Coma (cont.)

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Minor head injuries can cause brief loss of consciousness, but the brain is able to turn itself back on. Similarly, patients with seizures become unconscious - but gradually waken relatively quickly as the brain recovers from the seizure's "electrical storm." Those people with significant trauma or prolonged seizures may not wake quickly, and may remain in coma.

The skull is a rigid box that protects the brain. Unfortunately, if the brain is injured and begins to swell (edema), there is no space to accommodate additional fluid. As a result, increased pressure within the brain compresses the brain tissue against the skull bones and may cause a decreased level of consciousness. If the intracranial pressure continues to increase without being treated, the swelling will push the brain downward toward the opening at the base of the skull where the brain stem is locate. This crisis causes the brain to herniate, and turns off the reticular activating system. This can affect the ability of the brain to stimulate breathing and control blood pressure, leading to death.

The effect of trauma on the brain is not predictable. Relatively minor force to the skull and brain can be catastrophic. There does not have to be obvious injury visualized with computerized tomography (CT scan) imaging of the brain to cause significant damage. In fact, when shear injury occurs, the scan may be normal, even if the patient is in coma. Shear injury is microscopic injury to individual nerve connections within the brain without obvious swelling or bleeding.

Head trauma can cause different types of brain injury. The injury can occur to the brain tissue itself or it may cause bleeding to occur in the space between the brain and the skull, or in the ventricles deep within the brain tissue. Computerized tomography (CT) of the head may be able to identify most bleeding from trauma.

Medically Reviewed by a Doctor on 11/15/2013

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