Clinical-functional dissociation in bilateral vestibulopathy: determinants of disability beyond peripheral vestibular...

Bilateral vestibulopathy (BVP) is characterized by bilateral vestibular hypofunction and classically manifests with oscillopsia and postural instability. However, clinical severity is highly heterogeneous and poorly explained by the magnitude of peripheral vestibular loss alone.

To investigate the relationship between peripheral vestibular dysfunction, integrated postural-control measures, and clinical disability in BVP, and to identify functional determinants of oscillopsia, falls, and disability phenotypes.

In this retrospective multicenter study, 126 patients with definite BVP were included. Audiovestibular assessment comprised pure-tone audiometry, video Head Impulse Testing (vHIT), vestibular-evoked myogenic potentials, dynamic posturography (Sensory Organization Test [SOT], Limits of Stability [LOS]), and dynamic visual acuity (DVA). Patients were stratified into mild, moderate, and severe disability phenotypes based on oscillopsia and falls.

Oscillopsia was associated with reduced semicircular canal function, particularly lateral canal gain (LSC AUC = 0.637, p = 0.004), while DVA showed no consistent discrimination. In contrast, falls were primarily related to impaired postural control, with significant differences in SOT (AUC = 0.676, p = 0.031) and LOS (AUC = 0.699, p = 0.021), but not vHIT or VEMP parameters. Disability phenotypes differed significantly in etiological distribution (p < 0.001), with CANVAS and vestibulotoxicity overrepresented in severe cases, while no major differences were observed in vestibular test profiles across clusters.

In BVP, disability is only partially explained by peripheral vestibular loss. Oscillopsia is more related with canal dysfunction, whereas falls are associated with postural and multisensory impairment. These findings highlight the need for integrated frameworks combining vestibular physiology, compensation, and functional outcomes.