Facial Nerve Function Afier Cerebellopontine Angle Surgery and Prognostic Value of Intraoperative Facial Nerve Monitoring: A Critical Evaluation Giuseppe Magliulo, MD, and Francesco Zardo Purpose: Facial nerve monitoring is often used to predict postoperative facial function after acoustic neuroma tumor removal. In this study, three methods of predicting facial nerve function were compared. These methods used various parameters of the evoked electromyo- graphic monitoring. Materials and Methods: Thirty-four patients who underwent surgery for acoustic neuroma were retrospectively reviewed. Amplitude of ongoing electromyographic activity, stimulation current thresholds, and the amplitude of evoked response were analyzed. The predictive value of the three methods was compared with actual postoperative facial nerve function. Results: One method predicted the final postoperative facial function in 90% of the patients, one method in 84%, and the final method failed to predict the final Vllth nerve function in patients with current stimulation thresholds greater than 0.05 mA. Conclusion: Analysis of prognostic value showed that one of the three studied proved superior in predicting facial nerve function. Copyright 0 1998 by W.B. Saunders Company. Intraoperative facial nerve monitoring is an additional tool to aid facial nerve preserva- tion. It has proven to be useful, as objectively verified in numerous studies, in the manage- ment of posterior fossa lesions, particularly when the facial nerve is involved and dis- torted.1-*5 Facial nerve monitoring is also used to predict neural integrity at the end of the operation. Review of the available literature shows that few reports have been published on this spe- cific topic. Kirkpatrick et all6 identified a group of patients with small acoustic neuro- mas in whom the final postoperative facial function could be predicted using facial nerve stimulation at the end of operation. They failed to make reliable predictions in a group of large tumors. It is interesting to note, how- ever, that they did not correlate the thresholds or other parameters of the stimulation with the postoperative facial outcomes. Beck et all7 analyzed intraoperative facial From the IV Ear, Nose, and Throat Clinic, Universiti+ “La Sapienza,” Rome, Italy. Address reorint reouests to Giuseppe Maqliulo, MD, via Gregorio 31180, Odl65 Roma, ltali.’ - Copyright o 1998 by W.B. Saunders Company 0196-0709/98/l 902-0005$8.00/O nerve activity using various parameters: (1) a fixed threshold of stimulation at 0.05 mA; (2) an amplitude of facial muscle response; and (3) ongoing electromyographic activity. They observed that excellent immediate facial nerve results (postoperative grade I or II) were linked to an ongoing activity of less than 500 FV and having at least a 500 PV contraction. Berges et al I8 devised a mathematical ratio using the thresholds and amplitudes of stimu- lation. This ratio showed a significant prognos- tic value. Silverstein et alI9 measured the thresholds of stimulation necessary to evoke facial con- traction. They identified a strict relationship between the stimulation thresholds and VIIth nerve function, and concluded that the predic- tion of facial outcome can be based on intraop- erative threshold testing. The purpose of this report is to compare the accuracy of the methods proposed by Beck et a1,17 Berges et al,l* and Silverstein et all9 in predicting the postoperative facial function after surgery of the cerebellopontine angle for acoustic neuroma tumor. This study reviews 34 cases that focus on the effectiveness of each method and evaluates their specific sensitivity. 102 American Journal of Otolatyngology, Vol 19, No 2 (March-April), 1998: pp 102-l 06