[The pattern of neuropsychologic compromise in patients with Parkinson disease]

We carried out a neuropsychological study on cognitive impairment in 57 subjects affected by idiopathic Parkinson's Disease (P.D.) and 32 subjects affected by Alzheimer's Disease (A.D.). First, we found two different subgroups of parkinsonian patients, the first one with dementia and the second one without dementia. We clearly identified these two distinct subclinical entities regardless of mean age, age of onset, duration of treatment; on the contrary, the type of treatment seems to play a specific role on the appearance of dementia in P.D., anticholinergics being assumed almost exclusively by demented parkinsonian patients (chi square c. Yates = 422; p less than 0.05). Second, we showed two distinct patterns of cognitive impairment between P.D. with dementia and A.D. In fact, cognitive impairment is consistently more evident in Alzheimer patients than in parkinsonian ones with dementia; in addition, demented parkinsonians show a pattern of impairment similar to that exhibited by patients affected by frontal lobe lesions. This result supports neuroanatomical and neurochemical data on the involvement of the whole dopaminergic system in P.D. and the role played by the ventro-medial tegmental area projecting to the frontal cortex. In conclusion, our study, identifying a specific pattern of cognitive impairment in P.D., well-differenciated from demented patients of different aetiology, suggests beneficial effects with dopaminergic agonists in these patients; in fact, these agents, acting on the second neuron, may stimulate the prefrontal region that is probably involved in the cognitive impairment of parkinsonian patients.