Decoding the bilateral vestibulopathy spectrum: etiology-based phenotypes, clinical profiles and pathways to implant candidacy.

INTRODUCTION

Bilateral vestibulopathy (BVP) is a chronic, disabling disorder characterized by bilateral loss of vestibular function, leading to imbalance, oscillopsia, and falls. Despite established diagnostic criteria, clinical expression and rehabilitation potential vary widely across etiologies. Understanding these functional signatures is crucial for tailoring future neurostimulation strategies. The main objective of this study is to decode the etiological and functional heterogeneity of BVP and define clinical-functional profiles guiding vestibular or cochleo-vestibular implant candidacy.

METHODS

A multicenter retrospective study included 119 adults fulfilling Bárány Society criteria for definite BVP (>1 year). Comprehensive audiovestibular testing comprised pure-tone audiometry (PTA), video head impulse test (vHIT), vestibular evoked myogenic potentials (VEMPs), and dynamic posturography (SOT, LOS). Group comparisons used Kruskal-Wallis and Dunn-Bonferroni tests; oscillopsia predictors were analyzed by binary logistic regression.

RESULTS

Etiologies included idiopathic (29.41%), Ménière's disease (26.89%), iatrogenic (18.49%), post-infectious (14.29%), cerebellar ataxia/CANVAS (6.72%), and post-traumatic (4.20%). Oscillopsia was reported by 48.74% and falls by 22.69%. Significant inter-etiological differences were found for semicircular canal gains (p < 0.001), with idiopathic and Ménière phenotypes showing higher vHIT gains and CANVAS/vestibulotoxic forms the lowest. IAAR-VEMP amplitudes were higher in idiopathic and Ménière groups than in CANVAS and vestibulotoxic etiologies (p < 0.01). Posturography differed across groups (SOT p = 0.007; LOS p = 0.010), CANVAS showing the poorest stability. Logistic regression identified reduced VOR gain in both the lateral and posterior semicircular canals as significant predictors of oscillopsia (LSC: right OR 0.185, p = 0.036; left OR 0.149, p = 0.035; PSC: right OR 0.167, p = 0.043; left OR 0.182, p = 0.047), together with an increased right PR index (OR 1.045, p = 0.010). Fourteen patients (11.76%) were qualified for cochleo-vestibular and the same amount for vestibular implant candidacy.

CONCLUSION

BVP comprises etiology-specific phenotypes. Oscillopsia is driven mainly by VOR performance and PR index in LSC. Integrating auditory status, canal-otolith function, and compensation quality supports precision selection for vestibular versus cochleo-vestibular implantation.