Clinical Value Of Multimodality Intraoperative Monitoring For Facial Nerve And Prognosis Evaluation In Large Acoustic Neuroma

Objective To explore the clinical significance of intraoperative facial nerve monitoring for facial nerve preservation during the acoustic neuroma surgery and its evaluation for prognosis. Methods The Nicolet Endeavor-CR16 facility was used to observe the free-running and stimulus-triggered electromyography of facial nerve in 26 cases of large acoustic neuroma. When the neuroma was cut off, the brainstem of facial nerve was stimulated with various stimulating intensity to observe the trigged EMG. Facial nerve function was assessed using the H-B facial nerve grading system after surgery for two weeks and 6-12 months. Spearman rank correlation test was used to analyze the relationship between stimulating intensity at the end of the surgery and facial nerve function grade. Results The facial nerve was preserved anatomically in 25 patients. According to the H-B facial nerve grading system, 18 cases (70%) got preservation of facial nerve function in gradeⅠ～Ⅱ. When stimulating brainstem end after the total resection of tumor, stimulating intensity was positively correlated with H-B score at month 6-12 after surgery. Conclusion Combination of the triggered EMG with free-running EMG when stimulating from the distal to the proximal and from the strong to the weak can help to precisely locate the facial nerve and avoid its injury. Stimulate at the exit of facial nerbe from brainstem can predict acute and final facial nerve function following acoustic neuroma resection.