Coma – Types, Causes & Symptoms

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The word ‘coma’, come from the Greek word ‘koma’, meaning ‘deep sleep’. When a person is in a prolonged state of unconsciousness, they are said to be in a coma. It happens when there is temporary or permanent damage to the brain, affecting the consciousness. 

These damages can have the following outcomes:

  • Inability to wake-up
  • Unresponsive to pain, light and sound, known as stimuli
  • Unconsciousness

A person who is in a coma cannot think, move, speak or respond to the environment. Medications and other interventions like mechanical ventilation or airway pressure can be used to support the patient as life-supporting functions like blood circulation and breathing are impaired in most cases. 

It is important to act quickly when a person has a gradual or sudden loss of consciousness, as this gives the best chance of recovery for the patient. It is also crucial to maintain organ support till they recover when one is diagnosed with a coma. 

Generally, after a few weeks, some individuals wake from a coma, but there are also people who remain in a coma for years. During this time, they need to be supported with nutritional supplementation, breathing and heart function assistance. 

Types of coma

Medically induced

This type of temporary coma or deep state is induced to let the body heal and protect the brain from swelling after an injury. The loss of feeling or consciousness is achieved through a small administered dose of an anaesthetic. The person is placed in the intensive care unit (ICU), since this is the only place where medically induced coma can be administered, as the vitals of the person need to be closely monitored.  


Uncontrolled diabetes can be dangerous as the sugar levels are too high or too low; this can turn life-threatening as the person can slip into a coma. High sugar levels, called hyperglycemia, can be controlled through insulin, and when it is uncontrolled, the person gets affected by ketoacidosis, which leads to coma. In the case of low blood sugar, known as hypoglycemia, the brain doesn’t get enough energy to function significantly, eventually causing a coma. Both of them may lead to death without proper treatment. 

Toxic-metabolic encephalopathy

Causes of this condition varies from person to person and it is usually reversible. The causes might include infection, systematic illness, organ failure and many other conditions. It’s an acute condition in which the brain dysfunctions, causing symptoms like delirium and confusion. 

Anoxic brain injury

The lack of oxygen in the brain causes this coma, as it causes the brain cells to die. This may be caused due to a number of reasons like choking, cardiac arrest, drowning etc., 

Persistent vegetative state

In this type of coma, the person is incapable of movements and is unaware of their surroundings; it is basically a state of severe unconsciousness. With a continuous vegetative state, there is breathing, sleep-wake cycles and circulation but no higher brain function. 

Causes of coma

  • Coma can be caused because of tumours in the brainstem or the brain. 
  • Brain damage and coma may be caused by exposure to toxins like carbon monoxide. 
  • Diabetes is a disease where the blood sugar is either very high or too low. This can cause coma as well.
  • Brain injuries due to accidents or violence can result in coma.
  • Seizures can cause coma. 
  • Lack of oxygen to the brain can cause coma; this might occur in incidents like drowning or when a person who has been revived after a heart attack
  • Overdose due to drugs can cause coma.
  • Blocked arteries or burst blood vessels can stop the supply of blood from flowing to the brain. This might cause a coma. 
  • Swelling of the brain, tissues surrounding the brain and spinal cord due to infections like meningitis and encephalitis may result in coma, depending on the severity of the infection. 

Symptoms of coma

A person is said to be in a coma when they meet the following criteria:

  • Apart from reflex, there is no response in the limbs.
  • Unresponsive
  • Apart from reflex, no response to pain.
  • Closed eyes
  • Irregular breathing

In a few cases, people in coma might cough and swallow on their own. They may also be able to breath without help in few cases. 


In most cases, a coma might last for a week, but some may even stay in a coma for years. The extent of the damage to the brain and the cause are the two factors that determine the long-term results of coma. Some people may suffer from intellectual, physical or psychological conditions after recovering from a coma, while others may recover without long-lasting effects. 


1. What are the six types of coma?

The types of coma are:
– Medically induced
– Diabetic
– Toxic-metabolic encephalopathy
– Anoxic brain injury
– Persistent vegetative state


The Information including but not limited to text, graphics, images and other material contained on this blog are intended for education and awareness only. No material on this blog is intended to be a substitute for professional medical help including diagnosis or treatment. It is always advisable to consult medical professional before relying on the content. Neither the Author nor Star Health and Allied Insurance Co. Ltd accepts any responsibility for any potential risk to any visitor/reader.

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