Objective: The aim of this study was to know the changes in P300 potentials in early stages of Parkinson’s diseases (PD) in elderly patients (age >65 years) and effects of dopaminergic therapy on P300.
Design: Changes in cognitive function are an integral part of the clinical presentation of Parkinson's Disease. 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 in elderly patients (age>65years) and effects of levodopa therapy were investigated. P300 was done at fixed periods- before the start of therapy and 15 days, 3 and 6 months after the start of L-dopa therapy.
Materials and Methods: 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 17 newly diagnosed elderly patients (age>65years) with idiopathic PD. All patients were classified according to Hoehn and Yahr scale. Mini Mental Status Examination (MMSE) was done in all. Control group had 13 normal subjects.
Results: The mean age in both groups was comparable. The mean duration of illness was 22.12±13.07 months. The Hoehn and Yahr score of the patients did not exceed 2 in majority of patients. None of the patients at initiation was overtly demented, mean MMSE being 27±2.08. In 12 patients who completed the follow up, there was no change on MMSE though motor symptoms had shown significant improvement. The P300 latency was not significantly increased in early Parkinson's disease. This latency was reduced with levodopa therapy on 15th day, but increased later, i.e. at 3 and 6 months.
Conclusion: P300 provides us a diagnostic tool for assessing cognitive system at onset and at follow up in Parkinson’s disease patients. In early stages of Parkinsons’s disease in elderly patients, P300 remains unaffected. Levodopa therapy has adverse effect on P300, which might be due to over stimulation of regions responsible for its generation. Long term studies may provide more insight into pathogenesis of cognitive disturbances, its progression in Parkinson’s disease, and the effect of drugs on cognition.
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