Cerebral blood flow and cognitive impairment in Parkinson's disease

In Parkinson's disease, there is high prevalence of dementia, reduction of the regional cerebral blood flow (rCBF), and neuronal loss and Alzheimer-like pathologic changes in cerebral cortex. Since rCBF is also decreased in Alzheimer's dementia, it is theoretically possible that both decreases in rCBF and cognitive impairment in parkinsonians are caused by a similar mechanism, eg, reduced metabolic demand or loss of cholinergic neurons innervating cortex and microvessels. We therefore measured rCBF using the 133Xenon inhalation technique and evaluated cognitive function with a detailed neuropsychological test battery in 48 patients with Parkinson's disease. Mean brain, hemispheric, and regional flows were decreased in parkinsonians as compared with those in age-matched controls. Most of the cognitive functions were impaired in patients as compared with those in normal subjects. However, there was no correlation between the magnitude of rCBF reduction and the presence and severity of intellectual deterioration in parkinsonians, suggesting that each may be caused by a different mechanism.