Intraoperative evoked facial muscle responses and recovery process of the facial nerve in acoustic neuroma surgery

The prognostic value of intraoperative evoked facial muscle responses (EFMR ) was studied and correlated with the recovery process of the facial nerve during a follow-up period of 18 months. The patients were classified into f our groups according to EFMR amplitudes, group A (150 mu V or greater, 190. 8,SD28.9 mu V, n=24), group B (100-149 mu V, 125.7, SD14.3 mu V, n=14), gro up C (50-99 mu V, 79.0, SD17.0 mu V, n=13) and group D (less than 50 mu V, 22.1, SD13.3 mu V, n=15). Significant improved facial function appeared at 3 months after the operation in group A, at 6 months in group B, at 9 month s in group C and at 12 months in group D. The early postoperative facial fu nction and facial outcome of groups A and B were significantly better than those of groups C and D. Our data revealed that the intraoperative EFMR amp litudes have more prognostic value in predicting the recovery process of th e nerve than functional outcome.