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Understanding Stages of Coma

Three stages of coma

Often lumped under the label of “Coma” are three stages of disordered consciousness. Disorders of Consciousness (DOC) are a set of disorders that effect a person’s ability to be awake. DOC includes coma, the vegetative state (VS) and the minimally conscious state (MCS). These disorders (see sidebar at right for further information about each of these stages) are among the most misunderstood conditions in medicine.1  Published estimates of doctors making mistakes among people with disorders of consciousness range from 15%-43%.2,3,4

Coma – the battle to survive

A coma is a state of unconsciousness when a person cannot be wakened with touch or noise. The inability to waken makes coma different from sleep. It is the length of time that a person remains in coma that has commonly been used to label the severity of a person’s brain injury.

What causes a coma is an area of great interest. The brain stem is often injured. The brain stem processes automatic, unconscious controls (often called the vegetative functions) of the body including heart rate, blood pressure, body temperature, and breathing. The reticular activating system (RAS) is located within the brain stem, and is the important “on/off” switch for consciousness and sleep.

  • To be awake, the RAS and at least one cerebral hemisphere (we have two) must be functioning.
  • If a person loses consciousness, either the RAS has stopped working, or both cerebral hemispheres have shut down.
  • The reticular activating system stops working in two situations:
  • When there is brain stem bleeding or loss of oxygen. This shuts off the reticular activating system.
  • When there is swellingin the brain. The skull is a rigid box that protects the brain. Unfortunately, if the brain is injured and begins to swell, there is no room. Increased pressure within the brain (increased intracranial pressure) causes compression of the brain tissue against the skull bones. This swelling can affect other parts of the brain.

If the intracranial pressure continues to increase without being treated, the brain will continue to swell until it pushes down through the opening at base of the skull. This damages the brain stem where the reticular activating system is located. This also damages the breathing and blood pressure control centers of the brain and can be the reason for death in the hours or days after injury.

  • The Battle to Survive – Acute Care Treatment of Coma from Swelling

When the members of the medical trauma team are concerned about swelling of the brain, an intracranial pressure monitor may be placed inside the skull to read the pressure inside. A small hole is drilled into the skull and the monitor tip is placed inside the skull. Or, surgeons may temporarily remove a portion of the skull to minimize the risk of further injury to the brain due to the pressure. Later, sometimes months later, the skull is repaired through a surgery called a “cranioplasty”.

Doctors may also give medications to “induce” a coma if they are worried about brain swelling. Medications can be injected similar to providing a general anesthetic. An induced coma is used to decrease intracranial pressure and to rest the brain. An induced coma can make it difficult to use the Glasgow Coma Scale as a predictor of TBI severity.

Hospital staff may ask family members and friends to be very quiet when visiting when there is a concern about high pressure spikes in the brain.  The lighting of the room may be kept low and the room kept cool.  This is called “keeping the stimulation low” so that the brain can rest and recover.

Coma usually evolves into the vegetative state or a higher level of consciousness within two to four weeks for those who survive. 5,6


After Coma; Vegetative State and Minimally conscious States – Waiting for signs of improvement

There have been improvements in taking pictures of the brain and measuring the electrical activity of the brain in the last five years.  The results of new studies, and the well-documented reports of recovery months after the initial injury, challenge the long held view that people with long periods on unconsciousness cannot recover. Cases of late recovery point to the remarkable plasticity of the human brain and its potential for long-term recovery.1

The Vegetative State (VS) and the Minimally Conscious State (MCS) are stages on consciousness that can follow coma. They are different stages. The person’s awareness of their surroundings and prognosis (ability to recover) is different for VS and MCS.

■      The vegetative state can be a temporary or long-term state following coma in persons who have experienced TBI.  Both the terms “persistent” and “permanent” are controversial, with a practice guideline that the term “permanent” not be used until the VS state has lasted 12 months.7  Persons in VS may move in a non-purposeful manner and may smile, grimace, have tears in their eyes, and may moan. Individuals in VS generally do not follow people or objects with their eyes or remain visually focused on people or objects.  If a person can keep eye contact or follow movement with their eyes, it can often mean that the person is transitioning to MCS. Some people in VS have episodes of “autonomic storming” (refer to separate article in Visions). A sleep/wake pattern is reestablished and the “vegetative functions” of breathing, body temperature regulation start to normalize.

  • Prognosis for Recovery after months in a VS stage:  In the TBI population, 35% of individuals who remain in VS for 3 months will recover consciousness by 12 months post-injury.  Among this group, 20% will be left with severe disability, while the remaining 15% will have a moderate to good outcome.1 
  • Persons with MCS retain the brain functioning responsible for understanding language, despite their inability to communicate reliably. Persons may have a delayed and an inconsistent way that they respond to “yes” and “no” questions.  Persons may show different emotional response when loved ones are present.  He/she may show different facial expressions depending on the topic of conversation and may laugh or cry.  The storage of new memories and short term memory (knowing what day it is, knowing who visited yesterday) is thought to be impaired thought it is difficult to measure.
  • Prognosis for Recovery after months in a MCS stage:  The recovery for this population is slow and long. In the MCS group, 50% will have moderate to severe disability while 27% will have mild to moderate disability.8,9

Rehabilitation for People Who are Slow to Regain Consciousness

Hospitals will start discharge planning as soon as life-threatening medical problems have resolved.  People who are in a VS or MCS when they become stable medically (despite the fact that they still may have tubes) will need to leave the hospital.

There is no doubt that people who experience severe TBI need rehabilitation after their hospital stay. And chances are good that further recovery will occur. Choices of where to go next could be a rehabilitation facility (like Rainbow), a skilled nursing facility, or home with 24 hour family/caregiver assistance. In some instances, a person who is VS or MCS may be admitted to a rehab hospital for a short stay (2-4 weeks) for family teaching and the development of needed rehab equipment.

Rehabilitation for persons at this stage of recovery takes into consideration their unconsciousness and/or memory problems.

Rehabilitation and nursing goals can include:

  • To establish a normal pattern of being up and out of bed with the right wheelchair
  • To start sitting on the edge of the bed or matt and using a tilt table or standing table to put weight on feet
  • To get good nutrition for healing through a tube
  • To move and position the injured person regularly so that skin stays healthy
  • To establish a “yes”/”no” system through movement of eyes or mouth or hands or feet
  • To work on swallowing, a prerequisite of eating, and to keep lungs clear and healthy
  • To combat abnormal muscle spasticity that can occur when the brain is injured which can cause joints to get tight
  • To use medications and therapy that could improve wakefulness/arousal

Diagnostic Criteria


All of the following criteria must be evident on bedside examination:

  • No eye opening and absence of sleep-wake cycles on EEG.
  • No evidence of purposeful motor activity.
  • No response to command.
  • No evidence of language comprehension or expression.
  • Inability to discretely localize noxious stimuli.

Vegetative State

All of the following criteria must be evident on bedside examination:

  • No evidence of awareness of self or environment.
  • No evidence of sustained, reproducible, purposeful, or voluntary behavioral responses to visual, auditory, tactile, or noxious stimuli.
  • No evidence of language comprehension or expression.
  • Intermittent wakefulness manifested by the presence of sleep-wake cycles.
  • Sufficiently preserved hypothalamic and brain-stem autonomic functions to permit survival with medical and nursing care.
  • Bowel and bladder incontinence.
  • Variably preserved carian-nerve reflexes and spinal reflexes.

Minimally Conscious State

At least one of the following criteria must be clearly evident on bedside examination: 1

  • Simple command following.
  • Gestural or verbal yes/no responses.
  • Intelligible verbalization.
  • Movements or affective behaviors that occur in contingent relation to relevant environmental stimuli and are not attributable to reflexive activity. Any of the following examples provide sufficient evidence for this criterion:
  • Pursuit eye movement or sustained fixation that occurs in direct response to moving or salient stimuli.
  • Episodes of crying, smiling, or laughter in response to the linguistic or visual content of emotional but not neutral topics or stimuli.
  • Vocalizations or gestures that occur in direct response to the linguistic content of comments or questions.
  • Reaching for objects that demonstrates a clear relationship between object location and direction of reach.
  • Touching or holding objects in a manner that accommodates the size and shape of the object.

Tools used to measure level of consciousness10

Since consciousness cannot be directly measured, clinicians must observe behavior and draw conclusions about an individual’s underlying state of consciousness. Those observations are then used to fill out measurement scales.  Different scales are used in different settings.  Two measurement scales that are important to life saving, establishing a prognosis, and tracking recovery are as follows:

The Glasgow Coma Scale is used at the scene of the accident, in the Emergency Department, and during the life saving hospital stay.  It is a useful scale for doctors and nurses who want to track improvements in brain recovery or predict recovery.  A sudden decline in being awake can mean that the brain pressure is changing for the worse or that there may be an area of bleeding in the brain that needs attention. An increase in the number means that the brain is getting better. The Glasgow Coma Scale is rarely used after the initial hospital stay.

Glasgow Coma Scale
Eye Opening
Spontaneous 4
To loud voice 3
To pain 2
None 1
Verbal Response
Oriented 5
Confused, disoriented 4
Inappropriate words 3
Incomprehensible words 2
None 1
Motor Response
Obeys commands 6
Localizes pain 5
Withdraws from pain 4
Abnormal flexion posturing 3
Extensor posturing 2
None 1

A fully conscious patient has a Glasgow Coma Score of 15.

A person in a deep coma has a Glasgow Coma Score of 3 (there is no lower score).

The Rancho Level of Cognitive Functioning Scale (LCFS) is a scale used to assess cognitive functioning in people with brain injury.11 The first three levels are similar to the stages of coma, VS, and MCS. This scale is most often used in the first year after brain injury. This scale is available for free in its complete form at :

Level Explanation
I – No response Patient appears to be in a deep sleep and is completely unresponsive to external stimuli. COMA
II – Generalized Patient reacts inconsistently and non-purposefully to stimuli in a non-specific manner. Responses are limited in nature and are often the same regardless of stimulus presented. Responses may be physiological changes, gross body movements, and/or vocalization. Often the earliest response is to deep pain. Responses are likely to be delayed. VEGETATIVE STATE
III – Localized Patient reacts specifically but inconsistently to stimuli. Responses are directly related to the type of stimulus presented, as in turning head toward a sound or focusing on an object presented. The patient may withdraw an extremity and/or vocalize when presented with a painful stimulus. Simple commands may be followed in an inconsistent, delayed manner, such as closing eyes, squeezing or extending an extremity. Once external stimulus is removed, the patient may lie quietly. A vague awareness of self and body may be shown by responses to discomfort produced by pulling at  tube. Bias may be shown by responding to some persons (especially family/friends) but not to others. MINIMALLY CONSCIOUS STATE


  1. Berube J, Fins, J, Giacino J, et al. The Mohonk Report: A Report to Congress. Disorders of Consiousness: Assessment, Treatment, and Research Needs. 2011.
  2. Tresch DD, Sims FH, Duthie EH, Goldstein, MD, Lane PS. Clinical characteristics of patients in the persistent vegetative state. Arch Internal Med. 1991;151:930-932.
  3. Childs NL, Mercer WN, Childs HW. (1993). Accuracy of diagnosis of persistent vegetative state. Neurol, 43:1465-1467.
  4. Andrews K, Murphy L, Munday R, Littlewood C.  Misdiagnosis of the vegetative state: Retrospective study in a rehabilitation unit. BMJ. 1996; 313:13-16.
  5. Plum F, Posner J. The diagnosis of stupor and coma, 3rd Edition. Philadelphia: F.A. Davis. 1982.
  6. Multi-Society Task Force on the Persistent Vegetative State. Medical aspects of the persistent vegetative state, part I. N Engl J Med. 1994; 330:1499-1508.
  7. American Academy of Neurology. Practice parameter: Assessment and management of persons in the persistent vegetative state. Neurol. 1995; 45:1015-1018.
  8. Giacino JT, Kalmar K. The vegetative and minimally conscious states: A comparison of clinical features and functional outcome. J Head Trauma Rehabil. 1997; 12(4):36-51.
  9. Whyte J, Katz D, Long D, et al. Predictors of outcome in prolonged posttraumatic disorders of consciousness and assessment of medication effects: A multicenter study. Arch Phys Med Rehabil.  2005; 86: 453-462.
  10. Huff JS, Martin ML. Altered mental status and coma.  In: Worlfson AB, Hendey GW, Ling LJ, et al., eds. Harwood-Nuss’ Clinical Practice of Emergency Medicine. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2009: chap 14.
  11. Hagen C, Malkmus D, Durham P. Levels of cognitive functioning. Downey (CA): Rancho Los Amigos Hospital; 1972.

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