Facial Nerve Schwannomas of the Cerebellopontine Angle: The Mayo Clinic Experience

Background: Cerebellopontine angle (CPA) facial schwannomas (FNS) are infrequent, accounting for less than 20% of all FNS. There is often controversy regarding the most optimal management strategy and debate as to whether, when, and how to intervene in these patients. Here we present the Mayo Clinic experience and management paradigm for these rare tumors.

Methods: The clinical and radiological outcomes in 14 patients with cerebellopontine angle (CPA) facial nerve schwannomas treated at our institution from 1998 to 2011 were reviewed. Management modalities included observation, resection, and/or stereotactic radiosurgery. All patients were managed by the senior author (MJL).

Results: Patients presented with clinical facial nerve dysfunction (n = 7), hearing loss (n = 5), or brainstem symptoms (n = 2) at the time of treatment. Nine patients were followed conservatively for a mean and median time of 60 and 48 months, respectively, prior to treatment (range, 12–132 months). Eleven patients underwent surgery for exploration (n = 4), resection with anatomic nerve preservation (n = 3), and resection with nerve resection followed by hypoglossal-facial nerve anastomosis (n = 4). Six patients underwent gamma knife radiosurgery (GKS) at the time of clinical or radiographic progression. One patient remains under observation. Five out of the six tumors that underwent GKS were either stable or decreased in size, and one tumor showed cystic degeneration and enlargement. All those that underwent resection showed no evidence of tumor recurrence, and the tumor under observation remained unchanged with normal facial function at the time of the last follow-up. Collectively, in the patients that underwent surgical resection of their tumor, there was a decrease in facial function in 57%, no change in facial function in 14%, and an improvement in facial function in 29%. All six patients who underwent GKS had a pretreatment House-Brackmann (HB) of 1 to 2, and this remained unchanged in four patients (67%). Two of the patients who underwent GKS (33%) had complete facial paresis (HB 6) within the first week after treatment. Serviceable hearing was maintained in 50% of patients in the GKS group and in 67% of patients in the tumor resection group. Overall, the mean and median follow-up was 48 and 43 months, respectively (range, 12–95 months).

Conclusions: Facial nerve schwannomas of the CPA are rare, and the lack of a consistent treatment approach poses a challenge in the management of these tumors. Those with normal facial nerve function should be observed when encountered with what appears to be a facial nerve schwannoma, either radiographically or during an approach to a CPA tumor. Microsurgery with or without nerve resection and stereotactic radiosurgery can be used in particular circumstances with regard to a patient's preoperative facial nerve function, age, health, progressive neurologic symptoms, and tumor enlargement.