OUP user menu

COGNITIVE IMPAIRMENT IN EARLY, UNTREATED PARKINSON'S DISEASE AND ITS RELATIONSHIP TO MOTOR DISABILITY

JAMES A. COOPER, HARVEY J. SAGAR, NIGEL JORDAN, NORMAN S. HARVEY, EDITH V. SULLIVAN
DOI: http://dx.doi.org/10.1093/brain/114.5.2095 2095-2122 First published online: 1 October 1991

Summary

SUMMARY

Current knowledge of cognitive dysfunction in Parkinson's disease (PD) has largely been obtained from studies of chronically treated patients in whom effects of disease chronicity, treatment, depression and dementia are confounding factors. Studies of untreated patients have examined few cognitive domains and relationships between cognition, depression and motor disability have been imcompletely explored. Accordingly, we studied 60 consecutive patients with newly diagnosed, untreated, idiopathic PD and 37 matched, healthy control subjects; no subject had clinical dementia or depression. All subjects received tests of specific processes of memory and cognition, including working memory, verbal and non-verbal short-and longterm memory, language, visuospatial capacity, set-formation and shifting and sequencing. Patients also received quantitative global clinical measures of severity of dementia, depression and motor disability. The PD group as a whole showed deficits in immediate recall of verbal material, language production and semantic fluency, set-formation, cognitive sequencing and working memory and visuomotor construction. However, this group was unimpaired in immediate memory span, long-term forgetting, naming, comprehension and visual perception. Language deficits and more severe frontal lobe impairments were confined to those PD patients scoring abnormally on a Mini Mental State examination. Motor disability correlated strongly with severity of depression but weakly with cognitive impairment. Congnitive sequencing, setformation and set-shifting deficits tended to associate with depression, but otherwise there was no association between cognition and depression. The results indicate dissociation of cognition and motor control in early PD which suggests that cognitive dysfunction is largely independent of frontostriatal dopamine deficiency underlying motor disability. Some, but not all, of the frontal lobe deficits of chronic disease are detectable in early, untreated PD. The pathogenesis of the cognitive deficits shown here appears to involve extranstriatal dopamine systems or non-dopaminergic pathology. Logitudinal study in necessary to determine whether increasing disease duration exacerbates the early cognitive deficits and affects new cognitive domains, in addition to producing increasing motor disability.