MOTOR CORTEX CHANGES IN A PATIENT WITH HEMICEREBELLECTOMY

To evaluate reorganisation of motor pathways following a cerebellar le sion, we studied motor cortex excitatory responses and inhibitory effe cts after transcranial stimulation, together with segmental spinal cor d excitability, in one patient who had undergone hemicerebellectomy. W e compared the results obtained using different forms of stimulation c apable of activating the cortico-spinal tract at different sites. Resu lts were compared between sides. We previously reported that the thres hold for responses is higher in the motor cortex contralateral to the impaired hemicerebellum and the right/left threshold asymmetry is clea rly greater than normal when a circular coil centred over the vertex i s used. In the present study, using electrical anodal stimulation, no side difference was observed. Significant interside differences were a bsent also when the durations of the silent periods or the mean amplit ude of the flexor carpi radialis H reflex between the two sides were c ompared. The outcome is that the interside differences previously obse rved are mainly due to reduction in the intrinsic excitability propert ies of the motor cortex functionally related to the impaired hemicereb ellum and not to modification of the inhibitory properties of the cort ex or to spinal mechanisms.