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

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.