Effects of levodopa on cognitive functioning in moderate-to-severe Parkinson's disease (MSPD).

Although improved cognition has been reported in patients with mild Parkinson's disease (PD) following the administration of levodopa, mixed results have been found in moderately-to-severely affected PD patients (MSPD), particularly in studies conducted since 1980. In the present study, 16 MSPD patients were tested on separate days, once following overnight levodopa withdrawal and once while optimally treated. A battery of neuropsychological tests that assess a range of cognitive functions (i.e., attention, language, visuospatial, memory, and executive), as well as a measure of depression, were used. Although patients performed better on a measure of confrontation naming in the untreated than in the treated condition, there were no significant differences for any of the other cognitive variables or for the depression scale variable. Thus, these data suggest that there are generally no adverse or beneficial effects of levodopa therapy on cognition in MSPD patients.