Sunday, July 6, 2008

Traumatic Brain Injury

Description of TBI
Demographics of TBI Patients
About 1.9 million people in this country sustain a TBI annually, and within this group 50,000- 75,000 experience moderate to severe disability as a result. Most of these injuries occur in individuals between the ages of 15 and 24, and over the age of 75, and are 2-3 times more common in men than women. Primary causes of TBI include motor vehicle accidents, physical assaults, falls, and sports and other recreational related injuries (Rosenthal & Ricker, 2000).
Etiology of TBI
Harrison-Felix, Newton, Hall and Kreutzer (1996) have defined TBI as, “Damage to brain tissue caused by an external mechanical force, as evidenced by loss of consciousness due to brain trauma, posttraumatic amnesia, skull fracture, or objective neurological findings that can be reasonably attributed to TBI on physical examination or mental status examination (p.2).” The four primary types of TBI include: (1) contusions – bruising caused by direct impact, (2) compression – where the brain is forced against the skull as a result of direct impact, (3) rotational injuries and/or (4) pressure build up due to hemorrhaging (Stratton & Gregory, 1994).
In cases with contusions, damage occurs as the result of a blow at the immediate point of impact, and is referred to as the coup. The damage is often due to contusion and laceration, and can be either an open or a closed head injury. Open head injuries are due to the skull or brain being penetrated, often as the result of a gunshot wound or an assault to the head by a sharp object. Blunt traumas can also cause open head injuries as the result of a skill fracture that displaces bone into brain tissue. Closed head injuries are cases in which the skull is not fractured, which may occur in falls or other kinds of accidents involving direct impact (Stratton & Gregory, 1994).
Compression injuries are often referred to as a contrecoup. This kind of injury is the result of rapid acceleration and sudden deceleration, which forces the brain into motion. The brain impacts the skull opposite from the direction in which the force originated (Stratton & Gregory, 1994). These injuries frequently occur in car accidents, as a result of a sudden stop causing the brain tissue to come into abrupt contact with the internal surface of the skull.
Rotational acceleration of the brain, often the result of sustaining impact, as in the case of a car injury, can cause axonal shearing. Rotation injuries cause the brain to move quickly in one direction and then another. This movement produces a shearing force between the brain and the skull. Because the brain and the skull have different densities and characteristics of inertia, the brain moves and turns at a different speed than the skull. This shearing action may tear axons and veins attached to the surface of the brain (Stratton & Gregory, 1994).
Such an injury may cause hemorrhaging and will lead to the eventual deterioration of nerve fibers and a decrease in the cerebral white matter of the brain. Edema is a common secondary complication of a TBI. It occurs when there is an increase in water retention in brain tissue (Rosenthal & Ricker, 2000). Like hemorrhaging, edema can lead to the build up of increased intracranial pressure resulting in further brain damage.
The impairment that occurs from a TBI is frequently diffuse, and the frontal, temporal and occipital lobes of the cerebral cortex are especially prone to bruising. The cerebral cortex is the area of the brain responsible for higher levels of functioning (Brown & Miller, 1993; Lezak, 1995; Miller, L., 1999). Individuals that have sustained a TBI with damage to the frontal areas of the brain often demonstrate changes in cognition, personality and emotional responses (Lezak, 1995.)
Ovsiew and Yudofsky (1993) have stressed that it is important not to take the concept of specific brain centers or localization areas too literally, as it may be misleading. The location in which an injury disrupts a function is not necessarily the location of the function in a normal state, as brain functions are interrelated (Kennard & Swash, 1989). It is more accurate to view the brain in terms of “levels of organization,” with higher centers that involve executive functioning controlling and inhibiting the functions of lower centers. The lower centers are responsible for the more primitive and involuntary functions (Luria, 1973; Ovsiew & Yudofsky, 1993). Sequelae associated with frontal lobe impairment include disruption of the organization of the higher centers, and an inability to regulate the lower centers of the brain (Luria, 1973). LOC has been identified as a key factor in determining the degree of neuropsychological impairment. Generally the longer the duration of loss of consciousness from a head injury, the greater the severity of the brain damage. Recovery from a TBI is most dramatic within the first twelve months, and tapers off during the second year. Impairment that is still present after this period of time is generally considered to be permanent (Lezak, 1995).
Deficits in Executive Functioning
Executive functioning includes attention, concentration, abstract reasoning, formation of goals, concept formation, planning and initiation of purposeful actions, self-monitoring, self-awareness, third person perspective, frustration tolerance, impulse control, inhibition and ability to shift cues. Like batterers, individuals who have sustained a TBI often show impairment in executive functioning (Miller, 1999,Vermeiren, Clippele, Stone, Ruchin, & Deboutte, 2002; Elliot, 1989; Lezak, 1983).
Aspontaneity
Aspontaneity, defined as a lack of appropriate emotional response to external stimuli, has been noted in TBI patients (Lishman, 1968), and has been attributed to a lack of initiative, and impairment in the capacity for planning, goal setting, and anticipation (Struss & Benson, 1986). Patients with aspontaneity usually do not seek employment, and do not engage in rehabilitation programs (Prigatano, 1992). Kimberg and Farah (1993) observed that TBI patients appeared to disassociate between knowledge and behavior. On a test where higher scores could be achieved by following instructions, TBI patients did not follow the directions, even though they were able to describe the appropriate strategy post-test.

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