Cavitation in Boxing : a possible link with Traumatic Brain Injury*

Traumatic Brain Injury (TBI) is a major healthcare problem, increasingly occurring in sports like rugby, boxing or football. The occurrence of TBI is dependent on the head acceleration and the duration of the shock, as expressed by the empirical Wayne State Tolerance Curve (WSTC). One of the possible causes of TBI is the formation of cavitation bubbles in the cerebro-spinal fluid. To investigate this hypothesis, we experimentally observe the formation of cavitation bubbles due to a shock on a water tank, and we quantify the influence of the acceleration and timespan of the shock on the bubbles dynamics. In the cranial cavity, the cerebro-spinal fluid can flow in an out through the spinal cord. Using a flexible membrane to mimic this phenomenon, we show that this motion is a prerequisite for bubble growth. From the prediction of the bubbles sizes, we build a phase diagram of the damaging capacity of the bubbles on the brain as a function of the acceleration profile, in good agreement with the prediction of the WSTC.