Differential diagnosis of Alzheimer's disease.

Accurate diagnosis of dementia is essential to provide appropriate treatment as well as patient and family counseling. It may be difficult to differentiate dementia from delirium. In addition, several features distinguish dementia from depression, but the two can coexist and the distinction may be uncertain. Dementias can be grouped into two categories: dementia that presents without prominent motor signs and dementia that presents with prominent motor signs. Dementias without prominent motor signs include Alzheimer's disease, frontotemporal dementia, and Creutzfeld-Jakob and other prion diseases. Dementias characterized at onset by prominent motor signs include dementias with Lewy bodies, idiopathic Parkinson's disease, progressive supranuclear palsy, cortico-basal ganglionic degeneration, hydrocephalus, Huntington's disease, and vascular dementia. Routine diagnostic steps include a careful history, mental status screening, laboratory and imaging studies, and neuropsychologic testing. Genetic testing is available, but its use is controversial and raises complex ethical questions.