Home Health A-Z Coma : Causes, Types and Diagnosis

Coma : Causes, Types and Diagnosis

Verified By Apollo General Physician December 9, 2022 2407 0


Coma is a term people know of or hear from movies and news. But most individuals may be unsure of the causes, diagnostic methods, and treatments available. This blog addresses all factors surrounding coma, its causes, and treatment options.  

What is a coma? 

An extended period of unconsciousness is called a coma. A person in the coma is unaware of the surroundings and appears asleep. Unlike deep sleep, coma patients cannot be woken up by any provocation, including pain. 

What are the different types of comas? 

Comas are of different types. They are:  

  • Constant vegetative state: This is a profoundly unconscious state. The person cannot move independently and is ignorant of their surroundings. A person in a persistent vegetative state may be awake but won’t have any higher cognitive abilities. In this state, they continue to breathe, blood circulation occurs, and they follow a sleep-wake cycle. 
  • Toxic metabolic encephalopathy: Confusion and delirium are signs of this acute brain dysfunction disorder and are mostly curable. Different factors can lead to toxic-metabolic encephalopathy. Systemic disease, infections, organ failure, and other ailments are some of the causes. 
  • Medically induced: It is a kind of brief coma or profound sleep induced by medical professionals to prevent brain swelling following an injury and to give the body time to recuperate. A controlled amount of an anaesthetic is administered to the patient, causing a lack of sensation or awareness. Doctors keep a close eye on the patient’s vital signs. 

What leads a person to a coma? 

More than 50% of coma cases are due to head injuries or problems with the blood flow to the brain. Increased pressure, bleeding, oxygen loss or toxin buildup can all result in brain injury. Sometimes the damage may remain transient and recoverable, while other times, it may also be long-lasting. 

The following issues can result in coma : 

  • Anoxic brain damage: This neurological problem is due to the brain receiving zero oxygen – a few minutes without oxygen results in the death of brain tissue cells. Heart attack (cardiac arrest), drug overdose, head injury or trauma, drowning, or poisoning can all cause anoxic brain injury. 
  • Swelling: All swelling need not happen due to trauma. An oxygen deficit, an electrolyte imbalance, or infections  may bring on swelling. 
  • Head injuries: Brain bleeding or swelling can result from head injuries. The fluid in the brain pushes up against the skull as it swells due to trauma. As a result of the enlargement, the brain may eventually press against the brain stem, harming the RAS (Reticular Activating System), a part of the brain helping with arousal and awareness. 
  • Internal bleeding: Sometimes, a wound makes a portion of the brain swell and compress, allowing the blood to flow into the layers of the brain. The brain shifts due to this compression, harming the brainstem and the RAS. It may result in a coma. Non-traumatic causes of brain haemorrhage include high blood pressure and malignancies. 
  • Stroke: A coma may develop when a significant portion of the brain does not receive blood or when there is blood loss and swelling. 
  • Seizures: Coma is rarely caused by a single seizure. Continuous seizure episodes can cause coma. Frequent seizures can hamper the brain’s ability to recover between seizures, resulting in coma. 
  • Blood sugar: When blood sugar levels remain incredibly high, the person may slip into a coma. The medical term for such is hyperglycemia. A coma may develop due to hypoglycemia or very low blood sugar. Once the blood sugar is stabilised, this coma is typically recoverable. But persistent hypoglycemia can cause lifelong brain damage and unconsciousness. 
  • Infections: Coma can also be brought on by nervous system infections, such as meningitis and encephalitis
  • Heart issues: Oxygen is necessary for proper brain activity. A sudden cardiac arrest can cause an abrupt cessation of blood flow and oxygen supply to the brain. Survivors of cardiac arrest are frequently in coma after receiving cardiopulmonary resuscitation (CPR). Choking or drowning can also result in oxygen deprivation. 
  • Toxins: If the body cannot correctly eliminate certain substances, such as ammonia, carbon dioxide and urea, they can build up to toxic levels and cause harm. Large doses of alcohol and drugs can also impair brain neuron function. 

How is a coma diagnosed? 

For diagnosis of coma, a medical practitioner will need the help of the friends and relatives of the patient. They can help with any incidents or symptoms that may have contributed to the patient’s impairment of awareness. In addition, the healthcare provider will inquire about the person’s recent changes in life, medical background, and usage of prescription, over-the-counter, and recreational medications.  

Investigations may include:

Physical exam

The examination is likely to include:

  1. Observing breathing patterns to diagnose the cause of coma 
  2. Checking the affected individual’s reflexes, movements and response to painful stimuli, and pupil size
  3. Pressing on the angle of the jaw or peaking loudly or nail bed while watching for signs of arousal, like movement, eyes opening or vocal noises 
  4. Checking the skin for signs of bruises owing to trauma
  5. Squirting warm or cold into the affected individual’s ear canals and reactions of the eye 
  6. Testing reflexive eye movements to help find out the cause of coma and the location of brain damage

Laboratory tests

Blood samples will be extracted to check for:

  1. Glucose, electrolytes, thyroid, liver and kidney function
  2. Carbon monoxide poisoning
  3. Complete blood count
  4. Alcohol or drug overdose
  5. A lumbar puncture (spinal tap) can check for signs of infections in the nervous system

Brain scans

Imaging tests help doctors pinpoint areas of brain injury. Tests may include:

  • Electroencephalography (EEG)
  • MRI
  • CT scan

What is the Glasgow coma scale? 

Glasgow coma scale is a method to track changes in the patient over time and track whether a patient’s degree of consciousness is enhancing, stabilising, or declining. It is also used to rate the severity of the symptoms during a physical examination. This system measures elements like ‘verbal reaction’ on a scale of 1 to 5. 

  • 5 – oriented 
  • 4 – confused 
  • 3 – inappropriate words 
  • 2 – incomprehensible sounds 
  • 1 – no verbal response 

Is there effective medication for a coma? 

A coma is typically treated with supportive care. People in a coma are cared for in an intensive care unit and frequently need complete life support while waiting for their condition to improve. Also, the treatment of a coma depends upon the causal agent. With the help of family and friends, the healthcare provider can track down the condition’s origin. 

Treatment of potentially treatable coma is possible with prompt medical care. Doctors may administer antibiotics if a brain infection is a cause. In the event of a diabetic coma, glucose may be needed by the body and may cure the condition. Surgery may also be required to remove a tumour or reduce pressure on the brain if the causal agent is swelling. Swelling may be managed by medications also. Similar is the case with seizures. They may also be treated with medications.   


A coma brought on by head injuries often has a higher percentage of recovery than comas brought on by oxygen deprivation. A coma caused by drug usage can be cured with timely medical care. So, the cure is mostly dependent on the cause. 

When a person is in a coma, anticipating recovery can be exceedingly challenging. Since every person is unique, speaking with the healthcare provider is essential. The longer the coma period, the harder the prognosis. Despite this, many individuals can awaken from a coma after several weeks. They may, however, suffer from severe disabilities. But it is always advisable to continue medical support. 

Frequently Asked Questions (FAQs) 

Is recovery from a coma possible? 

Recovery from a coma depends upon the cause. Some can be cured with medication, therapy or surgery. At the same time, some remain in that stage life-long. Recovery of coma patients is almost unpredictable.  

What tests are used to diagnose coma? 

Blood checks, urine checks, and brain imaging tests like MRI, CT scans, and EEG may be conducted to finalise the treatment methodology for coma patients.  

Are brain death and coma the same? 

No. Brain death differs from a coma in terms of recovery. Brain death is non-reversible, whereas a coma gives the possibility of reversal. 

Verified By Apollo General Physician

Our expert general medicine specialists verify the clinical accuracy of the content to deliver the most trusted source of information, making the management of health an empowering experience.

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