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What is a coma?

A coma is a condition of unconsciousness that is deep. Some forms of infection may occur as a result of a traumatic injury, such as a blow to the head, or a medical condition, for instance.

Coma is distinct from sleep since it is difficult for the person to wake up.

It is not the same as death in the brain. The person is alive, but they can’t react to their environment in the usual way.

The issue that scientists are actually studying is whether or not they are alive, or how many individuals are conscious during a coma, or the extent of consciousness.

Consciousness and responsiveness levels can depend on how much of the brain works. Sometimes, a coma lasts a few days or weeks. It can rarely last for several years, too.

This is a medical emergency if a person enters a coma. To maintain life and brain function, urgent action may be required.

Important Facts about Coma

  • An individual does not respond to external stimuli during a coma and they may not show regular reflex responses.
  • Sleep-wake cycles are not present in comatose patients.
  • Intoxication, nervous system dysfunction, metabolic disease, infections, or stroke are causes for a coma.
  • A coma can occur rapidly or gradually, depending on the cause and extent of the injury, and it can last for several days to several years, but most last for days to weeks.

What is a coma?

A patient in coma
A coma is a deeply unconscious state.

It is impossible to awaken a person who is experiencing a coma, and they do not respond to the environment around them. They do not respond in the usual way to pain, light, or sound, and they do not perform voluntary actions.

Their body follows normal sleep patterns even though they do not wake up. Automatic functions, such as respiration and circulation, usually continue to work, but the thinking ability of the person is suppressed.

A person may sometimes grimace, laugh, or cry as a reflex, according to the National Institutes of Neurological Disorders and Stroke (NINDS).

Coma can occur for a variety of reasons, including toxicity, a disease or infection affecting the central nervous system (CNS), severe injury, and hypoxia or deprivation of oxygen.

Sometimes a doctor uses medicines to induce coma, for example to protect the patient from severe pain during a healing process, or to maintain a higher level of brain function after another form of brain trauma.

Usually, a coma does not last for more than a few weeks. If, after an extended period, the patient’s condition does not change, it may be reclassified as a persistent vegetative state.

The individual is unlikely to wake up if a persistent vegetative state lasts for months.


A person can not communicate during a coma, so diagnosis is through the outward signs.

They include:

  • closed eyes
  • limbs which do not react or voluntarily move, apart from reflex movements
  • lack of reaction to painful stimuli, apart from reflex movements

How long these will take to develop, and how long they will continue, rely heavily on the underlying cause.

A person with worsening hypoglycemia (low blood sugar) or hypercapnia (higher blood CO2 levels), for instance, will first experience mild agitation before entering a coma. Their ability to think clearly would steadily decline without treatment. They will, eventually, lose consciousness.

Symptoms can occur unexpectedly if a coma results from a serious brain injury or subarachnoid hemorrhage.

Anyone with the individual should try to recall what happened right before the coma began, as this data can help to identify the root cause and provide a clearer understanding of what medication to apply.

Recognizing symptoms

Using the AVPU scale, a first responder can start by attempting to measure the level of consciousness.

The size of the AVPU explores the following areas:

Alertness: How alert is the individual?

Vocal stimuli: Do they respond to the voice of another person?

Painful stimuli: Do they respond to pain?

Unconscious: Are they cognizant?

Alert is the most conscious state, and unconscious is the least. It allows the health professional to decide whether this is going to be an emergency. There is no chance of a coma if the person is alert.

Doctors can use the Glasgow coma scale (GCS) in the hospital to assess the condition of the person in more detail.

A risk of asphyxiation can be present in patients with deep unconsciousness. To protect the airways to ensure that they continue to breathe, they will require medical support. It may be a conduit that goes through the lungs, through the nose or mouth.

When they are in a coma, can an individual hear and think?

A person at coma
Sensory stimulation, such as holding a hand, may benefit a person in a coma.

There is some evidence that, during a coma, individuals can hear and understand spoken instructions.

In 2011, fMRI scanning technology neuroscientists observed brain activity in a man who had been in a coma for 12 years following a road traffic accident.

For instance, his brain activity reflected that he was thinking of doing these things when they asked the man to imagine he was playing tennis or walking around his house.

Scientists now believe that 15 to 20 percent of people may be fully conscious in a so-called vegetative state. Advances in technology mean that during a coma, we are better able to understand what individuals experience.

A person visiting a friend or family member who is in a coma can talk to them as they would usually, for instance, explain what happened during the day. How much they can comprehend is unclear, but there is a chance that the individual may be able to hear and understand. They might be fond of listening to music.

Research has also suggested that it may help the individual recover by stimulating the senses of touch, smell, sound, and vision. By wearing a favourite perfume or holding the hand of the person, a visitor could help.


The causes of a coma vary, but all of them involve some level of brain or CNS injury.

They include:

Diabetes: This is known as hyperglycemia if the blood sugar levels of a person with diabetes rise too much. This is hypoglycemia if they become too small. A coma can result if hyperglycemia or hypoglycemia continues for too long.

Hypoxia or lack of oxygen: If, for example, the oxygen supply to the brain is reduced or cut off during a heart attack, stroke, or near drowning, a coma may result.

Infection: Coma may result from severe inflammation of the brain, spinal cord, or tissues surrounding the brain. Encephalitis or meningitis are examples.

Toxins and drug overdoses: Exposure to carbon monoxide, like some drug overdoses, can lead to brain damage and coma.

Traumatic brain injuries: Coma can be caused by road traffic accidents, sports injuries and violent attacks involving a blow to the head.


Blood tests, physical tests, and imaging scans can help find the cause of a coma in a medical and recent history, and this helps decide which treatment to apply.

Medical history

If appropriate, friends, family, police, and witnesses may be asked:

If relevant, friends, relatives, police, and witnesses may be asked:

  • If the coma or symptoms began slowly or immediately beforehand,
  • If the person had any vision problems, dizziness, stupor or numbness before the coma, or seemed to have them,
  • If the patient has diabetes, any history of stroke or seizures, or any other illness or condition
  • What drugs the patient may have taken or other substances

Physical tests

The goal is to check the reflexes of the person, how they respond to pain, and the size of their pupil. Tests can include squirting the ear canals with very cold or warm water.

These tests can activate reflexive eye movements that vary. Based on the origin of the coma, the form of response varies.

Blood tests

These will be taken to determine:

  • blood count
  • signs of carbon monoxide poisoning
  • presence and levels of legal or illegal drugs or other substances
  • levels of electrolytes
  • glucose levels
  • liver function

Lumbar puncture (spinal tap)

This can scan for any CNS infection or disorder. The physician sticks a needle into the spinal canal of the patient, tests pressure, and collects fluid for examination.

Imaging scans of the brain

These can help decide if, and where, there is any brain damage or damage. Blockages or other anomalies are examined by a CT or CAT scan or an MRI. Electrical activity inside the brain is measured by electroencephalography (EEG).

Glasgow Coma Scale

To evaluate the level of brain damage after a head injury, the Glasgow Coma Scale (GCS) may be used.

Based on verbal responses, physical answers, and how quickly they can open their eyes, it gives patients a score.

Eyes: Scores range from 1 to 4, where 1 is when a person does not open their eyes, 2 is when they open their eyes in response to pain, 3 is when they open them in response to voice, and 4 is when they open them spontaneously.

Verbal: Scores vary from 1 to 5, where 1 implies that no sound is made by the person, 2 implies that they murmur but can not be understood, 3 is when offensive words are uttered, 4 is when they talk but are confused, and 5 is normal communication.

Motor or physical reflexes: A person’s reaction to pain is characterized by scores ranging from 1 to 6 and 1 to 5. An individual who scores 1 does not move, 2 is in response to pain when they straighten a limb, 3 is when they respond to pain in an odd way, 4 is when they move away from pain, and 5 is when they can locate where the pain is. A score of 6 means that the person is able to follow orders.

A score of a total of 8 or less suggests a coma. The condition is mild if the score is from 9 to 12. The impairment to consciousness is minor if the score is 13 or more.


A coma is a severe emergency medical condition.

To increase the amount of oxygen that enters the brain, health professionals will begin by ensuring the patient’s immediate survival and securing their respiration and circulation.

If the patient is in diabetic shock or has a brain infection, the doctor can administer glucose or antibiotics even before the results of the blood tests are ready.

For example, kidney failure, liver disease, diabetes, poisoning, and so on, treatment will depend on the underlying cause of the coma.

Surgery may be required to relieve the pressure if there is brain swelling.


If it is possible to successfully treat the cause of the coma, the person may eventually awaken without permanent damage.

At first, they are possibly puzzled, but then they generally recall what happened before the coma, and they can continue their lives. Any outpatient therapy is usually required.

Long-term impairment may result if brain damage has occurred. They will need to relearn basic skills if the individual awakens, and they may not know what happened.

However, with assistance, such as physical and occupational therapy, a decent quality of life can be experienced by many individuals.

In certain cases, the individual will not wake up.


Neurologists reported results in 2015 that indicate that there could be a way to predict when patients may wake up from a coma. Relevant patterns of neuronal contact seem to be impaired throughout a coma.

The scientists found that patients who maintained a specific intensity of neuronal contact were more likely to recover from a coma using functional MRI (fMRI) studies.

This could mean that fMRI could be capable of predicting the probability of recovery for a person.

Another research published in 2015 found evidence that the voices of family members and loved ones during a coma could help boost people’s responsiveness. FMRI scans show changes in the brains of those who have undergone FAST after 15 patients who received either familiar auditory sensory training (FAST) or placebo silence.


  • Coma. (2015, June 18)
  • Pape, T. L., Rosenow, J. M., Steiner, M., Parrish, T., Guemon, A., Harton, B., …Nemeth, A. J. (2015, July). Placebo-controlled trial of familiar auditory sensory training for acute severe traumatic brain injury: A preliminary report [Abstract]. Neurorehabilitation and neural repair, 29(6), 537-47
  • What you need to know about coma (LINK)
  • How science found a way to help coma patients communicate. (2017, September 5). The Guardian
  • Rupal, C. G. (2014, August). What is a coma? Retrieved from
  • Silva, S., de Pasquale, F., Vuillaume, C., Riu, B., Loubinoux, I., Geeraerts, T., …Peran, P. (2015, December). Disruption of posteromedial large-scale neural communication predicts recovery from coma. Neurology, 85(23), 2013-2044