Electromyographic silent period after transcranial brain stimulation in Huntington's disease.

The silent period evoked by transcranial (TCS) and nerve stimulation was studied in the hand muscles in 13 patients with Huntington's disease and in 11 normal subjects. The duration of the silent period after TCS was longer in patients and correlated significantly with the severity of chorea; in contrast, the duration of the silent period after nerve stimulation was similar in patients and controls. The prolongation of the cortical silent period suggests that the duration of the silent period is a functional correlate reflecting basal ganglia influence over the motor cortex.