Mechanisms of head injury details

1. What is a brain contusion and what sorts of deficits result?
2. Where in the brain is diffuse axonal injury seen and what is the mechanism of this injury?
3. What is the cause of brain swelling and when does it occur? How is it identified on CT?
4. What is the difference between brain swelling and brain edema?
5. What is the difference between vasogenic edema and cytogenic edema?

Answers:
1. It occurs on the undersurface of the frontal lobe and anterior temporal lobe, and can result from even a relatively low velocity impact. The deficits that result are focal, cognitive, and sensory-motor.
2. DAI is seen in the corpus collosum and other midline structures (parasagittal white matter, IV septum, walls of 3rd ventricle, and brain stem. It is responsible of a LOC during TBI. It results from acceleration-deceleration and rotations forces in high-velocity impact such as MVAs. There is damage to axonal transport causing increased Ca influx --> axonal swelling and detachment.
3. Brain swelling occurs within 24 of injury and is due to an increase in cerebral blood volume. On CT, it looks like a collapse of the ventricular system and loss of CSF cisterns around the midbrain.
4. Brain edema occurs later following injury than brain swelling. It is due to an increase in brain water content that leads to extravascular fluid.
5. Vasogenic edema is related to cerebral contusion and is due to outpouring of protein-rich fluid through vessels, resulting in extracellular edema. Cytogenic edema is related to hypoxic and ischemic brain damage and is due to failing of the cells' energy supply resulting in cell death and intracellular edema.