Exploring the Functioning of the Vestibulo-Masseteric Reflex Pathway in Individuals with Vestibular Neuritis

Background: Vestibular neuritis, typically caused by viral infections, is an inflammation of the vestibular nerve characterized by sudden onset of vertigo, nausea, and vomiting, without associated hearing loss or central nervous system involvement. Although vestibular function in vestibular neuritis has been extensively evaluated using conventional vestibular assessment tools, the role of masseter vestibular evoked myogenic potentials (mVEMP), a relatively novel measure reflecting the vestibulo-masseteric reflex, remains underexplored. Purpose: The purpose of the study was to investigate the vestibulo-masseteric reflex pathway in individuals with vestibular neuritis and to determine whether a significant correlation exists between cervical vestibular evoked myogenic potential (cVEMP), ocular vestibular evoked myogenic potential (oVEMP), and mVEMP responses. Research Design: The study followed a cross-sectional design. Study Sample: The study included 30 ears from individuals diagnosed with vestibular neuritis and 30 ears from age-matched healthy controls (20–60 years of age). Participants underwent thorough audio-vestibular evaluations that included recordings of 500-Hz evoked cVEMP, oVEMP, and mVEMP. Data Collection and Analysis: The cVEMP, oVEMP, and mVEMP responses were analyzed for absolute peaks, absolute peak latencies, peak-to-peak amplitudes, and interaural amplitude asymmetry ratios. Results: The mVEMP response rate in individuals with vestibular neuritis was 73 percent, whereas cVEMP and oVEMP response rates were 40 percent and 62.5 percent, respectively; in contrast, the controls demonstrated a 100 percent response rate for cVEMP, oVEMP, and mVEMP. There was no significant correlation observed between mVEMP and cVEMP responses (p > 0.05) or between mVEMP and oVEMP responses (p > 0.05). Furthermore, patients with vestibular neuritis displayed lower peak-to-peak mVEMP amplitudes, likely indicating compromised neural transmission due to inflammation. Conclusions: The observed dissociation between mVEMP and both cVEMP and oVEMP responses in vestibular neuritis supports the hypothesis that mVEMP is generated through a distinct neural mechanism, despite a potentially common otolithic origin. Clinical Relevance Statement: This study highlights the complexity of vestibular innervation and suggests that mVEMP may serve as a complementary diagnostic tool in evaluating vestibular pathologies. Further research is warranted to delineate the specific neural mechanisms underlying VEMP responses.