A careful mental status exam is necessary to diagnose dementia. It is very important to rule out reversible causes, such as depression,
A detailed history is vital to determining the diagnosis of dementia. It is important to determine whether the onset is gradual or sudden as well as the pattern of progression (continuous or stepwise). Naturally, medical illnesses must be considered, such as hypertension, stroke, diabetes, alcoholism and substance use. As discussed elsewhere, depressive disorders in older adults can give the appearance of dementia. Of course, it is not uncommon to see delirium superimposed on dementia.
The vast majority of dementias can be accounted for by Alzheimer's disease, Lewy body dementia, vascular dementia, or frontotemporal dementia. The remainder of the causes account of 10% or less of dementias.
Laboratory screening
Laboratory screening is vital for the diagnosis of dementia as any potentially reversible causes must be ruled out.
Laboratory values that should be obtained in the workup of dementia are listed here.
Neuroimaging
Neuroimaging has been a great advance for the diagnosis of dementia. For example, normopressure hydrocephalus can be ruled out and addressed.
Generally, structural imaging of the brain in a patient with dementia would reveal generalized atrophy and enlarged ventricles. In particular, early on one may see changes in the the temporal lobe and/or hippocampus. PET scanning can be beneficial in that one may see temporoparietal, cingulate, or hippocampal hypometabolism.
Dementia Rating Scales
There are a variety of dementia rating scales, such as the Alzheimer Disease Assessment Scale although in general these scales are of limited utility on a consultation service.