Chronic traumatic encephalopathy A progressive neurodegenerative disease believed to be caused by repeated trauma to the brain, including mild concussions and subconcussive blows. Its symptoms occur years or decades following head trauma and continue to worsen, and are distinct from the acute or postacute effects of a head injury. The early symptoms may include memory and cognitive difficulties, depression, impulse control problems, and behavior changes. Movement abnormalities are more common later; in many cases, full-blown dementia occurs.

Coma A state in which a patient is totally unconscious, unresponsive, unaware, and unarousable.

Compressive cranial neuropathy Cranial nerve injuries that may be caused by fractures, especially at the bottom of the skull. Damage to the facial nerve, the most commonly damaged, results in paralysis of facial muscles.

Computerized tomography (CT) A noninvasive test combining a series of X-ray views taken from many different angles to produce cross-sectional images of bones and soft tissues. In the head, CT scans can show bone fractures, hemorrhage, hematomas, contusion, and swelling.

Contusion Focal injuries with an area of cerebral bruising, particularly involving gray matter, in which blood leaks into extravascular space resulting in cell death and loss of tissue. Bleeding from damaged blood vessels is usually the most obvious feature on macroscopic or microscopic examination.

Diffuse axonal injury (DAI) An injury defined by diffuse damage to axons in the cerebral subcortical parasagittal white matter, corpus callosum, brain stem, and cerebellum. The loss of connections among neurons leads to breakdown of communication.

Diffuse traumatic brain injury A brain injury due to hypoxia, meningitis, or damage to blood vessels; can include DAI, ischemic brain injury, vascular injury, or swelling and resulting intracranial pressure. Such injuries, which may result from acceleration/deceleration injuries, are often microscopic, multifocal, and difficult to detect.

Disability Rating Scale A functional assessment developed specifically for patients with moderate to severe traumatic brain injury (TBI).

Edema Abnormal accumulation of fluid beneath the skin or in one or more cavities of the body.

Edema (cytotoxic) Intracellular water accumulation in neurons, astrocytes, and microglia irrespective of the integrity of the vascular endothelial wall. It is due to the increased cell permeability for ions, ionic pump failure, and cellular reabsorption of osmotically active solutes.

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