Several studies have shown that the presence of cerebrovascular lesions may play an important role for determining the severity of the clinical symptoms of dementia. But no study to date has explored the clinical effect of cerebrovascular disease in Parkinson's disease with dementia (PDD), although cerebrovascular disease is common causes of dementia in elderly population. Therefore we conducted this study to evaluate the relationship between silent cerebrovascular lesions and cognitive decline in PDD.

Only 27 patients with PDD were chosen; 17 patients had PDD with silent cerebral ischemic lesions (PDDI) and 10 patients had PDD without silent cerebral ischemic lesions (pure PDD). These subjects received the global cognitive function testing and were all evaluated with detailed neuropsychological tests including attention, memory, language, and also the visuospatial and frontal function.

There were no significant differences between pure PDD and PDDI group on general cognitive functions tests. Regard to mean time duration of suffering from Parkinson motor symptoms and motor function scale, pure PDD group showed more long duration than PDDI group but there was no significant difference between two groups. Furthermore, there were not any significant differences between the two groups on detailed neuropsychological tests.

We concluded that silent cerebrovascular lesions do not contribute to neuropsychological severity of PDD, although vascular disease is a common cause of cognitive impairment in the elderly. Thus the results of the present study suggest that factors other than cerebrovascular disease contribute to severity of PDD.