In a comparative clinicopathologic study of 13 patients who had a clinical diagnosis of Parkinson disease (PD) with late onset of dementia and 6 patients who had PD without dementia, Apaydin et al,1 at postmortem examination, revealed findings of diffuse or transitional Lewy body disease (LBD) in 12 patients and progressive supranuclear palsy in 1 patient, all with dementia. These patients showed almost a 10-fold increase of Lewy bodies in the neocortex and limbic areas compared with subjects without dementia. Alzheimer disease (AD) was modest: only 1 patient with dementia met the National Institute on Aging and the Reagan Institute Working Group on the Diagnostic Criteria for the Neuropathologic Assessment of Alzheimer's Disease (NIA-R)2 criteria for intermediate probability of AD. On the other hand, changes caused by AD (both plaques and tangles) were highly correlated with Lewy body counts, suggesting common origins or mutual triggering.
Jellinger KA, Seppi K, Wenning GK. Neuropathologic Changes in Parkinson Disease With Late Onset of Dementia. Arch Neurol. 2003;60(3):452-453. doi:10.1001/archneur.60.3.452-a