Problems and solutions of intraoperative facial nerve electrophysiologic monitoring for acoustic neuroma

Objective To explore the solutions to some problems of intraoperative facial nerve monitoring during operation for acoustic neuroma and evaluate the function of anatomically preserved facial nerve. Methods The tumors were resected with suboccipital retrosigmoid approaches under microscope in 25 cases. Intraoperative monitoring was used to protect facial nerve and evaluated its function. Results Total removal was achieved in 25 patients( 100% ). The facial nerve was preserved anatomically in 23 cases(92% ),H - B Grade Ⅰ～Ⅱ in 19 cases, Grade Ⅲ～Ⅳ in 5, Grade Ⅴ～Ⅵ in 1. Stimulative intensity at the end of tumor resection was related to the function of facial nerve, and the lower was the better. The function of facial nerve might be Ⅰ～Ⅱ grade when stimulative intensity was lower than 0. 5 mA, and facial electromyograph response amplitudes was greater than 100 μV. The function of facial nerve was not ideal when stimilative intensity was above 2 mA and response amplitude was not clear. Conclusions Skilled technique of intraoperative facial nerve electrophysiologic monitoring can obviously increase the rate of anatomical and functional preservation of facial nerve, and quantitative analysis of electromyogram may help to evaluate its postoperative function. Key words: Neuroma, acoustic;  Facial nerve;  Electrophysiologic monitoring;  Neurosurgical procedures