Prediction of long-term facial nerve outcomes with intraoperative nerve monitoring

Objective: Evaluate the utility of a statistical equation using two independent intraoperative monitoring parameters in predicting long-term facial nerve function. Study Design: Retrospective case review. Setting: Tertiary care hospital. Patients: Sixty patients undergoing resection of vestibular schwannomas with intraoperative facial nerve monitoring at a single institution. Intervention: All patients underwent microsurgical resection of vestibular schwannomas with the use of intraoperative cranial nerve monitoring. Main Outcome Measure: Final facial nerve outcome measured using the House-Brackmann scale at least 6 months after microsurgical resection. Results: Five out of 60 (8.3%) patients demonstrated significant long-term weakness (i.e., House-Brackmann grade III or worse). Intraoperative monitoring parameters (proximal stimulation threshold, proximal-to-distal response amplitude ratio) were accurate in predicting increased risk of long-term facial nerve dysfunction when used in a logistic regression model. A Student's t test confirmed the equation result was statistically significant in differentiating long-term facial nerve outcomes. Conclusion: Patients with immediate weakness are at higher risk of having long-term poor facial nerve function. The use of intraoperative monitoring parameters was reliable in predicting facial nerve outcomes. Patients with permanent facial nerve dysfunction often require rehabilitative procedures. The ability to predict facial nerve outcomes with intraoperative monitoring may allow early rehabilitative procedures to improve quality of life and prevent ocular complications.