Biomechanics of blast traumatic brain injury

Blast pressure waves are a likely cause of brain tissue damage. There is evidence of astroglial scarring of brain tissue at its interface with the cerebrospinal fluid — for example at the lining of the ventricles — and we used computational and physical simulations of blast brain loading to explore whether pressure wave propagation within the brain explains this pathological observation.

We developed a simplified cylindrical model representing the skull and cerebrospinal fluid and exposed it to pressure waves typical of blast. This produced CSF cavitation at the back of the cylinder, in the contrecoup region, followed by collapse of the cavitation bubbles into microjets. We then developed an anatomically detailed model of the human brain and exposed it to blast overpressure to predict the negative pressure at the contrecoup region and uncover its mechanism.

Both models produced negative pressure at the contrecoup region, large enough to cause fluid cavitation. We found that this negative pressure is produced by the delay between the stress waves propagating through the brain and through the skull, and that the mechanism depends on the size of the cranium — small craniums are unlikely to produce the negative pressure, suggesting that animal models are unlikely to show this mechanism.

This study provides new insight into potential mechanisms of blast traumatic brain injury.