Changes in the gray matter volume during compensation after vestibular neuritis: a longitudinal VBM study

Peripheral vestibular dysfunction following vestibular neuritis (VN) often persists but functional recovery of balance can be variable. The authors compared structural changes in the brain before and after post-VN compensation and related it to the functional recovery.

Nine patients diagnosed with unilateral VN were included. Brain MRI and clinical observation were performed within 2 days of acute VN diagnosis and were repeated 3 months after the first exam. Voxel-based morphometry (VBM) analysis for longitudinal data was performed using VBM8 toolbox running within SPM8. Changes in local grey matter volume (GMV) were examined using a paired t-test and clinical relevance was tested using correlation analyses with functional improvement.

Significant increases in GMV were observed in the vestibular cortex, bilateral hippocampus, visual cortices and the cerebellum. GMV decreased in cerebellar regions, including the vermis, and in the prefrontal cortex. Increases in GMV in visual cortices and cerebellum were associated with the poorest recovery of balance, which might be explained by functional substitution.

The structural layout of vestibular compensation suggests that memory and motor planning are closely related to this process. Vision seems to be a major source of functional substitution, as has been previously demonstrated. This study, however, is the first longitudinal analysis of brain structural changes associated with recovery of balance following unilateral VN.