A coma is a state of prolonged unconsciousness that results from changes in the structure of the brain. Most brain function shuts down and comatose patients may appear as if they are sleeping. Due to reduced brain function, patients with comas typically have no or minimal response to external stimuli. However, brain activity for the body’s basic functions, such as the respiratory, circulatory and digestive systems, is maintained. 

Comas may result from a physical injury, disease or toxin. Any severe head injury has the potential to physically change the structure of the brain. Diseases and toxins may alter the typical chemical processes of the brain and cause it to shut down. Medications may also be used to induce a coma to reduce brain swelling due to trauma or reduce the risk of severe complications during brain surgery.

Most comas last several days to a few weeks, though some may last many months. Following this period, patients may improve and gain more awareness of their environment. In contrast, some patients may instead enter a persistent vegetative state or become brain dead, which means that damage to the brain is irreversible and body functions can be maintained only with artificial means.

Treatment for comas focuses on the cause. For physical injuries, surgery may be necessary to repair the skull or remove foreign objects or injured nervous tissue. For comas caused by disease, medications may be administered. When drugs or toxins cause a coma, treatment may require a combination of medications, vitamins and modifying blood sugar to normalize brain function. Beyond supportive care, there is little that healthcare professionals can do to revive a comatose patient.

Preventing comas requires preventing their causes. Basic safety measures help reduce the occurrence of the many causes of head injuries that may lead to comas. These include using a seatbelt or helmet when appropriate and safely handling firearms. Patients with diabetes, seizure disorders and other conditions should follow their physician’s recommendations to reduce the chance of a coma occurring.