TRANSCRANIAL MAGNETIC STIMULATION IN MULTIPLE SYSTEM AND LATE-ONSET CEREBELLAR ATROPHIES

Central motor conduction time (CMCT) after transcranial magnetic stimu lation (TMS) of the cortex, electromyography and nerve conduction velo city were performed in 24 patients with multiple system (MSA) and late onset cerebellar atrophy (LOCA) (often olivopontocerebellar atrophy - OPCA -). CMCT was abnormal in 7 patients with OPCA and one with LOCA. CMCT abnormalities (43% of cases) and increased threshold (68%) were more often found within OPCA group than in another multisystem atrophy and LOCA. Reduction in amplitude of the response after TMS was signif icantly correlated with cerebral hemispheres's atrophy. Increased thre shold was correlated with upper vermal hemisphere atrophy and enlargem ent of the fourth ventricle. Electrophysiologic signs of mixed periphe ral neuropathy were found in 8 patients. TMS abnormalities were not re lated to peripheral nerve involvement. Marked variation in CMCT sugges ts heterogeneity in these diseases. However, the percentage of CMCT ab normalities in OPCA group suggests that TMS seems to play a role in th e neurophysiological diagnosis of these heterogeneous disorders.