The study on intraoperative monitoring of cranial nerve in large acoustic neuroma

Objective To study the effect of continuous EMG monitoring of facial muscle on the neural anatomy and function reserving of facial nerve during and after operation. Methods A total of 100 patients with acoustic neuroma were enrolled in this study. According to Gormley's classification of intracranial tumor, in 100 patients the diameters of acoustic neuromas were 4.0-4.9 cm (82 cases), 5.0-5.9 cm (16 cases) and ≥ 6.0 cm (2 cases). Preoperative evaluation with House facial nerve function scale demonstrated there were Grade Ⅰ 65 cases, Grade Ⅱ 33 cases and Grade Ⅲ 2 cases. These patients were performed microsurgical resection of tumor via retrosigmoidal approach, direct electric stimulus and monitoring the facial nerve EMG during operation. Results In the 100 patients there were total or subtotal resection of tumor in 94 cases and more than half resection of tumor in 6 cases. The facial nerves were cut off during resection of tumors in 2 patients and then end to end anastomosis were performed at the same time. In another 2 patients their facial nerve were cut off about 1/2 then the breaking end anastomosis were performed. Postoperative two weeks, the evaluation of facial nerve function demonstrated that there were Grade Ⅰ 30 cases, Grade Ⅱ 50 cases, Grade Ⅲ 10 cases and Grade Ⅴ 10 cases. There were Grade Ⅰ 76 cases, Grade Ⅱ 14 cases, Grade Ⅲ 7 cases and Grade Ⅴ 3 cases in facial nerve function 1 year postoperative following up. Conclusion It is demonstrated the intraoperative monitoring of facial nerve function with EMG during surgical treatment of large size acoustic neuroma is significantly effective in anatomical and functional preserving for facial nerve.