Jun 15 2021

Waking from Coma

There are many amusing movie tropes, mostly used as a shorthand for directors to communicate with the audience. Bags of groceries always have either a loaf of bread or a leafy vegetable sticking out the top, so that you know at a glance they are groceries. Live mics always give a burst of feedback when someone steps up to them. Holograms always glitch, so you know they are holograms. People falling in love always spray water on each other and shop in open-air markets. All raptors sound like red-tailed hawks.

Some tropes, however, are not benign. They are based on and perpetuate a misunderstanding of reality. A pernicious one I have had to deal with professionally is the motion that someone can wake from a prolonged coma and suddenly be neurologically high functioning. They wake up, they are bleary eyed and confused but otherwise intact. As an aside, another trope is that as soon as the person wakes up whoever is present yells for a doctor as if it is an emergency. Here’s a pro tip – it might be an emergency when someone suddenly falls unconscious, but not when they wake up.

Typically there may be a period of physical recovery so they can get their strength back, but neurologically waking up from a coma is presented as flipping on a switch. The problem with this trope is that it almost never occurs (and I am saying “almost” just to be cautious – I am not aware of any cases). This does not mean that meaningful recovery cannot happen, but we have to put this into perspective. The trope also goes beyond entertainment. We see it in news reporting as well, even if only by glossing over important details. Here is a recent BBC report of a woman waking from a 10 month coma. A non-expert reading this would almost certainly come away with a distorted impression of what likely happened (I have no inside information on this specific case, I am only basing that assessment on the BBC report).

To put coma into a more medical perspective, lets divide them into two broad categories, but first let’s give a basic definition of coma. This is a technically vague term, neurologists would use a more specific term in individual cases, but it essentially refers to what we call impairment of consciousness, to the point that someone is unable to maintain wakeful consciousness. The two broad categories are those that are due to reversible causes and those that are due to brain damage. We can put someone in an induced coma with drugs, and they should wake up and be neurologically intact once the drugs wear off. In addition to drugs there are a number of metabolic derangements that are reversible, infections, or seizures. These are all things that can get better, and once they do the person can just wake up. Recovery might be a matter of hours or days.

When coma is due to brain injury, however, that is not considered a reversible cause. That does not mean there is no potential for healing and recovery, just that there is nothing reversible on the short term. In order to assess how much injury has been done to a brain, we need to treat all reversible causes and then assess the patient for neurological damage. There is also supporting data from anatomical studies like MRI scan and functional studies like EEG. Like all medical conditions, we can break down brain injury into acute, subacute, and chronic. An acute injury just happened, subacute is days to weeks, and chronic is generally more than three months. These is no sharp demarcation line, however, this is a spectrum. Generally speaking the longer someone goes in a coma not due to reversible causes the lower their chance of meaningful recovery, with imaging, the details of their neurological exam, and functional testing for added context. There are published studies looking at hundreds of cases and correlating these factors with their probability of recovery. Mechanism of injury is also a factor, with more diffuse injury having a worse prognosis.

Therefore, if someone is in a coma for months or years they must have serious brain injury. These are the cases that are not going to simply “wake up” and be near normal. Again there are two broad categories here – those who have diffuse brain injury and those with focal brain injury. Diffuse injury is the easier to prognose because they almost always do very poorly. The whole brain is damaged, and there is insufficient brain activity to generate wakeful consciousness. In these cases, however, people may still slowly recover due to brain healing. The brain can heal to some degree, and this can occur for 2-3 years before it largely plateaus. The younger the patient the greater their healing potential. This process is slow, however. But a person can cross the threshold of wakefullness, and in this sense can “wake up”. However, this threshold means they will go from being barely comatose to barely awake. They may be able to open their eye, to attend to things and people in their environment.

The key point, however, is that such patients would not go from being in a prolonged coma due to diffuse brain injury to being high functioning. They will needs months or even years of neurological rehab to slowly regain function. Further, their new baseline, once they recover as much as they can, will likely be very different from their pre-injury self. In these situations managing expectations is important, and so it is useful for everyone to know that a person with this level of brain injury will likely be significantly impaired. They may not regain the ability to talk, or walk, or participate in their activities of daily living. This is still meaningful recovery, and generally loved-ones will take what they get and are grateful to have any semblance of the person they love back.

I am not writing this to be a downer or to minimize meaningful recovery. Rather, physicians learn the incredible importance of giving families accurate expectations. They have important decisions to make, and they have a lot of emotions on the line. Unrealistic or even impossible expectations cause tremendous harm – insult on top of injury.

For patients with focal injury prognosis is a bit more difficult, and we do need to hedge or bets a little. This is because in such cases there may be parts of the cortex, the thinking part of the brain, that are relatively intact. However, the brain cannot generate consciousness because more automatic parts of the brain needed to do so are injured. Or the patient may have injury to the parts of their brain that allow them to hear, speak, or move. They may therefore look like they have greater impairment of consciousness than they do. Recent research has been focused on trying to better prognosticate in these difficult cases.

Still, after prolonged coma due to brain injury, even with parts of the brain being intact, recovery will be long and difficult. But there may be more potential here than in cases with diffuse brain injury.

This is a quick overview of a complex topic, but the take-home is that the notion of someone suddenly “waking up” from a prolonged coma due to brain injury, to suddenly be their smiling old self, is a fiction. It’s too dramatic a story, however, for the media or entertainment industry (even when there is a meaningful difference between the two) to give up. So they perpetuate the myth, which doctors then have to undue when dealing with families with loved-ones in this unfortunate situation.

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