Cyclic Head Rotations Produce Modest Brain Injury in Infant Piglets

Repetitive back-and-forth head rotation due to vigorous shaking is purported to be a central mechanism responsible for diffuse white matter injury, subdural hemorrhage and retinal hemorrhage in some cases of abusive head trauma (AHT) in young children. Although animal studies have identified mechanisms of traumatic brain injury (TBI) associated with single rapid head acceleration-decelerations at levels experienced in a motor vehicle crash, few experimental studies have investigated TBI from repetitive head rotations. The objective of this study was to systematically investigate the post-injury pathological time-course after cyclic, low-velocity head rotations in the piglet, and compare them to single head rotations. Injury metrics were the occurrence and extent of axonal injury (AI), extra-axial hemorrhage (EAH), red cell neuronal/axonal change (RCNAC), and ocular injury (OI). Hyperflexion/extension of the neck were purposefully avoided in the study, resulting in unscaled angular accelerations at the lower end of reported infant surrogate shaking kinematics. All findings were at the mild end of the injury spectrum, with no significant findings at 6 hours post-injury. However, cyclic head rotations produced modest AI that significantly increased with time post-injury (p<0.035), and had significantly greater amounts of RCNAC and EAH than non-cyclic head rotations after 24 hours post-injury (p<0.05). No OI was observed. Future studies should investigate the contributions of additional physiological and mechanical features associated with AHT (e.g. hyperflexion/extension, increased intracranial pressure due to crying or thoracic compression, and more than two cyclic episodes) to enhance our understanding of the causality between proposed mechanistic factors and AHT in infants.