Causes of Alzheimer’s disease

Synonyms in a broader sense

Alzheimer’s disease causes, dementia causes, Alzheimer’s dementia

Alzheimer’s dementia is characterized by the destruction of brain cells, which manifests itself in a shrinkage (atrophy) of the affected brain regions. The cerebral cortex of the frontal, temporal and parietal lobe and the hippocampus are particularly affected. The hippocampus is a central switching station of the limbic system, which is responsible for intellectual performance, among other things.

In the later course of the disease, the medullary canal with the pathways of the brain cells is also affected. The decrease in the number of synapses is related to the clinical symptoms affecting the mind (cognitive). However, the clinical symptoms do not necessarily correspond to the extent of the recognizable changes.

Regularly affected is also the nucleus basalis Meynert, a nucleus of the central nervous system, which is directly connected to the frontal lobe (frontal cortex). The connecting pathways contain the messenger substance (neurotransmitter) acetylcholine, which is present in the brain in a reduced concentration in the case of degeneration of the nucleus basalis Meynert. In addition, other pathways with the neurotransmitters norepinephrine and serotonin, which lead to the hippocampus, can be affected.

The deficiency of these neurotransmitters may explain some of the symptoms. In autopsy preparations of the brains of deceased Alzheimer’s patients, increased deposits of certain “protein lumps” (senile plaques) and “threads” (Alzheimer’s fibrils) appear under the microscope. These deposits only form in the later course of the disease and lead to the loss of function and death of nerve cells (neurons).

The fibrils are located in the cells (intracellular) and consist of the protein. The plaques are found outside the cells (extracellular) in the hippocampus, cortex and other brain regions. The plaques also occur to a much lesser extent in the normal aging process or other brain diseases, but are nevertheless suspected to be a cause of the progressive degradation processes in the brain of Alzheimer’s patients. The Alzheimer’s fibrils and amyloid plaques are therefore characteristic, but not specific, for Alzheimer’s disease in a certain quantity that cannot yet be determined quantitatively!