Prognostic significance of preoperative electrophysiologic investigation for facial nerve outcome in acoustic neuroma surgery.

The prognostic significance of transcranial magnetic stimulation and nasal muscle F-wave recording to predict postoperative facial nerve function was assessed in 24 patients with unilateral acoustic neuromas (mean diameter, 31 mm) and clinically intact facial nerve function. Latency of F waves and response to cortical magnetic stimulation, as well as F ratios, central motor conduction time, and the ratio of response latency to cortical and cisternal magnetic stimulation were significantly increased. Outcome analysis revealed no significant correlation between preoperative electrophysiologic changes and postoperative facial nerve function. However, a significant correlation with tumor diameter was detected. Thus, acoustic neuroma size seems to be the best predictor of facial nerve function after surgery.