Electrodiagnostic Testing in Acute Facial Palsy: Outcomes and Comparison of Methods

Abstract Objective To study the relationship between various electrodiagnostic modalities in acute facial palsy. Setting Academic tertiary care center. Patients One‐hundred and six patients who presented with traumatic or non‐traumatic acute facial paralysis (House‐Brackmann, HB, grade 6/6) between 2008 and 2017 and underwent acute electrodiagnostic testing. Intervention Electroneurography (ENoG) using nasolabial fold (NLF) or nasalis muscle (NM) methods, and volitional electromyography (EMG) in all patients. Main outcome measures Percent degeneration of ipsilateral facial nerve compound muscle action potentials (CMAP) on NLF‐ and NM‐ENoG, presence or absence of muscle unit potentials (MUPs) on EMG. Results Extent of facial nerve degeneration measured by NLF‐ and NM‐ENoG were highly correlated (r = 0.85, P < .01) on each test and on serial testing. NLF‐ and NM‐ENoG concordantly diagnosed ≥90% degeneration in 44 patients (80%), of whom 32 patients were diagnosed to have 100% degeneration by both methodologies. Absence of MUPs on EMG was 63% sensitive and 92% specific for ≥90% degeneration on ENoG, with a positive predictive value of 90%. For patients with Bell's palsy, percent degeneration on ENoG was also correlated to HB score at 1 year. Surgical decompression resulted in mean HB scores of 2.2 and 3.0 for patients with Bell's palsy and trauma, respectively. Conclusions NM‐ENoG may be a valid and comparable method to NLF‐ENoG for predicting the recovery of facial nerve function in acute paralysis. Absence of MUPs on EMG is a specific measure of severe degeneration and highly predictive of candidacy for surgical decompression. Level of evidence Level 3.