Predictive value of facial nerve F wave in facial paralysis after acoustic neuroma surgery

Objective To investigate the predictive value of preoperative facial nerve F wave in postoperative facial paralysis following acoustic neuroma surgery. Methods A retrospective analysis was conducted on 37 patients with unilateral cerebellopontine angle acoustic neuroma without facial paralysis admitted to Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University from January 2016 to January 2017. The latency parameters of facial nerve F wave in healthy and affected sides were measured before operation. Facial nerve function was evaluated based on the House-Brackmann (H-B) grading system at 12 months post surgery. Patients with Grade Ⅲ-Ⅵ were categorized into postoperative facial paralysis group (8 cases) and those with Grade Ⅰ was classified as postoperative non-facial paralysis group (29 cases). The preoperative F wave latency, F-M wave latency, F wave side-to-side difference, and F-M wave side-to-side difference were compared between the 2 groups. The operating characteristic curve (ROC) was plotted and the area under the curve (AUC) was calculated to evaluate the predictive value of F wave of facial nerve before operation in postoperative facial paralysis. Results The latency of F wave and F-M wave on the affected side was longer than that on the affected side (both P<0.05). The latencies of F wave and F-M wave on the affected side in the facial paralysis group were longer than that in the non-facial paralysis group (both P<0.05), and the latencies of F wave and F-M wave side-to-side difference in the facial paralysis group were larger than those in the non-facial paralysis group (both P<0.05). The preoperative F-wave latency, F-M wave latency, F-wave latency side-to-side difference and F-M wave latency side-to-side difference could be used to predict the H-B grade of facial nerve after operation (AUC: 0.813, 0.920, 0.793 and 0.996, respectively, all P<0.05). Conclusion The latency and latency side-to-side difference of F wave and F-M wave of preoperative facial nerve in patients with acoustic neuroma seem to be able to predict the risk of postoperative facial paralysis. Key words: Neuroma, acoustic; Facial nerve; Facial paralysis; Latency of F-wave