Continuous intraoperative facial nerve monitoring in predicting postoperative injury during parotidectomy.

Abstract

To assess whether the use of continuous intraoperative facial nerve monitoring correlates to postoperative facial nerve injury during parotidectomy. A retrospective analysis. Forty-five consecutive parotidectomies were performed using an electromyograph (EMG)-based intraoperative facial nerve monitor. Of those, 37 had complete data for analysis. Intraoperative findings and final interpretation of the EMGs were analyzed by a senior neurologist and neurophysiologist. All patients were analyzed, including those with preoperative weakness and facial nerve sacrifice. The overall incidence of facial paralysis (House-Brackmann scale > 1) was 43% for temporary and 22% for permanent deficits. This includes an 11% incidence of preoperative weakness and 14% with intraoperative sacrifice. An abnormal EMG occurred in only 16% of cases and was not significantly associated with permanent or temporary facial nerve paralysis (chi, P < 1.0; Fisher's exact P < .68). Of the eight patients with permanent paralysis, only two had abnormalities on the facial nerve monitor. Also, only one of five patients with intraoperative sacrifice of the facial nerve had an abnormal EMG. Factors significantly associated with the incidence of facial paralysis include malignancy, advanced age, extent of parotidectomy, and dissection beyond the parotid gland (chi and Fisher's, P < .05). The results suggest that abnormalities on the intraoperative continuous facial nerve monitor during parotidectomy do not predict facial nerve injury. The incidence of permanent and temporary facial nerve paralysis compare favorably with the literature given that this study includes patients with revision surgery, intraoperative sacrifice, and preoperative paralysis. Standard of care implications will be discussed.