Principles of Traumatic Brain Injury.
So first we’re going to start talking about some of the principles of traumatic brain injury. And typically what we think about is you’re going to see this in the setting of some type of traumatic mechanism. So whether or not this was a high speed motor vehicle accident or some other type of non-accidental trauma you will likely have some type of traumatic mechanism that is the cause of the brain injury.
You may see things like skull fractures or cranial deformation or you could see things that are more subtle such as just intracranial bleeding that perhaps you see on an infant who had a head CT for irritability or extreme lethargy. And in the setting of this you might see things like epidural hematomas, subdural hematomas, subarachnoid hemorrhages. And the thing to think about is if you get a story where you don’t have a traumatic mechanism to explain these findings of intracranial bleeding to always think about non-accidental trauma in your differential diagnosis.
And the reason for this is these types of bleeding can occur from having have rotational or torsional injuries in which a baby is actually shaken back and forth such that the brain gets compressed against the bony prominences of the skull and can lead to some bridging veins that tear and have bleeding into the intracranial space in the forms of the hemorrhages described. The additional finding that you can see in severe brain injury includes diffuse axonal injury, in which the white matter is injured. And typically this happens quite frequently in children compared to adults.
The thing to know about traumatic brain injury is that all of the types of injuries we’re talking about right now in terms of intracranial bleeding and diffuse axonal injury are often primary injuries that we see. However, our management in terms of brain injury really focuses at preventing some of the secondary injury that can happen when the brain starts to swell after having a primary injury. Typically, peak swelling occurs within two to three days post-injury. And what we see is this type of mixed edema form in which we have a vasogenic component in which the blood-brain barrier has been disrupted. And then we also have a cytotoxic component.