Overview

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.

Source: http://www.mayoclinic.com

Symptoms

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.

Source: http://www.mayoclinic.com

Causes

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.

Source: http://www.mayoclinic.com

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.

Source: http://www.mayoclinic.com

Complications

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.