Future directions in brain injury research.

This paper reviews the potential future directions that are important for brain injury research, especially with regard to concussion. The avenues of proposed research are categorized according to current concepts of concussion, types of concussion, and a global schema for globally reducing the burden of concussion.

Acute and subacute changes in neural activation during the recovery from sport-related concussion.

To study the natural recovery from sports concussion, 12 concussed high school football athletes and 12 matched uninjured teammates were evaluated with symptom rating scales, tests of postural balance and cognition, and an event-related fMRI study during performance of a load-dependent working memory task at 13 h and 7 weeks following injury. Injured athletes showed the expected postconcussive symptoms and cognitive decline with decreased reaction time (RT) and increased RT variability on a working memory task during the acute period and an apparent full recovery 7 weeks later. Brain activation patterns showed decreased activation of right hemisphere attentional networks in injured athletes relative to controls during the acute period with a reversed pattern of activation (injured > controls) in the same networks at 7 weeks following injury. These changes coincided with a decrease in self-reported postconcussive symptoms and improved cognitive test performance in the injured athletes. Results from this exploratory study suggest that decreased activation of right hemisphere attentional networks mediate the cognitive changes and postconcussion symptoms observed during the acute period following concussion. Conversely, improvement in cognitive functioning and postconcussive symptoms during the subacute period may be mediated by compensatory increases in activation of this same attentional network.

Neuropathological findings in disabled survivors of a head injury.

We investigated how the occurrence and severity of the main neuropathological types of traumatic brain injury (TBI) influenced the severity of disability after a head injury. Eighty-five victims, each of whom had lived at least a month after a head injury but then died, were studied. Judged by the Glasgow Outcome Scale (GOS), before death 35 were vegetative, 30 were severely and 20 were moderately disabled. Neuropathological assessment showed that 71 (84%) victims had sustained cerebral contusions, 49 (58%) had diffuse axonal injury (DAI), 57 (67%), had ischemic brain damage (IBD), 58 (68%) had symmetrical ventricular enlargement, and in 47 (55%) intracranial pressure (ICP) had been increased. Thirty-five (41%) had undergone evacuation of an intracranial hematoma. Brainstem damage was seen in only 11 (13%). Analysis (χ(2) test for trends) of the relationship between these features and outcome showed that findings of DAI, raised ICP, thalamic damage, or ventricular enlargement (all p<0.005), and IBD (p=0.04) were associated with an increasingly worse outcome. Conversely, moderate or severe contusions (p=0.001) were increasingly associated with better outcomes, and evacuation of a hematoma was associated (p=0.001) with outcomes likely to be better than vegetative. We conclude that diffuse or multifocal neuropathological patterns of TBI from primary axonal injury or secondary ischemic damage are most likely to be associated with the most severely impaired outcomes after a head injury.

Severe-to-fatal head injuries in motor vehicle impacts.

Severe-to-fatal head injuries in motor vehicle environments were analyzed using the United States Crash Injury Research and Engineering Network database for the years 1997-2006. Medical evaluations included details and photographs of injury, and on-scene, trauma bay, emergency room, intensive care unit, radiological, operating room, in-patient, and rehabilitation records. Data were synthesized on a case-by-case basis. X-rays, computed tomography scans, and magnetic resonance images were reviewed along with field evaluations of scene and photographs for the analyses of brain injuries and skull fractures. Injuries to the parenchyma, arteries, brainstem, cerebellum, cerebrum, and loss of consciousness were included. In addition to the analyses of severe-to-fatal (AIS4+) injuries, cervical spine, face, and scalp trauma were used to determine the potential for head contact. Fatalities and survivors were compared using nonparametric tests and confidence intervals for medians. Results were categorized based on the mode of impact with a focus on head contact. Out of the 3178 medical cases and 169 occupants sustaining head injuries, 132 adults were in frontal (54), side (75), and rear (3) crashes. Head contact locations are presented for each mode. A majority of cases clustered around the mid-size anthropometry and normal body mass index (BMI). Injuries occurred at change in velocities (DeltaV) representative of US regulations. Statistically significant differences in DeltaV between fatalities and survivors were found for side but not for frontal impacts. Independent of the impact mode and survivorship, contact locations were found to be superior to the center of gravity of the head, suggesting a greater role for angular than translational head kinematics. However, contact locations were biased to the impact mode: anterior aspects of the frontal bone and face were involved in frontal impacts while temporal-parietal regions were involved in side impacts. Because head injuries occur at regulatory DeltaV in modern vehicles and angular accelerations are not directly incorporated in crashworthiness standards, these findings from the largest dataset in literature, offer a field-based rationale for including rotational kinematics in injury assessments. In addition, it may be necessary to develop injury criteria and evaluate dummy biofidelity based on contact locations as this parameter depended on the impact mode. The current field-based analysis has identified the importance of both angular acceleration and contact location in head injury assessment and mitigation.

Withdrawal of life support in critically ill neurosurgical patients and in-hospital death after discharge from the neurosurgical intensive care unit. Clinical article.

OBJECT: The aim of this study was to examine the variables influencing the mode and location of death in patients admitted to a neurosurgical intensive care unit (NICU), including the participation of a newly appointed neurointensivist (NI). METHODS: Data from all patients admitted to a university hospital NICU were prospectively collected and compared between 2 consecutive 19-month periods before and after the appointment of an NI. RESULTS: One thousand eighty-seven patients were admitted before and 1279 after the NI's appointment. The withdrawal of life support (WOLS) occurred in 52% of all cases of death. Death following WOLS compared with survival was independently associated with an older patient age (OR 1.04/year, 95% CI 1.03-1.05), a higher University Hospitals Consortium (UHC) expected mortality rate (OR 1.05/%, 95% CI 1.04-1.07), transfer from another hospital (OR 3.7, 95% CI 1.6-8.4) or admission through the emergency department (OR 5.3, 95% CI 2.4-12), admission to the neurosurgery service (OR 7.5, 95% CI 3.2-17.6), and diagnosis of an ischemic stroke (OR 5.4, 95% CI 1.4-20.8) or intracerebral hemorrhage (OR 5.7, 95% CI 1.9-16.7). On discharge from the NICU, 54 patients died on the hospital ward (2.7% mortality rate). A younger patient age (OR 0.94/year, 95% CI 0.92-0.96), higher UHC-expected mortality rate (OR 1.01/%, 95% CI 1-1.03), and admission to the neurosurgery service (OR 9.35, 95% CI 1.83-47.7) were associated with death in the NICU rather than the ward. There was no association between the participation of an NI and WOLS or ward mortality rate. CONCLUSIONS: The mode and location of death in NICU-admitted patients did not change after the appointment of an NI. Factors other than the participation of an NI-including patient age and the severity and type of neurological injury-play a significant role in the decision to withdraw life support in the NICU or dying in-hospital after discharge from the NICU.

A finite element study of blast traumatic brain injury - biomed 2009.

An idealized finite element human head model was constructed to study biomechanical responses in the brain due to blast overpressure loading from a blast of 10 kg TNT at 1 meter. Brain strain in the coup and contrecoup regions were 4-7x higher than the central region, and high brain strain (15%) large deformation (4 mm) occurred in the brainstem region, indicating a higher probability of injury in the peripheral brain and brainstem regions due to blast overpressure loading.

Traumatic brain injury after frontal crashes: relationship with body mass index.

BACKGROUND: Previous studies had demonstrated that injury severity and risk of death after motor-vehicle crashes are related to human body characteristics. The purpose of this study was to clarify the relationship between body mass index (BMI) and head injury severity in front seat passengers after a frontal collision. METHODS: Data from all front seat occupants with at least one injury, older than 16 years old involved in a frontal collision from 1993 to 2005 were retrieved from the National Automotive Sampling System (NASS) database. Patient and collision characteristics were analyzed. Two cohorts were defined according to BMI < or > or =30 kg/m2. RESULTS: A total of 6,977 patients were included in this study, 5,918 (85%) had complete data on weight and height. Patient's mean age was 37 +/- 18 years old, the median ISS was 6, interquartile range (IQR) 15, and 61% were men. The mortality rate was positively associated to the crash delta velocity (DV) (p < 0.0001). The use of restraint system reduced the risk of death (p = 0.01). There was a significant increase in fatal outcome (p < 0.0001; RR 1.84 95% CI 1.61-2.1) and injury severity (ISS >25 p < 0.0001; RR 1.36 95% CI 1.19-1.54) in the obese cohort. Obese patients had higher chances of having a maximum head injury (Abbreviated Injury Score head = 6) than those not obese (p = 0.003; RR 1.97 95% CI 1.52-2.55). CONCLUSION: Obese passengers are more likely to suffer a more severe head trauma after a frontal collision. Further studies with computational models are needed to determine the precise role of BMI on brain injury-related biomechanical metrics.

Association of contact loading in diffuse axonal injuries from motor vehicle crashes.

BACKGROUND: Although studies have been conducted to analyze brain injuries from motor vehicle crashes, the association of head contact has not been fully established. This study examined the association in occupants sustaining diffuse axonal injuries (DAIs). METHODS: The 1997 to 2006 motor vehicle Crash Injury Research Engineering Network database was used. All crash modes and all changes in velocity were included; ejections and rollovers were excluded; injuries to front and rear seat occupants with and without restraint use were considered. DAI were coded in the database using Abbreviated Injury Scale 1990. Loss of consciousness was included and head contact was based on medical- and crash-related data. RESULTS: Sixty-seven occupants with varying ages were coded with DAI. Forty-one adult occupants (mean, 33 years of age, 171-cm tall, 71-kg weight; 30 drivers, 11 passengers) were analyzed. Mean change in velocity was 41.2 km/h and Glasgow Coma Scale score was 4. There were 33 lateral, 6 frontal, and 2 rear crashes with 32 survivors and 9 were fatalities. Two occupants in the same crash did not sustain DAI. Although skull fractures and scalp injuries occurred in some impacts, head contact was identified in all frontal, rear, and far side, and all but one nearside crashes. CONCLUSIONS: Using a large sample size of occupants sustaining DAI in 1991 to 2006 model year vehicles, DAI occurred more frequently in side than frontal crashes, is most commonly associated with impact load transfer, and is not always accompanied by skull fractures. The association of head contact in >95% of cases underscores the importance of evaluating crash-related variables and medical information for trauma analysis. It would be prudent to include contact loading in addition to angular kinematics in the analysis and characterization of DAI.

Experimental study of blast-induced traumatic brain injury using a physical head model.

This study was conducted to quantify intracranial biomechanical responses and external blast overpressures using physical head model to understand the biomechanics of blast traumatic brain injury and to provide experimental data for computer simulation of blast-induced brain trauma. Ellipsoidal-shaped physical head models, made from 3-mm polycarbonate shell filled with Sylgard 527 silicon gel, were used. Six blast tests were conducted in frontal, side, and 45 degrees oblique orientations. External blast overpressures and internal pressures were quantified with ballistic pressure sensors. Blast overpressures, ranging from 129.5 kPa to 769.3 kPa, were generated using a rigid cannon and 1.3 to 3.0 grams of pentaerythritol tetranitrate (PETN) plastic sheet explosive (explosive yield of 13.24 kJ and TNT equivalent mass of 2.87 grams for 3 grams of material). The PETN plastic sheet explosive consisted of 63% PETN powder, 29% plasticizer, and 8% nitrocellulose with a density of 1.48 g/cm3 and detonation velocity of 6.8 km/s. Propagation and reflection of the shockwave was captured using a shadowgraph technique. Shockwave speeds ranging from 423.3 m/s to 680.3 m/s were recorded. The model demonstrated a two-stage response: a pressure dominant (overpressure) stage followed by kinematic dominant (blast wind) stage. Positive pressures in the brain simulant ranged from 75.1 kPa to 1095 kPa, and negative pressures ranged from -43.6 kPa to -646.0 kPa. High- and normal-speed videos did not reveal observable deformations in the brain simulant from the neutral density markers embedded in the midsagittal plane of the head model. Amplitudes of the internal positive and negative pressures were found to linearly correlate with external overpressure. Results from the current study suggested a pressure-dominant brain injury mechanism instead of strain injury mechanism under the blast severity of the current study. These quantitative results also served as the validation and calibration data for computer simulation models of blast brain injuries.

Influence of angular acceleration-deceleration pulse shapes on regional brain strains.

Recognizing the association of angular loading with brain injuries and inconsistency in previous studies in the application of the biphasic loads to animal, physical, and experimental models, the present study examined the role of the acceleration-deceleration pulse shapes on region-specific strains. An experimentally validated two-dimensional finite element model representing the adult male human head was used. The model simulated the skull and falx as a linear elastic material, cerebrospinal fluid as a hydrodynamic material, and cerebrum as a linear viscoelastic material. The angular loading matrix consisted coronal plane rotation about a center of rotation that was acceleration-only (4.5 ms duration, 7.8 krad/s/s peak), deceleration-only (20 ms, 1.4 krad/s/s peak), acceleration-deceleration, and deceleration-acceleration pulses. Both biphasic pulses had peaks separated by intervals ranging from 0 to 25 ms. Principal strains were determined at the corpus callosum, base of the postcentral sulcus, and cerebral cortex of the parietal lobe. The cerebrum was divided into 17 regions and peak values of average maximum principal strains were determined. In all simulations, the corpus callosum responded with the highest strains. Strains were the least under all simulations in the lower parietal lobes. In all regions peak strains were the same for both monophase pulses suggesting that the angular velocity may be a better metric than peak acceleration or deceleration. In contrast, for the biphasic pulse, peak strains were region- and pulse-shape specific. Peak values were lower in both biphasic pulses when there was no time separation between the pulses than the corresponding monophase pulse. Increasing separation time intervals increased strains, albeit non-uniformly. Acceleration followed by deceleration pulse produced greater strains in all regions than the other form of biphasic pulse. Thus, pulse shape appears to have an effect on regional strains in the brain.

In vitro and in vivo characterization of neurally modified mesenchymal stem cells induced by epigenetic modifiers and neural stem cell environment.

Mesenchymal stem cell (MSC)-mediated tissue regeneration is a promising strategy to treat several neurodegenerative diseases and traumatic injuries of the central nervous system. Bone marrow MSCs have great potential as therapeutic agents, since they are easy to isolate and expand and are capable of producing various cell types, including neural cells. Recently we developed a highly efficient methodology to produce neural stem-like and neural precursor-like cells from mice bone marrow-derived MSCs that eventually differentiate into neuronal- and glial-like cells in vitro. The aim of this study is to further elucidate neural expression profile of neurally induced mesenchymal stem cells (NI-MSCs) and their ability to retain neural differentiation potential when grafted into the intact spinal cord of rats. To this end, we further characterized in vitro and in vivo properties of NI-MSCs by immunocytochemistry, Western blot, ELISA, and immunohistochemistry. Immunocytochemical data demonstrated that NI-MSCs express several mature neural markers such as B3T, GFAP MAP-2, NF-200, and NeuN, which were confirmed through Western blot. ELISA data showed that NI-MSCs release nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). In vivo studies demonstrated that grafted NI-MSCs survived after transplantation into intact spinal cord and produced cells that expressed neural markers. All these data suggest that neurally modified MSCs, induced by recently developed methodology, could be a potential source of cells to replace damaged neurons and glia in injured spinal cord, and/or to promote cell survival and axonal growth of host tissue.

Chest deflections and injuries in oblique lateral impacts.

A majority of laboratory-driven side-impact injury assessments are conducted using postmortem human subjects (PMHS) under the pure lateral mode. Because real-world injuries occur under pure and oblique modes, this study was designed to determine chest deflections and injuries using PMHS under the latter mode. Anthropometrical data were obtained and x-rays were taken. Specimens were seated on a sled and lateral impact acceleration corresponding to a change in velocity of 24 km/h was applied such that the vector was at an angle of 20 or 30 degrees. Chestbands were fixed at the level of the axilla (upper), xyphoid process (middle), and tenth rib (lower) location. Deflection contours as a function of time at the levels of the axilla and mid-sternum, representing the thorax, and at the tenth rib level, representing the abdomen, were evaluated for peak magnitudes. All data were normalized using mass-scaling procedures. Injuries were identified following the test at autopsy. Trauma graded according to the Abbreviated Injury Score, 1990 version, indicated primarily unilateral rib fractures and soft tissue abnormalities such as lung contusion and diaphragm laceration occurred. Mean peak deflections at the upper, middle, and lower levels of the chest for the 30-degree tests were 96.2, 78.5, and 76.8 mm. For the 20-degree tests, these magnitudes were 77.5, 89.9, and 73.6 mm. Statistical analysis indicated no significant (p > 0.05) differences in peak chest deflections at all levels between the two obliquities although the metric was significantly greater in oblique than pure lateral impacts at the mid and lower thoracic levels. These response data are valuable in oblique lateral impact assessments.

How to test brain and brain simulant at ballistic and blast strain rates.

Mechanical properties of brain tissue and brain simulant at strain rate in the range of 1000 s-1 are essential for computational simulation of intracranial responses for ballistic and blast traumatic brain injury. Testing these ultra-soft materials at high strain rates is a challenge to most conventional material testing methods. The current study developed a modified split Hopkinson bar techniques using the combination of a few improvements to conventional split Hopkinson bar including: using low impedance aluminum bar, semiconductor strain gauge, pulse shaping technique and annular specimen. Feasibility tests were conducted using a brain stimulant, Sylgard 527. Stress-strain curves of the simulant were successfully obtained at strain rates of 2600 and 2700 s-1 for strain levels up to 60%. This confirmed the applicability of Hopkinson bar for mechanical properties testing of brain tissue in the ballistic and blast domain.

New rat model for diffuse brain injury using coronal plane angular acceleration.

A new experimental model was developed to induce diffuse brain injury (DBI) in rats through pure coronal plane angular acceleration. An impactor was propelled down a guide tube toward the lateral extension of the helmet fixture. Upon impactor-helmet contact, helmet and head were constrained to rotate in the coronal plane. In the present experimental series, the model was optimized to generate rotational kinematics necessary for concussion. Twenty-six rats were subjected to peak angular accelerations of 368 +/- 30 krad/sec2 (mean +/- standard deviation) with 2.1 +/- 0.5-msec durations. Following rotational loading, unconsciousness was defined as time between reversal agent administration and return of corneal reflex. All experimental rats demonstrated transient unconsciousness lasting 8.8 +/- 3.7 min that was significantly longer than control rats. Macroscopic damage was noted in 51% of experimental animals: 38% subarachnoid hemorrhage, and 15% intraparenchymal lesion. Microscopic analysis indicated no evidence of axonal swellings at sacrifice times of 24, 48, 72, and 96 h. All rats survived rotational loading without skull fracture. Injuries were classified as concussion based on transient unconsciousness, scaled biomechanics, limited macroscopic damage, and minimal histological abnormalities. The experimental methodology remains adjustable, permitting investigation of increasing DBI severities through modulation of model parameters, and inclusion of further functional and histological outcome measures.

Biomechanical correlates of mild diffuse brain injury in the rat.

The relationship between diffuse brain injury (DBI) occurrence and impact biomechanics is well documented. Previous studies attempted to develop injury thresholds based on various biomechanical parameters and have demonstrated inconsistent results. The spectral nature of DBI requires robust metrics capable of predicting injury occurrence and severity. In the present study impact biomechanics reported previously were correlated to rat unconsciousness time. Significant correlation was identified in three parameters including square angular velocity, change in rotational velocity, and Head Impact Power. Results suggest rotational loading of the rat head has similar correlates to the human condition. In addition, certain biomechanical parameters demonstrate capacity for predicting DBI severity.

High-speed 3-D kinematics from whole-body lateral impact sled tests.

While lateral impact sled studies have been conducted to determine injuries, injury mechanisms, and derive human tolerance using post mortem human subject (PMHS) for the chest and pelvis regions of the human body, there is a paucity of three-dimensional (3-D) motions at high-speeds. Since out-of-position occupants respond with 3-D motions even under pure frontal and lateral impacts, it is important to determine such kinematics at high-speeds in the temporal domain. Consequently, the objective of the study was to determine lateral impact-induced 3-D temporal motions at 1,000 frames per sec. PMHS were screened, seated on a sled, restrained using belt systems, and 13.5 g lateral impact acceleration was applied. Retroreflective photographic markers were placed at various locations including the head, first thoracic vertebra, sacrum, dorsal spine, and sled. 3-D coordinates of the anatomical locations of PMHS, fiducially placed markers, and sled were obtained pretest and post test. Kinematics of the head with respect to sled, head with respect to first thoracic vertebra, and first thoracic vertebra with respect to sled in the Cartesian system of reference were determined using a nine-camera system. Head and first thoracic vertebral kinematic data are reported in the paper. 3-D motions induced from lateral impacts supplement sensor-based data for improved crashworthiness evaluations.

Mechanics of fresh, refrigerated, and frozen arterial tissue.

Arterial grafts and experimental soft tissues are commonly preserved using refrigeration and freezing. The present study was designed to investigate effects of common storage protocols on arterial mechanics. Porcine aortas were axially distracted to failure implementing fresh, refrigerated, and frozen storage conditions. Fresh tissues were tested within 24 h of sacrifice; refrigerated tissues were stored at +4 degrees C for 24 or 48 h prior to testing, and frozen tissues were stored at -20 or -80 degrees C for 3 months prior to testing. Blunt arterial injury experimentally occurred in distraction with intimal subfailure before ultimate failure in 82% of specimens. Subfailure stress decreased in refrigerated (0.59 +/- 0.19 MPa) compared to fresh (0.83 +/- 0.39 MPa) and frozen (0.99 +/- 0.41 MPa) specimens. Ultimate stress was also significantly decreased in refrigerated (0.83 +/- 0.19 MPa) compared to fresh (1.15 +/- 0.39 MPa) and frozen (1.32 +/- 0.31 MPa) specimens. Subfailure and ultimate strain were not significantly dependent upon storage technique. Young's modulus significantly decreased in refrigerated (1.89 +/- 0.63 MPa) compared to fresh (2.98 +/- 1.45 MPa) and frozen (3.49 +/- 1.32 MPa) specimens. Physiological, subfailure, and ultimate failure mechanics between fresh and frozen specimens were not significantly different. Clinically relevant intimal failures can be reproduced and injury mechanics determined while adhering to experimental protocols of freezing specimens before testing. However, short-term tissue refrigeration may affect mechanics.

Biomechanics of side impact: injury criteria, aging occupants, and airbag technology.

This paper presents a survey of side impact trauma-related biomedical investigations with specific reference to certain aspects of epidemiology relating to the growing elderly population, improvements in technology such as side airbags geared toward occupant safety, and development of injury criteria. The first part is devoted to the involvement of the elderly by identifying variables contributing to injury including impact severity, human factors, and national and international field data. This is followed by a survey of various experimental models used in the development of injury criteria and tolerance limits. The effects of fragility of the elderly coupled with physiological changes (e.g., visual, musculoskeletal) that may lead to an abnormal seating position (termed out-of-position) especially for the driving population are discussed. Fundamental biomechanical parameters such as thoracic, abdominal and pelvic forces; upper and lower spinal and sacrum accelerations; and upper, middle and lower chest deflections under various initial impacting conditions are evaluated. Secondary variables such as the thoracic trauma index and pelvic acceleration (currently adopted in the United States Federal Motor Vehicle Safety Standards), peak chest deflection, and viscous criteria are also included in the survey. The importance of performing research studies with specific focus on out-of-position scenarios of the elderly and using the most commonly available torso side airbag as the initial contacting condition in lateral impacts for occupant injury assessment is emphasized.

Biomechanical characterization of internal layer subfailure in blunt arterial injury.

Blunt carotid artery injuries occur in 0.3% of blunt injured patients and may lead to devastating neurological consequences. However, arterial mechanics leading to internal layer subfailure have not been quantified. Twenty-two human carotid artery segments and 18 porcine thoracic aorta segments were opened to expose the intimal side and longitudinally distracted to failure. Porcine aortas were a geometrically accurate model of human carotid arteries. Internal layer subfailures were identified using videography and correlated with mechanical data. Ninety-three percent (93%) of vessels demonstrated subfailure prior to catastrophic failure. All subfailures occurred on the intimal surface. Initial subfailure occurred at 79% of the stress and 85% of the strain to catastrophic failure in younger porcine specimens, compared to 44% and 60%, respectively, in older human specimens. In most cases, multiple subfailures occurred prior to catastrophic failure. Due to limitations in human specimen quality (age, prior storage), young and fresh porcine aorta specimens are likely a more accurate model of clinical blunt carotid artery injuries. Present results indicate that vessels are acutely capable of maintaining physiologic function following initial subfailure. Delayed symptomatology commonly associated with blunt arterial injuries is explained by this mechanics-based and experimentally quantified onset of subcatastrophic failure.

Lateral impact injuries with side airbag deployments--a descriptive study.

The present study was designed to provide descriptive data on side impact injuries in vehicles equipped with side airbags using the United States National Automotive Sampling System (NASS). The database was queried with the constraint that all vehicles must adhere to the Federal Motor Vehicle Safety Standards FMVSS 214, injured occupants be in the front outboard seats with no rollovers or ejections, and side impacts airbags be deployed in lateral crashes. Out of the 7812 crashes in the 1997-2004 weighted NASS files, AIS > or = 2 level injuries occurred to 5071 occupants. There were 3828 cases of torso-only airbags, 955 cases of torso-head bag combination, and 288 inflatable tubular structure/curtain systems. Side airbags were not attributed to be the cause of head or chest injury to any occupant at this level of severity. The predominance of torso-only airbags followed by torso-head airbag combination reflected vehicle model years and changing technology. Head and chest injuries were coupled for the vast majority of occupants with injuries to more than one body region. Comparing literature data for side impacts without side airbag deployments, the presence of a side airbag decreased AIS=2 head, chest, and extremity injuries when examining raw data incidence rates. Although this is the first study to adopt strict inclusion-exclusion criteria for side crashes with side airbag deployments, future studies are needed to assess side airbag efficacy using datasets such as matched-pair occupants in side impacts.