Diagnosis of Alzheimer's dementia

For an adult, Alzheimer disease is primarily a clinical diagnosis supported by the pattern and progression of cognitive and functional decline, after evaluating competing causes. No single cognitive score or routine imaging finding establishes the diagnosis.

Dementia vs mild cog impairment

Acquired cognitive decline that interferes with independence in everyday activities and is not occurring exclusively during delirium or better explained by another mental disorder is dementia

Office Testing

Objective cognitive assessment, such as the Montreal Cognitive Assessment or Mini-Mental State Examination. A low score alone does not diagnose dementia.

Other types of dementia

Probable Alzheimer dementia requires established dementia plus an insidious onset, clear progressive worsening, and objective impairment documented through history, informant report, and cognitive testing. The usual initial presentation is impaired learning and recall of new information, although language-predominant, visuospatial, and executive presentations occur. Substantial cerebrovascular disease, core Lewy body features, prominent frontotemporal features, another active neurologic or medical disorder, or a medication with major cognitive effects makes “probable” Alzheimer dementia less secure and may support a possible or mixed presentation  instead. 

Lewy Body dementia

Frontotemporal dementia

MRI

Medial temporal or hippocampal and posterior temporoparietal atrophy can support Alzheimer disease but are nonspecific and remain probabilistic.

Treatment for Alzheimer's disease

Leqembi (lecanemab)

Lecanemab is FDA-approved for early-stage Alzheimer disease (mild cognitive impairment or mild dementia) with confirmed brain amyloid pathology, and it modestly slows clinical decline rather than improving cognition or function. It is approved for early-stage Alzheimer disease with confirmed amyloid pathology, and trial data show a modest slowing of decline with uncertain clinical meaningfulness.

Lecanemab candidate

Eligibility generally requires mild cognitive impairment or mild dementia plus documented amyloid positivity (amyloid PET or CSF biomarkers), along with pretreatment evaluation including cognitive assessment, brain MRI to exclude contraindications, and APOE genotyping to inform ARIA risk.