Motor excitability in a patient with a somatosensory cortex lesion.

OBJECTIVE: We report a patient with an ischemic lesion in right somatosensory cortex who developed dystonic posturing and pseudo-athetotic involuntary left-sided finger movements during voluntary muscle contractions. METHODS: Motor excitability was assessed using transcranial magnetic stimulation techniques and electrical peripheral nerve stimulation. Results obtained from abductor digiti minimi muscles of both hands were compared. RESULTS: On the affected side, silent period duration and intracortical inhibition were reduced, indicating a loss of inhibitory properties. Intracortical facilitation was enhanced. Stimulus-response curves showed a smaller increase of motor evoked potential amplitudes when recorded during muscle relaxation, but not during voluntary muscle activation. CONCLUSIONS: The results suggest that, under normal conditions, somatosensory cortex modifies inhibitory as well as excitatory properties in the motor system.