Does endolymphatic hydrops affect cochlear and vestibular nerve volumes? An MRI-based morphometric study

Objective To investigate the relationship between the severity of endolymphatic hydrops (EH) and volumetric changes in cochlear and vestibular nerves using high-resolution MRI, and to assess associations with clinical audiovestibular symptoms. Methods A cohort of 108 patients with clinically and radiologically confirmed EH underwent 3 T MRI to obtain volumetric measurements of the cochlear and vestibular nerves. Nerve volumes were compared across EH grades using non-parametric statistics. Cochlear nerve volumes in affected and unaffected ears were compared in a subgroup with unilateral hearing loss. Associations between EH severity and symptoms (hearing loss, vertigo, tinnitus, aural fullness) were evaluated. Results Cochlear nerve volumes did not differ significantly between EH grades ( p = 0.057), with a nonsignificant tendency toward larger volumes in mild EH that did not survive correction for multiple testing. Vestibular nerve volumes did not differ significantly by vestibular EH grade ( p = 0.64). Comparisons of cochlear nerve volume between affected and unaffected ears in patients with unilateral hearing loss also showed no significant differences ( p = 0.56). EH severity was not significantly associated with prevalence of hearing loss, vertigo, tinnitus, or aural fullness. Conclusion EH severity does not significantly affect cochlear or vestibular nerve volumes measurable by MRI, nor does it strongly correlate with prevalence of clinical symptoms. These findings indicate that volumetric MRI, while reproducible and feasible, may have limited sensitivity as an imaging biomarker of EH. This underscores the need to explore alternative MRI-based structural or functional markers in future multimodal and longitudinal studies.