Plasma carnitine is associated with fatigue in chronic hepatitis C but not in irritable bowel syndrome : Carnitine and fatigue in hepatitis C

International audienceObjectives Fatigue is an important determinant of altered quality of life in patients affected by chronic hepatitis C (CHC) or the irritable bowel syndrome (IBS). In this study, we aimed at determining the contributory role of plasma levels of leptin and carnitine on fatigue in CHC and IBS. Methods We enrolled 70 patients with CHC, 42 with IBS and 44 healthy subjects. Fatigue was evaluated using the Fatigue Impact Scale questionnaire. Body composition was assessed through impedance analysis. Plasma carnitine and leptin were measured. Results Fatigue scores were significantly more elevated in patients with CHC and IBS than in healthy subjects. Patients with CHC, but not with IBS, had significant lower plasma levels of total and free carnitine adjusted for fat mass compared to healthy subjects. In patients with CHC, and not with IBS, fatigue scores were negatively correlated with plasma levels of carnitine. Levels of free carnitine were significantly and independently associated with the severity of fatigue in patients with CHC (OR=2.019, p=0.02, CI 95% [1.01-1.23]).Conclusions In patients with CHC, the severity of fatigue is associated with low level of carnitine, suggesting that an oral supplementation may be effective to relieve fatigue in CHC. The underlying mechanism of fatigue in IBS does not seem to involve carnitine

Assessment of mechanical properties of human head tissues for trauma modelling

[EN] Many discrepancies are found in the literature regarding the damage and constitutive models for head tissues as well as the values of the constants involved in the constitutive equations. Their proper definition is required for consistent numerical model performance when predicting human head behaviour, and hence skull fracture and brain damage. The objective of this research is to perform a critical review of constitutive models and damage indicators describing human head tissue response under impact loading. A 3D finite element human head model has been generated by using computed tomography images, which has been validated through the comparison to experimental data in the literature. The threshold values of the skull and the scalp that lead to fracture have been analysed. We conclude that (1) compact bone properties are critical in skull fracture, (2) the elastic constants of the cerebrospinal fluid affect the intracranial pressure distribution, and (3) the consideration of brain tissue as a nearly incompressible solid with a high (but not complete) water content offers pressure responses consistent with the experimental data.Generalitat Valenciana, Grant/Award Number: PROMETEO 2016/007; Ministerio de Economia y Compatitividad and Fondo Europeo de Desarrollo Regional, Grant/Award Number: RTC-2015-3887-8Lozano-Mínguez, E.; Palomar-Toledano, M.; Infante, D.; Rupérez Moreno, MJ.; Giner Maravilla, E. (2018). Assessment of mechanical properties of human head tissues for trauma modelling. International Journal for Numerical Methods in Biomedical Engineering. 34(5):1-17. https://doi.org/10.1002/cnm.2962S117345Hyder, A. A., Wunderlich, C. A., Puvanachandra, P., Gururaj, G., & Kobusingye, O. C. (2007). The impact of traumatic brain injuries: A global perspective. NeuroRehabilitation, 22(5), 341-353. doi:10.3233/nre-2007-22502Meaney, D. F., Morrison, B., & Dale Bass, C. (2014). The Mechanics of Traumatic Brain Injury: A Review of What We Know and What We Need to Know for Reducing Its Societal Burden. Journal of Biomechanical Engineering, 136(2). doi:10.1115/1.4026364Report Violence and Injury Prevention and Disability (VIP)-neurotrauma 2010 http://www.who.int/violence_injury_prevention/road_traffic/activities/neurotrauma/en/Deng, X., Potula, S., Grewal, H., Solanki, K. N., Tschopp, M. A., & Horstemeyer, M. F. (2013). Finite element analysis of occupant head injuries: Parametric effects of the side curtain airbag deployment interaction with a dummy head in a side impact crash. Accident Analysis & Prevention, 55, 232-241. doi:10.1016/j.aap.2013.03.016Marjoux, D., Baumgartner, D., Deck, C., & Willinger, R. (2008). Head injury prediction capability of the HIC, HIP, SIMon and ULP criteria. Accident Analysis & Prevention, 40(3), 1135-1148. doi:10.1016/j.aap.2007.12.006Bolander, R., Mathie, B., Bir, C., Ritzel, D., & VandeVord, P. (2011). Skull Flexure as a Contributing Factor in the Mechanism of Injury in the Rat when Exposed to a Shock Wave. Annals of Biomedical Engineering, 39(10), 2550-2559. doi:10.1007/s10439-011-0343-0Li, G., Zhang, J., Wang, K., Wang, M., Gao, C., & Ma, C. (2016). Experimental research of mechanical behavior of porcine brain tissue under rotational shear stress. Journal of the Mechanical Behavior of Biomedical Materials, 57, 224-234. doi:10.1016/j.jmbbm.2015.12.002YOGANANDAN, N., PINTAR, F. A., SANCES, A., WALSH, P. R., EWING, C. L., THOMAS, D. J., & SNYDER, R. G. (1995). Biomechanics of Skull Fracture. Journal of Neurotrauma, 12(4), 659-668. doi:10.1089/neu.1995.12.659Motherway, J. A., Verschueren, P., Van der Perre, G., Vander Sloten, J., & Gilchrist, M. D. (2009). The mechanical properties of cranial bone: The effect of loading rate and cranial sampling position. Journal of Biomechanics, 42(13), 2129-2135. doi:10.1016/j.jbiomech.2009.05.030Lakatos, É., Magyar, L., & Bojtár, I. (2014). Material Properties of the Mandibular Trabecular Bone. Journal of Medical Engineering, 2014, 1-7. doi:10.1155/2014/470539Boruah, S., Subit, D. L., Paskoff, G. R., Shender, B. S., Crandall, J. R., & Salzar, R. S. (2017). Influence of bone microstructure on the mechanical properties of skull cortical bone – A combined experimental and computational approach. Journal of the Mechanical Behavior of Biomedical Materials, 65, 688-704. doi:10.1016/j.jmbbm.2016.09.041McElhaney, J. H., Fogle, J. L., Melvin, J. W., Haynes, R. R., Roberts, V. L., & Alem, N. M. (1970). Mechanical properties of cranial bone. Journal of Biomechanics, 3(5), 495-511. doi:10.1016/0021-9290(70)90059-xKleiven, S. (2003). Influence of Impact Direction on the Human Head in Prediction of Subdural Hematoma. Journal of Neurotrauma, 20(4), 365-379. doi:10.1089/089771503765172327Miller, L. E., Urban, J. E., & Stitzel, J. D. (2016). Development and validation of an atlas-based finite element brain model. Biomechanics and Modeling in Mechanobiology, 15(5), 1201-1214. doi:10.1007/s10237-015-0754-1Tse, K. M., Tan, L. B., Lee, S. J., Lim, S. P., & Lee, H. P. (2015). Investigation of the relationship between facial injuries and traumatic brain injuries using a realistic subject-specific finite element head model. Accident Analysis & Prevention, 79, 13-32. doi:10.1016/j.aap.2015.03.012Kimpara, H., Nakahira, Y., Iwamoto, M., Miki, K., Ichihara, K., Kawano, S., & Taguchi, T. (2006). Investigation of Anteroposterior Head-Neck Responses during Severe Frontal Impacts Using a Brain-Spinal Cord Complex FE Model. SAE Technical Paper Series. doi:10.4271/2006-22-0019Brands, D. W. A., Bovendeerd, P. H. M., & Wismans, J. S. H. M. (2002). On the Potential Importance of Non-Linear Viscoelastic Material Modelling for Numerical Prediction of Brain Tissue Response: Test and Application. SAE Technical Paper Series. doi:10.4271/2002-22-0006Kleiven, S. (2007). Predictors for Traumatic Brain Injuries Evaluated through Accident Reconstructions. SAE Technical Paper Series. doi:10.4271/2007-22-0003Ho, J., Zhou, Z., Li, X., & Kleiven, S. (2017). The peculiar properties of the falx and tentorium in brain injury biomechanics. Journal of Biomechanics, 60, 243-247. doi:10.1016/j.jbiomech.2017.06.023Dassault Systèmes Abaqus 6.12 User's Manual 2012Systèmes D Abaqus 6.12 Analysis User's Manual 2012Tadepalli, S. C., Erdemir, A., & Cavanagh, P. R. (2011). Comparison of hexahedral and tetrahedral elements in finite element analysis of the foot and footwear. Journal of Biomechanics, 44(12), 2337-2343. doi:10.1016/j.jbiomech.2011.05.006Hüeber, S., Mair, M., & Wohlmuth, B. I. (2005). A priori error estimates and an inexact primal-dual active set strategy for linear and quadratic finite elements applied to multibody contact problems. Applied Numerical Mathematics, 54(3-4), 555-576. doi:10.1016/j.apnum.2004.09.019Kleiven, S., & von Holst, H. (2002). Consequences of head size following trauma to the human head. Journal of Biomechanics, 35(2), 153-160. doi:10.1016/s0021-9290(01)00202-0Zhou C Khalil TB King AI A new model comparing impact responses of the homogeneous and inhomogeneous human brain 1995WILLINGER, R., TALEB, L., & KOPP, C.-M. (1995). Modal and Temporal Analysis of Head Mathematical Models. Journal of Neurotrauma, 12(4), 743-754. doi:10.1089/neu.1995.12.743Ruan JS Khalil TB King AI Finite element modeling of direct head impact 1993 https://doi.org/10.4271/933114Tan, L. B., Chew, F. S., Tse, K. M., Chye Tan, V. B., & Lee, H. P. (2014). Impact of complex blast waves on the human head: a computational study. International Journal for Numerical Methods in Biomedical Engineering, 30(12), 1476-1505. doi:10.1002/cnm.2668Nahum AM Smith R Ward CC Intracranial pressure dynamics during head impact 1977Gilchrist, M. D., & O’Donoghue, D. (2000). Simulation of the development of frontal head impact injury. Computational Mechanics, 26(3), 229-235. doi:10.1007/s004660000179Willinger, R., Kang, H.-S., & Diaw, B. (1999). Three-Dimensional Human Head Finite-Element Model Validation Against Two Experimental Impacts. Annals of Biomedical Engineering, 27(3), 403-410. doi:10.1114/1.165Yang, B., Tse, K.-M., Chen, N., Tan, L.-B., Zheng, Q.-Q., Yang, H.-M., … Lee, H.-P. (2014). Development of a Finite Element Head Model for the Study of Impact Head Injury. BioMed Research International, 2014, 1-14. doi:10.1155/2014/408278Mihai, L. A., Budday, S., Holzapfel, G. A., Kuhl, E., & Goriely, A. (2017). A family of hyperelastic models for human brain tissue. Journal of the Mechanics and Physics of Solids, 106, 60-79. doi:10.1016/j.jmps.2017.05.015Han, I. S., & Kim, Y. E. (2014). Development of a new head/brain model for the prediction of subdural hemorrhage. International Journal of Precision Engineering and Manufacturing, 15(11), 2405-2411. doi:10.1007/s12541-014-0607-3Moran, R., Smith, J. H., & García, J. J. (2014). Fitted hyperelastic parameters for Human brain tissue from reported tension, compression, and shear tests. Journal of Biomechanics, 47(15), 3762-3766. doi:10.1016/j.jbiomech.2014.09.030Mendis, K. K., Stalnaker, R. L., & Advani, S. H. (1995). A Constitutive Relationship for Large Deformation Finite Element Modeling of Brain Tissue. Journal of Biomechanical Engineering, 117(3), 279-285. doi:10.1115/1.2794182Sahoo, D., Deck, C., & Willinger, R. (2014). Development and validation of an advanced anisotropic visco-hyperelastic human brain FE model. Journal of the Mechanical Behavior of Biomedical Materials, 33, 24-42. doi:10.1016/j.jmbbm.2013.08.022Belingardi G Chiandussi G Gaviglio I Development and validation of a new finite element model of human head Proceedings of 19th International Technical Conference on the Enhanced Safety of Vehicles 2005Tse, K. M., Tan, L. B., Lee, S. J., Lim, S. P., & Lee, H. P. (2013). Development and validation of two subject-specific finite element models of human head against three cadaveric experiments. International Journal for Numerical Methods in Biomedical Engineering, 30(3), 397-415. doi:10.1002/cnm.2609Yang, J. (2011). Investigation of Brain Trauma Biomechanics in Vehicle Traffic Accidents Using Human Body Computational Models. Computational Biomechanics for Medicine, 5-14. doi:10.1007/978-1-4419-9619-0_2Mao, H., Gao, H., Cao, L., Genthikatti, V. V., & Yang, K. H. (2013). Development of high-quality hexahedral human brain meshes using feature-based multi-block approach. Computer Methods in Biomechanics and Biomedical Engineering, 16(3), 271-279. doi:10.1080/10255842.2011.617005Yan, W., & Pangestu, O. D. (2011). A modified human head model for the study of impact head injury. Computer Methods in Biomechanics and Biomedical Engineering, 14(12), 1049-1057. doi:10.1080/10255842.2010.506435Baeck K Goffin J Vander Sloten J The use of different CSF representations in a numerical head model and their effect on the results of FE head impact analyses 2011 http://www.dynalook.com/8th-european-ls-dyna-conference/session-7/Session7_Paper3.pdfKleiven, S. (2006). Evaluation of head injury criteria using a finite element model validated against experiments on localized brain motion, intracerebral acceleration, and intracranial pressure. International Journal of Crashworthiness, 11(1), 65-79. doi:10.1533/ijcr.2005.0384Galford, J. E., & McElhaney, J. H. (1970). A viscoelastic study of scalp, brain, and dura. Journal of Biomechanics, 3(2), 211-221. doi:10.1016/0021-9290(70)90007-2Bradshaw D Morfey C Pressure and shear response in brain injury models Proceedings of the 17th International Technical Conference on the Enhanced Safety of Vehicles 2001 1 10Mooney, M. (1940). A Theory of Large Elastic Deformation. Journal of Applied Physics, 11(9), 582-592. doi:10.1063/1.1712836Large elastic deformations of isotropic materials IV. further developments of the general theory. (1948). Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences, 241(835), 379-397. doi:10.1098/rsta.1948.0024Melvin JW McElhaney JH Roberts VL Development of a mechanical model of the human head-determination of tissue properties and synthetic substitute materials 1970Raul, J.-S., Baumgartner, D., Willinger, R., & Ludes, B. (2005). Finite element modelling of human head injuries caused by a fall. International Journal of Legal Medicine, 120(4), 212-218. doi:10.1007/s00414-005-0018-1Sahoo, D., Deck, C., Yoganandan, N., & Willinger, R. (2016). Development of skull fracture criterion based on real-world head trauma simulations using finite element head model. Journal of the Mechanical Behavior of Biomedical Materials, 57, 24-41. doi:10.1016/j.jmbbm.2015.11.014Silver, F. H. (1994). Biomaterials, Medical Devices and Tissue Engineering: An Integrated Approach. doi:10.1007/978-94-011-0735-8Dassault Systèmes Section 1.2.19 VUSDFLD, Abaqus User Subroutines Reference Manual 2012Hambli, R. (2012). A quasi-brittle continuum damage finite element model of the human proximal femur based on element deletion. Medical & Biological Engineering & Computing, 51(1-2), 219-231. doi:10.1007/s11517-012-0986-5Harrison, N. M., McDonnell, P., Mullins, L., Wilson, N., O’Mahoney, D., & McHugh, P. E. (2012). Failure modelling of trabecular bone using a non-linear combined damage and fracture voxel finite element approach. Biomechanics and Modeling in Mechanobiology, 12(2), 225-241. doi:10.1007/s10237-012-0394-7Vavalle, N. A., Davis, M. L., Stitzel, J. D., & Gayzik, F. S. (2015). Quantitative Validation of a Human Body Finite Element Model Using Rigid Body Impacts. Annals of Biomedical Engineering, 43(9), 2163-2174. doi:10.1007/s10439-015-1286-7Delye, H., Verschueren, P., Depreitere, B., Van Lierde, C., Verpoest, I., Berckmans, D., … Goffin, J. (2005). Biomechanics of Frontal Skull Fracture. Solid Mechanics and Its Applications, 185-193. doi:10.1007/1-4020-3796-1_19Ruan, J. S., Khalil, T., & King, A. I. (1994). Dynamic Response of the Human Head to Impact by Three-Dimensional Finite Element Analysis. Journal of Biomechanical Engineering, 116(1), 44-50. doi:10.1115/1.2895703Chafi, M. S., Dirisala, V., Karami, G., & Ziejewski, M. (2009). A finite element method parametric study of the dynamic response of the human brain with different cerebrospinal fluid constitutive properties. Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine, 223(8), 1003-1019. doi:10.1243/09544119jeim631Ruan, J., & Prasad, P. (2006). The influence of human head tissue properties on intracranial pressure response during direct head impact. International Journal of Vehicle Safety, 1(4), 281. doi:10.1504/ijvs.2006.01123

A comparative study of cranial, blunt trauma fractures as seen at medicolegal autopsy and by Computed Tomography

<p>Abstract</p> <p>Background</p> <p>Computed Tomography (CT) has become a widely used supplement to medico legal autopsies at several forensic institutes. Amongst other things, it has proven to be very valuable in visualising fractures of the cranium. Also CT scan data are being used to create head models for biomechanical trauma analysis by Finite Element Analysis. If CT scan data are to be used for creating individual head models for retrograde trauma analysis in the future we need to ascertain how well cranial fractures are captured by CT scan. The purpose of this study was to compare the diagnostic agreement between CT and autopsy regarding cranial fractures and especially the precision with which cranial fractures are recorded.</p> <p>Methods</p> <p>The autopsy fracture diagnosis was compared to the diagnosis of two CT readings (reconstructed with Multiplanar and Maximum Intensity Projection reconstructions) by registering the fractures on schematic drawings. The extent of the fractures was quantified by merging 3-dimensional datasets from both the autopsy as input by 3D digitizer tracing and CT scan.</p> <p>Results</p> <p>The results showed a good diagnostic agreement regarding fractures localised in the posterior fossa, while the fracture diagnosis in the medial and anterior fossa was difficult at the first CT scan reading. The fracture diagnosis improved during the second CT scan reading. Thus using two different CT reconstructions improved diagnosis in the medial fossa and at the impact points in the cranial vault. However, fracture diagnosis in the anterior and medial fossa and of hairline fractures in general still remained difficult.</p> <p>Conclusion</p> <p>The study showed that the forensically important fracture systems to a large extent were diagnosed on CT images using Multiplanar and Maximum Intensity Projection reconstructions. Difficulties remained in the minute diagnosis of hairline fractures. These inconsistencies need to be resolved in order to use CT scan data of victims for individual head modelling and trauma analysis.</p

Head injury mechanisms of the human head during an accident

La tête constitue le segment anatomique renfermant l'organe le plus important du corps humain : le cerveau. Ce dernier est protégé des agressions extérieures, notamment mécaniques, par la peau, le crâne, les méninges et le liquide céphalorachidien. Mais cPas de résum

Mécanismes de lésion de la tête humaine en situation de choc

La tête constitue le segment anatomique renfermant l’organe le plus important du corps humain : le cerveau. Ce dernier est protégé des agressions extérieures, notamment mécaniques, par la peau, le crâne, les méninges et le liquide céphalorachidien. Mais ces protections sont impuissantes face aux agressions de la vie moderne car les chargements mécaniques de la tête dépassent aisément ses limites de tolérance. L’accidentologie indique que beaucoup reste à faire et cela passe par une meilleure optimisation des systèmes de protection. Pour l’instant, ceux-ci sont élaborés sur la base d’un critère de lésion utilisé depuis plus de trente ans : le Head Injury Cirterion (HIC). Il est calculé à partir de l’accélération linéaire résultante d’une tête de mannequin rigide, sur laquelle le système de protection est testé. Le critère ne tient donc compte, ni des accélérations angulaires, ni de l’orientation du choc, ni de la déformation intracrânienne. Pourtant, l’état de l’art montre que la technique des éléments finis rend possible l’accès à des variables spécifiques à chacun des mécanismes de lésion de la tête : l’énergie interne de déformation des éléments modélisant le crâne et ceux modélisant le liquide céphalo-rachidien pour, respectivement, les fractures et les hématomes sous-duraux ou sous arachnoïdiens ; la déformation principale ou la contrainte de Von Mises des éléments modélisant le cerveau pour les lésions axonales diffuses. Ainsi, dans cette thèse, la capacité prédictive des critères de lésion tels le HIC ou ceux issus des variables intracrâniennes a été évaluée sur une centaine d’accidents réels. Ces derniers ont été rassemblés dans une base de données qui rassemble les bilans lésionnels codifiés et les données cinématique permettant la simulation du traumatisme crânien. Une étude statistique a alors permis d’élaborer des courbes de risque qui montrent la meilleure précision des critères basés sur des modèles éléments finis de tête. Par la suite, de nouvelles variables plus physiques et de nouvelles façons de les exploiter ont été proposées. Elles tentent de corriger l’hypothèse posée dans les modèles actuels selon laquelle le cerveau est homogène et isotrope. L’originalité tient dans le fait que l’hétérogénéité et l’anisotropie sont appréhendées sous l’angle, non pas mécanique, mais physiologique : le cerveau a été divisé en zones fonctionnelles et une carte tridimensionnelle issue de l’IRM par diffusion donnant les orientations privilégiées des faisceaux d’axones dans le cerveau a été exploitée afin de calculer des élongations axonales. Les premiers résultats sont prometteurs et les limites de tolérance obtenues rejoignent celles issues des observations faites à l’échelle d’un seul nerf.The head encloses the most vital organ: the brain. It is protected against external mechanical aggressions thanks to the scalp, the skull, the meninges and the cerebrospinal fluid. But these natural protections are obsolete against the modern life aggressions: the tolerance limits are easily exceeded by the mechanical loadings involved in road or sport accidents. In order to prevent the head from reaching these tolerance limits, head protection devices are developed. There optimization are based on criteria such as the Head Injury Criterion (HIC, 1972). But it is computed using the solely resultant linear acceleration of an un-deformable head dummy. In other words, neither the angular accelerations, nor the impact orientation, nor the intracranial mechanical behaviour are taken into account. However, the finite element technique provides the description of this intracranial mechanical behaviour. Therefore, new metrics which are specifics to each injury mechanism have been proposed in the literature: the internal deformation energy of the skull and of the elements modelling the cerebrospinal fluid is calculated for, respectively, fractures and subdural or subarachnoidal haematomas; brain elements main strain or Von Mises stress are proposed for the diffuse axonal injuries. In this thesis, the injury prediction capability of criteria such the HIC or those deriving from finite element head models has been evaluated on a set of a hundred real world accidents. The cases have been gathered in a database which provides a codification of the injuries and the kinematical needed data for the simulation of the head traumatism. Then, a statistical study has been carried out and the provided injury risk curves have shown a clearly better accuracy for the criteria calculated using finite element head models. Besides, more physical metrics and new ways to exploit them have been proposed. The aim is to avoid the hypothesis of a brain considered as homogeneous and isotropic. But here, the heterogeneity and the anisotropy have been considered with a physiological and functional point of view: the brain has been divided between functional zones; thus, a three-dimensional map of the axonal beam orientations provided by the diffusion MRI has been utilized so that axonal elongations could be computed. The first results show excellent perspectives and the resultant tolerance limits tend towards those obtained in experimental works on real nerves

Influence de polymorphismes génétiques à risque dans l'évolution de la maladie de Crohn

NICE-BU Médecine Odontologie (060882102) / SudocSudocFranceF

Mécanismes de lésion de la tête humaine en situation de choc

La tête constitue le segment anatomique renfermant l organe le plus important du corps humain : le cerveau. Ce dernier est protégé des agressions extérieures, notamment mécaniques, par la peau, le crâne, les méninges et le liquide céphalorachidien. Mais ces protections sont impuissantes face aux agressions de la vie moderne car les chargements mécaniques de la tête dépassent aisément ses limites de tolérance. L accidentologie indique que beaucoup reste à faire et cela passe par une meilleure optimisation des systèmes de protection. Pour l instant, ceux-ci sont élaborés sur la base d un critère de lésion utilisé depuis plus de trente ans : le Head Injury Cirterion (HIC). Il est calculé à partir de l accélération linéaire résultante d une tête de mannequin rigide, sur laquelle le système de protection est testé. Le critère ne tient donc compte, ni des accélérations angulaires, ni de l orientation du choc, ni de la déformation intracrânienne. Pourtant, l état de l art montre que la technique des éléments finis rend possible l accès à des variables spécifiques à chacun des mécanismes de lésion de la tête : l énergie interne de déformation des éléments modélisant le crâne et ceux modélisant le liquide céphalo-rachidien pour, respectivement, les fractures et les hématomes sous-duraux ou sous arachnoïdiens ; la déformation principale ou la contrainte de Von Mises des éléments modélisant le cerveau pour les lésions axonales diffuses. Ainsi, dans cette thèse, la capacité prédictive des critères de lésion tels le HIC ou ceux issus des variables intracrâniennes a été évaluée sur une centaine d accidents réels. Ces derniers ont été rassemblés dans une base de données qui rassemble les bilans lésionnels codifiés et les données cinématique permettant la simulation du traumatisme crânien. Une étude statistique a alors permis d élaborer des courbes de risque qui montrent la meilleure précision des critères basés sur des modèles éléments finis de tête. Par la suite, de nouvelles variables plus physiques et de nouvelles façons de les exploiter ont été proposées. Elles tentent de corriger l hypothèse posée dans les modèles actuels selon laquelle le cerveau est homogène et isotrope. L originalité tient dans le fait que l hétérogénéité et l anisotropie sont appréhendées sous l angle, non pas mécanique, mais physiologique : le cerveau a été divisé en zones fonctionnelles et une carte tridimensionnelle issue de l IRM par diffusion donnant les orientations privilégiées des faisceaux d axones dans le cerveau a été exploitée afin de calculer des élongations axonales. Les premiers résultats sont prometteurs et les limites de tolérance obtenues rejoignent celles issues des observations faites à l échelle d un seul nerf.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF