Long-Term Facial Nerve Outcomes Following Microsurgical Resection of Vestibular Schwannomas in Patients with Preoperative Facial Nerve Palsy

Introduction: Preoperative facial nerve palsy is a relatively rare presentation of vestibular schwannoma (VS). In our experience, preoperative facial nerve palsy often occurs in the setting of large, compressive tumors. Decompression of the facial nerve and surrounding neurovascular structures is one potential benefit of microsurgical resection, however, long-term facial nerve outcomes in these patients is lacking in the literature. To our knowledge, this is the first series studying long-term facial nerve outcomes in patients with VS and a preoperative facial nerve palsy.

Methods: A retrospective review yielded 130 patients with confirmed vestibular schwannoma since implementation of the electronic medical record at our institution. A chart review was performed to determine demographic variables, preoperative facial nerve function, surgical approach, extent of resection, and postoperative treatment and outcomes. Preoperative imaging studies and radiology reports were examined to determine maximum tumor diameter and Koos grade. Patients that underwent a prior operation were excluded, and no patients in our series had prior radiosurgical treatment. The most recent clinical follow-up was utilized to determine the final House-Brackmann (HB) scale of facial nerve function.

Results: Of the 130 patients eligible for review, eight patients were confirmed to have documented preoperative facial nerve dysfunction, for an estimated incidence of 6% at our institution. Seven out of eight patients had Koos grade 3 or 4 tumors, with a mean tumor diameter of 2.9 cm (range: 2.0–4.4) in this series. Three patients underwent a retrosigmoid approach and five patients underwent translabyrinthine approach. Six tumors were subtotally resected and three patients underwent postoperative radiosurgery for the residual. Follow-up greater than 6 months was available for seven patients (median: 1.8 years; range: 6 months to 6.8 years). One patient currently only has 1 month follow-up.

Five patients had a preoperative HB score of 2/6; 3 patients had HB 3/6 or worse preoperatively. Of the patients with preoperative HB 2/6, one patient improved to HB ⅙, two patients were stable, and two patients worsened to HB 3/6. Of the patients with HB 3/6 or worse, two patients remained stable at 1.1 and 3.9 years of follow-up and one patient improved from HB 6/6 to HB 3/6 with 1.9 years of follow-up.

Conclusions: Preoperative facial nerve palsy is a rare occurrence in patients with vestibular schwannoma and tends to occur in relatively large lesions. Long-term outcomes of facial nerve function after microsurgical resection are lacking, however, our series suggests that good outcomes can be achieved. 75% of patients had either stable or improved facial nerve outcomes, however, GTR rates were relatively low in these patients. This may be secondary to difficulty identifying the nerve with visualization or stimulation. These outcomes are important to consider when counseling patients on surgery for vestibular schwannoma and facial nerve dysfunction. Surgery results in a relatively good facial nerve outcome, however, GTR appears to be less likely.