Both reaction time and movement time tend to be prolonged in Parkinson's disease, but they are often impaired independently of each other. Prolongation of RT is relatively slight, while MT undergoes more substantial and consistent disturbance. Choice RT and kinaesthetic RT do not have any advantage over simple visual RT as measurements of neurological deficit in parkinsonism, since they are all impaired to the same extent. MT is more useful than RT as an objective indicator of therapeutic efficacy, but further studies of RT (with tests requiring programming of displacement, velocity, and accuracy) may provide insights into the nature of the central motor disorder in Parkinson's disease.

SUMMARY One hundred and eight noninstitutionalised patients with Parkinson's disease were studied to find out whether the age of disease onset affects patients' cognitive, memory and psychomotor performance. "Early onset" patients (whose disease began before 60 years of age) showed a wide spectrum of impairments in neuropsychological performance compared with age-matched normal subjects. However, only one (2%) of these patients was demented according to DSM III criteria. Dementia was more frequent in patients with equivalent disease duration, but with late onset of disease (over 60 years); 13 of such patients (25%) were demented. The present study supports previous findings which show that dementia increases with advancing age in Parkinson's disease. It also suggests that cognitive changes are also found in patients with early onset of disease.The great variation in the cognitive performance of individual patients and the differences in the severity of their extrapyramidal symptoms has given rise to the idea that idiopathic Parkinson's disease may encompass several subgroups. Some studies13 indicate that dementia, greater motor disability and rapid symptom progression are linked with a later age of onset. Thus the existence of two groups has been suggested: a late onset "malignant" form and an early onset "benign" form of Parkinson's disease. The issue is controversial, however. Mjones4 observed the opposite to be the case, whereas Lesser et al reported that individuals affected more severely are younger and have a shorter disease duration, and Hoehn and Yahr6 found no connection between the age of onset and progression of the disease. These studies were not based on formal neuropsychological evaluation but on brief estimations of mental state, which are recognised as carrying a high false-positive rate. We have endeavoured to determine whether more comprehensive formal neuropsychological evaluation of cognitive functions could clarify the role of age at disease onset in modifying the cognitive performance and disease progression.

We studied the effect of entacapone, a selective catechol-O-methyltransferase inhibitor, on the bioavailability and clinical effect of levodopa in Parkinson's disease (PD). On day 1 (control day), nine patients received their own levodopa (plus benserazide) medication only; for the next 7 days they received 200 mg of entacapone with each dose of levodopa (tid or qid). We evaluated disability in the morning (8 AM) before drug administration and then at 1-hour intervals until 6 PM on days 1, 2, and 8, using a modified motor part of the Unified Parkinson's Disease Rating Scale. Repeated blood samples were taken before and during the 4 hours after the morning drugs for pharmacokinetic evaluation of entacapone and of levodopa and its metabolites. Added to the levodopa treatment, entacapone decreased clinical disability by about 16% (p < 0.05) from day 1 to day 8. The area under the curve (AUC) of levodopa increased by 38% (p < 0.01) after administration of a single dose of entacapone and by 40% (p < 0.05) after 7 days of multiple dosing with entacapone. Entacapone did not change the Tmax and Cmax values of levodopa. After 7 days of treatment with entacapone, the AUC of 3-O-methyldopa had decreased by 44% (p < 0.01) and of homovanillic acid by 26% (p < 0.05) as compared with treatment with levodopa alone. Four patients became slightly more dyskinetic during entacapone treatment than before it. The combination of entacapone and levodopa was well tolerated, judged by the lack of significant changes in hemodynamic and safety variables.(ABSTRACT TRUNCATED AT 250 WORDS)