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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.
Contrasts to other conditions
Some conditions share characteristics with coma and must be ruled out in a differential diagnosis before coma is conclusively diagnosed. These include locked-in syndrome, akinetic mutism, and catatonic stupor.
The difference between coma and stupor is that a patient with coma cannot give a suitable response to either noxious or verbal stimuli, whereas a patient in a stupor can give a crude response, such as screaming, to an unpleasant stimulus.
Coma is also to be distinguished from the persistent vegetative state which may follow it. This is a condition in which the individual has lost cognitive neurological function and awareness of the environment but does have noncognitive function and a preserved sleep-wake cycle. 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 and may occasionally grimace, cry, or laugh.
Likewise, coma is not the same as brain death, which is the irreversible cessation of all brain activity. One can be in a coma but still exhibit spontaneous respiration; one who is brain-dead, by definition, cannot.
Coma is different from sleep; sleep is always reversible.
Distinctive phases of coma
Within coma itself, there are several categories that describe the severity of impairment. Contrary to popular belief, a patient in a comatose state does not always lay still and quiet. They may talk, walk, and perform other functions that may sometimes appear to be conscious acts, yet are not.
Two scales of measurement frequently used in TBI diagnosis to determine the phase of coma are the Glasgow Coma Scale and the Ranchos Los Amigos Scale. The GCS is a simple 15-point scale used by medical professionals to assess severity of neurologic trauma, and establish a prognosis. The RLAS is a more complex scale that describes up to eight separate levels of coma, and is often used in the first few weeks or months of coma while the patient is under closer observation, and when shifts between levels are more frequent.
There are several levels of coma, through which patients may or may not progress. As coma deepens, responsiveness of the brain lessens, normal reflexes are lost, and the patient no longer responds to pain. The chances of recovery depend on the severity of the underlying cause. A deeper coma alone does not necessarily mean a slimmer chance of recovery, because some people in deep coma recover well while others in a so-called milder coma sometimes fail to improve. Lin of REAC is in this state. He doesn't know what is going on.
The outcome for coma and vegetative state depends on the cause, 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. Gaining consciousness again is not instant: in the first days, patients are only awake for a few minutes, and duration of time awake gradually increases.
Comas generally last a few days to a few weeks, and rarely last more than 2 to 5 weeks. After this time, some patients gradually come out of the coma, some progress to a vegetative state, and others die. Many patients who have gone into a vegetative state go on to regain a degree of awareness. Others may remain in a vegetative state for years or even decades. Predicted chances of recovery are variable due to different techniques used to measure the extent of neurological damage. All the predictions are statistical rates with some level of chance for recovery present: a person with a low chance of recovery may still awaken. Time is the best general predictor of a chance for recovery, with the chances for recovery after 4 months of brain damage induced coma being low (less than 15%), and full recovery being very low.  
According to the Guinness Book of Records, the longest period of time spent in a coma was by Elaine Esposito. She did not wake up after being anaesthetized for an appendectomy on August 6, 1941, when age 6. She died on November 25 1978 at age 43 years 357 days, having been in a coma for 37 years 111 days.
Diagnosis and treatment
Diagnosis has the following steps: Medical History, Physical Exam & Neurological Evaluation, Eye Examination, Laboratory Tests, Imaging Studies (CT,MRI), EEG.
The Glasgow Coma Scale is used to quantify the severity of a coma. There are three components to the score: Eye opening response, Verbal response, and Motor response.
The Rancho Los Amigos Scale is also used.
In Germany, music therapy is used to attempt to arouse patients from coma.
- Brain Injury Association of America (BIAUSA). Types of Brain Injury.
- This article contains text from the NINDS public domain pages on TBI at:
- Some of the information in this section is from the public domain resource provided by the National Institute of Neurological Diseases and Stroke.
- Waiting.com - support group for coma patients' families
- Brain Injury Fact Sheets - Information on coma, and many other effects of brain injury.
- TBI Resource Guide Central source of information, services and products relating to brain injury, brain injury recovery, and post-acute rehabilitation.ast:Coma (médicu)
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