Otolithic Dysfunction in Normal-Hearing Individuals With Tinnitus

OBJECTIVES: In individuals with normal hearing, tinnitus may be the initial manifestation of cochleovestibular lesions. Tinnitus is a multifactorial symptom arising from complex interactions within the auditory pathway and related neural networks. Anatomically, the auditory and vestibular system is one unit and functions as an integrated whole; therefore, tinnitus should be approached not only from the auditory perspective but also from the vestibular perspective, in particular, the otolith organs. This study aimed to assess the sacculo-collic, utriculo-ocular, and vestibulo-masseteric reflex pathways to investigate potential vestibular involvement in normal-hearing individuals with tinnitus. DESIGN: Two age-matched groups of 35 participants each were included: normal-hearing individuals with unilateral tinnitus (group I) and normal-hearing individuals without tinnitus (group II). In group I, 14 participants had right-ear tinnitus, and 21 had left-ear tinnitus. The mean duration of tinnitus in group I was 16.2 ± 3.2 mo. Around 37.14% of the individuals of group I demonstrated a moderate level of tinnitus-related handicap, and 62.86% exhibited a severe level of handicap, as assessed using the Tinnitus Handicap Inventory. Cervical, ocular, and masseter vestibular evoked myogenic potentials (VEMP) were recorded in all participants in both groups. RESULTS: Response rates for all 3 VEMP modalities were 100% across both groups. No significant interaural differences in amplitude or latency were observed in group II. However, group I showed significantly reduced peak-to-peak amplitudes in tinnitus ears across all three VEMPs, compared with non-tinnitus ears within the same group and with group II. In addition, group I demonstrated significantly higher interaural amplitude asymmetry ratio for all three VEMPs compared with group II. Latency parameters did not differ significantly between groups or between ears within group I. Spearman's rank correlation revealed a significant negative correlation between the duration of tinnitus and tinnitus ear amplitude of all three VEMPs. Also, there was a significant correlation observed between the duration of tinnitus and the interaural amplitude asymmetry ratio obtained using all three VEMPs. CONCLUSIONS: There is an evident abnormality of the peripheral vestibular apparatus in the ears with tinnitus among normal-hearing individuals with tinnitus. Longer duration of tinnitus appears to be linked with progressive peripheral vestibular deterioration in the ear with tinnitus. The present study affirms that the cervical, ocular, and masseter VEMPs can be used as a clinical biomarker to signify the presence of peripheral vestibular abnormality among normal-hearing individuals with tinnitus.