What Happens When You’re In A Coma? Your Body Reacts In Strange Ways When Your Brain Function Shuts Down

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If you've never experienced a coma yourself, you may think about it through a dramatic lens informed by Grey's Anatomy reruns. However, what happens to your body when you're in a coma tells a very different story than the "deep sleep"  observers can see.

The word "coma" itself emerged from the Greek for "deep sleep" (koma) in around the 17th century, and methods throughout history for helping those in comas have included bloodletting from the head, emptying the stomach, cooling the body dramatically, blistering, laxatives and all kinds of deeply unpleasant treatments. We know now that coma medicine is a deeply complex and neurologically labyrinthine field. So what actually happens, on a basic level, to the body when it's in a coma?

Comas are very different from sleep. They're a variety of unconsciousness whereby the patient cannot be roused by any external stimuli, whether you tickle your feet or blow a trumpet in their ear. People in comas display neither reactivity — the responses of the body to things like light or touch — nor perceptivity — neurological responses like language or moving away from threats. Comas occur both as a result of trauma and as part of deliberate treatment by doctors (The Big Sick, the 2017 rom-com starring Kumail Nanjiani, tells the true story of his then-girlfriend's medically induced coma). And while the body in coma may look docile and completely inert, there's actually quite a lot going on under the surface.

There Are Different Types Of Coma

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Comas can be caused by a whole host of medical or environmental issues, from meningitis to a drug overdose to a hard blow to the head. But the idea of a uniform "coma state" is actually a myth. The unconsciousness of a coma comes in varied forms. A state of prolonged unconsciousness regarded as a coma may be classed as a vegetative state (in which the body makes movements and may grunt or yawn, but has no reaction to stimuli), catatonia (where there's no movement or response of any kind), or brain death, in which the brain function is destroyed, but some of the body's autonomic functions can possibly continue. There are different clinical ways to assess coma severity on a scale, by testing things like the eye's iris reflex and motor movement.

If you can be awakened — for instance, if you're in a stupor, which means you're pretty heavily unconscious but can be aroused with some effort — you're not technically in a coma. (A medically induced coma, by contrast, ends when the drugs that are inducing the coma are cut off, thus arousing the patient.) Comas are by definition states from which you can't be aroused.

What Happens In The Brain Of A Person In A Coma?

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Given the different types of coma out there, there's not a one-size-fits-all example of the brain patterns of comatose people. However, it's generally accepted that, neurologically speaking, to qualify as "in a coma" your brain should likely show zero awareness or cognitive processing that would occur while awake, and be unable to demonstrate response to any external stimuli. Consciousness, in the comatose person's brain, appears to have been "turned off" by an interference with the brain's communication between the brain stem and the cerebrum, which effectively controls cognitive consciousness. The system that does this communicating is the reticular activating system, and its malfunction is the mechanism behind comatose states. In an awake person's brain, thinking for oneself and seeing light or something else would show up neural patterns of activation that, in those who are comatose, are absent. Brain activity can be measured in a lot of ways: by an electroencephalogram, or EEG, by an MRI, and other attempts to spot the electrical firings of elements of the brain tissue.

There is, however, quite a lot we still don't know about the comatose brain. Doctors in 2013 treating an epileptic man in a coma and no activity on his EEG were extremely puzzled to find brain activity they didn't expect to notice: in the hippocampus. They replicated the findings in cats who were placed under general anesthetic, which we now understand is exceptionally close to a reversible coma. They don't think this changes anything fundamental about how people in comas are able to communicate or "know" anything about their condition, but it indicates that the brain in a comatose state might be doing something neurologically to try and protect itself.

The neurological pictures of people who are in vegetative states is slightly different. They're in what's medically qualified as "partial arousal", but are believed to be incapable of producing responses to exterior stimuli — though scientists have developed tests on brain activity that may allow them to communicate with certain vegetative patients by "reading" firing neurone patterns. This remains a very controversial and fraught area of neurology, though.

The Rest Of Your Body Isn't Affected By The Coma

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People in comas show the difference between two types of brain function: the kind that controls our higher consciousness, our ability to make jokes and be self-aware, and the kind that helps our bodies continue to function while we're down for the count. These features, such as breathing, heart rate and digestion, are part of the autonomic nervous system, and might be able to continue on for themselves while the brain is in a coma, depending on the cause of the issue and how it has affected other parts of the body. It was discovered in 2014, for instance, that patients who went into comas after cardiac arrests were more likely to recover if their heart rates showed a certain pattern.

Some people in comas will need respiratory help with an artificial breathing apparatus; all will require some way of keeping them hydrated and fed, a process usually done by IV injection into the veins. If coma patients are now lacking the reflexes to swallow and clear their airways of saliva, they'll choke or develop airway issues, and will need to be intubated (have an artificial breathing tube put in place).

One of the most common issues facing coma patients who recover is the level of muscle atrophy they've sustained during their period of unconsciousness. Caused by prolonged inactivity, this kind of muscle wastage isn't just restricted to coma patients; muscles require continual use to maintain strength and size, and being still for long periods means they fade away.

We're discovering new things about comas, recovery and how the brain's lack of consciousness works all the time. In 2017, for instance, scientists made headlines by making a 35-year old man who'd been in a persistent vegetative state since he was 20 enter a state of "minimal consciousness" by stimulating the vagus nerve, one of the biggest in the entire body. But this didn't mean he was "awake": minimal consciousness means he's got far more brain activity and reacts to stimuli, from following things with his eyes to showing surprise on his face, but he can't talk or show higher attentional function. It's a big step forward, but it's also not a conclusive one, because comas differ radically between people and the brain is a hugely complex, interesting organ that does many complicated things when hurt.