Structural brain alterations in hemifacial spasm: A voxel-based morphometry and diffusion tensor imaging study

Hemifacial spasm (HFS) is characterized by involuntary, irregular clonic or tonic movement of muscles innervated by the facial nerve. We evaluated structural reorganization in brain gray matter and white matter and whether neuroplasticity is linked to clinical features in HFS patients.

High-resolution structural magnetic resonance imaging and diffusion tensor imaging data were acquired by 3.0 T MRI from 42 patients with HFS and 30 healthy subjects. The severity of the spasm was assessed according to Jankovic disability rating scale. Voxel-based morphometry (VBM) and tract-based spatial statistics (TBSS) analysis were performed to identify regional grey matter volume (GMV) changes and whole-brain microstructural integrity disruption measured by fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD).

The VBM analysis showed that patients with HFS reduced GMV in the right inferior parietal lobule and increased GMV in the cerebellar lobule VIII, when compared with healthy subjects. Furthermore, within the HFS disease group, GMV decreased with the disease duration in the right inferior parietal lobule. TBSS did not identify group differences in diffusivity parameters.

While no white matter integrity disruption was detected in the brain of patients with HFS, our study identified evident GMV changes in brain areas which were known to be involved in motor control.

Our results suggest that HFS, a chronic neurovascular conflict disease, is related to structural reorganization in the brain.