Closed head injury refers to brain damage arising from the forces generated when the head is rapidly accelerated or decelerated as a result of trauma—for example, hitting a car windscreen in a traffic accident or striking the ground with the head in a fall. The ensuing BRAIN INJURY has both focal and diffuse components. Focal injuries often include a LESION (in the form of contusion) of the extremities of the brain, notably the frontal and temporal polar regions, and haematomas (blood clots) arising from the rupture of blood vessels. Diffuse injury arises from the stretching and shearing of axons, known as DIFFUSE AXONAL INJURY. Diffuse axonal injury is widespread through the brain, its severity proportional to the strength of the accelerative force generated during the trauma. Long axons, such as those comprising the CORPUS CALLOSUM are particularly at risk.
The immediate effects of a severe closed head injury invariably include a period of unconsciousness (COMA).
In the most severe cases, there is no recovery, and the patient remains in a PERSISTENT VEGETATIVE STATE or dies. More commonly, coma is followed by a period of confusion, characterized by an inability to recall or to place events in their proper order (post-traumatic AMNESIA), which is followed in turn by a return to normal CONSCIOUSNESS. The psychological impairments arising from closed head injury can be profound, even in cases where the injury is only moderately severe, and the ensuing periods of coma and post-traumatic injury relatively brief. Typically, patients will suffer from a range of cognitive impairments, including poor MEMORY and concentration, and slowed DECISION-MAKING. These impairments are often accompanied by personality changes, which frequently resemble those that are seen in patients with focal damage to the FRONTALLOBE. The impairments reflect the combined effects of the focal and diffuse components of the brain damage arising from the injury, which are difficult to separate. Not infrequently, the impairments are of sufficient severity to prevent a patient from returning to employment or leading a normal life.
MICHAEL D.RUGG
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