[Mental dysfunction in Parkinson's disease]

In Parkinson's disease, mental disturbances frequently accompany the typical motor disorder. Subcortical dementia develops in 10 to 20% of patients. Contrary to the dementia of Alzheimer's type, the apraxia-aphasia-amnesia syndrome is uncommon. Depression and specific impairment of speech, visuospatial functions, and memory are present in an important proportion of patients. As a principal feature of cognitive disorder, deficit of executive functions can be characterised by decreased mental flexibility and inability to cope with changing external conditions. Further, psychiatric complications of pharmacological treatment of Parkinson's disease are briefly described. Finally, presumed pathophysiological mechanisms of cognitive dysfunction are characterized involving dopaminergic and non-dopaminergic changes and complex interactions on the subcortico-cortical level.