A medical expert has outlined what may be happening inside the body when someone is in a coma.
Cleveland Clinic describes a coma as:
‘is a deep unconscious state where you can’t wake up or respond, even to pain or loud sounds.’
More broadly, clinicians define coma as a medical emergency in which a person is unconscious, unresponsive and unaware of what is going on around them, usually because normal brain function has been disrupted by damage to both sides of the brain or to the brain’s arousal systems.
People can enter a coma for several different reasons, such as a stroke, a serious infection, a drug overdose, or a traumatic head injury. Other recognised causes include a lack of oxygen to the brain after events such as cardiac arrest or drowning, very low or very high blood sugar, and severe liver or kidney problems that affect the brain.
Doctors also note that most comas do not last indefinitely. Cleveland Clinic says they typically do not last longer than a couple of weeks, although some patients move into other prolonged disorders of consciousness or are left with major long-term disabilities depending on the cause and the extent of brain injury.
Dr Marcus Thompson, who says he has devoted a decade to studying comas, explained on the YouTube channel Inside the Feeling that:
‘certain areas of your brain are still processing information’
“We know this because some coma patients show brain responses to voices, especially familiar voices,” he says. “To touch, to pain. They’re not awake, but some part of their brain is still receiving and processing input.”
Even so, because consciousness is not present in the usual way, doctors still cannot fully determine what a patient is actually experiencing.
That uncertainty remains one of the biggest unanswered questions in coma care. In recent years, brain imaging and EEG studies have shown that a meaningful minority of patients who appear entirely unresponsive may still have signs of hidden or ‘covert’ consciousness, with one large 2024 study finding evidence of this in about one in four brain-injured patients tested. That does not mean every comatose patient is aware, but it has strengthened the view that some patients may still process parts of their surroundings.
Thompson says:
‘every coma is different,’
That uncertainty is why there is no universal answer about whether patients retain some level of awareness. After recovery, some people report:
‘not remembering anything’
While others say they recall:
‘voices or sensations’
This is one reason relatives are often encouraged to speak calmly and normally at the bedside. While doctors cannot assume that a patient can fully hear or understand them, familiar voices may still be processed in some cases.
While the mental side of a coma remains difficult to pin down, doctors have a clearer understanding of the physical effects caused by long periods without movement.
In many cases, a person in a coma may remain still for weeks or even months. During that time, intensive care teams are not only treating the cause of the coma but also trying to prevent the complications that come with prolonged immobility.
Thompson explains:
“Your muscles need movement to survive,” he explains.
He says that after only 24 hours without movement, muscles begin to:
‘atrophy,’
In other words, tissue starts to waste away either partially or completely. The medical phrase he uses for this process is:
‘disuse atrophy’
He adds:
“If you’re not using a muscle, your body decides you don’t need it, and starts cannibalizing it for protein,” he says. The muscle fibres shrink, and mitochondria decrease.
According to Thompson, roughly five percent of muscle mass can be lost after one week in a coma. After two weeks, that figure may climb to between 10 and 15 percent, and after a month it can reach around 30 percent. He also notes that the loss is not spread evenly, with the legs typically affected more than the arms.
That is one reason many coma patients need significant physical rehabilitation once they wake up. Weakness from bed rest can also affect breathing muscles, making it harder for some patients to come off a ventilator after prolonged critical illness.
He also explains why physical therapists repeatedly move the limbs of coma patients throughout the day.
The reason, he says, is that:
‘tendons and ligaments also deteriorate,’
As the connective tissues that support the joints become stiffer, patients may develop contractures.
Cleveland Clinic defines these as:
“structural changes to your soft and connective tissues that cause them to stiffen, tighten and contract.”
Thompson says this can lead to fingers curling into the shape of a fist, while elbows and knees may also lock into place.
Passive range-of-motion exercises, careful positioning, splints and regular turning are all used in hospital to try to prevent this. They also help reduce the risk of pressure sores, another common danger for people who cannot move by themselves.
He adds that the heart, being a muscle as well, can become:
‘less efficient’
Because it is no longer working in the same way it would during normal activity.
Coma care also involves protecting the rest of the body while the brain heals. Depending on the patient, teams may need feeding tubes for nutrition, catheters, ventilator support, blood clot prevention, and close monitoring for infections such as pneumonia or urinary tract infections.
In short, a coma is not simply ‘sleeping deeply’. It is a severe disorder of consciousness with effects across the whole body, and recovery can depend as much on preventing secondary complications as on treating the original brain injury or illness that caused it.