Abstract
Background and Purpose: Hemifacial spasm (HFS) is a rare neuromuscular disorder characterized by unilateral, involuntary, and paroxysmal contractions of orofacial muscles. To elucidate the central neural mechanisms of HFS, we investigated brain gray matter and resting-state functional connectivity (rsFC) in HFS patients.Methods: Thirty patients with HFS and 30 age- and sex-matched healthy participants consented to the study. T1-weighted structural magnetic resonance imaging (MRI) and resting-state BOLD images were collected in all participants. Cortical gray matter thickness was assessed, and subcortical volumetric analysis was performed. Seed-based rsFC analysis was performed on structurally abnormal regions in HFS patients. Post hoc correlations with HFS severity and measures of mood (i.e., depression and anxiety) were performed to characterize rsFC alterations.Results: There were no significant differences in cortical thickness in HFS patients compared to healthy controls. Patients with HFS presented smaller right amygdala volume in contrast to healthy controls (q < 0.05, false-discovery rate corrected). We found that the right amygdala had increased rsFC with bilateral medial prefrontal cortex (mPFC), bilateral orbital frontal cortex (OFC), and left posterior insula (L postIns; voxel-wise p < 0.05, family-wise error corrected). Moreover, the connections of amygdala–postIns and amygdala–mPFC were positively related to HFS severity and anxiety, respectively.Conclusions: This is the first study to show structural and functional brain abnormalities in HFS. The volumetric and rsFC amygdala abnormalities were potentially driven by HFS, providing novel insights into HFS pathophysiology.
Highlights
Hemifacial spasm (HFS) is a neuromuscular movement disorder characterized by unilateral, involuntary, and paroxysmal contractions of the muscles innervated by the facial nerve [1, 2]
The unbiased whole-brain vertex-wise comparison showed no significant differences that survived multiple comparisons (FDR correction of p < 0.05 at a cluster level followed by a cluster-forming threshold of p < 0.001) in patients with HFS compared with healthy controls
The volumetric analysis of subcortical structures showed significantly reduced subcortical volume merely in the right amygdala in patients with HFS compared to healthy controls (q < 0.05, false-discovery rate (FDR) corrected; Figure 1)
Summary
Hemifacial spasm (HFS) is a neuromuscular movement disorder characterized by unilateral, involuntary, and paroxysmal contractions of the muscles innervated by the facial nerve [1, 2]. Surface-based analyses (SBAs) can detect thickness differences in the cortical sheets between patients and healthy controls. This method accounts for interindividual anatomical variability of the cortical surface through gyral and sulcal geometry, which can directly measure cortical thickness and areas with subvoxel precision [10]. This increases the sensitivity to gray matter abnormalities. To elucidate the central neural mechanisms of HFS, we investigated brain gray matter and resting-state functional connectivity (rsFC) in HFS patients
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