Cognitive decline correlates with neuropathological stage in Parkinson's disease.

Recently, the relationship between cognitive status and the neuropathological stages of a newly proposed staging procedure for Parkinson's disease (PD) was assessed in a cohort of 88 individuals. None of the patients had received the clinical diagnosis of dementia with Lewy bodies. The topographic distribution pattern of the cerebral Lewy body pathology was evaluated semiquantitatively in alpha-synuclein immunoreactions. MMSE scores from the last neurological examination prior to death were used to determine cognitive status and the degree of cognitive decline. Four subgroups of Mini-Mental State Examination (MMSE) scores ranging from nonsignificantly impaired to severely impaired cognition were analyzed statistically with nonparametric tests. Each of the 88 cases could be assigned to one of the PD stages 3-6, and MMSE scores correlated significantly with the aforementioned stages. Since the median MMSE scores decreased from stages 3-6, it is probable that the risk of developing dementia in PD becomes greater as the disease process in the brain progresses.