There are two types of impacts on skull and the sound wave elicited by the impact. The first at the site where the force is applied, the second where the advancing segments of the accelerated brain are brought suddenly to rest by the forces that resist its forward motion.
• Countercoup lesions of the brain were once thought to be caused by the brain moving within the skull in a straight line with the force of the blow striking against its opposite side, but from experiments on mechanics of head injuries it has been demonstrated that countercoup lesions are chiefly due to local distortions of the skull and the sudden rotation of the head as result of a blow, which arouse shear strains or slide produced by the pulling apart of the constituent particles of the brain .
• Shear strains occur due to pulling apart of the constituent particles of the brain. Shear strains occur in all parts of the brain, but they occur to a large extent at the base of the frontal lobe and the tip of the temporal lobe. This is because the skull gets a good grip on the brain in this region owing to the projecting ridge of the sphenoid bone. Hence, severe and extensive injuries occur in this region when a blow is struck on the occiput.
• On the other hand, countercoup injuries which are caused by rotation will not occur if the head is so well fixed that it cannot rotate at all when it receives a blow. Cerebral contusions and tears have been reported in autopsy as a result of trauma.
(Contributed by Dr Sudhir Gupta)
• Countercoup lesions of the brain were once thought to be caused by the brain moving within the skull in a straight line with the force of the blow striking against its opposite side, but from experiments on mechanics of head injuries it has been demonstrated that countercoup lesions are chiefly due to local distortions of the skull and the sudden rotation of the head as result of a blow, which arouse shear strains or slide produced by the pulling apart of the constituent particles of the brain .
• Shear strains occur due to pulling apart of the constituent particles of the brain. Shear strains occur in all parts of the brain, but they occur to a large extent at the base of the frontal lobe and the tip of the temporal lobe. This is because the skull gets a good grip on the brain in this region owing to the projecting ridge of the sphenoid bone. Hence, severe and extensive injuries occur in this region when a blow is struck on the occiput.
• On the other hand, countercoup injuries which are caused by rotation will not occur if the head is so well fixed that it cannot rotate at all when it receives a blow. Cerebral contusions and tears have been reported in autopsy as a result of trauma.
(Contributed by Dr Sudhir Gupta)
No comments:
Post a Comment