Degeneration of the brain
Of the degenerative diseases in the brain and the central nervous system the most serious is ALS - Amyotrophic Lateral Sclerosis as it is always fatal and develops fast. Very few victims live more than 5 years from the diagnosis.
Of the degenerative diseases Dementia and Alzheimers are the best known as many elderly people are affected. Read more about these diseases and about Parkinson's and Neuromuscular diseases which are also degenerative diseases.