Asymmetrical cognitive deterioration in demented and Parkinson patients.

Patients with Parkinson's disease and patients with dementia showed greater deterioration on functions attributed to the right cerebral hemisphere, than on functions attributed to the left. Relative to matched controls, Parkinson patients were significantly impaired on right hemisphere tests, but did not differ on left hemisphere tests. Demented patients were significantly deficient on all tests, but right decline was greater than left. Ninety-six patients were tested: 32 diagnosed as senile or presenile dementia, 32 Parkinson patients, and 32 non-neurological patients matched for age, sex and education. Functional performance was assessed by a battery of validated tests for left and right hemisphere cognitive functions. Patients were defined with two scores based on the results of the test: Cognitive Laterally Quotient (CLQ) reflecting the averaged performance on the left hemisphere tests, subtracted from the average performance on right hemisphere tests, and Cognitive Performance Quotient (CPQ), reflecting the total level of performance of both hemispheres. These measures defined a characteristic cognitive profile for each group.