Coma and Persistent Vegetative State

What Is It?

Coma is a deep and prolonged state of unconsciousness resulting from disease, injury or poisoning. The word coma usually refers to the state in which a person appears to be asleep, but cannot be awakened. There also is another type of coma, called persistent vegetative state or awake coma, in which the person appears to be awake, but does not respond to the outside world. In this type of coma, the person's eyes may be open and there may be some yawning, grunting or other vocalizations. In both cases, the patient is alive, but the brain does not function fully.

Some causes of coma include:

• Head trauma, such as may be sustained in a car accident, sports injury or falling injury
• Complication of an underlying disease, such as seizure disorder, diabetes or liver or kidney failure
• Poisoning, usually involving an overdose of drugs that depress the nervous system, such as tranquilizers or alcohol
• Stroke

Symptoms

A person in a coma will be unconscious and unable to communicate, but still breathing and alive. The person cannot be aroused from this state.

Diagnosis

Coma is usually a straightforward diagnosis because the signs of unconsciousness and unresponsiveness are clear. The cause of the coma can be more difficult to determine.

When coma results from traumatic head injury, the cause usually is clear from the injuries. Other clues to the cause of coma may be available from the people who called for help. For example, observers can tell health care providers whether the person took a large quantity of medication, what symptoms occurred immediately before the coma, and how quickly the person lost consciousness. Doctors also will want to know about the patient's medical history, because some disorders can lead to coma, including diabetes, seizure disorder and a history of heart, lung, liver, kidney or other disease. A physical examination can give other clues. For example, very small (pinpoint) pupils that do not react to bright light are seen in narcotic overdose.

Specific tests that may be used to diagnose coma include:

• Blood and urine tests to check for disease, metabolic disorders or toxins
• magnetic resonance imaging or Computed tomography scans to look for bleeding in the brain, tumors, infection or stroke from decreased blood flow
• Electroencephalogram , a graph of the electrical output of the brain that may indicate a metabolic imbalance or persistent seizure activity
• Lumbar puncture (spinal tap) to examine the cerebrospinal fluid for signs of meningitis and encephalitis