Which is the most common cause of dementia, characterized by gradual memory and personality decline with plaques and beta-amyloid and tau tangles?

• A. Lewy body dementia
• B. Vascular dementia
• C. Alzheimer disease
• D. Frontotemporal dementia

Answer: (C)

Alzheimer disease is the most common form of dementia. It progresses gradually, with memory loss that is typically the first and most prominent symptom, followed by difficulties in thinking, language, and changes in personality or behavior as the disease advances. The defining brain changes are extracellular beta-amyloid plaques and intracellular tau tangles, which disrupt neuron function and lead to widespread brain atrophy, especially in memory-related areas. This combination of a gradual, progressive memory decline and characteristic pathologic plaques and tangles is what distinguishes Alzheimer disease from other dementias. For example, Lewy body dementia involves Lewy bodies and often early visual hallucinations and parkinsonian features; vascular dementia results from cerebrovascular disease with stepwise declines; frontotemporal dementia affects behavior and language earlier and may not present with the same early memory impairment or the same tau/amyloid pathology.