74 Whiplash and Coup-Contrecoup


In most scenarios in which the skull experiences a large , it will soon after accelerate in the other direction (if it did not, then it would never stop moving). For example, if the skull impacts a hard surface, but neither the skull and the surface are deformed beyond their , then they will behave elastically and the skull will “bounce” back. This type of collision is known as an (more on these in the next unit). When the initial collision stopped the skull, the inertia of the brain led to an impact on the front of the brain. Now as the brain and skull move backward the head moves back, the spine and neck muscles will apply forces that stop its backward motion. tells us that the spine and neck will feel those same forces back from the head, possibly inducing a neck injury known as whiplash.

First image: The spine in a near vertical position while the head is moving from an extreme rearward position forward to a face-down position. Force pairs of equal length and opposite direction shown the force of the neck on the head and head back on the neck. Second and third images: Regions of injury on the front of the neck (soft tissue) and back of the neck (soft tissue and spine) are highlighted.
Top: Forces on the head from the neck (black) and on the neck from the head (red) during rapid forward-back motion of the head. Bottom: Sites of whiplash injury. Image Credit: 3rd Law Whiplash is a derivative of Whiplash Injury by BruceBlaus, via Wikimedia Commons



After the bounce, as the neck forces the skull to slow down on the way backward, the inertia of the brain may lead to a second impact on the back of the brain, as illustrated in the following image.

A human skull moving forward and impacting a solid wall. A cutaway of the skull shows the brain inside moving forward, impacting the front of the skull, then moving backward and impacting the back of the skull. Injured areas on the front (frontal lobe) and rear (occipital lobe) of the brain are highlighted.
The alternating accelerations of the skull and the inertia of the brain combine to cause impacts on opposing sides of the brain during a coup contrecoup injury. Image credit: Contrecoup by Patrick J. Lynch, medical illustrator via Wikimedia Commons


Aside from an additional brain tissue injury, the combined swelling of the two opposed injuries will put much more pressure on the brain, increasing the likelihood of permanent injury. This type of injury is known as a Coup Countrecoup , or translated from French by Google Translate, blow, counter blow.

  1. 3rd Law Whiplash is a derivative of Whiplash Injury by BruceBlaus [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons
  2. Contrecoup by Patrick J. Lynch, medical illustrator [CC BY 2.5 (https://creativecommons.org/licenses/by/2.5), GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons


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