Heterogeneity of cognitive dysfunction in Parkinson's disease: a cohort study

The aim of this study was to examine the heterogeneity of cognitive dysfunction in Parkinson's disease (PD) and to evaluate the contribution of cognitive criteria to the diagnosis of dementia in PD.

In a sample of 100 consecutive PD patients with motor fluctuations, an extensive neuropsychological test battery was administered. Each PD patient's cognitive profile was then compared with current cognitive criteria for dementia in PD.

Principal component analysis of the major test variables resulted in three components: one concerned with memory/attention, one with visuospatial, and one with executive/motor functions. Eighteen percent of our cohort showed no significant impairment on either domain. Fifty-one percent showed impairment in one cognitive domain, most frequently in the executive/motor component (88%). Twenty-four percent performed below normal on two cognitive components, most often executive/motor and memory/attention deficits (96%), and only 7% of our cohort had significant impairment on each derived cognitive component. Depending on the used criteria, 10-30% percent of our cohort could be categorized as PD patients with dementia.

Future guidelines for a uniform diagnosis of dementia in PD are needed for clinical use and therapeutic management.