Differences in vestibulo-ocular reflexes between vestibular neuritis and labyrinthitis

Objective: To expand our understanding of the pathophysiological mechanisms underlying vestibular neuritis and labyrinthitis by identifying any difference in the vestibulo-ocular reflex for each semicircular canal.Study Design: Retrospective analysis.Setting: The Department of Otorhinolaryngology - Head and Neck Surgery, Chosun University Hospital, from January 2015 to December 2021.Methods: We included 23 vestibular neuritis and 27 labyrinthitis patients who had been hospitalized. Pure-tone audiometry, a bithermal caloric test, and a video head-impulse test were performed within 5 days of symptom onset.Results: In the vestibular neuritis group, mean vestibulo-ocular reflex gains were decreased to 0.51 in the ipsilesional horizontal canal and 0.55 in anterior canal, lead-ing to marked asymmetry, whereas the gain of the ipsilesional posterior canal was rel-atively preserved at 0.85. In the labyrinthitis group, the mean vestibulo-ocular reflex gain was 0.72 in the ipsilesional horizontal canal, 0.73 in the ipsilesional anterior canal, and 0.55 in the ipsilesional posterior canal. We observed statistical differences in the vestibulo-ocular reflex gain and incidence of corrective saccades on the ipsile-sional side in three semicircular canals between the groups (p = .002 for horizontal canal, p = .003 for anterior canal, and p < .001 for posterior canal). The receiver operating characteristic curve showed that pure-tone audiometry, ipsilesional poste-rior canal gain, and gain asymmetry of posterior canal were excellent parameters for distinguishing labyrinthitis from vestibular neuritis.Conclusion: Vestibular neuritis and labyrinthitis patients have different degrees and patterns of video head-impulse test involvement in the three semicircular canals, sug-gesting that the two distinct disorders may have different etiologies.