Coma

In medicine, a coma (from the Greek koma, meaning deep sleep) is a profound state of unconsciousness. A comatose patient cannot be awakened, fails to respond normally to pain or light, does not have sleep-wake cycles, and does not take voluntary actions. Coma may result from a variety of conditions, including intoxication, metabolic abnormalities, central nervous system diseases, acute neurologic injuries such as stroke, and hypoxia. It may also be deliberately induced by pharmaceutical agents in order to preserve higher brain function following another form of brain trauma.