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Abstract
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Injury to the head and intracranial structures may occur as a result of direct or indirect forces. An injury by a direct force occurs when an object strikes the head. Indirect injury to the head may take place when an object accelerates or decelerates the body, with injury to the head and contents occurring indirectly. The significance of direct and indirect types of injury lies in the fact that with direct injury, there is a greater likelihood of involvement of the head and contents only, whereas, in indirect injury to the head the entire body may be involved and the possibility of injury not only to the head but to other parts of the body as well is likely.
As energy is absorbed by the head upon impact, the skull deforms and the head is either accelerated or decelerated. With regard to the production of injury the following may result. (a) There will be deformation of the skull with possible fracture or compression of the intracranial contents or both. This compression of the intracranial contents results from a decrease in the volume of the head due to deformation of the skull. (b) Sudden increase in intracranial pressure due to the acceleration or deceleration of the head at the time of impact; (c) mass movements of intracranial contents due to different acceleration rates of the skull and its contents; (d) distortion of the skull and dural septae as seen particularly in birth injuries; (e) shearing off a portion of the head without necessarily producing an appreciable increase in intracranial pressure; (f) shearing and tearing of intracranial contents due to greatly increased intracranial pressure as in bullet and shell fragment injuries; (g) a combination of any of these effects, (5). This last possibility is probably the most common mechanism as one or more of the above effects combine to cause the head injury in most cases.
The injury to the head and intracranial contents occurs as a result of the following mechanisms: (a) There may be compression or squeezing of the tissues. (b) There may be tension or tearing apart of the tissues. (c) There may be shearing or sliding of the tissues over each other. These three mechanisms may operate simultaneously or in combination in different areas or in different directions in the same area.
Concussion is a term describing a state of post-traumatic unconsciousness associated with pallor and a shock-like state in the human. It may be of varying intensity from completely recoverable states to those of continued coma and death. Concussion is caused by derangement of brain stem reticular formation. Open wounds of the head, contusions and lacerations of the brain may or may not be associated with concussion or such derangement.
The mechanism of contusions and lacerations of the brain, electrical changes and chemical alterations after head injury are discussed and evaluated. |