Motor circuit gray matter changes in idiopathic cervical dystonia

Idiopathic cervical dystonia (ICD), the most common adult-onset focal dystonia, is clinically characterized by involuntary uni- or bilateral contractions of head and neck musculature. One crucial criterion for the diagnosis of ICD is normal results on MRI of the brain. To test the hypothesis whether subtle brain structure changes occur in ICD. Using voxel-based morphometry, the authors compared the brain structure of 10 patients with ICD with that of 10 healthy sex- and age-matched controls using high-resolution MRI. Patients with ICD showed an increase in gray matter density bilaterally in the motor cortex and in the cerebellar flocculus and unilaterally in the right globus pallidus internus. In addition, a decrease in gray matter density was observed in the right caudal supplementary motor area as well as in the right dorsal lateral prefrontal and visual cortex. These results demonstrate for the first time in vivo subtle morphologic alterations in ICD. These data challenge the principal concept that patients with ICD have no brain structure abnormalities and that this movement disorder is solely due to abnormal cerebral function.