A coma is a state of prolonged unconsciousness that can be caused by a variety of problems — traumatic head injury, stroke, brain tumor, drug or alcohol intoxication, or even an underlying illness, such as diabetes or an infection.
A coma is a medical emergency. Swift action is needed to preserve life and brain function. Doctors normally order a battery of blood tests and a brain CT scan to try to determine what's causing the coma so that proper treatment can begin.
A coma seldom lasts longer than several weeks. People who are unconscious for a longer period of time may transition to a persistent vegetative state.
Depending on the cause of a coma, people who are in a persistent vegetative state for more than one year are extremely unlikely to awaken.
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The signs and symptoms of a coma commonly include:
- Closed eyes
- Depressed brainstem reflexes, such as pupils not responding to light
- No responses of limbs, except for reflex movements
- No response to painful stimuli, except for reflex movements
- Irregular breathing
When to see a doctor
A coma is a medical emergency. Seek immediate medical care.
Many types of problems can cause coma. Some examples are:
- Traumatic brain injuries. Traumatic brain injuries, often caused by traffic collisions or acts of violence, are common causes of comas.
- Stroke. Reduced or interrupted blood supply to the brain (stroke), which may be caused by blocked arteries or a burst blood vessel, can result in a coma.
- Tumors. Tumors in the brain or brainstem can cause a coma.
- Diabetes. In people with diabetes, blood sugar levels that become too high (hyperglycemia) or too low (hypoglycemia) can cause a coma.
- Lack of oxygen. People who have been rescued from drowning or those who have been resuscitated after a heart attack may not awaken due to lack of oxygen to the brain.
- Infections. Infections such as encephalitis and meningitis cause swelling (inflammation) of the brain, spinal cord or the tissues that surround the brain. Severe cases of these infections can result in brain damage or a coma.
- Seizures. Ongoing seizures may lead to a coma.
- Toxins. Exposure to toxins, such as carbon monoxide or lead, can cause brain damage and a coma.
- Drugs and alcohol. Overdosing on drugs or alcohol can result in a coma.
Although many people gradually recover from a coma, others enter a vegetative state or die. Some people who recover from a coma may have major or minor disabilities.
Complications may develop during a coma, including pressure sores, bladder infections, blood clots in the legs and other problems.
Sept. 12, 2018
- Overview of coma and impaired consciousness. The Merck Manual Professional Edition. http://www.merckmanuals.com/professional/neurologic-disorders/coma-and-impaired-consciousness/overview-of-coma-and-impaired-consciousness. Accessed July 15, 2015.
- Edlow JA, et al. Diagnosis of reversible causes of coma. The Lancet. 2014; 384:2064.
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- 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.
- NINDS coma information page. National Institute of Neurological Disorders and Stroke. https://www.ninds.nih.gov/Disorders/All-Disorders/Coma-Information-Page. Accessed Sept. 7, 2018.
- Marx JA, et al. Rosen's Emergency Medicine: Concepts and Clinical Practice. 8th ed. Philadelphia, Pa.: Mosby Elsevier; 2014. http://www.clinicalkey.com. Accessed July 15, 2015.
- Rabinstein AA (expert opinion). Mayo Clinic, Rochester, Minn. July 20, 2015.
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