Definition of Brain Injury

Traumatic brain injury (TBI) is an insult to the brain, not of a degenerative or congenital nature, but caused by external physical force that may produce a diminished or altered state of consciousness, which results in an impairment of cognitive abilities or physical functioning. Profound disturbances of cognitive, emotional, and behavior functioning after TBI may produce permanent impairments that result in partial or total functional disability and psychosocial maladjustment.

In 1997, the Brain Injury Association Board of Directors adopted a definition of acquired brain injury to broaden the definition of brain in jury beyond that only produced by trauma. An acquired brain injury (ABI) is an injury to the brain that has occurred after birth. The injury commonly results in a change in neuronal activities that effects the physical integrity, the metabolic activity, or the functional ability of the cell. Causes of acquired brain injury include external forces applied to the head and/or neck (e.g., traumatic brain injury with or without skull fracture), anoxic/hypoxic injury (e.g., cardiopulmonary arrest, carbon monoxide poisoning, airway obstruction, hemorrhage), intracranial surgery, vascular disruption, arteriovenous malformation (AVM, thromboembolic events, fat emboli), infectious diseases, intracranial neoplasms, metabolic disorders (e.g., hypo/hyperglycemia, hepatic encephalopathy, uremic encephalopathy), seizure disorders and toxic exposure (e.g., substance abuse, ingestion of lead and inhalation of volatile agents).

There are three generally acknowledged levels of severity of TBI:

Mild traumatic brain injury is a trauma to the head that results in a confused state or a loss of consciousness of less than 30 minutes, the initial Glasgow Coma Scale of 13 - 15, and posttraumatic amnesia lasts less than 24 hours.

Moderate traumatic brain injury is a trauma to the head that results in a loss of consciousness of 30 minutes to 24 hours, an initial Glasgow Coma Scale of 9 - 12. Posttraumatic amnesia can last 24 hours to seven days.

Severe traumatic brain injury is a trauma to the head that results in a loss of consciousness of greater than 24 hours, an initial Glasgow Coma Scale of 3 - 8, and a posttraumatic amnesia period of greater than seven days.

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