Neck Flexion Induces Larger Deformation of the Brain Than Extension at a Rotational Acceleration, Closed Head Trauma

A closed head trauma induces incompletely characterized temporary movement and deformation of the brain, contributing to the primary traumatic brain injury. We used the pressure patterns recorded with light-operated miniature sensors in anaesthetized adult rabbits exposed to a sagittal plane rotational acceleration of the head, lasting 1 ms, as a measure of brain deformation. Two exposure levels were used and scaled to correspond to force levels reported to cause mild and moderate diffuse injury in an adult man, respectively. Flexion induced transient, strong, extended, and predominantly negative pressures while extension generated a short positive pressure peak followed by a minor negative peak. Low level flexion caused as strong, extended negative pressures as did high level extension. Time differences were demonstrated between the deformation of the cerebrum, brainstem, and cerebellum. Available X-ray and MRI techniques do not have as high time resolution as pressure recordings in demonstrating complex, sequential compression and stretching of the brain during a trauma. The exposure to flexion caused more protracted and extensive deformation of the brain than extension, in agreement with a published histopathological report. The severity and extent of the brain deformation generated at a head trauma thus related to the direction at equal force