Which disease is the most common cause of dementia, characterized by plaques and beta-amyloid and tau tangles?

• A. Dementia with Lewy bodies
• B. Alzheimer disease
• C. Frontal lobe dementia
• D. Vascular dementia

Answer: (B)

Alzheimer disease is the disease most commonly causing dementia, and it is defined by the presence of extracellular beta-amyloid plaques and intracellular neurofibrillary tangles made of hyperphosphorylated tau protein. These abnormal protein accumulations disrupt neural networks, especially in memory-related regions like the hippocampus, leading to the characteristic gradual decline in memory and other cognitive abilities that spreads over time. Clinically, people often first notice trouble with memory, followed by difficulties in language, reasoning, and daily functioning.

Other forms of dementia have different pathological hallmarks and clinical patterns. Dementia with Lewy bodies involves Lewy bodies and often presents with early visuospatial issues, visual hallucinations, and parkinsonian features. Frontal lobe (frontotemporal) dementia shows early changes in personality, behavior, or language with memory impairment appearing later. Vascular dementia results from cerebrovascular disease and typically shows a stepwise decline linked to strokes.