Gray matter differences in patients with functional movement disorders

Abstract

Objective: To explore alterations in gray matter volume in patients with functional movement disorders.

Methods: We obtained T1-weighted MRI on 48 patients with clinically definite functional movement disorders, a subset of functional neurologic symptom disorder characterized by abnormal involuntary movements, and on 55 age- and sex-matched healthy controls. We compared between-group differences in gray matter volume using voxel-based morphometry across the whole brain. All participants in addition underwent a thorough neuropsychological battery, including the Hamilton Anxiety and Depression Scales and the Childhood Trauma Questionnaire. To determine whether confounding factors such as comorbid depression, anxiety, or childhood trauma exposure contributed to the observed structural changes, nonparametric correlation analysis was performed.

Results: Patients with functional movement disorders exhibited increased volume of the left amygdala, left striatum, left cerebellum, left fusiform gyrus, and bilateral thalamus, and decreased volume of the left sensorimotor cortex (whole-brain corrected p ≤ 0.05). Volumetric differences did not correlate with measures of disease duration or patient-rated disease severity.

Conclusion: This study demonstrates that patients with functional movement disorders exhibit structural gray matter abnormalities in critical components of the limbic and sensorimotor circuitry. These abnormalities may represent a premorbid trait rendering patients more susceptible to disease, the disease itself, or a compensatory response to disease.

Figure 1. Gray matter differences associated with functional movement disorders (FMDs)

Panels show T1-weighted axial images illustrating regions of increased (A) and decreased (B) gray matter volume in patients with FMD as compared to healthy controls. Group differences are adjusted for differences in age and intracranial volume. p ≤ 0.05, whole brain corrected. Image left is brain right; z coordinates indicated in upper left.

Figure 2. Gray matter differences associated with functional movement disorders (FMDs), female-only cohort

Panels show T1-weighted axial images illustrating regions of increased (A) and decreased (B) gray matter volume in female patients with FMD as compared to healthy controls. Group differences are adjusted for differences in age and intracranial volume. p < 0.05, whole brain corrected. Image left is brain right; z coordinates indicated in upper left.

Figure 3. No effect of laterality of patient symptoms on volumetric findings

(A–H) Dotplot illustrates lack of between-group differences in gray matter volume among patients with functional movement disorders with bilateral, left-lateralizing, and right-lateralizing symptoms.