Structural changes in the human brain following vestibular neuritis indicate central vestibular compensation

Vestibular neuritis (VN) is a sudden unilateral vestibular failure (UVF) with a variable course. Caloric hyporesponsiveness often persists, and it is largely unknown why patients with the same degree of hyporesponsiveness show different functional recovery. As the peripheral vestibular deficit alone does not seem to determine functional recovery, it was the aim of this study to elucidate whether structural (morphological) brain changes (1) contribute to central vestibular compensation, and (2) account for the variability of clinical recovery in VN. Structural global gray-matter volume (GMV) changes in 15 VN patients were compared with age-matched controls. Morphometric changes in multisensory vestibular cortices, which may be related to functional disability scores, were hypothesized. Patients were examined with neuro-otological tests and clinical scores to assess vestibular disability. Using voxel-based morphometry (VBM, SPM2), categorical comparison revealed GMV increase in patients' multisensory vestibular cortices [insula, inferior parietal lobe (IPL), superior temporal gyrus (STG)], cerebellum, and motion-sensitive areas in the middle temporal area (MT). GMV decrease was found in the midline pontomedullary junction. Simple regression analysis revealed (1) GMV increase in insula and retroinsular vestibular cortex and STG with improving clinically assessed vestibular deficits, and (2) GMV increase in insula vestibular cortex and STG with improving self-assessed vestibular impairment. For the first time, these data suggest structural cortical plasticity in multisensory vestibular-cortex areas in VN that are related to clinical vestibular function and vertigo. As increase of GMV was related to an improvement of vestibular function, structural alterations may be related to central vestibular compensation.