Case Report: Vestibular cortex morphometry in Usher Syndrome: a case-based study

Background and objectives The vestibular cortex is a critical component of a complex, distributed network supporting balance and spatial orientation. Despite its importance, the impact of vestibular loss on vestibular cortex structure in conditions associated with bilateral vestibular failure remains largely unexplored. Usher Syndrome (USH), a genetic disorder causing deafness, vestibular dysfunction, and visual impairment, offers a unique model to investigate these effects. This study explores the existence of potential changes on vestibular cortex morphometry of two USH patients, one with mild (type 2) (USH2) and the other with severe bilateral vestibular impairment (type 1) (USH1), respectively. Methods One USH1 and one USH2 patient underwent comprehensive evaluations of vestibular function (calorics, video Head Impulse Test (vHIT), Vestibular Evoked Myogenic Potentials (VEMPs), and posturography), auditory function (audiometry), and brain structure using MRI volumetry. MRI was analyzed using the VolBrain platform to quantify gray matter volume (GMV) in regions associated with vestibular function and plasticity (insula, parietal operculum, precuneus, hippocampus, occipital gyrus, lingual gyrus, and cerebellar lobule X). A descriptive analysis of clinical and paraclinical findings was performed. Results USH1 patient exhibited increased GMV in the left precuneus and marked asymmetry index between the right and left posterior insula volume. USH2 patient showed no significant differences in these regions. There was no volume reduction in hippocampal GMV in neither patient, despite the presence of bilateral vestibular loss in USH1. Both patients exhibited reduced GMV in cerebellar lobule X and heterogeneous occipital gyri, asymmetries. Conclusions Vestibular cortex morphometry appears to reflect functional differences between USH subtypes, distinguishing USH1 and USH2. The preserved hippocampal volume in USH1 suggests compensatory neuroplasticity in early-onset deprivation. Heterogeneous visual cortex findings and cerebellar atrophy highlight the complex interplay between multisensory deprivation and brain plasticity and warrants further investigation. This analysis emphasizes the need for an exhaustive evaluation of the impact of multisensory deprivation on the vestibular cortex in a larger number of USH patients in order to support our exploratory data. A clearer understanding of the vestibular network could improve treatment strategies for vestibular disorders, enhancing patient quality of life.