Complete lack of consciousness, with loss of reaction to stimulus and of spontaneous nervous activity.
It is usually associated with cerebral injury of metabolic or physical origin. Simple concussion s cause short losses of consciousness. Coma from lack of oxygen may last several weeks and is often fatal. Coma caused by stroke can be sudden, while that caused by metabolic abnormalities (as in diabetes mellitus ) or cerebral tumour s comes on gradually. Treatment depends on the cause.