Coma is a deep state of unconsciousness where the affected individual is alive but is not able to react or respond to external stimuli.
Sometimes, comatose patients are totally unaware of their states and environments; sometimes they are partially or fully aware but cannot communicate. There is lack of consciousness, self-awareness, sleep-wake cycle and purposeful movements in a comatose patient. But the basic life support functions, like breathing and blood circulation are retained.
Coma is not a disease. It is a symptom of a disease or a response to an event, such as a severe head injury, seizure or metabolic problem. Coma may appear slowly in conditions where there are preceding medical or neurological problems, including the secondary brain swelling that surrounds a pre-existing lesion.
The outcome of coma ranges from full recovery to death. Whether a person recovers, and to what extent, depends upon the cause of the coma and the type and extent of brain damage. It is very important to know that the outcome may remain unknown for many months.
Most comas last no longer than four weeks. However, some people in a coma shift to a persistent vegetative state, which can last for years, depending on the medical circumstances and the cause.
Initial emergency treatment of a comatose patient focuses on stabilizing the vital signs. This may rapidly reverse the coma. After emerging from a coma, many people can recover fully; some require lifelong physical and occupational therapy, while others may recover only basic functions.