INTRAOPERATIVE FACIAL-NERVE MONITORING - ITS PREDICTIVE VALUE AFTER SKULL BASE SURGERY

Purpose: Facial nerve monitoring can be used to predict post-operative facial function after skull base surgery. In this study three methods of prediction of facial function were compared. These methods utilize various parameters of the evoked electromyographic monitoring. Materi al and methods: Twenty-three patients who underwent surgery for skull base diseases were retrospectively reviewed. Amplitude of ongoing elec tromyographic activity, stimulation current thresholds and amplitude o f evoked response were analysed. The predictive value of the three met hods was correlated with post-operative facial nerve function. Results : The method that used only the stimulation thresholds predicted the f inal post-operative facial function in 86.9 per cent of the patients. The second employed a mathematical ratio which combined the amplitude of evoked response and the stimulation current thresholds and confirme d the prediction of the facial function in 91.3 per cent of the patien ts. The last method does not consider the stimulation thresholds great er than 0.05 mA and failed to predict the final VIIth nerve function i n patients in whom the stimulation was greater than 0.05 mA. Conclusio n: Analysis of prognostic value demonstrates that the first two method s had the smaller degree of variation showing the better sensitivity.