The hallmark of Alzheimer’s disease is development of plaques and tangles of certain proteins in the brain. The plaques, sometimes called clumps, are made up of a form of protein called amyloid. The tangles are due to clustering of a protein called tau within the brain cells. If you have been diagnosed with dementia or have participated in clinical trials in the past, you may have undergone tests (i.e., a positron emission tomography (PET), magnetic resonance imaging (MRI) scan, or lumbar puncture) and may have been told whether the tests revealed the presence of amyloid plaques and tau deposits in your brain or cerebrospinal fluid. The presence of these biomarkers provides evidence of Alzheimer’s disease and assists with diagnosis. Another important feature of Alzheimer’s disease is the progressive loss of brain cells. However, loss of brain cells is common to most forms of dementia and therefore is not specific to Alzheimer’s disease.
Alzheimer’s disease can be only speculatively diagnosed based on memory and cognitive assessments alone, since declines in memory and cognition are common to other forms of dementia. Therefore, biological tests are becoming more widely used.
For further information on Amyloid Plaques, Professor John O’Brien from the University of Cambridge explains more in this video.