MRI-based measurement of inner ear fluids reveals increased endolymph volume variability in patients with endolymphatic hydrops and hearing instability.

Lack of proven biomarkers for hearing instability (HI) disorders leads to difficulty and delays in diagnosis. Given the association of HI with endolymphatic hydrops (EH), imaging-based techniques for quantification of endolymph and perilymph may be useful for improved clinical management. This study longitudinally characterizes variations in endolymph fluid volume and correlations with hearing changes. This prospective cohort study (2021-2024) followed 14 patients (age 29-73) meeting criteria for HI over 15 months and 12 healthy volunteers (age 22-75). Contrast Enhanced Delayed (CED)-MRI using 3D FLAIR and STIR sequences was performed every 3-6 months, under a deep phenotyping protocol including standard hearing threshold testing. Perilymph and endolymph volumes were quantified using a semi-automatic MRI processing and analysis pipeline. Individual endolymph-to-perilymph (E/P) ratio variance over time was higher in ears with fluctuating hearing and MRI-designated EH (Mann-Whitney U Test: U = 39, 27; p = 0.01, 0.003 respectively). On linear regression, increasing vestibule E/P ratio correlated with worse hearing (Estimate = 45.31, SE = 7.88, p < 0.001) and visit-to-visit change in E/P ratio increased with shifts to worse hearing thresholds (Estimate = 141.84, SE = 45.69, p = 0.003). Longitudinal assessment of HI patient imaging therefore allows detection of quantifiable fluctuations in EH that correlate with hearing changes. This methodology could improve monitoring of HI and evaluation of potential therapies. Trial registration number: NCT04806282.