The Presence of the Temporal Horn Exacerbates the Vulnerability of Hippocampus during Head Impacts

2021 ◽  
Author(s):  
Zhou Zhou ◽  
Xiaogai Li ◽  
August Domel ◽  
Emily Dennis ◽  
Marios Georgiadis ◽  
...  
Keyword(s):  
Collegiate Athletes ◽  
Human Head ◽  
Hippocampal Volume ◽  
Arbitrary Lagrangian Eulerian ◽  
Predisposing Factor ◽  
Head Impacts ◽  
Strain And Strain Rate ◽  
Temporal Horn ◽  
Cornu Ammonis ◽  
Coupling Approach

Hippocampal injury is common in traumatic brain injury (TBI) patients, but the underlying pathogenesis remains elusive. In this study, we hypothesize that the presence of the adjacent fluid-containing temporal horn exacerbates the biomechanical vulnerability of the hippocampus. Two finite element models of the human head were used to investigate this hypothesis, one with and one without the temporal horn, and both including a detailed hippocampal subfield delineation. A fluid-structure interaction coupling approach was used to simulate the brain-ventricle interface, in which the intraventricular cerebrospinal fluid was represented by an arbitrary Lagrangian-Eulerian multi-material formation to account for its fluid behavior. By comparing the response of these two models under identical loadings, the model that included the temporal horn predicted increased magnitudes of strain and strain rate in the hippocampus with respect to its counterpart without the temporal horn. This specifically affected cornu ammonis (CA) 1 (CA1), CA2/3, hippocampal tail, subiculum, and the adjacent amygdala and ventral diencephalon. These computational results suggest the presence of the temporal horn is a predisposing factor for the prevalence of hippocampal injury, advancing the understanding of hippocampal injury during head impacts. A corresponding analysis in an imaging cohort of collegiate athletes found that temporal horn size negatively correlates with hippocampal volume in the same subfields, suggesting a possible real-world correlation whereby a larger temporal horn may be associated with decreased hippocampal volume. Our biomechanical and neuroimaging effort collectively highlight the mechanobiological and anatomical interdependency between the hippocampus and temporal horn.

A destructible headform for the assessment of sports impacts

2021 ◽  
pp. 175433712110559
Author(s):  
Ben Stone ◽  
Sean Mitchell ◽  
Yusuke Miyazaki ◽  
Nicholas Peirce ◽  
Andy Harland
Keyword(s):  
Human Subjects ◽  
Permanent Deformation ◽  
Human Head ◽  
Local Deformation ◽  
Resonance Excitation ◽  
Destructive Testing ◽  
Head Impacts ◽  
Resonance Frequencies ◽  
Hybrid Iii ◽  
Athletic Equipment

Commercially available headforms, such as the Hybrid-III and EN 960 headforms, have been used effectively to investigate the mechanics of head impacts. These headforms may result in accelerations that are unrepresentative of a human head in some impact scenarios. This may be important when considering impacts that produce areas of high pressure, since skull deformation and resonance excitation may influence the dynamic response. The National Operating Committee on Standards for Athletic Equipment (NOCSAE) headform may produce a more suitable response during these types of impacts due to the more representative skull component. However, permanent deformation may occur in some unprotected impact scenarios, resulting in the entire headform needing to be replaced. This paper outlines the development of a novel, modular and destructible headform (LU headform) that can be used in potentially destructive testing, where individual components can be replaced. The LU headform was modelled after a UK 50th percentile male. The inertial properties of the LU headform were within 6% of those observed in humans. The skull simulant properties were within the range of values reported for human tissue in two build orientations, but lower in one build orientation. The lowest and highest resonance frequencies observed in the headform model were within 5% of those observed in humans. Drop and projectile tests were conducted in line with previous cadaver tests with the observed accelerations within the range reported for post-mortem human subjects. The LU headform offers a practical means of simulating head dynamics during localised unprotected impacts or in protected impacts where local deformation and/or resonance frequency excitation remains possible.

scholarly journals Concussion BASICS II

Neurology ◽  
2018 ◽  
Vol 91 (23) ◽  
pp. e2123-e2132 ◽  
Author(s):  
Breton M. Asken ◽  
Russell M. Bauer ◽  
Steven T. DeKosky ◽  
Zachary M. Houck ◽  
Charles C. Moreno ◽  
...  
Keyword(s):  
Collegiate Athletes ◽  
Head Impact ◽  
Amyloid Peptide ◽  
Serum Biomarker ◽  
Cumulative Exposure ◽  
Head Impacts ◽  
Clinical Assessments ◽  
Recent Exposure ◽  
Impact Index ◽  
Concussion History

ObjectiveTo examine the effect of concussion history and cumulative exposure to collision sports on baseline serum biomarker concentrations, as well as associations between biomarker concentrations and clinical assessments.MethodsIn this observational cohort study, β-amyloid peptide 42 (Aβ42), total tau, S100 calcium binding protein B (S100B), ubiquitin carboxy-terminal hydrolyzing enzyme L1 (UCH-L1), glial fibrillary acidic protein, microtubule associated protein 2, and 2′,3′-cyclic-nucleotide 3′-phosphodiesterase serum concentrations were measured in 415 (61% male, 40% white, aged 19.0 ± 1.2 years) nonconcussed collegiate athletes without recent exposure to head impacts. Regression analyses were used to evaluate the relationship between self-reported history of concussion(s), cumulative years playing collision sports, clinical assessments, and baseline biomarker concentrations. Football-specific analyses were performed using a modified Cumulative Head Impact Index. Clinical assessments included symptom, cognitive, balance, and oculomotor tests.ResultsAthletes with a greater number of concussions had a higher baseline Aβ42 concentration only (ρ = 0.140, p = 0.005, small effect size). No biomarker concentrations correlated with cumulative exposure to collision sports. Race status fully mediated the correlations of S100B, UCH-L1, and Aβ42 with cognitive scores. Football exposure, specifically, was not associated with serum biomarker concentrations or clinical assessment scores based on the modified Cumulative Head Impact Index.ConclusionConcussion-related serum biomarkers showed no consistent association with concussion history, cumulative exposure to collision sports, or clinical assessments in a sample of healthy collegiate athletes. Serum Aβ42 concentrations could increase following multiple previous concussions. Considering race status is essential when investigating links between biomarkers and cognition. The biomarkers studied may not detect residual effects of concussion or repetitive head impact exposure in otherwise asymptomatic collegiate athletes without recent exposure to head impacts. Much more research is needed for identifying reliable and valid blood biomarkers of brain trauma history.

scholarly journals Developing Brain-Strain-Based Scaling to Inform the Clinical Relevance of Mouse Models of Concussion Induced by Rotation

2021 ◽  
Author(s):  
Xingyu Liu ◽  
Lihong Lu ◽  
Kewei Bian ◽  
Arthur Brown ◽  
Haojie Mao
Keyword(s):  
Brain Injury ◽  
Real World ◽  
Clinical Relevance ◽  
Neuronal Damage ◽  
Animal Experiments ◽  
Human Head ◽  
Axial Rotation ◽  
Head Impacts ◽  
Flexion Extension ◽  
Human And Mouse

Abstract Background Laboratory animal experiments are an invaluable tool for studying mild traumatic brain injury (mTBI)/concussion. Among them, rodent neurotrauma experiments have been most widely used, as transgenic and gene targeting technologies in mice allow us to test the roles of different genes in recovery from brain injury. Furthermore, the clinical relevance of rodent concussion studies can be improved by using these technologies to study concussions in animals that carry the human versions of genes known to play a role in neurological disease. However, delivering concussion injuries to the mice that are relevant to real-world human head impacts is challenging, as the mouse and human heads are dramatically different in shape and size. In the vast majority of mouse concussion experiments, the pathological and behavioral consequences of the injuries are evaluated without considering whether the injury model produces brain stretches (maximum principal strains) of the same magnitude as those experienced by human brains undergoing similar impacts. Methods We conducted a total of 201 computational simulations to understand both human and mouse brain strains that are directly linked to neuronal damage during closed-head concussive impacts. To represent real-world human head impacts we simulated mouse head impacts with durations of 1.5 ms (Type 1 scaling), followed by simulations with durations between 1 and 2 ms (Type 2), and finally, simulations with durations from 0.75 to 4.5 ms (Type 3) to develop scaling between human and mouse, as well as to reveal the predicted effects of small and large changes in impact durations on brain strain. Results Guided by these simulations we calculated that peak rotational velocities in mice could be achieved by scaling human peak rotational velocities with factors of 5.8, 4.6, and 6.8, for flexion/extension, lateral bending, and axial rotation, respectively, to reach equal brain strains between human and mouse. The effects of impact durations on scaling were also calculated and longer-duration mouse head impacts needed larger scaling factors to reach equal strain. Conclusions The scaling method will help us to create brain injury in the mouse with brain strain loading equivalent to those experienced in real-world human head impacts.

Head Impact Modeling to Support a Rotational Combat Helmet Drop Test

2021 ◽  
Author(s):  
Ryan Terpsma ◽  
Rika Wright Carlsen ◽  
Ron Szalkowski ◽  
Sushant Malave ◽  
Alice Lux Fawzi ◽  
...  
Keyword(s):  
Human Head ◽  
Mechanical Stimulus ◽  
Scientific Basis ◽  
Test Method ◽  
Drop Test ◽  
Head Impacts ◽  
Digital Twin ◽  
Brain Deformation ◽  
Acceleration Time Histories ◽  
Hybrid Iii

ABSTRACT Introduction The Advanced Combat Helmet (ACH) military specification (mil-spec) provides blunt impact acceleration criteria that must be met before use by the U.S. warfighter. The specification, which requires a helmeted magnesium Department of Transportation (DOT) headform to be dropped onto a steel hemispherical target, results in a translational headform impact response. Relative to translations, rotations of the head generate higher brain tissue strains. Excessive strain has been implicated as a mechanical stimulus leading to traumatic brain injury (TBI). We hypothesized that the linear constrained drop test method of the ACH specification underreports the potential for TBI. Materials and Methods To establish a baseline of translational acceleration time histories, we conducted linear constrained drop tests based on the ACH specification and then performed simulations of the same to verify agreement between experiment and simulation. We then produced a high-fidelity human head digital twin and verified that biological tissue responses matched experimental results. Next, we altered the ACH experimental configuration to use a helmeted Hybrid III headform, a freefall cradle, and an inclined anvil target. This new, modified configuration allowed both a translational and a rotational headform response. We applied this experimental rotation response to the skull of our human digital twin and compared brain deformation relative to the translational baseline. Results The modified configuration produced brain strains that were 4.3 times the brain strains from the linear constrained configuration. Conclusions We provide a scientific basis to motivate revision of the ACH mil-spec to include a rotational component, which would enhance the test’s relevance to TBI arising from severe head impacts.

Experimental investigation of cranial fracture initiation in blunt human head impacts

2019 ◽  
Vol 300 ◽  
pp. 51-62 ◽  
Author(s):  
Mariyam I. Isa ◽  
Todd W. Fenton ◽  
Alexis C. Goots ◽  
Elena O. Watson ◽  
Patrick E. Vaughan ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Human Head ◽  
Fracture Initiation ◽  
Head Impacts

scholarly journals Spectrum of acute clinical characteristics of diagnosed concussions in college athletes wearing instrumented helmets

2012 ◽  
Vol 117 (6) ◽  
pp. 1092-1099 ◽  
Author(s):  
Ann-Christine Duhaime ◽  
Jonathan G. Beckwith ◽  
Arthur C. Maerlender ◽  
Thomas W. McAllister ◽  
Joseph J. Crisco ◽  
...  
Keyword(s):  
Collegiate Athletes ◽  
Head Impact ◽  
Ice Hockey ◽  
Future Research ◽  
Impact Event ◽  
Head Impacts ◽  
Presenting Symptoms ◽  
Wide Range ◽  
Impact Events ◽  
Specific Impact

Object Concussive head injuries have received much attention in the medical and public arenas, as concerns have been raised about the potential short- and long-term consequences of injuries sustained in sports and other activities. While many student athletes have required evaluation after concussion, the exact definition of concussion has varied among disciplines and over time. The authors used data gathered as part of a multiinstitutional longitudinal study of the biomechanics of head impacts in helmeted collegiate athletes to characterize what signs, symptoms, and clinical histories were used to designate players as having sustained concussions. Methods Players on 3 college football teams and 4 ice hockey teams (male and female) wore helmets instrumented with Head Impact Telemetry (HIT) technology during practices and games over 2–4 seasons of play. Preseason clinical screening batteries assessed baseline cognition and reported symptoms. If a concussion was diagnosed by the team medical staff, basic descriptive information was collected at presentation, and concussed players were reevaluated serially. The specific symptoms or findings associated with the diagnosis of acute concussion, relation to specific impact events, timing of symptom onset and diagnosis, and recorded biomechanical parameters were analyzed. Results Data were collected from 450 athletes with 486,594 recorded head impacts. Forty-eight separate concussions were diagnosed in 44 individual players. Mental clouding, headache, and dizziness were the most common presenting symptoms. Thirty-one diagnosed cases were associated with an identified impact event; in 17 cases no specific impact event was identified. Onset of symptoms was immediate in 24 players, delayed in 11, and unspecified in 13. In 8 cases the diagnosis was made immediately after a head impact, but in most cases the diagnosis was delayed (median 17 hours). One diagnosed concussion involved a 30-second loss of consciousness; all other players retained alertness. Most diagnoses were based on self-reported symptoms. The mean peak angular and rotational acceleration values for those cases associated with a specific identified impact were 86.1 ± 42.6g (range 16.5–177.9g) and 3620 ± 2166 rad/sec2 (range 183–7589 rad/sec2), respectively. Conclusions Approximately two-thirds of diagnosed concussions were associated with a specific contact event. Half of all players diagnosed with concussions had delayed or unclear timing of onset of symptoms. Most had no externally observed findings. Diagnosis was usually based on a range of self-reported symptoms after a variable delay. Accelerations clustered in the higher percentiles for all impact events, but encompassed a wide range. These data highlight the heterogeneity of criteria for concussion diagnosis, and in this sports context, its heavy reliance on self-reported symptoms. More specific and standardized definitions of clinical and objective correlates of a “concussion spectrum” may be needed in future research efforts, as well as in the clinical diagnostic arena.

scholarly journals Computational Modeling of Skull Bone Structures and Simulation of Skull Fractures Using the YEAHM Head Model

Biology ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 267 ◽  
Author(s):  
Alcino Barbosa ◽  
Fábio A. O. Fernandes ◽  
Ricardo J. Alves de Sousa ◽  
Mariusz Ptak ◽  
Johannes Wilhelm
Keyword(s):  
Computational Models ◽  
Soft Tissues ◽  
Constitutive Models ◽  
Human Head ◽  
Head Model ◽  
Head Impacts ◽  
Skull Model ◽  
Linear Behavior ◽  
Local Material ◽  
Direct Head

The human head is a complex multi-layered structure of hard and soft tissues, governed by complex materials laws and interactions. Computational models of the human head have been developed over the years, reaching high levels of detail, complexity, and precision. However, most of the attention has been devoted to the brain and other intracranial structures. The skull, despite playing a major role in direct head impacts, is often overlooked and simplified. In this work, a new skull model is developed for the authors’ head model, the YEAHM, based on the original outer geometry, but segmenting it with sutures, diploë, and cortical bone, having variable thickness across different head sections and based on medical craniometric data. These structures are modeled with constitutive models that consider the non-linear behavior of skull bones and also the nature of their failure. Several validations are performed, comparing the simulation results with experimental results available in the literature at several levels: (i) local material validation; (ii) blunt trauma from direct impact against stationary skull; (iii) three impacts at different velocities simulating falls; (iv) blunt ballistic temporoparietal head impacts. Accelerations, impact forces, and fracture patterns are used to validate the skull model.

scholarly journals Temperature fields in linear stage of friction stir welding: Effect of different material properties

2019 ◽  
Vol 23 (6 Part B) ◽  
pp. 3985-3992
Author(s):  
Darko Veljic ◽  
Marko Rakin ◽  
Bojan Medjo ◽  
Mihailo Mrdak ◽  
Aleksandar Sedmak
Keyword(s):  
Friction Stir Welding ◽  
Numerical Models ◽  
Welding Process ◽  
High Strength ◽  
Temperature Fields ◽  
Arbitrary Lagrangian Eulerian ◽  
Friction Stir ◽  
Strain And Strain Rate ◽  
The Difference ◽  
Weld Area

Friction stir welding is one of the procedures for joining the parts in solid state. Thermo-mechanical simulation of the friction stir welding of high-strength aluminium alloys 2024 T3 and 2024 T351 is considered in this work. Numerical models corresponding to the linear welding stage are developed in Abaqus software package. The material behaviour is modelled by Johnson-Cook law (which relates the yield stress with temperature, strain and strain rate), and the Arbitrary Lagrangian-Eulerian technique is applied. The difference in thermo-mechanical behaviour between the two materials has been analysed and commented. The main quantities which are considered are the temperature in the weld area, plastic strain, as well as the rate of heat generation during the welding process.

An Assessment of Primary Blast Injury in Human Brains: A Numerical Simulation

2007 ◽  
Author(s):  
Mahdi Sotudehchafi ◽  
Ghodrat Karami ◽  
Mariusz Ziejewski
Keyword(s):  
Numerical Simulation ◽  
Blast Wave ◽  
Human Head ◽  
Blast Injury ◽  
Element Formulation ◽  
Pressure Waves ◽  
Arbitrary Lagrangian Eulerian ◽  
Wave Interactions ◽  
Structure Interaction ◽  
Human Brains

Most blast-related injuries happen as a result of complex pressure waves generated by the explosion. In this paper, we model the explosion from detonation and examine the blast propagation in air using Arbitrary Lagrangian–Eulerian (ALE) finite element formulation. The results of the simulation agree well with those of physical data obtained from blast wave experiments. Such results set the circumstances necessary for an examination of brain injury exposed to such situations. Thus the model will be coupled with a Fluid/Structure Interaction (FSI) algorithm to implicitly examine the blast wave interactions with a human head and to study the creation of high regions of biomechanics pressure and stress gradients.

Evaluation of Blast Simulation Methods for Modeling Blast Wave Interaction with Human Head

2021 ◽  
Author(s):  
Sunil Sutar ◽  
Shailesh Ganpule
Keyword(s):  
Blast Wave ◽  
Wave Interaction ◽  
Human Head ◽  
Coupling Method ◽  
Radius Of Curvature ◽  
Simulation Methods ◽  
Arbitrary Lagrangian Eulerian ◽  
Element Analysis ◽  
Modeling Methodology ◽  
Blast Wave Interaction

Abstract Blast induced traumatic brain injury (bTBI) research is crucial in asymmetric warfare. The finite element analysis is an attractive option to simulate the blast wave interaction with the head. The popular blast simulation methods are ConWep based pure Lagrangian, Arbitrary-Lagrangian-Eulerian, and Coupling method. This study examines the accuracy and efficiency of ConWep and Coupling methods in predicting the biomechanical response of the head. The simplified cylindrical, spherical surrogates and biofidelic human head models are subjected to field-relevant blast loads using these methods. The reflected overpressures at the surface and pressures inside the brain from the head models are qualitatively and quantitatively evaluated against the available experiments. Both methods capture the overall trends of experiments. Our results suggest that the accuracy of the ConWep method is mainly governed by the radius of curvature of the surrogate head. For the relatively smaller radius of curvature, such as cylindrical or spherical head surrogate, ConWep does not accurately capture decay of reflected blast overpressures and brain pressures. For the larger radius of curvature, such as the biofidelic human head, the predictions from ConWep match reasonably well with the experiment. For all the head surrogates considered, the reflected overpressure-time histories predicted by the Coupling method match reasonably well with the experiment. Coupling method uniquely captures the shadowing and union of shock waves governed by the geometry driven flow dynamics around the head. Overall, these findings will assist the bTBI modeling community to judiciously select an objective-driven modeling methodology.

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