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A coma is a condition in which an individual is in a state of deep sleep and cannot be awakened. A coma may be caused by many things, including trauma, drugs, toxins, or certain diseases.
Most studies suggest that once brain cells are destroyed or damaged, for the most part, they do not regenerate. However, recovery after brain injury can take place, as, in some cases, other areas of the brain compensate for the injured tissue, or the brain learns to reroute information and function around the damaged areas.
The exact amount of recovery is not predictable at the time of injury and may be unknown for months or even years. Each brain injury and rate of recovery is unique. Recovery from a severe brain injury often involves a prolonged or life-long process of treatment and rehabilitation.