A coma is a profound or deep state of unconsciousness. The affected individual is alive but is not able to react or respond to life around him/her. Coma may occur as an expected progression or complication of an underlying illness, or as a result of an event such as head trauma. A persistent vegetative state, which sometimes follows a coma, refers to a condition in which individuals have lost cognitive neurological function and awareness of the environment but retain noncognitive function and a perserved sleep-wake cycle. It is sometimes described as when a person is technically alive, but his/her brain is dead. However, that description is not completely accurate. In persistent vegetative state the individual loses the higher cerebral powers of the brain, but the functions of the brainstem, such as respiration (breathing) and circulation, remain relatively intact. Spontaneous movements may occur and the eyes may open in response to external stimuli, but the patient does not speak or obey commands. Patients in a vegetative state may appear somewhat normal. They may occasionally grimace, cry, or laugh.
Once the patient is out of immediate danger, although still in coma or vegetative state, the medical care team will concentrate on preventing infections and maintaining the patient's physical state as much as possible. Such maintenance includes preventing pneumonia and bed sores and providing balanced nutrition. Physical therapy may also be used to prevent contractures (permanent muscular contractions) and orthopedic deformities that would limit recovery for the patients who emerge from coma.
The outcome for coma and vegetative state depends on the cause and on the location, severity, and extent of neurological damage: outcomes range from recovery to death. People may emerge from a coma with a combination of physical, intellectual, and psychological difficulties that need special attention. Recovery usually occurs gradually, with patients acquiring more and more ability to respond. Some patients never progress beyond very basic responses, but many recover full awareness. Patients recovering from coma require close medical supervision. A coma rarely lasts more than 2 to 4 weeks. Some patients may regain a degree of awareness after vegetative state. Others may remain in a vegetative state for years or even decades. The most common cause of death for a person in a vegetative state is infection such as pneumonia.
The NINDS supports research on neurological conditions such as coma and persistent vegetative state. This research is aimed at finding ways to prevent, treat, and cure these conditions.
These articles, available from a medical library, are sources of in-depth information on coma:
Plum, F. "Disturbances of Consciousness and Arousal." In Cecil Textbook of Medicine, 19th edition, W.B. Saunders Co., Philadelphia, pp. 2048-2063 (1992).
Harris, J, and Berger, J. "Clinical Approach to Stupor and Coma." Chapter 5 in Neurology in Clinical Practice, Vol. 1, Butterworth-Heinemann, Boston, pp. 43-63 (1991).
National Institute of Neurological Disorders and Stroke
National Institutes of Health
Bethesda, MD 20892