The accurate diagnosis of dementia is necessary to identify treatable, and sometimes reversible, causes, as well as to prognosticate and allow long-term planning. Precise diagnosis has become increasingly important as we begin to attempt rational therapeutic interventions. The differential diagnosis of dementia is necessarily complex, and there are few established biologic markers that reliably can differentiate specific causes of dementia. The clinician's judgment therefore remains paramount. This article discusses the usefulness of various diagnostic modalities in the evaluation of patients with dementia.

The diagnostic criteria for dementia used in most research studies are those of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IIIR),<sup>8 American Psychiatric Association   Diagnostic and Statistical Manual of Mental Disorders, revised, ed 3 Washington, DC: American Psychiatric Press (1987). 

Cliquez ici pour aller à la section Références</sup> which have several limitations when applied to clinical practice. First, the DSM-IIIR criteria require memory loss, which would exclude conditions such as progressive supranuclear palsy (PSP) or normal pressure hydrocephalus (NPH), in which true memory loss is unusual in the early stages. The DSM-IIIR also requires deficits in multiple spheres. This would exclude some cases of Alzheimer's disease (AD), which may be restricted to memory loss early on, and focal degenerative conditions such as primary progressive aphasia. Finally, most clinicians think of dementia as a progressive condition that usually has an insidious onset. The acute onset of a static encephalopathy such as that arising from head trauma, herpes simplex encephalitis, anoxia, or a strategically located stroke may meet DSM-IIIR criteria for dementia but should not be confused with conditions causing progressive deterioration, such as AD.

For clinical purposes, the definition of dementia should differentiate it fromnormal aging, static encephalopathies, and impairments of consciousness. We use the following: