Relationship and influencing factors between the amplitude change of supramaximal facial nerve stimulation during acoustic neuroma removal and facial function outcome

Abstract

To investigate the relationship between the amplitude change of supramaximal facial nerve stimulation during acoustic neuroma removal and facial function outcome, and discuss its influencing factors. Retrospective study of 34 acoustic neuroma patients. Intraoperative amplitude by supramaximal stimulation, facial function outcome, tumor size, surgical approach, facial nerve course pattern, and tumor cystic status, as well as tumor adhesion degree were collected and analyzed by SPSS 17.0. Acoustic neurnomas were removed in all 34 patients without intra- and postoperative complications, the facial nerve were all anatomically preserved. Two weeks later, 5 cases showed facial function HB Grade Ⅰ, 13 HB Ⅱ, 11 HB Ⅲ and 5 HB Ⅳ. The amplitude changes under supramaximal stimulation after tumor removal were 12.9%-100%, average (63.9±25.7)%. The facial function outcomes were poor (HB Ⅳ) in the cases whose intraoperative amplitude decreases were more than 70%. Different postoperative facial function group showed significantly different intraoperative amplitude changes (F=7.585, P=0.001), except HB Ⅰ group and HB Ⅱ group. The existence of cystic degeneration showed strong correlation (r=-0.635) to the amplitude changes, the level of tumor adhesion showed moderately negative correlation (r=-0.455), and tumor size showed weak negative correlation (r=-0.292), surgical approach and the facial nerve course pattern were not statistically relevant. The amplitude change of facial nerve supramaxial stimulation can predict the postoperative facial function. The amplitude change is valuable for early treatment of facial nerve damage.