The Issue Board of Governors Staff Membership Information Giving	The Issue Brain Injury (also called "head injury") is defined as an injury to the brain caused by any one or combination of the following events: external physical force (this is commonly known as "traumatic brain injury", or TBI); rapid acceleration or deceleration of the head; lack of sufficient oxygen to the brain; bleeding within or around the brain; or, toxic substance passing through the blood-brain barrier. The degree of neurologic injury is influenced by the both the mechanics of the event and the neurochemical response or reaction to the traumatic event. Injury to the brain is considered significant because its role as an organ within the body is essential to the functioning and well-being of the body as a whole. Of all types of injury, those to the brain are among the most likely to result in death or permanent disability. Damage to the brain may alter physical, cognitive, and/or behavioral status; alteration in function may be temporary or permanent.	The impact of acquired brain injury cannot be underestimated. Worldwide annual mortality rates for traumatic brain injury alone range from about 15 to 30 per 100,000 population. It is estimated that in the United States of America there are 5.3 million people living with brain injury-related disability. Annual expenditures (excluding indirect costs) for brain injury in the U.S. total several billion dollars. The human toll of acquired brain injury -- loss of life, identity, relationships, and employment -- is incalculable.