What is the distinguishing feature of brain imaging for Alzheimer's Disease?

The distinguishing feature of brain imaging for Alzheimer's Disease is the presence of both beta-amyloid plaques and tau protein tangles in the brain. In Alzheimer's, these two pathological hallmarks can be visualized using specific imaging techniques, such as positron emission tomography (PET) with radiotracers that bind to beta-amyloid and tau.

Beta-amyloid plaques are abnormal clusters of protein fragments that accumulate between nerve cells, while tau protein tangles are twisted fibers found inside brain cells that disrupt normal function. The detection of both beta-amyloid and tau is critical for diagnosing Alzheimer's disease, as their presence correlates closely with the progression of the disease. This dual presence can help differentiate Alzheimer's from other forms of dementia, as other conditions may show varying patterns of amyloid and tau distribution or may not exhibit both pathologies at all.

The other possibilities mentioned do not align with the known pathology of Alzheimer's. For instance, the absence of amyloid and tau would suggest a different type of neurodegenerative disorder, while tau present without amyloid typically points more towards other types of dementia. Pure alpha-synuclein is mainly associated with Parkinson's disease and Lewy body dementia, further differentiating it from the amyloid and tau pathology