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Many experts recommend that people being assessed for dementia have a brain imaging test such as MRI or CT scan.⁹ These tests may rule out brain tumors, strokes, normal-pressure hydrocephalus, or other conditions that could cause dementia symptoms.

MRI can show shrinkage in parts of the brain that occurs in some types of dementia. MRI and CT scan also can show evidence of strokes from vascular dementia.

Two other forms of imaging-single photon emission CT (SPECT) and PET scan-are not used routinely to diagnose dementia. But they may be useful if the symptoms are confusing or odd. These tests can help identify several forms of dementia, including vascular dementia and frontotemporal dementia.

In some cases, electrical activity in the brain may be measured using an electroencephalogram (EEG). Doctors seldom use this test to diagnose dementia, but they may use it to distinguish dementia from delirium and to look for unusual brain activity found in Creutzfeldt-Jakob disease, a rare cause of dementia.

In rare cases, a brain biopsy may be done if a treatable cause of dementia is suspected.

After death, an autopsy may be done to find out for sure what caused dementia. This information may be helpful to family members concerned about genetic causes. For more information, see the topic Alzheimer's Disease.