Causes

Information about your environment is normally passed from the brainstem into the rest of the brain. This feedback allows a person to be aware of and react to the environment. A coma is caused by a breakdown in this system.

Brainstem and Cerebrum

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The system may be interrupted by:

• Severe head injury—most often a result of car accidents, violence, or falls.
• Brain illness such as:
  • Brain tumor
  • Brain hemorrhage or stroke
  • Brain infection
• Lack of oxygen to the brain which may be due to:
  • Very high blood pressure
  • Very low blood pressure or shock
  • Cardiac arrest
  • Severe seizures
• Severe general illness such as:
  • 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

• Severe illness
• Diabetes
• Liver, kidney, or cardiovascular disease
• Tendency to have blood clots
• Exposure to poisonous substances (such as 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

• 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 (including the auditory nerves) of the body

Clinical findings of comatose patients can be rated according to the Glasgow Coma Scale (GCS). This scale assesses three different functions: eye opening, motor response, and verbal response. Scores can range from 15 to 3. A lower score indicates less responsiveness. Scores are interpreted as follows:

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

• 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, playing contact sports, skiing, snowboarding, and riding a motorcycle.
• Wear athletic mouth guards while playing sports.
• Do not 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.