Intracortical inhibition of the motor cortex is normal in chorea

Intracortical inhibition of the motor cortex was investigated using a paire d pulse magnetic stimulation method in 14 patients with chorea caused by va rious aetiologies (six patients with Huntington's disease, one with chorea acanthocytosis, a patient with systemic lupus erythematosus with a vascular lesion in the caudate, three with senile chorea and three with chorea of u nknown aetiology). The time course and amount of inhibition was the same in the patients as in normal subjects, suggesting that the inhibitory mechani sms of the motor cortex studied with this method are intact in chorea. This is in striking contrast with the abnormal inhibition seen in patients with Parkinson's disease or focal hand dystonia, or those with a lesion in the putamen or globus pallidus. It is concluded that the pathophysiological mec hanisms responsible for chorea are different from those producing other inv oluntary movements.