P300 in newly diagnosed non-dementing Parkinson's disease: effect of dopaminergic drugs.

Changes in cognitive function are an integral part of the clinical presentation of Parkinson's Disease (PD). P300 potential studies in early stages of Parkinson's disease are lacking and effect of L-dopa therapy on these potentials is controversial. In this study, changes in P300 potentials in early stages of PD and effects of dopaminergic therapy were investigated. P300 waves were elicited by standard auditory 'odd ball' paradigm and were recorded before the start of therapy and 15 days, 3 and 6 months after the start of L-dopa therapy in 25 newly diagnosed patients with idiopathic PD. All patients were classified according to Hoehn and Yahr scale. Minimental status examination (MMSE) was done in all. Control group had 20 normal subjects. The P300 latency was not significantly increased in early Parkinson's disease. This latency was reduced with dopaminergic therapy on 15th day, but increased later. Implications of the data are discussed.