Iatrogenic Facial Nerve Injury in Head and Neck Surgery in the Presence of Intraoperative Facial Nerve Monitoring With Electromyography: A Systematic Review

The facial nerve is the seventh of 12 cranial nerves found in the head and neck region that facilitates several nerve fibers and pathways to perform various functions. Iatrogenic facial nerve injury during surgeries of the head and neck is common, ranging from 4-6%, particularly in procedures that involve mobilization or resection of associated anatomical structures. Any injury to the facial nerve or its branches impacts the quality of life and patient satisfaction as the degree of iatrogenic injury may result in partial or complete facial nerve paralysis. Of the various implementable techniques available to avoid injury, electromyography (EMG) has recently been widely used to monitor facial nerve function intraoperatively to determine the degree of injury and predict postoperative weakness. The purpose of this study was to analyze and review existing scientific literature in determining the role of intraoperative facial nerve monitoring (IFNM) with EMG in decreasing the incidence and degree of intraoperative facial nerve injury among commonly performed surgeries involving the facial nerve.A systematic review was conducted from articles published between September 2006 and December 2022. Suitable articles were identified from the MEDLINE/PubMed databases using relevant terms to meet the inclusion criteria. Articles were subsequently coded based on the inclusion/exclusion criteria as well as the type of surgery performed with concurrent use of EMG and the results from intraoperative monitoring. A total of 47 articles were found in relation to the use of IFNM, including studies to reduce the incidence and determine preventative measures to decrease nerve injury. Eleven articles were used to evaluate the use of EMG during various head and neck surgeries in decreasing the incidence of intraoperative facial nerve injury.Sources found were primarily divided based on the type of surgery performed when determining the use of EMG. Four sources tested the efficacy of EMG during parotidectomy, four sources during vestibular schwannoma resection, two sources during cochlear implant surgeries, and one during a lymphatic malformation surgery. IFNM also decreased the duration of surgery, the severity of facial nerve palsy, and the average time of facial nerve paralysis recovery. IFNM was found to not significantly predict facial nerve injury in the setting of intraoperative nerve injury but tended to preserve potential facial nerve function in vestibular schwannoma cases.The surgical setting determined the efficacy and use of IFNM in decreasing the incidence of facial nerve weakness and paralysis. IFNM had the best preventative and prognostic value when used in vestibular schwannoma resection, and the least in cochlear implants, with mixed evidence seen in the setting of parotidectomy. Overall, IFNM using EMG as an adjunct during surgery may reduce the risk of iatrogenic injury; however, additional studies must be performed to determine the degree of long-term patient satisfaction and quality of life achieved in the setting of IFNM.