Global term for any neurological disorder in which the primary symptoms involve a deterioration of mental functioning-loss of ability to care for themselves and recognize familiar surroundings and people

Neurodegenerative disease

Explanation:

   Neurodegenerative Disease is a generic term for a range of diseases that affect neurons in the human brain.  Neurons are the base unit of the nervous system (brain and spinal cord). Normally, neurons do not reproduce or replace themselves, so when they are damaged or die they cannot be replaced. Parkinson's disease, Alzheimer's and Huntington's disease are some examples of neurodegenerative diseases.

   They are incurable and debilitating diseases that result in progressive degeneration and / or death of neurons. They cause problems of movement (ataxias) or mental function (dementia).