Parkinson-related dementias.

Recent advances in neurogenetics, molecular biology, and immunocytochemical staining methods have expanded the spectrum of neurodegenerative disorders now known to cause dementia associated with parkinsonism. This review concentrates on those rare disorders in which cognitive impairment/dementia and parkinsonism coexist: corticobasal syndrome/corticobasal degeneration, progressive supranuclear palsy, multiple system atrophy, and frontotemporal dementia with parkinsonism linked to chromosome 17. The clinical, neuropsychologic, neuroradiologic, and neuropathologic similarities and differences in these disorders are compared and contrasted with each other and with Alzheimer's disease, Parkinson's disease, Parkinson's disease with dementia, and dementia with Lewy bodies, highlighting the features critical for identifying the correct diagnosis.