The Anatomically Intact but Electrically Unresponsive Facial Nerve Following Vestibular Schwannoma Resection

Objective/Background: Permanent facial nerve paresis following vestibular schwannoma (VS) surgery is devastating to both the patient and surgeon. Intraoperative electrophysiological testing has proven invaluable in reducing the incidence of severe facial nerve injury and may assist in prognosticating long-term function. To the authors' knowledge, no study to date has specifically evaluated functional outcomes among patients with an intact but electrically unresponsive facial nerve.

Study Design: A retrospective chart review was conducted.

Materials and Methods: All patients undergoing VS surgery between 2000 and 2010 at a single tertiary academic referral center were identified. Intraoperative facial nerve testing (minimum proximal threshold and supramaximal stimulation ratios) and definitive facial nerve outcomes were reviewed, and all patients with an anatomically intact but electrically unresponsive facial nerve were included. Data were collected with respect to preoperative, immediate postoperative, and definitive postoperative facial nerve scores using the House-Brackmann facial nerve grading (HBG) system, tumor characteristics, and basic demographic data.

Results: Over the last decade, 350 patients underwent microsurgical resection of VS; of these, 12 patients (median age 49 years, 8 women) met inclusion criteria. The median (mean, range) preoperative, and definitive postoperative facial nerve scores were 1 (1.5, 1–5), and 3 (3.3, 2–5) respectively. All, patients experienced immediate complete facial nerve paralysis following surgery. The median time to definitive facial nerve recovery was 10 months.

Conclusions: Following VS resection, a small subset of patients is left with an anatomically intact but electrophysiologically unresponsive facial nerve. Most patients will recover to a HBG 2 to 4 over a period of approximately 1 year. Although somewhat unpredictable, these outcomes are on par or better than what could be expected with interposition graft or reinnervation techniques. These data can help guide operative decision making and postoperative patient counseling.