Neurodegenerative disease (Greek νέυρο-, néuro-, "nerval" and Latin dēgenerāre, "to decline" or "to worsen") is a condition in which cells of the brain and spinal cord are lost. The brain and spinal cord are composed of neurons that do different functions such as controlling movements, processing sensory information, and making decisions. Cells of the brain and spinal cord are not readily regenerated en masse, so excessive damage can be devastating. Neurodegenerative diseases result from deterioration of neurons or their myelin sheath which over time will lead to dysfunction and disabilities resulting from this.

Some sources limit the term "degenerative" to conditions primarily affecting gray matter that are not associated with a obvious inciting event.

For more information about Neurodegenerative disease, read the full article at Wikipedia.
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