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When we talk about traumatic brain injury,

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we talk about various mechanisms of the trauma.

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There is the whiplash injury,

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also referred to as the coup contrecoup injury, in which the

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head hits a stationary object, and the brain within the

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calvarium sloshes forward and back, secondary to the

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acceleration motion of the brain from the injury.

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For example,

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if the head were to hit the windshield of a car,

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one would have the coup injury anteriorly,

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where the head strikes the windshield.

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However,

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because the brain is moving forward

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and then recoils backwards,

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we also have injury generally to the posterior portion

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of the brain in the contrecoup fashion.

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So, coup would be at the site of the actual impact,

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whereas the contrecoup would be in the

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opposite direction from that.

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However, sometimes we have additional injury,

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in which case it's a rotational injury,

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in which the brain is moving in multiple directions.

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And when we talk about that,

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that's usually the mechanism for what we call

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diffuse axonal injury or shearing injuries,

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where there is both a forward and back, as well

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as a rotational component to the trauma.

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This is a diagram of the brain in the sagittal plane.

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As I previously mentioned,

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when we think about where to search for traumatic

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injuries to the brain, in general,

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the locations that we look at most closely are along the

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anterior aspect of the frontal lobes, where the brain

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and the head usually will hit the various objects.

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However, if a patient falls backwards, for example,

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we would call the coup portion, the more posterior portion,

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and look at the occipital region.

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But in either case,

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we are looking at both directions

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for the coup contrecoup injury.

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This is a diagram of the brain in axial section.

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In addition to the anterior frontal lobes where

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we see coup and contrecoup injuries,

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the other area that we are more interested in

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looking at is the anterior temporal lobe.

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The reason for this is because of the

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greater wing of the sphenoid bone.

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This greater wing of the sphenoid bone has sharp edges,

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and as the temporal lobe goes forward and

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back with a coup contrecoup injury,

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that temporal lobe gets sheared at

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the greater wing of the sphenoid.

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And so it's not unusual for us to see hemorrhages along

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the anteriormost aspect of the temporal lobes.

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And in follow-up of patients,

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this is an area where one typically sees encephalomalacia,

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that is the end product of the injury to the brain.

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In addition, we have the tentorium edge,

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which is a fixed fibrous tissue.

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In a coup contrecoup injury with back and forth injuries,

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one often sees injury to the posterior

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portion of the midbrain,

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which is thrust upon the tentorial edge and gets injured

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on that basis.

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In addition, as one would expect,

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the occipital lobes will be affected in those cases where

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the frontal portion of the head has a coup injury,

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looking at the contrecoup portion.

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This is a coronal diagram of the brain.

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Once again, the areas of most concern when looking for

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trauma are the anterior temporal lobes, bilaterally,

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and one also will look at the gyrus rectus region.

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The gyrus rectus region is the portion of the

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frontal lobe, which is the furthest anterior.

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This is usually at the cribriform plate and will

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be found on either side of the midline.

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And the gyrus rectus region is another area where

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long-term encephalomalacia often occurs.

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The cribriform plate and the cristagalli are irregular

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surfaces of the bone anterior cranial fossa floor,

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and the frontal lobes will scrape along that irregular bone,

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causing injury to the gyrus rectus region and sometimes

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the orbital frontal regions. So on this diagram,

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those are the areas where we be most concerned.