[Dementia in morbus Parkinson: reasonable diagnostics and rational therapy]

Cognitive decline is a common disorder in idiopathic Parkinson's syndrome, the risk for the development of a dementia is four- to six-fold higher for Parkinsonian patients. The cognitive profile in Parkinson's disease dementia (PDD) differs from that of Alzheimer-type dementias. The affected cognitive functions include attention, executive functions, visual-spatial functions and recall. The main differential diagnosis for PDD is the Lewy body dementia (LBD), which can be differentiated through the temporal development of motor and cognitive symptoms. Cognitive symptoms in Parkinsonian syndromes have a relevant negative impact on quality of life, on the burden for the care-givers, on the prognosis of the disease and on the possible referral to a nursing home. Dementias in Parkinsonian syndromes (PDD and LBD) need a confirmatory diagnosis at an early stage in order to initiate further therapeutic steps with, e. g., acetylcholine esterase inhibitors or, perspectively, neuropsychological training methods.