Acquired brain injury is defined as damage to the brain that occurs after birth and is not related to a congenital disorder or a degenerative disease. Damage may be caused by a traumatic injury to the head or by a non-traumatic cause such as a tumor, aneurysm, anoxia or infection.

Acquired brain injury takes place at the cellular level within the brain. Therefore, injury from acquired brain injury can affect cells throughout the entire brain, instead of just in specific areas as with traumatic brain injury.

Causes of acquired brain injury can include, but are not limited to:

An acquired brain injury commonly results in a change in neuronal activity, which affects the physical integrity, the metabolic activity, or the functional ability of the cell. An acquired brain injury may result in mild, moderate, or severe impairments in one or more areas, including cognition, speech-language communication; memory; attention and concentration; reasoning; abstract thinking; physical functions; psychosocial behavior; and information processing.