Monday 24 December 2012

Emedinews:Insights on Medicolegal Issues:Countercoup injury of brain



  • Two types of impact occur 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.
  • Counter coup 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, experiments on mechanics of head injuries have demonstrated these 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 and pull apart the constituent particles of the brain. These are produced in all parts of the brain, but to a large extent at the base of the frontal lobe and the tip of the temporal lobe, as the skull gets a good grip on the brain in this region due to the projecting ridge of the sphenoid bone. Hence, severe and extensive injuries occur in this region with a blow 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.
(Ref: Modi’s Medical Jurisprudence, 25th Edition)

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