A potential whiplash mechanism for cerebral concussion

The clinical presentations of concussion and whiplash injury have considerable overlap, although the mechanisms for these two injuries are different. Concussion is generally attributed to a relatively short‐duration, high‐acceleration impact to the head, whereas whiplash injury is generally attributed to inertial loading of neck tissues by the head mass—often in concert with a relatively long‐duration, low‐acceleration head impact with the head restraint. Despite these differences, the head’s angular velocity change during some rear‐end impacts is similar to that observed in some reconstructed concussive head impacts. This similarity raises the possibility of concussion during rear‐end impacts typically associated with whiplash injuries. Here the authors sought to compare the brain tissue deformation that develops during football‐related head impacts and rear‐end crashes to better understand the relative potential for concussion during these two exposures. Linear and angular head kinematics were taken from two previously published experiments of rear‐end crashes and football helmet impacts. One rear‐end crash generated average and 90th percentile maximum principal strains in the brain that were similar to those generated in a 9.3 m/s helmet impact, which itself yielded larger linear and angular velocity changes than the two concussive rear impacts amongst the 25 previously reconstructed football concussions. This rear‐end crash involved the dummy’s head wrapping onto the top of a full‐down head restraint during a 15 km/h speed change and generated a head angular velocity change of 46.1 rad/s. The average and 90th percentile maximum principal strains correlated best with head angular velocity change, even though the durations of the head‐to‐head‐restraint impacts were about four times longer than typical football helmet impacts. This finding supports prior studies showing a correlation between brain strain and head angular velocity change [5‐6], and extends this correlation to longer duration rear head impacts.