Current state of intraoperative neuromonitoring of the facial nerve during skull base surgery: A systematic review.

Intraoperative neuromonitoring of the facial nerve (cranial nerve VII) is critical during skull base surgery due to the nerve's proximity to surgical pathologies and the significant morbidity associated with a facial nerve injury. Objective: This systematic review aims to summarize and describe the numerous intraoperative neuromonitoring techniques available to the skull base surgeon for identification, preservation, and prognostication of facial nerve function during skull base surgery. A systematic review was performed in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) checklist. Terms related to related to intraoperative neuromonitoring of the facial nerve and the skull base were searched on PubMed/MEDLINE, Embase via Elsevier, and the Web of Science Core Collection via Clarivate databases. Title/abstract and full-text screening was performed by two reviewers. Data on monitoring type, pathology, and surgical approach were collected. The review identified commonly utilized neuromonitoring methods including free-running and stimulated facial nerve electromyography (FEMG), facial corticobulbar motor evoked potentials (FCoMEP), abnormal muscle responses (AMR), and the blink reflex. Less frequently discussed methods were also identified such as the Z-L response. FEMG was the most commonly reported modality, described in 80.50 % of studies, followed by FCoMEPs (25.86 %) and AMR (21.26 %). Each technique demonstrated unique strengths and limitations regarding specificity, sensitivity, and integration into surgical workflow. This systematic review underscores the importance of a multidisciplinary and standardized approach in facial nerve IONM, emphasizing continued collaboration among surgeons, neurophysiologists, and anesthesiologists to enhance patient safety and surgical outcomes.