Current recommendations from the American Academy of Neurology (AAN) include measurement of the vitamin B12 level and a thyroid function screening test to rule out other disorders in patients with suspected Alzheimer's disease. Additional investigations are left up to the physician, to be tailored to the particular needs of each patient.
The AAN recommends that structural neuroimaging with either a noncontrast CT or MRI is appropriate in the initial evaluation of patients with dementia, in order to detect lesions that may result in cognitive impairment (eg, stroke, small-vessel disease, tumor). Imaging studies are particularly important for ruling out potentially treatable causes of progressive cognitive decline, such as chronic subdural hematoma or normal-pressure hydrocephalus. In patients with Alzheimer's disease, brain MRI or CT can show diffuse cortical and/or cerebral atrophy, but these findings are not diagnostic.
Brain scanning with single-photon emission CT or PET is not recommended for the routine workup of patients with typical presentations of Alzheimer's disease. These modalities may be useful in atypical cases or when a form of frontotemporal dementia is a more likely diagnosis.
Cerebrospinal fluid levels of tau and phosphorylated tau are often elevated in Alzheimer's disease, whereas amyloid levels are usually low. At present, however, routine measurement of cerebrospinal fluid tau and amyloid is not recommended, except in research settings. Lumbar puncture for measurement of tau and amyloid may become part of the diagnostic workup when effective therapies that slow the rate of progression of Alzheimer's disease are developed, particularly if the therapies are specific for Alzheimer's disease and carry significant morbidity.
Learn more about the workup of Alzheimer's disease.
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Cite this: Helmi L. Lutsep. Fast Five Quiz: Alzheimer's Disease - Medscape - May 06, 2022.