Alzheimer’s disease is characterized by the abnormal accumulation of beta-amyloid plaques and the tau protein in specific brain regions. A recent international study focused on the accumulation and spread of the tau protein. The study found that spread of tau in the brain has at least 4 clear patterns. Depending on the spread pattern, people with Alzheimer’s develop different symptoms of the disease. Based on these 4 patterns the researchers proposed 4 subtypes of Alzheimer’s.

The study selected 1.143 participants from Sweden, Canada, USA and Korea, who had not yet developed any symptoms (so-called pre-symptomatic Alzheimer’s), participants with mild memory difficulties and those with fully developed Alzheimer’s dementia. The tau PET images along with new methods of machine learning were used to identify and characterize the following 4 patterns of Alzheimer’s.

Pattern 1: tau spreads mainly within the temporal lobe and primarily affects memory (33% of all cases)

Pattern 2: tau spreads in the rest of the cerebral cortex. People have less memory problems than in the first pattern, but greater difficulties with executive functions, such as the ability to plan and perform an action (18% of all cases)

Pattern 3: the accumulation of tau takes place in the visual cortex, i.e. in the part of the cerebrum where information from the optic nerve is processed and classified. People with this visuospatial processing pattern have difficulty orienting themselves, distinguishing shapes and contours, distance, movement and the location of objects in relation to other objects (18% of all cases)

Pattern 4: tau spreads asymmetrically in the left hemisphere and primarily affects the one’s language ability (19% of all cases)

The researchers plan a longer follow-up study over 5 to 10 years to be able to confirm the 4 identified patterns with even greater accuracy. They believe that their findings can give people with Alzheimer’s more individualized treatment in the future.

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