Correlation between Electrophysiological Change and Facial Function in Parotid Surgery Patients.

Feng-Yu Chiang,Tzer-Zen Hwang,Chien-Chung Wang,I-Cheng Lu,Tzu-Yen Huang,Pi-Ying Chang,Yi-Chu Lin,Chih-Chun Wang,Che-Wei Wu,Ching-Feng Lien

doi:10.3390/jcm10245730

Abstract

This observational study investigated intraoperative electrophysiological changes and their correlation with postoperative facial expressions in parotidectomy patients with visual confirmation of facial nerve (FN) continuity. Maximal electromyography(EMG) amplitudes of the facial muscles corresponding to temporal, zygomatic, buccal and mandibular branches were compared before/after FN dissection, and facial function at four facial regions were evaluated before/after parotidectomy in 112 patients. Comparisons of 448 pairs of EMG signals revealed at least one signal decrease after FN dissection in 75 (67%) patients. Regional facial weakness was only found in 13 of 16 signals with >50% amplitude decreases. All facial dysfunctions completely recovered within 6 months. EMG amplitude decreases often occur after FN dissection. An amplitude decrease >50% in an FN branch is associated with a high incidence of dysfunction in the corresponding facial region. This study tries to establish a standard facial nerve monitoring (FNM) procedure and a proper facial function grading system for parotid surgery that will be useful for the future study of FNM in parotid surgery.

Highlights

Facial dysfunction caused by facial nerve (FN) injury is a common and serious complication after surgery for parotid tumors
When facial nerve monitoring (FNM) is applied in parotid surgery, EMG is used as a diagnostic technique to assess the function of facial muscles and the corresponding FN
Measurements of EMG amplitude may correlate with the number of motor units that contribute to polarization [26,27]

Summary

Introduction

Facial dysfunction caused by facial nerve (FN) injury is a common and serious complication after surgery for parotid tumors. FN injury can cause facial asymmetry, mastication difficulty, drooling, and corneal ulceration. These dysfunctions have severe impacts on the patients’ quality of life and might lead to medical legal litigation. To preserve FN function, identifying the main trunk of the FN and meticulously dissecting the FN branches are standard procedures in parotid surgery. Unrecognized nerve injury during FN dissection and unexpected postoperative facial dysfunction or weakness can occur even when anatomical integrity of FN continuity is confirmed intraoperatively

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Conclusion