Coma: The Silent Epidemic

  1. definition of coma - a period of unconsciousness lasting more than hour in which the patient's eyes are closed (note: sleep is not "unconsciousness" in this sense in that you can be aroused from sleep)
    1. causes - oxygen deprivation, drug overdose, gunshot wound, deceleration injury (see below), and hundreds of others
    2. at any one time, the are 10-15,000 people in the US in comas or vegetative states
    3. with increasing ability to keep the body alive, coma has become more common in the absence of techniques to maintain brain function
  2. one of the most common causes of coma is deceleration injury to the brain
    1. occurs when the head stops moving abruptly (as in automobile accidents)
    2. the brain continues to move in the cranium and slaps against the inside of the skull
    3. the immediate result is edema (swelling) - if the swelling increases intracranial pressure sufficiently, it will interrupt blood flow to the brain
      1. loss of blood supply to the cortex usually occurs first - loss of consciousness and, if prolonged, death of cortical cells
      2. loss of blood supply to the brainstem - loss of vegetative functions, results in death if prolonged
    4. extent and nature of recovery depends on how quickly function returns to various areas of the brain
    5. mechanical damage also occurs in which axons and dendrites are stretched and broken in widespread areas of the brain - abnormal release of neurotransmitters and other chemicals can contribute to the edema
  3. severity of, length of, and recovery from coma
    1. Glasgow Coma Score (GCS) - a scale of 0-15, on which 9 is minimally conscious and 3 represents profound coma
    2. the longer a coma goes on, the worse the prognosis becomes - there is virtually no possibility of recovery if:
      1. a coma from oxygen deprivation (e.g., drowning) lasts more than three months
      2. a coma from brain damage (e.g., automobile accident) lasts more than twelve months
    3. people don't just suddenly "come out" of comas, sit up, and begin speaking (as they do in the movies and on soap operas) - when recovery occurs, it is slow and often incomplete
    4. certain kinds of mental experiences during the comatose state have been reported by people who have recovered - these sound like dreamlike states or hallucinations and indicate that some minimal functioning was occurring in the cortex
    5. states into which coma resolve
      1. brain death
      2. vegetative state - reflex actions (such as breathing, coughing, sneezing, blinking, yawning, grimacing, sighing, crying, and sleep/waking) are possible due to recovery of the brainstem, but consciousness is absent due to failure of the cortex to recover
      3. minimally conscious state - patients can sometimes make simple responses to commands and sometimes cannot
      4. locked-in state - patient is conscious and aware of his or her surroundings but completely paralyzed and unable to move, thus appearing vegetative or minimally conscious (very rare)
    6. it is often very difficult, even for experienced experts, to differentiate between these states
    7. there are no documentated cases of "miraculous" recoveries from prolonged coma, and only five cases in which any recovery at all occurred ("prolonged coma" defined as in III.B.1-2 above)
      1. these are sometimes reported in the press
      2. but investigations show that these patients either:
        1. were not in a true coma
        2. were not actually recovered
        3. had recovered only briefly and later relapsed and died
        4. or some combination of these (the "coma cop" case of 1996)
  4. treatments
    1. there are no known cures or successful treatments for prolonged coma or vegetative states
    2. evidence for some controversial treatments is minimal or nonexistent (although properly controlled studies on coma are almost impossible to do)
      1. hyperbaric oxygen (HBO) treatments - there are promising-appearing case histories, but (as with all case histories) it is not possible to attribute any cause and effect to the treatments and recoveries (it's possible that the patients would have recovered anyway without the treatment)
      2. sensory hyperstimulation training
    3. medical science is skeptical of these controversial treatments, not only because of the lack of evidence that they work, but also because they are based on common myths of how the brain functions
      1. myth 1 - stunned brain cells exist in an idling state and need only to be fired up
      2. myth 2 - we use only 10% of our brains, and the remaining 90% can take over the function of cells that are killed by injury