Motor system inhibition in dopa-responsive dystonia and its modulation by treatment.

Dopa-responsive dystonia (DRD) causes dystonia-parkinsonism, which is abolished by levodopa. The authors assessed short intracortical inhibition and facilitation, silent period, blink reflex recovery cycle, and reciprocal inhibition in seven patients with DRD on and off treatment. Short intracortical inhibition and blink reflex recovery cycle were reduced, but increased with treatment. Silent period was normal on and off treatment. Third phase of reciprocal inhibition was reduced on and off treatment. A discrete pattern of motor inhibitory dysfunction occurs in DRD.