Short-latency median nerve somatosensory evoked potentials in three cases of parkinsonism and dopa responsive dystonia.

We studied somatosensory evoked potentials after median nerve stimulation in a sporadic case of dopa responsive dystonia and in two brothers with different combinations of dystonia and parkinsonism. The latencies of all potentials were normal. The amplitude of the P20-N30 frontal complex showed a significant reduction in all cases. Our results suggest a common neurophysiopathological pattern underlying these two conditions.