G31: Other degenerative diseases of nervous system, not elsewhere classified

G31.1: Senile degeneration of brain, not elsewhere classified

The brain is made up of several areas. For example, the cerebrum is used to think and plan actions. In the cerebellum, movements are initialized and coordinated. The brain stem is responsible for various unconscious tasks such as breathing. The brain stem passes into the spinal cord.

As we age, the brain or certain parts of the brain can slowly get smaller. Depending on which areas of the brain are getting smaller, one may have different symptoms.