Traumatic Brain Injury

TRAUMATIC BRAIN INJURY
Traumatic brain injury (TBI), also called intracranial injury, occurs when physical trauma
injures the brain. TBI is one of two subsets of acquired brain injury (ABI, brain damage that is
not congenital); the other subset of ABI is non-traumatic brain injury, or injuries that do not
involve external mechanical force (e.g. stroke, meningitis, insufficient oxygen). TBI is usually
classified as mild, moderate, or severe, depending on the extent of loss of consciousness, loss
of memory, and score on a neurological scale following the injury. TBI can result from a closed
head injury or a penetrating head injury and may occur in a specific location or may be diffuse,
occcurring over a more widespread area. Head injury usually refers to TBI, but is broader
because it can involve damage to structures other than the brain such as the scalp and skull.
In addition to the damage caused at the moment of injury, brain trauma initiates a variety of
chemical events within the brain that contribute to damage in the hours and days following the
injury. This so-called “second injury” presents the opportunity to discover new treatments that
limit the damage caused by TBI by interfering with these damaging cascades.
Imaging techniques such as computed tomograpy and magnetic resources imaging are used for
diagnosis. In mild cases, TBI may require little treatment; in severe cases, medications and
emergency surgery may be required to lower the pressure within the skull. Physical therapy,
speech therapy, and occupational therapy may be employed for rehabilitation. TBI can cause
a host of physical, cognitive, and social effects. Outcome can be anything from near-complete
recovery to permanent disability or death.
Focal vs. diffuse
The damage from TBI can be focal or diffuse, confined to one area of the brain or involving more
than one area, respectively. Types of injuries considered diffuse include concussion and diffuse
axonal injury. The shaking that causes shaken baby symdrome results in diffuse injury. Diffuse
injuries can result from sudden acceleration or deceleration of the head, and are commonly caused
by rotational forces. Diffuse axonal injury involves damage to axons after forces such as rotation
subject them to stress.
Focal injuries are those that occur in a specific location in the brain. These localized injuries
are often associated with symptoms corresponding to the part of the brain that was injured, for
example manifesting in hemiparesis or other focal neurological deficits. Types of focal brain
injury include intracranial hemorrhage, heavy bleeding in the skull that is not mixed with tissue,
and brusing with blood that has leaked from damaged blood vessels. Hemorrahage, due to
rupture of a blood vessel in the head, can be extra-axial, (occurring within the skull but outside
of the brain) or intra-axial (occurring within the brain tissue). Extra-axial hemorrhages can be
further divided into subdural hematoma, epidural hematoma, and subarachnoid hemorrhage.
An epidural hematoma involves bleeding into the area between the skull and the heavy, outermost
membrane that surrounds the brain, the dura matter. With a subdural hematoma, the most
common traumatic mass lesion, bleeding occurs between the dura and the arachnoid mater. A
subarachnoid hemorrhage involves bleeding between the surface of the brain and the arachnoid
membrane that lies just above the brain. Subarachnoid hemorrhage usually results from a tear
in a blood vessel on the surface of the brain. Subarachnoid hemorrhages, common after head
trauma, do not cause a mass effect because the blood is able to spread out, but they can cause
blood vessels to spasm, potentially constricting enough to cause damage to the brain from
insufficient blood flow. Http://en.wikipedia.org/wiki/Traumatic_brain_injury