BACKGROUND: Structural abnormalities were detected in bilateral primary sensorimotor areas in writer's cramp. Evidence in other primary dystonia, including blepharospasm and cervical dystonia, suggest that structural abnormalities may be observed in other brain areas such as the cerebellum in writer's cramp. OBJECTIVE: To test the hypothesis that structural abnormalities are present along the sensorimotor and cerebellar circuits in patients with writer's cramp. METHODS: Using voxel-based morphometry, the authors compared the brain structure of 30 right-handed patients with writer's cramp with that of 30 healthy control subjects matched for gender, age, and handedness. RESULTS: Gray matter decrease was found in the hand area of the left primary sensorimotor cortex, bilateral thalamus, and cerebellum (height threshold p < 0.01, cluster significant at p < 0.05 corrected for multiple comparisons). CONCLUSIONS: These results demonstrate in writer's cramp the presence of structural abnormalities in brain structures interconnected within the sensorimotor network including the cerebellum and the cortical representation of the affected hand. These abnormalities may be related to the pathophysiology of writer's cramp, questioning the role of the cerebellum, or to maladaptive plasticity in a task-related dystonia.