Once alzheimer’s disease develops due to the various causes described above, cholinergic neurons and synapses become affected and gradually degenerate or die. Many brain regions then display amyloid plaques and neurofibrillary tangles. Distributions of amyloid plaques can be classified into three stages (stage A, B, C). It is known  that they form relatively constant patterns. Neurofibrillary tangles show a regular pattern of aggregation. The disease starts in the transentorhinal cortex and progressively spreads to the entohirnal cortex, the hippocampus, and the cerebral cortex. With the clear manifestation of neuronal cell death, memory and cognitive functions gradually decline along with the progression of dementia, while accelerating the patient’s death.