A coma is a state of deep unconsciousness from which a person cannot be aroused. A person in a coma cannot react to events in his environment.


Normally, information from a person’s surroundings is passed from the brainstem into the cerebrum. This feedback allows a person to be conscious of and react to his environment. When this system breaks down and a person is no longer able to respond, a coma can result.

Brainstem and Cerebrum

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A coma may be caused by:

  • Severe head injury, most commonly from:
    • Motor vehicle accidents
    • Violence
    • Falls
  • Primary brain disorder
  • Lack of oxygen to the brain due to:
  • Severe general illness:
    • Severe bodily infections
    • Severe acute liver or kidney failure
    • High carbon dioxide levels
    • ]]>Carbon monoxide poisoning]]>
    • Toxicity from poisons, medication, ]]>alcohol]]> , or ]]>drugs]]>
    • Abnormal hormone levels, such as from the thyroid or adrenal gland
    • Abnormal blood chemistries, such as sodium or calcium
    • Very low or very high levels of blood sugar
    • Very low or very high body temperatures
    • Severe nutrient deficiency
    • Liver failure
    • ]]>Kidney failure]]>
    • Inherited metabolic diseases


Risk Factors

Risk factors for coma include:

  • Severe illness
  • Diabetes]]>
  • Liver, kidney, or cardiovascular disease
  • Tendency to have blood clots
  • Exposure to poisonous substances (eg, carbon dioxide)
  • Cancer and ]]>chemotherapy]]>

Risk factors for brain injury include:

  • Age: 5 years or younger, 15-24 years old, and 75 years or older
  • Sex: male
  • Traveling in a vehicle at a high rate of speed or at night
  • Lack of sleep
  • A previous head injury



Symptoms of a coma include the following:

  • No response to outside stimuli, such as:
    • Pain
    • Sound
    • Touch
    • Sight
  • Spontaneous body movements, such as:
    • Jerking
    • Shaking
    • Trembling
    • Eyes opening and closing
    • Irregular breathing


Since the patient cannot speak, information from friends, family members, and witnesses is important when diagnosing the cause of a coma. The doctor will want to know about the person’s medical history, as well as any drug or alcohol use. It is important to provide honest information in order to help with treatment.

The doctor will test reflexes, listen to breathing, examine the eyes, and perform neurological and physical exams. In addition, the following tests may be done:

  • Blood tests—to check blood glucose levels, organ function and screen for infection and toxic substances
  • Urine test—to test for the presence of drugs
  • Imaging tests, such as:
    • Neck x-rays]]> —in cases where head and neck trauma may have occurred, a test that uses radiation to take pictures of structures inside the body
    • ]]>MRI scan]]> —a test that uses magnetic and radio waves to make pictures of the inside of the body, in this case the brain
    • ]]>CT scan]]> —a type of x-ray that uses a computer to make pictures of the inside of the head
    • SPECT or Xenon—enhanced CT scan to test for blood flow and metabolic activity within the brain
  • ]]>Electroencephalogram (EEG)]]> —a test that records the brain's activity by measuring electrical currents through the brain
  • ]]>Spinal tap (lumbar puncture)]]> —removal of a small amount of cerebrospinal fluid to check for pressure, blood, and infection
  • Evoked potentials—a test for brain wave activity after stimulation of the sensory nerves of the body

Comas are rated according to the Glasgow Coma Scale (GCS), which assesses three different functions: eye opening, motor response, and verbal response. Scores can range from 15 to 3. A lower score indicates a person is less responsive. Scores are interpreted as follows:

  • 15-13—mild brain injury
  • 12-9—moderate brain injury
  • 8 or less—a severe brain injury



A coma is a medical emergency. Any unconscious person should be taken to the emergency room immediately.

Emergency Treatment

Oxygen and intravenous fluids will be given, and the person’s vital signs monitored closely. He may be put on a ventilator]]> . Doctors will work quickly to determine the cause of the coma, and further treatment will depend on the cause.

Usually, glucose is given by IV in case low blood sugar is causing the coma. Naloxone can also be given by IV if a narcotics overdose is suspected. Thiamine (vitamin B1) may be given with glucose if ]]>alcoholism]]> or malnutrition is suspected. In some cases, surgery may correct the cause of a coma.

Ongoing Treatment

Once the person is stabilized, treatment will focus on providing adequate nutrition and preventing infections and ]]>bed sores]]> .



The following can help decrease your risk of coma:

  • Wear a seatbelt. Make sure infants and small children are securely fastened in a child safety seat.
  • Children aged 12 years and under should ride in the back seat of a vehicle.
  • Wear an appropriate helmet while biking, rollerblading, or playing contact sports.
  • Wear athletic mouth guards while playing sports.
  • Don’t abuse alcohol or drugs]]> .
  • If you have diabetes, see your doctor regularly and take appropriate steps to regulate your blood sugar levels.
  • If you are ill or take medicine, see your doctor regularly for check-ups.