Evaluating depth of coma

While we are all being remarkably patient (we don’t really have a choice, do we?) as Michael’s injuries heal and his state stabilises, I thought it would be useful for what’s to come to explain a bit of how doctors evaluate coma patients. This includes assessing how “deep” the coma is, as well as tracking the patient’s progress as the clinical situation evolves.

Now I’m sure that Michael’s care team will NOT be releasing any of this stuff when they begin lightening his sedation, but I still think it’s useful that we have an idea of what’s going on, how it’s done, and that we can interpret any details that do manage to filter out.

Because by definition a coma is defined as a prolonged state of diminished consciousness making meaningful contact between the patient and his environment impossible, we can’t just ask the patient a series of questions and go from there. What’s needed is a tool to evaluate more basic levels of brain function, in a reproducible, standardised and validated way. This tool is called the Glasgow Coma Score (GCS).

The GCS was described in 1974 by a duo of neurosurgeons working in Glasgow. For those of you interested in the original article, a landmark in neurointensive care, here is the reference:

Assessment of coma and impaired consciousness. A practical scale. Teasdale G, Jennett B; Lancet, 1974, July 13; 2(7872):81-4

The GCS involves observing the patient spontaneously, and if necessary determining his or her response to graded levels of stimulation. The initial stimulus is speaking to the patient. If needed, a painful (but harmless) stimulus is applied. There are several ways of doing this – steady heavy pressure on the forehead, deeply pinching the trapezius muscle, or deep pressure on a fingernail bed.

Three criteria are scored: the patient’s eye opening, motor response, and verbal output. As you can see if you look at the scoring criteria, the points for each parameter go from higher (representing a “higher” level of function) to lower scores, representing “worse” function.

In terms of eye opening, 4 points are assigned if the patients opens his or her eyes spontaneously, 3 points if they open to vocal stimulation, 2 if they only open to pain, and 1 if there is no eye opening at all.

Attention then turns to the patient’s verbal responses. Appropriate, oriented responses to simple questions get 5 points. Confusion or disorientation is scored 4; inappropriate, unrelated words “earn” 3 points. If the patient only makes incomprehensible sounds in response to stimulation, 2 points are given, and as with the eyes, if there is no verbal response only 1 point is given. Obviously this criteria cannot be assessed accurately when the patient is intubated, and this fact is noted, often by assigning a “value” of “T” to this criteria.

Motor responses are extremely important. If the patient follows simple commands (wiggle your toes, move your index finger, etc) he or she gets 6 points. When the response to the painful stimulus is an oriented attempt to remove the stimulus, 5 points are assigned. Next comes a withdrawal response (4 points), an unorganised series of movements representing a primitive response to escape from the stimulus. If the coma is still deeper, the patient will respond to painful stimulation with an abnormal flexion of the arms and/or legs (3 points), a response that originates in mid-levels of the brainstem. Still deeper is abnormal extension, because this is integrated at even lower levels of the brainstem. This is assigned 2 points. And as above, no motor response at all gets 1 point. If there is a difference in the response of the right and left sides, the BEST response is used in scoring (but the “score” of the other side is noted also).

As you can see, scores range from a high of 15 to a low of 3. The GCS score is evaluated quite often (several times a day), and provides a reliable and reproducible way of assessing whether the patient is “emerging”, “plunging”, or staying the same. It is also used to roughly stratify the severity of injury.  Scores from 13-15 are considered to be “mild” (and often correspond to what’s seen in concussion patients). Moderate head injury is present if the score is 9 to 13, while a score from 3-8 is defined as severe head injury. A patient with a score of 8 or less is considered to be in a coma.

The Glasgow Coma Score cannot be reliably evaluated until sedation is off, temperature is normalised, and other factors that could confound the scoring are taken into consideration.

Other elements are also evaluated of course including the size, symmetry and reactivity of the pupils, imaging, sometimes electroencephalography, in order to get a picture of how the patient is progressing and where the problem areas of the brain are.

Hope this helps.

follow Gary on Twitter (@former_f1doc)

12 thoughts on “Evaluating depth of coma

  1. Hi Gary. I want to share with you that it might be a chance to treat Michael for his brain damage. A scientist already developed and proved a treatment that works on most cases of brain damage. You may want to contact him for more information sergiocruz@neurodig.com His is also the director of Mentall Naturals Inc based on Toronto canada.

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  3. I can’t tell you how much I appreciate the information you have published surrounding Michael’s accident and ensuing treatment.

    You mention EEG – is there any other kind of scan / tool that would allow for measuring responses at a “biological” level that would help indicate areas of the brain which might be damaged (beyond a basic EEG)? Modern imaging technology seems so advanced that there might be a way.

    Thank you again for helping to inform us.

    • Indeed various modes of magnetic resonance imaging can yield interesting and potentially prognostically useful information (early days yet for this research) concerning energy metabolism and reserves in various areas of the brain. The spatial resolution of some of these techniques is not perfect but they are promising . . . for the future.

      The integrity of (primarily) sensory pathways can be assessed by sending small impulses from various regions of the body (hands, feet) and looking for the impulses to be received at the corresponding area of the cortex, using surface electrodes. These are called somatosensory evoked potentials (SSEPs). They can help to localise areas of damage along the pathways leading from the periphery to the cortex (peripheral nerve damage, spinal cord, brainstem relays, etc). But SSEPs aren’t particularly useful either for prognosticating.

      • CNN is doing story this week on a teen with Traumatic Brain Injury and the role of Omega-3 fatty acids [in fish oil] in his recovery…Seven such cases of TBI have been positively impacted using this since 2006. Google CNN and story about Grant Virgin…may be worth checking into and passing on to appropriate parties…Looks like it makes sense….What if it could help Michael?….

  4. Thanks for your writings both here and on twitter, it has been very helpful in understanding Michael’s condition and what can be expected. I would like to recommend Richard Hammond’s book “On the Edge”, about his jet car crash and his recovery from the injuries, and also his DVD “Hammond Meets Moss”, with him and Stirling Moss talking about their head injuries and recovery.

    It appears that Richard’s injuries were not as severe as Michael’s, and Stirling’s possibly a bit worse (with lass advanced medical care), and both were able to recover in due time.

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  6. Clearly no case is the same, but what conclusions, if any, can be drawn from the length of of time Michael Schumacher has been in his medically induced coma? Is two weeks or so a little, or a lot, in the context of the healing process for brain trauma?

  7. Thanks very much. We wait patiently, and patient we must be. At least when we eventually hear something we are better able to understand what the situation really is. Thank you.

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