What is a coma?

What is a coma?

A coma is a state of deep unconsciousness where the person cannot by aroused. It is generally characterized by the absence of spontaneous eye movements, response to painful stimuli, and vocalization. Loss of consciousness typically involves injuries to the brain stem, the oldest part of the brain, which is responsible for basic life functions such as alertness, arousal, heartbeat, and breathing.

A patient’s degree of consciousness is often used to determine the severity of his/her brain injury. Instruments such as the Glasgow Coma Scale (GCS) use the patient’s visual, motor, and IL verbal responsiveness to measure level of consciousness. Scores of 8 or below are considered to represent a true coma (no eye opening, no response to simple commands, and unable to communicate) and to indicate a severe brain injury. However, it is important to note that many medical professionals adhere to a broader definition of coma. Thus, patients who may have their eyes open some of the time and even stare and look around at times, may be still be referred to as being in coma if they can’t communicate or follow commands. Scores from 9 – 12 on the GCS are suggestive of a moderate brain injury. GCS scores of 13 and above are thought to indicate that the brain injury is mild.

The duration or length of coma (LOC) is also used to measure severity of injury and to predict outcome. The longer the LOC, the more severe the brain injury. LOC greater than 6 hours post-admission is considered to be a severe brain injury. LOC between 20 minutes and 6 hours post-admission is considered to be moderate brain injury. LOC of less than 20 minutes is considered to be indicative of a mild brain injury.

The general misunderstanding of the definition of true coma can often interfere with the measurement of LOC. It is rare for true coma to last more than several weeks, and in fact, almost all patients will eventually awaken from a coma. However, it is important to understand that emergence from a coma is a gradual process in which the brain injured patient may go through several stages including periods of disorientation, post-traumatic or anterograde amnesia (patient has no memory of recent events), agitation. Some of these patients may require medication or even physical restraints to prevent them from harming themselves or others. The Rancho Los Amigos Scale is a commonly used instrument to record the stage of emergence from coma.


At present, we do not know whether a patient in a coma can feel pain or whether they can hear what we are saying, We do know however, that some studies have shown that coma stimulation, the process of providing sensory stimulation to coma patients including familiar stimuli such as familiar voices and music, has been shown in some studies to improve coma recovery.


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