Brain injury without head impact?

Bicycle injuries: A systematic review for forensic evaluation

Bicycles are employed as means of transportation across various age groups, from young students to the elderly, for work, education, health, and leisure trips. Despite not achieving high speeds, bicyclists remain vulnerable to severe and even fatal injuries when they are involved in traffic accidents. Although the rising awareness of ecological issues and traffic law enforcement mean that cyclists are increasingly susceptible to road traffic crashes and injuries. Injuries resulting from a traffic accident involving cyclists can show distinct and specific characteristics depending on the manner of occurrence. The aim of this study is to provide a systematic review of the literature on injuries sustained in cyclists involved in road accidents describing and analysing elements useful for forensic assessment. The literature search was performed using PubMed, Scopus, and Web of Science from January 1970 to March 2023. Eligible studies have investigated issues of interest to forensic medicine about traffic accidents involving bicycles. A total of 128 studies satisfied the inclusion criteria and were categorized and analyzed according to the anatomical regions of the body affected (head, neck, thoraco-abdominal, and limb injuries), and the assessment of lesions in reconstruction of the bicycle accident was examined and discussed. This review highlights that injuries resulting from a traffic accident involving cyclists can show distinct and specific characteristics depending on the manner of occurrence and the energy levels involved in the crash. The assessment of injuries offers valuable insights that integrated with circumstantial and engineering data perform the reconstruction of accident dynamics.

Motorcycle injuries: a systematic review for forensic evaluation

The intricate interplay of exposure and speed leave motorcyclists vulnerable, leading to high mortality rates. During the collision, the driver and the passenger are usually projected away from the motorcycle, with variable trajectories or final positions. Injuries resulting from the crash can exhibit distinct and specific characteristics depending on the circumstances of the occurrence.The aim of this study is to provide a systematic review of the literature on injuries sustained by motorcyclists involved in road accidents describing and analyzing elements that are useful for forensic assessment.The literature search was performed using PubMed, Scopus and Web of Science from January 1970 to June 2023. Eligible studies have investigated issues of interest to forensic medicine about during traffic accidents involving motorcycle. A total of 142 studies met the inclusion criteria and were classified and analyzed based on the anatomical regions of the body affected (head, neck, thoraco-abdominal, pelvis, and limb injuries). Moreover, also the strategies for preventing lesions and assessing injuries in the reconstruction of motorcycle accidents were examined and discussed.This review highlights that, beyond injuries commonly associated with motorcycle accidents, such as head injuries, there are also unique lesions linked to the specific dynamics of accidents. These include factors like the seating position of the passenger or impact with the helmet or motorbike components. The forensic assessment of injury distribution could serve as support in reconstructing the sequence of events leading to the crash and defining the cause of death in trauma fatalities.

Multifetal gestations after traumatic brain injury: a nationwide register-based cohort study in Finland

BACKGROUND

There is a paucity of information regarding the association between traumatic brain injuries (TBIs) and subsequent multifetal gestations. Since TBIs are known to negatively affect the neuroendocrine system, we hypothesized that the functions of the whole reproductive system might be disturbed as a result. The aim of this study is to determine the association between previous TBIs and the risk of multifetal gestations using nationwide registers.

METHODS

In this retrospective register-based cohort study, data from the National Medical Birth Register (MBR) were combined with data from the Care Register for Health Care. All fertile-aged women (15-49 years) who had sustained a TBI before pregnancy were included in the patient group. Women with prior fractures of the upper extremity, pelvis, and lower extremity were included in the control group. A logistic regression model was used to assess the risk for multifetal gestation after TBI. Odds ratios (ORs) and adjusted odds ratios (aOR) with 95% confidence intervals (CIs) between the groups were compared. The model was adjusted by maternal age and maternal BMI during pregnancy and previous births. The risk for multifetal gestations were evaluated during different periods following the injury (0-3 years, 3-6 years, 6-9 years, and 9 + years).

RESULTS

A total of 14 153 pregnancies occurred after the mother had sustained a TBI, and 23 216 pregnancies occurred after the mother had sustained fractures of the upper extremity, pelvis, or lower extremity. Of these, 201 (1.4%) women had multifetal gestations after TBI and 331 (1.4%) women had multifetal gestations after fractures of the upper extremity, pelvis, or lower extremity. Interestingly, the total odds of multifetal gestations were not higher after TBI when compared to fractures of the upper extremity, pelvis, and lower extremity (aOR 1.04, CI 0.86-1.24). The odds were highest at 6-9 years (aOR 1.54, 1.03-2.29) and lowest at 0-3 years (aOR 0.84, CI 0.59-1.18).

CONCLUSION

The risk for multifetal gestations after TBIs was not higher than after the other traumas included in this study. Our results provide good baseline information on the effects of TBIs on the risk for multifetal gestations, but further research is required on this topic.

Biomechanical Perspectives on Concussion in Sport

Concussions can occur in any sport. Often, clinical and biomechanical research efforts are disconnected. This review paper analyzes current concussion issues in sports from a biomechanical perspective and is geared toward Sports Med professionals. Overarching themes of this review include the biomechanics of the brain during head impact, role of protective equipment, potential population-based differences in concussion tolerance, potential intervention strategies to reduce the incidence of injury, and common biomechanical misconceptions.

Maxillofacial fractures and craniocerebral injuries - stress propagation from face to neurocranium in a finite element analysis

Background

Severe facial trauma is often associated with intracerebral injuries. So it seemed to be of interest to study stress propagation from face to neurocranium after a fistlike impact on the facial skull in a finite element analysis.

Methods

A finite element model of the human skull without mandible consisting of nearly 740,000 tetrahedrons was built. Fistlike impacts on the infraorbital rim, the nasoorbitoethmoid region, and the supraorbital arch were simulated and stress propagations were depicted in a time-dependent display.

Results

Finite element simulation revealed von Mises stresses beyond the yield criterion of facial bone at the site of impacts and propagation of stresses in considerable amount towards skull base in the scenario of the fistlike impact on the infraorbital rim and on the nasoorbitoethmoid region. When impact was given on the supraorbital arch stresses seemed to be absorbed.

Conclusions

As patients presenting with facial fractures have a risk for craniocerebral injuries attention should be paid to this and the indication for a CT-scan should be put widely. Efforts have to be made to generate more precise finite element models for a better comprehension of craniofacial and brain injury.

Electronic supplementary material

The online version of this article (doi:10.1186/s13049-015-0117-z) contains supplementary material, which is available to authorized users.

Evaluation of impact-induced traumatic brain injury in the Göttingen Minipig using two input modes

OBJECTIVES

Two novel injury devices were used to characterize impact-induced traumatic brain injury (TBI). One imparts pure translation, and the other produces combined translation and rotation. The objective of this study was to evaluate the neuropathology associated with two injury devices using proton magnetic resonance spectroscopy (1H-MRS) to quantify metabolic changes and immunohistochemistry (IHC) to evaluate axonal damage in the corpus callosum.

METHODS

Young adult female Göttingen minipigs were exposed to impact-induced TBI with either the translation-input injury device or the combined-input injury device (n=11/group). Sham animals were treated identically except for the injury event (n=3). The minipigs underwent 1H-MRS scans prior to injury (baseline), approximately 1 h after injury, and 24 h post injury, at which point the brains were extracted for IHC. Metabolites of interest include glutamate (Glu), glutamine (Gln), N-acetylaspartate (NAA), N-acetylaspartylglutamate (NAAG), and γ-aminobutyric acid (GABA). Repeated measures analysis of variance with a least significant difference post hoc test were used to compare the three time points. IHC was performed on paraffin-embedded sections of the corpus callosum with light and heavy neurofilament antibodies. Stained pixel percentages were compared between shams and 24-h survival animals.

RESULTS

For the translation-input group (27.5-70.1 g), 16 significant metabolite differences were found. Three of these include a significant increase in Gln, both 1 h and 24 h postinjury, and an increase in GABA 24 h after injury. For the combined-input group (40.1-95.9 g; 1,014.5-3,814.9 rad/s2; 7.2-10.8 rad/s), 20 significant metabolite differences were found. Three of these include a significant increase in Glu, an increase in the ratio Glu/Gln, and an increase in the ratio Glu/NAAG 24 h after injury. The IHC analysis revealed significant increases in light and heavy neurofilament for both groups 24 h after injury.

CONCLUSIONS

Only five metabolite differences were similar between the input modes, most of which are related to inflammation or myelin disruption. The observed metabolite differences indicate important dissimilarities. For the translation-input group, an increase in Gln and GABA suggests a response in the GABA shunt system. For the combined-input group, an increase in Glu, Glu/Gln, and Glu/NAAG suggests glutamate excitotoxicity. Importantly, both of these input modes lead to similar light and heavy neurofilament damage, which indicates axonal disruption. Identifying neuropathological changes that are unique to different injury mechanisms is critical in defining the complexity of TBI and can lead to improved prevention strategies and the development of effective drug therapies.

Towards clinical management of traumatic brain injury: a review of models and mechanisms from a biomechanical perspective

Traumatic brain injury (TBI) is a major worldwide healthcare problem. Despite promising outcomes from many preclinical studies, the failure of several clinical studies to identify effective therapeutic and pharmacological approaches for TBI suggests that methods to improve the translational potential of preclinical studies are highly desirable. Rodent models of TBI are increasingly in demand for preclinical research, particularly for closed head injury (CHI), which mimics the most common type of TBI observed clinically. Although seemingly simple to establish, CHI models are particularly prone to experimental variability. Promisingly, bioengineering-oriented research has advanced our understanding of the nature of the mechanical forces and resulting head and brain motion during TBI. However, many neuroscience-oriented laboratories lack guidance with respect to fundamental biomechanical principles of TBI. Here, we review key historical and current literature that is relevant to the investigation of TBI from clinical, physiological and biomechanical perspectives, and comment on how the current challenges associated with rodent TBI models, particularly those involving CHI, could be improved.

Impaired axoplasmic transport is the dominant injury induced by an impact acceleration injury device: an analysis of traumatic axonal injury in pyramidal tract and corpus callosum of rats

Traumatic axonal injury (TAI) involves neurofilament compaction (NFC) and impaired axoplasmic transport (IAT) in distinct populations of axons. Previous quantification studies of TAI focused on limited areas of pyramidal tract (Py) but not its entire length. Quantification of TAI in corpus callosum (CC) and its comparison to that in Py is also lacking. This study assessed and compared the extent of TAI in the entire Py and CC of rats following TBI. TBI was induced by a modified Marmarou impact acceleration device in 31 adult male Sprague Dawley rats by dropping a 450 gram impactor from either 1.25 m or 2.25 m. Twenty-four hours after TBI, TAI was assessed by beta amyloid precursor protein (β-APP-IAT) and RMO14 (NFC) immunocytochemistry. TAI density (β-APP and RMO14 axonal swellings, retraction balls and axonal profiles) was counted from panoramic images of CC and Py. Significantly high TAI was observed in 2.25 m impacted rats. β-APP immunoreactive axons were significantly higher in number than RMO14 immunoreactive axons in both the structures. TAI density in Py was significantly higher than in CC. Based on our parallel biomechanical studies, it is inferred that TAI in CC may be related to compressive strains and that in Py may be related to tensile strains. Overall, IAT appears to be the dominant injury type induced by this model and injury in Py predominates that in CC.

Injury predictors for traumatic axonal injury in a rodent head impact acceleration model

A modified Marmarou impact acceleration injury model was developed to study the kinematics of the rat head to quantify traumatic axonal injury (TAI) in the corpus callosum (CC) and brainstem pyramidal tract (Py), to determine injury predictors and to establish injury thresholds for severe TAI. Thirty-one anesthetized male Sprague-Dawley rats (392±13 grams) were impacted using a modified impact acceleration injury device from 2.25 m and 1.25 m heights. Beta-amyloid precursor protein (β-APP) immunocytochemistry was used to assess and quantify axonal changes in CC and Py. Over 600 injury maps in CC and Py were constructed in the 31 impacted rats. TAI distribution along the rostro-caudal direction in CC and Py was determined. Linear and angular responses of the rat head were monitored and measured in vivo with an attached accelerometer and angular rate sensor, and were correlated to TAI data. Logistic regression analysis suggested that the occurrence of severe TAI in CC was best predicted by average linear acceleration, followed by power and time to surface righting. The combination of average linear acceleration and time to surface righting showed an improved predictive result. In Py, severe TAI was best predicted by time to surface righting, followed by peak and average angular velocity. When both CC and Py were combined, power was the best predictor, and the combined average linear acceleration and average angular velocity was also found to have good injury predictive ability. Receiver operator characteristic curves were used to assess the predictive power of individual and paired injury predictors. TAI tolerance curves were also proposed in this study.

Experimental traumatic brain injury

Traumatic brain injury, a leading cause of death and disability, is a result of an outside force causing mechanical disruption of brain tissue and delayed pathogenic events which collectively exacerbate the injury. These pathogenic injury processes are poorly understood and accordingly no effective neuroprotective treatment is available so far. Experimental models are essential for further clarification of the highly complex pathology of traumatic brain injury towards the development of novel treatments. Among the rodent models of traumatic brain injury the most commonly used are the weight-drop, the fluid percussion, and the cortical contusion injury models. As the entire spectrum of events that might occur in traumatic brain injury cannot be covered by one single rodent model, the design and choice of a specific model represents a major challenge for neuroscientists. This review summarizes and evaluates the strengths and weaknesses of the currently available rodent models for traumatic brain 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.

Biomechanical assessment of brain dynamic responses due to blast pressure waves

A mechanized and integrated computational scheme is introduced to determine the human brain responses in an environment where the human head is exposed to explosions from trinitrotoluene (TNT), or other high-yield explosives, in military applications. The procedure is based on a three-dimensional (3-D) non-linear finite element method (FEM) that implements a simultaneous conduction of explosive detonation, shock wave propagation, blast-head interactions, and the confronting human head. The processes of blast propagation in the air and blast interaction with the head are modeled by an Arbitrary Lagrangian-Eulerian (ALE) multi-material FEM formulation, together with a penalty-based fluid/structure interaction (FSI) algorithm. Such a model has already been successfully validated against experimental data regarding air-free blast and plate-blast interactions. The human head model is a 3-D geometrically realistic configuration that has been previously validated against the brain intracranial pressure (ICP), as well as shear and principal strains under different impact loadings of cadaveric experimental tests of Hardy et al. [Hardy W. N., C. Foster, M. Mason, S. Chirag, J. Bishop, M. Bey, W. Anderst, and S. Tashman. A study of the response of the human cadaver head to impact. Proc. 51 ( st ) Stapp. Car Crash J. 17-80, 2007]. Different scenarios have been assumed to capture an appropriate picture of the brain response at a constant stand-off distance of nearly 80 cm from the core of the explosion, but exposed to different amounts of a highly explosive (HE) material such as TNT. The over-pressures at the vicinity of the head are in the range of about 2.4-8.7 atmosphere (atm), considering the reflected pressure from the head. The methodology provides brain ICP, maximum shear stresses and maximum principal strain within the milli-scale time frame of this highly dynamic phenomenon. While focusing on the two mechanical parameters of pressure, and also on the maximum shear stress and maximum principal strain to predict the brain injury, the research provides an assessment of the brain responses to different amounts of over-pressure. The research also demonstrates the ability to predict the ICP, as well as the stress and strain within the brain, due to such an event. The research cannot identify, however, the specific levels of ICP, stress and strain that necessarily lead to traumatic brain injury (TBI) because there is no access to experimental data regarding head-blast interactions.

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.

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.

Contemporary issues in mild traumatic brain injury11No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the author(s) or upon any organization with which the author(s) is/are associated

OBJECTIVES

To determine (1) minimum criteria in adults for clinical diagnosis of mild traumatic brain injury (TBI) and (2) whether persistent postconcussive syndrome exists as a nosologic entity.

DATA SOURCES

PubMed search by MEDLINE of head injuries from January 1977 to July 2002.

STUDY SELECTION

All reviews and studies of mild TBI with special reference to those on persistent postconcussive syndrome having a general trauma cohort as a control comparison.

DATA EXTRACTION

Review of design and other methodologic issues. Studies dependent on superior strength of evidence (as defined by the American Academy of Neurology) concerning the biologic nature of persistent postconcussive syndrome.

DATA SYNTHESIS

A period of altered awareness with amnesia brought on by a direct craniofacial blow is the starting point in determining whether diffuse mild TBI has occurred. An amnestic scale is more helpful than Glasgow Coma Scale score in grading mild injury and in formulating minimum inclusion criteria for mild TBI. Neuropsychologic test results coupled with self-reported symptoms should not be taken as the primary source of evidence for mild TBI. Prolonged cognitive impairment after injury is not unique to brain trauma.

CONCLUSIONS

Persistent postconcussive syndrome after mild brain trauma, uncomplicated by focal injury, is biologically inseparable from other examples of the posttraumatic syndrome. To account for the persistent cognitive and behavioral sequelae of posttraumatic states, including persistent postconcussive syndrome, we need further studies on the emerging concept of limbic neuronal attrition occurring as a maladaptive response to pain and stress.

Biomechanical changes in the head associated with penetrating injuries of the maxilla and mandible: an experimental investigation

PURPOSE

In this experiment, we studied the craniocerebral injury that occurs due to the transmission of forces when maxillofacial gunshot wounds are sustained by the facial bones and cranium.

MATERIALS AND METHODS

Forty fresh pigs' heads were wounded by one of the following methods: steel spheres weighing 1.03 g at an impact velocity of 1,400 m/s, steel spheres weighing 1.03 g at an impact velocity of 800 m/s, M193 military bullets, or M56 military bullets. Pressure waves in the brain, acceleration of the head, and stress changes in the facial bones and cranium at the moment of the impact were recorded by pressure and acceleration transducers and strain gauges and were statistically compared.

RESULTS

Some obvious differences between the mechanical values obtained from high-and low-velocity missile wounds were found. A negative relationship between the peak value of the pressure wave in the brain and the distance from the point of impact to the transducer was obtained. The acceleration of the head in the direction of the ballistic path was the strongest in absolute value. There were differences in the stress values between the mandible and the temporal bone.

CONCLUSIONS

Acceleration of the head, pressure wave changes in the brain, and injury from bony stress conduction all play important roles in associated craniocerebral damage after maxillofacial firearm wounds.

Head injury mechanisms in helmet-protected motorcyclists: prospective multicenter study

BACKGROUND

In a prospective study, three research groups at Hannover (H) and Munich (M) in Germany and Glasgow (G) in the United Kingdom collected data from motorcycle crashes between July 1996 and July 1998 to investigate head injury mechanisms in helmet-protected motorcyclists.

METHODS

The head lesions of motorcyclists with Abbreviated Injury Score-Head (AISHead) 2+ injuries and/or helmet impact were classified into direct force effect (DFE) and indirect force effect (IFE) lesions. The effecting forces and the force consequences were analyzed in detail.

RESULTS

Two-hundred twenty-six motorcyclists (H, n = 115; M, n = 56; and G, n = 55) were included. Collision opponents were cars (57.8%), trucks (8.0%), pedestrians (2.3%), bicycles (1.4%), two-wheel motor vehicles (0.8%), and others (4.2%). In 25.4% no other moving object was involved. The mean impact speed was 55 km/h (range, 0-120 km/h) and correlated with AISHead. Seventy-six (33%) motorcyclists had no head injury, 21% (n = 48) AISHead 1, and 46% (n = 103) AISHead 2+. Four hundred nine head lesions were further classified: 36.9% DFE and 63.1% IFE. Lesions included 20.5% bone, 51.3% brain, and 28.1% skin. The most frequent brain lesions were subdural hematomas (22.4%, n = 47) and subarachnoid hematomas (25.2%, n = 53). Lesions of skin or bone were mainly DFE lesions, whereas brain lesions were mostly IFE lesions.

CONCLUSION

A modification of the design of the helmet shell may have a preventative effect on DFE lesions, which are caused by a high amount of direct force transfer. Acceleration or deceleration forces induce IFE lesions, particularly rotation, which is an important and underestimated factor. The reduction of the effecting forces and the kinetic consequences should be a goal for future motorcycle helmet generations.

A head impact model of early axonal injury in the sheep

Axonal injury (AI), one of the principal determinants of clinical outcome after head injury, may evolve over several hours after injury, raising the future possibility of therapeutic intervention during this period. A new head impact model of AI in sheep was developed to examine pathological and physiological changes in the brain resulting from a graded traumatic insult. In this preliminary study 10 anesthetized and ventilated Merino ewes were used. Head injury was produced by impact from a humane stunner to the temporal region of an unrestrained head. Eight sheep were studied for 1, 2, 4, or 6 h after impact. Two sham animals (no impact, 6 h survival) were also examined. Arterial blood pressure, intracranial pressure, and cerebral blood flow were monitored continuously. A physiological index of injury severity was calculated by weighting the percentage shift from preinjury values for each monitored parameter over the first hour after injury. Immunostaining with amyloid precursor protein (APP) was used as a marker of axonal damage and the distribution of APP positive axons was recorded according to a sector scoring method (APPS). Widespread AI was identified in 7 of the 8 impacted animals, around cerebral contusions and in hemispheric white matter, central gray matter, brain stem, and cerebellum, and was detected as early as 1 h after injury. The degree of axonal injury (APPS) correlated well with an index of physiological response to injury (r = 0.83, p = 0.005).