunction in 18 and 43% of patients reported some imbalance at 1-year postoperatively.

Conclusion: MFC approach for removal of selected small VS is a safe technique, with low rates of facial nerve injury and hearing preservation rates that are comparable to radiotherapy when performed by an experienced surgical team.