This study characterized brain injuries with a focus on diffuse axonal injuries using the Crash Injury Research Engineering Network (CIREN) database, developed by the National Highway Safety Administration (NHTSA). Tier one and tier two medical- and crash-related data from 1997 to 2006 were used in the retrospective analysis. Diffuse axonal injuries injuries were assessed using the 1990 version of the Abbreviated Injury Scale. In addition, other brain injuries and bony trauma to this body region were extracted. Potential head contact data were determined based on an evaluation of medical information such as x-rays and CT scans. Crashrelated variables such as change in velocity, principal direction of force, and impact modality were obtained.

Case-by-case analyses were grouped as a function of the number head injuries sustained by each occupant. Out of the 3,178 medical cases from 2,823 crashes, 67 occupants, 11 months to 85 years of age, sustained diffuse axonal injuries. Change in velocity ranged from 4 to 24 m/s. Twenty-eight passengers and 39 drivers and were involved in 49 lateral, 15 frontal, and three rear impacts. There were 32 female and 35 male occupants. In no case two occupants sustained diffuse axonal injuries in the same crash. Head contact was identified in a majority of occupants. Airbags were not attributed to be the cause of injury in more than 90% of the cases, implying its minimal role in severe head trauma. These preliminary findings appear to support the hypothesis that diffuse axonal injuries occur with impact loading to the head. In addition, this type of injury occurs more in side crashes than frontal impacts. Furthermore, these results suggest a decreasing trend for the incidence of diffuse axonal injuries in modern vehicular environments, possibly with newer technologies and increased restraint usage.