The American Academy of Neurology states that structural neuroimaging, preferably with brain MRI, is appropriate in the initial evaluation of patients with suspected AD. MRI is the preferred neuroimaging approach because it enables accurate measurement of the three-dimensional volume of brain structures, particularly the size of the hippocampus and related regions. CT can be used when MRI is not possible.
Electroencephalography is used when Creutzfeldt-Jakob disease or another prion-related disease is suspected. Sporadic high-amplitude sharp waves are eventually detected in most cases of Creutzfeldt-Jakob disease. Creutzfeldt-Jakob disease is not suspected, so this form of testing would not be appropriate in this case.
Mutations in the amyloid precursor protein (APP), presenilin 1 (PSEN1), and presenilin 2 (PSEN2) genes have been associated with early-onset familial AD. According to a practice resource from the American College of Medical Genetics and the National Society of Genetic Counselors, testing for the APP and presenilin genes should be offered to:
Symptomatic patients with early-onset AD who have a family history of dementia or an unknown family history (eg, because of adoption)
Persons with a family history of autosomal dominant dementia with one or more cases of early-onset AD
This test would not be appropriate for this patient, given the lack of family history.
Lumbar puncture is another test that is used in specific circumstances. For example, lumbar puncture can be used to exclude conditions such as normal-pressure hydrocephalus or central nervous system infection (eg, neurosyphilis, neuroborreliosis, cryptococcosis). In May 2022, the US Food and Drug Administration (FDA) approved the first in vitro diagnostic test for the early detection of AD. The test detects amyloid plaques that are associated with AD in adults ≥ 55 years of age who are being evaluated for AD and other causes of cognitive decline. Presently, this test is not routinely used in the workup for AD, though that may change if effective therapies specific for AD are developed.
The patient undergoes MRI testing, which supports the clinical diagnosis of mild AD.
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Cite this: Jasvinder P. Chawla. Skill Checkup: A 70-Year-Old Woman With History of Depression and Mild Cognitive Impairment Presents With Memory Lapses - Medscape - Dec 22, 2022.