Diagnosis

Because people in a coma can't express themselves, doctors must rely on physical clues and information provided by families and friends. Be prepared to provide information about the affected person, including:

  • Events leading up to the coma, such as vomiting or headaches
  • Details about how the affected person lost consciousness, including whether it occurred suddenly or over time
  • Any noticeable signs or symptoms prior to losing consciousness
  • The affected person's medical history, including other conditions he or she may have had in the past, such as a stroke or transient ischemic attacks
  • Recent changes in the affected person's health or behavior
  • The affected person's drug use, including prescription and over-the-counter medications as well as unapproved medications or illegal, recreational drugs

Physical exam

In a physical exam, doctors will check the affected person's movements and reflexes, response to painful stimuli, and pupil size. Doctors will observe breathing patterns to help diagnose the cause of the coma. Doctors also may check the skin for signs of any bruises due to trauma.

To determine the affected person's level of consciousness, doctors may speak loudly or press on the angle of the jaw or nail bed. Doctors will watch for signs of arousal, such as vocal noises, eyes opening or movement.

Doctors will test reflexive eye movements. These tests can help determine the cause of the coma and the location of brain damage.

Doctors also may squirt ice-cold or warm water into the affected person's ear canals and observe eye reactions.

Laboratory tests

Blood samples will be taken to check for:

  • Complete blood count
  • Electrolytes, glucose, thyroid, kidney and liver function
  • Carbon monoxide poisoning
  • Drug or alcohol overdose

A spinal tap (lumbar puncture) can check for signs of infections in the nervous system. During a spinal tap, a doctor or specialist inserts a needle into the spinal canal and collects a small amount of fluid for analysis.

Brain scans

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

  • Computerized tomography (CT) scan. A CT scan uses a series of X-rays to create a detailed image of the brain. A CT scan can show a brain hemorrhage, tumors, strokes and other conditions. This test is often used to diagnose and determine the cause of a coma.
  • Magnetic resonance imaging (MRI). An MRI uses powerful radio waves and magnets to create a detailed view of the brain. An MRI can detect brain tissue damaged by an ischemic stroke, brain hemorrhages and other conditions. MRI scans are particularly useful for examining the brainstem and deep brain structures.
  • Electroencephalography (EEG). An EEG measures the electrical activity inside the brain. Doctors attach small electrodes to the scalp. Doctors send a low electrical current through the electrodes. The brain's electrical impulses are then recorded. This test can determine if seizures may be the cause of a coma.

Treatment

A coma is a medical emergency. Doctors will first check the affected person's airway and help maintain breathing (respiration) and circulation. Doctors may give breathing assistance, blood transfusions and other supportive care.

Emergency personnel may administer glucose or antibiotics intravenously, even before blood test results return, in case of diabetic shock or an infection affecting the brain.

Treatment varies, depending on the cause of the coma. A procedure or medications to relieve pressure on the brain due to brain swelling may be needed.

If the coma is the result of drug overdose, doctors will give medications to treat the condition. If the coma is due to seizures, doctors will administer medications to control seizures.

Other treatments may focus on medications or therapies to address an underlying disease, such as diabetes or liver disease.

Sometimes the cause of a coma can be completely reversed and the affected person will regain normal function. But if the affected person has suffered severe brain damage, he or she may sustain permanent disabilities or may never regain consciousness. The person may enter a persistent vegetative state or become brain dead.

Preparing for your appointment

A coma is an emergency medical condition. If you are with a person who develops signs and symptoms of a coma, call 911 or your local emergency number immediately.

When you arrive at the hospital, emergency room staff will need as much information as possible from family and friends about what happened to the affected person before the coma. On the way to the hospital, you may be asked the following questions while riding in the ambulance:

  • Did the coma start abruptly or gradually?
  • Were there problems with vision, dizziness or numbness beforehand?
  • Does the affected person have any history of diabetes, seizures or strokes?
  • Did you notice any changes in the affected person's health in the time leading up to the coma, such as a fever or worsening headache?
  • Did you notice any changes in the affected person's ability to function in the time leading up to the coma, such as frequent falls or confusion?
  • Did the affected person use any prescription or nonprescription drugs?
Aug. 14, 2015
References
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  2. Edlow JA, et al. Diagnosis of reversible causes of coma. The Lancet. 2014; 384:2064.
  3. Rosengart A, et al. Coma. In: Critical Care Medicine: Principles of Diagnosis and Management in the Adult. Philadelphia, Pa.: Elsevier; 2014. http://www.clinicalkey.com. Accessed July 15, 2015.
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  5. Daroff RB, et al. Bradley’s Neurology in Clinical Practice. 6th ed. Philadelphia, Pa.: Saunders Elsevier; 2012. http://www.clinicalkey.com Accessed July 15, 2015.
  6. NINDS coma information page. National Institute of Neurological Disorders and Stroke. http://www.ninds.nih.gov/disorders/coma/coma.htm. Accessed July 15, 2015.
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