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  • 1.
    Leng, Yan
    et al.
    Sun Yat Sen Univ, Affiliated Hosp 1, Dept Rehabil Med, Guangzhou, Guangdong, Peoples R China..
    Wang, Zhu
    Sun Yat Sen Univ, Inst Diagnost & Intervent Ultrasound, Affiliated Hosp 1, Dept Med Ultrason, Guangzhou, Guangdong, Peoples R China..
    Bian, Ruihao
    Sun Yat Sen Univ, Affiliated Hosp 1, Dept Rehabil Med, Guangzhou, Guangdong, Peoples R China..
    Lo, Wai Leung Ambrose
    Sun Yat Sen Univ, Affiliated Hosp 1, Dept Rehabil Med, Guangzhou, Guangdong, Peoples R China..
    Xie, Xiaoyan
    Sun Yat Sen Univ, Inst Diagnost & Intervent Ultrasound, Affiliated Hosp 1, Dept Med Ultrason, Guangzhou, Guangdong, Peoples R China..
    Wang, Ruoli
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, BioMEx. Karolinska Inst, Dept Womens & Childrens Hlth, Stockholm, Sweden.
    Huang, Dongfeng
    Sun Yat Sen Univ, Affiliated Hosp 1, Dept Rehabil Med, Guangzhou, Guangdong, Peoples R China.;Sun Yat Sen Univ, Affiliated Hosp 7, Dept Rehabil Med, Shenzhen, Peoples R China..
    Li, Le
    Sun Yat Sen Univ, Affiliated Hosp 1, Dept Rehabil Med, Guangzhou, Guangdong, Peoples R China..
    Alterations of Elastic Property of Spastic Muscle With Its Joint Resistance Evaluated From Shear Wave Elastography and Biomechanical Model2019In: Frontiers in Neurology, ISSN 1664-2295, E-ISSN 1664-2295, Vol. 10, article id 736Article in journal (Refereed)
    Abstract [en]

    This study aims to quantify passive muscle stiffness of spastic wrist flexors in stroke survivors using shear wave elastography (SWE) and to correlate with neural and non-neural contributors estimated from a biomechanical model to hyper-resistance measured during passive wrist extension. Fifteen hemiplegic individuals after stroke with Modified Ashworth Scale (MAS) score larger than one were recruited. SWE were used to measure Young's modulus of flexor carpi radialis muscle with joint from 0 degrees (at rest) to 50 degrees flexion (passive stretch condition), with 10 degrees interval. The neural (NC) and non-neural components i.e., elasticity component (EC) and viscosity component (VC) of the wrist joint were analyzed from a motorized mechanical device NeuroFlexor (R) (NF). Combining with a validated biomechanical model, the neural reflex and muscle stiffness contribution to the increased resistance can be estimated. MAS and Fugl-Meyer upper limb score were also measured to evaluate the spasticity and motor function of paretic upper limb. Young's modulus was significantly higher in the paretic side of flexor carpi radialis than that of the non-paretic side (p < 0.001) and it increased significantly from 0 degrees to 50 degrees of the paretic side (p < 0.001). NC, EC, and VC on the paretic side were higher than the non-paretic side (p < 0.05). There was moderate significant positive correlation between the Young's Modulus and EC (r = 0.565, p = 0.028) and VC (r = 0.645, p = 0.009) of the paretic forearm flexor muscle. Fugl-Meyer of the paretic forearm flexor has a moderate significant negative correlation with NC (r = -0.578, p = 0.024). No significant correlation between MAS and shear elastic modulus or NF components was observed. This study demonstrated the feasibility of combining SWE and NF as a non-invasive approach to assess spasticity of paretic muscle and joint in stroke clinics. The neural and non-neural components analysis as well as correlation findings of muscle stiffness of SWE might provide understanding of mechanism behind the neuromuscular alterations in stroke survivors and facilitate the design of suitable intervention for them.

  • 2.
    Manouchehrinia, Ali
    et al.
    Karolinska Inst, Karolinska Univ Hosp Solna, Dept Clin Neurosci, Stockholm, Sweden..
    Hedstrom, Anna Karin
    Karolinska Inst, Inst Environm Med, Unit Cardiovasc Epidemiol, Stockholm, Sweden..
    Alfredsson, Lars
    Karolinska Inst, Inst Environm Med, Unit Cardiovasc Epidemiol, Stockholm, Sweden.;Stockholm Cty Council, Ctr Occupat & Environm Med, Stockholm, Sweden..
    Olsson, Tomas
    Karolinska Inst, Karolinska Univ Hosp Solna, Dept Clin Neurosci, Stockholm, Sweden..
    Hillert, Jan
    Karolinska Inst, Karolinska Univ Hosp Solna, Dept Clin Neurosci, Stockholm, Sweden..
    Ramanujam, Ryan
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.). Karolinska Inst.
    Association of Pre-Disease Body Mass Index With Multiple Sclerosis Prognosis2018In: Frontiers in Neurology, ISSN 1664-2295, E-ISSN 1664-2295, Vol. 9, article id 232Article in journal (Refereed)
    Abstract [en]

    Both high body mass index (BMI) and smoking tobacco are known risk factors for developing multiple sclerosis (MS). However, it is unclear whether BMI, like smoking, is a risk factor for the secondary progressive (SP) course. We, therefore, sought to determine if high/low BMI at age 20 is associated to risk of SP development, in the context of smoking status. Using data from MS patients with BMI and smoking information available, we examined relapsing onset patients with MS onset after 20 years of age. Cox regressions were conducted on smokers and non-smokers, with BMI as the main exposure. In total, 5,598 relapsing onset MS patients were included. The models demonstrated that BMI > 30 was associated to increased risk of SPMS in smokers (hazard ratio 1.50, p = 0.036). This association of obesity at age 20 with increased risk of SP was not observed in non-smokers (hazard rate 0.97, p = 0.900). Since the risk is confined to smokers, the interaction observed may give insight to disease driving mechanisms.

  • 3.
    Montanino, Annaclauida
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Kleiven, Svein
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Neuronic Engineering.
    Utilizing a Structural Mechanics Approach to Assess the Primary Effects of Injury Loads Onto the Axon and Its Components2018In: Frontiers in Neurology, ISSN 1664-2295, E-ISSN 1664-2295, Vol. 9, no 643, p. 1-12Article in journal (Refereed)
    Abstract [en]

    Diffuse axonal injury (DAI) occurs as a result of the transmission of rapid dynamic loads from the head to the brain and specifically to its neurons. Despite being one of the most common and most deleterious types of traumatic brain injury (TBI), the inherent cell injury mechanism is yet to be understood. Experimental observations have led to the formulation of different hypotheses, such as mechanoporation of the axolemma and microtubules (MTs) breakage. With the goal of singling out the mechanical aspect of DAI and to resolve the ambiguity behind its injury mechanism, a composite finite element (FE) model of a representative volume of an axon was developed. Once calibrated and validated against published experimental data, the axonal model was used to simulate injury scenarios. The resulting strain distributions along its components were then studied in dependence of strain rate and of typical modeling choices such as the applied MT constraints and tau proteins failure. Results show that oversimplifying the MT bundle kinematic entails a systematic attenuation (cf = 2.33) of the computed maximum MT strain. Nevertheless, altogether, results support the hypothesis of axolemma mechanoporation as a cell-injury trigger. Moreover, for the first time the interconnection between the axolemma and the MT bundle is shown to play a role in damage localization. The proposed FE axonal model is a valuable tool to understand the axonal injury mechanism from a mechanical perspective and could be used in turn for the definition of well-informed injury criteria at the tissue and organ level.

  • 4.
    von Holst, Hans
    et al.
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering. Section of Neurosurgery, Division of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden.
    Li, Xiaogai
    KTH, School of Technology and Health (STH), Medical Engineering, Neuronic Engineering.
    Consequences of the dynamic triple peak impact factor in traumatic brain injury as measured with numerical simulation2013In: Frontiers in Neurology, ISSN 1664-2295, E-ISSN 1664-2295, Vol. 4 MARArticle in journal (Refereed)
    Abstract [en]

    There is a lack of knowledge about the direct neuromechanical consequences in traumatic brain injury (TBI) at the scene of accident. In this study we use a finite element model of the human head to study the dynamic response of the brain during the first milliseconds after the impact with velocities of 10, 6, and 2 meters/second (m/s), respectively. The numerical simulation was focused on the external kinetic energy transfer, intracranial pressure (ICP), strain energy density and first principal strain level, and their respective impacts to the brain tissue. We show that the oblique impacts of 10 and 6 m/s resulted in substantial high peaks for the ICP, strain energy density, and first principal strain levels, however, with different patterns and time frames. Also, the 2 m/s impact showed almost no increase in the above mentioned investigated parameters. More importantly, we show that there clearly exists a dynamic triple peak impact factor to the brain tissue immediately after the impact regardless of injury severity associated with different impact velocities. The dynamic triple peak impacts occurred in a sequential manner first showing strain energy density and ICP and then followed by first principal strain. This should open up a new dimension to better understand the complex mechanisms underlying TBI. Thus, it is suggested that the combination of the dynamic triple peak impacts to the brain tissue may interfere with the cerebral metabolism relative to the impact severity thereby having the potential to differentiate between severe and moderate TBI from mild TBI.

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