A state of profound unconsciousness caused by disease, injury or poison. This can include head injury, encephalopathy/encephalitis, meningitis, stroke, major multiple trauma, neurological disorder, seizure Disorder, intoxication, metabolic abnormalities, and hypoxia.

An individual in a coma is unable to react to their environment and has no response to any form of stimulation.  The person is not “just sleeping”, as the brain wave activity in a comatose person is different than a sleeping person.

There are several levels of coma a patient can be in that describe the severity of impairment.  There are two scales of measurement frequently used to determine the phase of coma a patient is in.  They are the Glasgow Coma Scale (GCS) and the Rancho Los Amigos Scale (RLAS).

The GCS is a simple 15-point scale used by medical professionals to assess the severity of the altered consciousness, and establish a prognosis.  There are three components to the score: Eye opening response, Verbal response, and Motor response.

The RLAS is more complex and describes emergence from coma in patients with traumatic brain injury.  This scale is often used in the first few weeks or months after injury, while the patient is under closer observation.  This scale is useful to therapists and families to help understand the behavior and progression of the head injury survivor.  This scale is used in the first weeks or months following the injury and is not intended to predict improvement over the long term. 

There are 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 fail to improve.

The outcome for a patient in a coma or vegetative state depends on the cause of the coma, location of damage, and the severity and extent of neurological damage: outcomes range from recovery to death.  People do emerge from coma with a combination of physical, intellectual and psychological difficulties that need special attention.  Recovery is a gradual process, as the patient acquires more and more ability to respond.  Some patients may never progress beyond very basic responses, but many recover full awareness.  Gaining consciousness is not something that happens instantly, as is often seen on television: at first, the person may only awaken for a few minutes, then gradually the time awake increases, along with the level of responsiveness as measured by the RLAS.

Generally, coma will last a few days to a few weeks, but rarely more than 2 to 4 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 and function.  Others may remain in a vegetative state for years or even decades. Time is the best general predictor of a chance for recovery.