Intra-Operative Facial-Nerve Monitoring in Total Parotidectomy: A Retrospective Cohort Analysis of Nerve Preservation...

The research evaluated IONM's impact on postoperative results for patients who underwent total parotidectomy while creating an operational system to detect patients who would experience early facial weakness. The research team analyzed 38 patients who received total parotidectomy surgery at a tertiary cancer center from January 2019 through December 2024. The majority of patients underwent IONM monitoring through a four-channel electromyography system. The House-Brackmann (HB) grading scale evaluated facial nerve function at three time points: 24 h after surgery and at 1 month and 6 months postoperatively. The researchers used logistic regression to identify early facial weakness predictors which they used to develop a three-tier bedside risk score. The patient population had an average age of 45.1 years with a male-to-female ratio of 52%. The initial examination revealed that 42% of patients had HB grade ≥ III weakness but 92% of these patients recovered their strength by the third month and 3 patients (7.9%) maintained palsy. The factors that predicted day-1 paresis included longer nerve identification time and EMG amplitude drop ≥ 0.2 mA and malignant histology. EMG drop emerged as the most significant independent factor that predicted the outcome. The developed score enabled the classification of patients into three risk categories with strong predictive accuracy (AUC 0.84). IONM improves surgical safety but does not eliminate the risk of temporary paresis. The proposed risk score offers a simple tool to guide decisions and patient counseling, especially in resource-limited oncology settings.