Although most cases of Alzheimer disease are sporadic (ie, not inherited), familial forms are recognized. Autosomal dominant Alzheimer disease, which accounts for less than 5% of cases, is almost exclusively early-onset Alzheimer disease; cases occur in at least three individuals in two or more generations, with two of the individuals being first-degree relatives. Familial clustering represents approximately 15%-25% of Alzheimer disease cases and most often involves late onset. In familial clustering, at least two of the affected individuals are third-degree relatives or closer.
At the time of initial diagnosis, a complete physical examination, including a detailed neurologic examination and a mental status examination, should be performed to evaluate disease stage and rule out comorbid conditions. Initial mental status testing should include evaluation of the following:
Attention and concentration
Recent and remote memory
Praxis (ie, ability to perform skilled motor tasks without nonverbal prompting)
Cognitive features of early Alzheimer disease include memory loss, mild anomic aphasia, and visuospatial dysfunction. At all subsequent follow-up visits, a full mental status examination should be performed to evaluate disease progression and identify the development of any new neuropsychiatric symptoms.
Alzheimer disease is a clinical diagnosis. However, ancillary imaging studies (eg, CT, MRI, single-photon emission CT, PET) and laboratory tests may be used. These tests help exclude other possible causes of dementia (eg, cerebrovascular disease, cobalamin [vitamin B12] deficiency, syphilis, thyroid disease).
The National Institutes of Health-Alzheimer's Disease and Related Disorders Association (NIH-ADRDA) criteria for the diagnosis of Alzheimer disease require the finding of slowly progressive memory loss of insidious onset in a fully conscious patient. Alzheimer disease cannot be diagnosed in patients with clouded consciousness or delirium. Toxic metabolic conditions and brain neoplasms must also be excluded as potential causes of the patient's dementia.
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 disease, brain MRI or CT can show diffuse cortical and/or cerebral atrophy, but these findings are not diagnostic of Alzheimer disease.
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Cite this: Helmi L. Lutsep. Fast Five Quiz: Dementia Key Aspects - Medscape - May 21, 2020.