Parkinsonian syndromes: Parkinson's disease dementia, dementia with Lewy bodies and progressive supranuclear palsy

The recognition of dementia in Parkinson's disease (PDD) is relatively new compared with the first description of 'shaking palsy' by James Parkinson in 1817. Physicians who currently diagnose and manage PDD patients, not uncommonly evaluate mysterious cases having a variety of cognitive and extrapyramidal features. In this large group, diagnostic uncertainty has limited clinical research, including pharmaceutical trials. However, the classic teaching still holds ground: typically, dementia in Parkinson's disease (PD) does not manifest from the onset of clinical signs. In spite of lacking temporal definition, this clinical criterion is still the one used to make a clinical distinction between PDD and the closely associated extrapyramidal dementia syndrome, dementia with Lewy bodies (DLB). Patients with PD developing dementia some years later diagnosed as having PDD, whereas patients presenting with fluctuating cognition, visual hallucinations and then parkinsonism would be diagnosed with DLB. In DLB, dementia Occurs before parkinsonism or shortly thereafter. However, as discussed below. one might consider this distinction arbitrary. There is active research examining the relationship between DLB and PD using clinical, genetic, pathologic, and biochemical data. (C) 2004 Elsevier B.V. All rights reserved.