Coma is a prolonged period of unconsciousness. Unconsciousness is the lack of appreciation of (or reaction to) a stimulus. Coma differs from sleep in that one cannot be aroused from a coma.

Coma involves two different concepts:

1.) Reactivity: Reactivity refers to the innate (or inborn) functions of the brain, i.e., the telereceptors (eyes and ears), the nociceptors (responses to pain), the arousal reaction (wakefulness) and the orienting response (turning one's head toward the source of sound or movement). We could also refer to these as reflexive movements.

2.) Perceptivity: Perceptivity refers to the responses of the nervous system to stimuli, which have been learned or acquired, i.e., language, communication skills, individual methods of movement such as gestures, etc. Perceptivity also refers to less complex learned or acquired reactions such as flinching when threatened. We can also think of these as conscious movements.

A person in a coma does not exhibit reactivity or perceptivity. He/she can not be aroused by calling his/her name or in response to pain.

As a person begins to emerge from a coma, they may begin to react to certain stimuli. To regain "consciousness" however, reactivity and perceptivity must both be present. These two elements are necessary for a state of awareness. Often, many of the elements of perceptivity must be relearned, such as speech, self-care, etc.

Many people are surprised that all stages of coma do not resemble what we have been taught to expect; a deep sleep. The person in the coma may exhibit movement, make sounds, and experience agitation. It is important to keep in mind that the coma patient may exhibit reflex activities which mimic conscious activities. Coma patients may be restrained to keep them from removing tubes or dislodging IVs. The progress of coma is measured by the patient's increasing awareness of external stimuli. There are many levels of coma which the patient will pass through as functionality increases.

Sometimes a coma is induced by chemical means to aid in medical treatment and recovery.

It is very important to remember to speak positively to and in the presence of the person in a coma. Some patients claim to remember very distinctly events while they were in a coma. And although we cannot be positive about the level of awareness in any particular case, studies show that a positive attitude may be beneficial to the recovery of the patient. Conversations about the possible negative outcomes with doctors, nurses, and family should be conducted with discretion.

It is also important to keep in mind that different injuries produce different outcomes. While we can expect that a patient may slowly emerge over time, some patients can suffer from "locked in" syndrome in which they are awake but unable to react or act upon their environment, or recover to a point where they have limited capacities, or have a limited recovery which will require long term care.

Last updated April 22, 2004