Supramaximal stimulation during intraoperative facial nerve monitoring as a simple parameter to predict early functional outcome after parotidectomy.

CONCLUSION

A supramaximal stimulation at 2 mA during intraoperative electromyographic (EMG) facial nerve monitoring appears to be a simple and effective parameter to predict immediate postoperative injury.

OBJECTIVES

To assess the role of systematic intraoperative facial nerve monitoring in predicting the early functional outcomes obtained after parotidectomy.

METHODS

Data were collected from patients who underwent parotidectomy. Intraoperative EMG monitoring of the facial nerve was performed by registering two parameters, event intensity (>100 μV) and amplitude of response after a supramaximal stimulation at 2 mA, at the beginning and end of gland removal. Early postoperative clinical functional facial nerve disorder was assessed at day 2.

RESULTS

Overall, 50 patients were included and an early facial dysfunction was detected in 27 cases (54%). The maximal response amplitude after supramaximal stimulation at the trunk of the facial nerve was higher in patients with normal facial function compared with those with poor outcomes at the end of surgery (p < 0.01). The postdissection to predissection ratios of maximal response amplitude, but not the stimulation thresholds, were indicative of a nerve conduction block and were significantly lower in the patient group with a poor outcome compared with the group with a normal facial outcome (p < 0.02).