Relationship between cognitive impairments, event-related potentials, and motor disability scores in patients with Parkinson's disease: 2-year follow-up study.
We studied event-related potentials and the cognitive state for 2 years in 29 patients with Parkinson's disease (PD). Of those patients, 11 were at stage II and 18 were at stage III at initial assessment, as measured on the Hoehn and Yahr scale. The peak latency of P300 in patients at stage III was significantly prolonged, as compared with that in age-matched normal controls or PD patients at stage II. There was no significant change in P300 latency among patients whose motor ability remained unchanged at stage II or stage III during follow-up period. The mean P300 latency prolonged significantly in patients whose motor ability worsened from stage III to stage IV. The cognitive state in the patients with PD was characterized by impairment in the categories of orientation, recall and constructional ability. The degree of impairment of these items increased as the motor disability increased. These results suggest that cognitive dysfunctions and abnormality of P300 latency increased as the motor disabilities progressed.