Abstract: Objective: To investigate the difference in motor evoked potentials (MEP) between idiopathic Parkinson's disease (PD) and multiple system atrophy (MSA), analyze its value for the differential diagnosis of PD and MSA. Methods: Single-pulse transcranial magnetic stimulation (sTMS)-MEP examination was performed in 12 patients with MSA and 12 sex and age matched idiopathic PD patients. MEP parameters were compared between the two groups of patients. Receiver operating characteristic curve was used to screen the parameters suitable for differential diagnosis. Results: The differences of motor threshold, MEP amplitude and central motor conduction time (CMCT) between idiopathic PD and MSA patients were not statistically significant(P>0.05). The waveform of MEP differed significantly between idiopathic PD and MSA patients (P<0.01). The MEP duration showed a trend of prolonging in MSA patients than in idiopathic PD patients, but was not statistically significant (P>0.05). Conclusions: Both duration and waveform of MEP may help the differential diagnosis of MSA from idiopathic PD.

Key words: Parkinson's disease, Multiple system atrophy, Transcranial magnetic stimulation, motor evoked potentials