What Is a Traumatic Brain Injury?

A traumatic brain injury (TBI) is any injury to the brain caused by an outside force. TBI can range from mild (such as a concussion) to severe, and can involve a wide range of symptoms. Mild TBI often resolves spontaneously; moderate to severe TBI, however, may require intervention from an expert.

Distinguishing between a mild TBI and a moderate to severe TBI is one of the first steps in moving forward from the injury. Moderate to severe TBI is often accompanied by loss of consciousness (“blacking out”) as well as amnesia (memory loss). Amnesia can be for the time before the actual injury, in which case it is called retrograde amnesia, and for events after the injury, when it is called post-traumatic amnesia. With severe TBI, retrograde amnesia can occur for days, weeks, or even months, and post-traumatic amnesia can last through weeks of an acute care hospitalization and even through their time in rehabilitation.

While mild TBIs are generally not visible on neuroimaging, moderate to severe TBIs may result in skull fracture, bleeding or swelling in the brain, or injury to the brain tissue itself. Moderate to severe TBI can be open, as in a gunshot wound or skull fracture with fragments entering the brain (“depressed skull fracture”), or closed, as in a blow to the head without anything penetrating the brain. They can be accidental, as in a fall, or deliberate, as in an assault. Although brain surgery is not technically a TBI, it can produce signs and symptoms similar to a TBI.

Differentiating a mild TBI from a more serious one requires consultation with an expert, and is crucial in establishing an appropriate plan for recovery.