Yoganandan 1 CHARACTERIZING DIFFUSE BRAIN INJURIES FROM REAL-WORLD MOTOR VEHICLE IMPACTS

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 medicaland 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. INTRODUCTION Motor vehicle impacts continue to be a source of unintentional injury to the human head [1-4]. The recent brain injury symposium held in Washington, DC, in February 2007, emphasizes the importance of trauma to this region of the human body in vehicular environments. In neurosurgical and other clinical literatures, head injuries are commonly classified as open or closed depending on the integrity of the dura. Another classification is based on whether the injury is focal or diffuse [5]. Although national and international databases such as the Cooperative Crash Injury Study, CCIS, in England, and the National Automotive Sampling System, NASS, and Fatal Analysis Reporting System, FARS, in USA have been developed in the past, CIREN database provides opportunities to conduct detailed analyses of trauma from medical and clinical perspectives. Studies have begun to appear in published literature using this database. For example, a study on fractures of the second cervical vertebra was reproted using CIREN and NASS databases [6]. Injury mechanisms were derived based on the analysis of medicaland crashrelated data from CIREN [7] Outcomes were correlated with clinical and laboratory studies [7, 8]. Recent presentations at CIREN meetings and the Society of Automotive Engineers – Government Industry conferences held in the United States have adopted a similar approach for analyzing injuries and injury mechanisms to other body regions. Chest injuries and injury mechanisms from pole-induced lateral impacts were described in 2006 [9]. Because head injuries continue to have significant societal impact and are a byproduct of motor vehicle crashes, similar analyses are needed. To the best of our knowledge, such studies for this body region are lacking in published literature. With this as a focus, the present preliminary study was designed to characterize brain injuries. Specifically, diffuse axonal injuries were characterized at the occupant