What are neurofibrillary tangles in Alzheimer disease?

In the context of Alzheimer disease, neurofibrillary tangles are twisted fibers found within neurons. These structures are composed of a protein known as tau, which is normally present in nerve cells.12

When tau molecules are incorrectly processed, they clump together to form these pathological tangles. They are characterized as accumulations of paired helical filaments, primarily located in the cytoplasm of neurons within areas such as the cerebral cortex and the hippocampus.12

Along with neuritic plaques, these tangles are used to diagnose the disease during an autopsy. While they are thought to interfere with normal cellular functioning, it remains scientifically uncertain whether these tangles are a primary cause or a consequence of the disease.1