| The problem of disability caused by road traffic accidents has always been one of the focuses of researchers at home and abroad.Every year,more than 50 million people in the world are disabled due to traffic accidents.In China,with the rapid development of economy and the rapid increase of car ownership,the number of road traffic accidents in China is increasing day by day,and the craniocerebral injury caused by traffic accidents is one of the main causes of death and injury in traffic injuries.Because the brain has a very complex anatomical structure and contains the most important human central nervous system,it is urgent and difficult to study the mechanism of brain injury.In the brain injury caused by road traffic accidents,the brain stem is the prone part of the injury,which is often easy to be cut / stretched,resulting in neuronal axonal injury.AIS(abbreviate injury scale)is a global injury severity scoring standard based on anatomy.It quantifies and grades the injury degree of various organs and tissues from the perspective of injury biomechanics.AIS is a fast and concise evaluation method and system,in which the rating of intracranial and peripheral nerve injury is mainly based on the changes of neural histomorphological structure,which has its applicability and practicability in many qualitative diagnosis fields.On the other hand,in the field of quantitative research,as the tissue mainly responsible for signal transduction,feedback and control in the organism,when it is damaged,the morphological structure has not changed significantly and the corresponding physiological function has changed.Based on this,this subject takes traffic injury as the background,and uses the detection method of motor evoked potential to quantitatively explore the degree of functional injury of brain stem caused by strain rate loading.Based on the study of biomechanical mechanism of craniocerebral impact injury,combined with motor evoked potential(MEP)of neuroelectrophysiology,this paper analyzes the changes of neural signal transduction in brainstem before and after loading at different strain rates.The main research contents and conclusions are as follows:1)The mechanical injury and neurophysiological detection model of rat brainstem were established.A quantitative brain stem injury model was established according to the classical marmarou impact acceleration model and the relevant parameters of the improved marmarou model of Wayne State University.Conclusion: according to the relevant parameters of marmarou model improved by Wayne State University,the velocity of the established model is tested to ensure that the effective collision velocity under the impact of 1.25 m and 2.25 m meets the velocity range given in the paper;Because the foam buffer material used in the experiment will undergo obvious deformation during the impact process to prolong the impact duration and absorb part of the impact energy,the foam material was compressed in the experiment,and compared with the stress-strain curve in the literature,and the type of foam buffer material was determined to minimize the error in the experiment.2)Explore the experimental boundary conditions.Before the detection of brain stem injury and neuroelectrophysiology,there are aspects that may affect the detection results,such as anesthetics and measuring electrode spacing.Measure the motor evoked potential after anesthesia to ensure that the anesthetic will not affect the experimental results with the increase of time in a short time.In the measurement of motor evoked potential,the measurement electrode spacing will affect the measurement results,so a feasible standard for measuring electrode spacing is determined through experiments.Conclusion: the experimental results show that chloral hydrate anesthesia has little effect on the stability of rat brainstem MEP in a short time;The standard of measuring electrode spacing for motor evoked potential is 5mm..3)Relying on the electromechanical effect platform previously constructed by the research group,combined with the anatomical characteristics of brainstem pyramidal tract,the brain stereotactic instrument was used to determine the position of MEP detection stimulation electrode of brainstem pyramidal tract in rats,stimulate brainstem pyramidal tract,and detect and obtain the signal waveform of motor evoked potential at the same time.Conclusion: combined with the anatomical characteristics of brainstem pyramidal tract,MEP stimulation electrode is placed at the front of brainstem pyramidal tract by brain stereotactic instrument.Stable MEP waveform can be obtained through measurement.Therefore,it is obtained that the location of stimulation electrode is flush with the ear of rats.4)The rats were impacted with a height of 1.25 m and 2.25 m respectively to produce Tai(trauma axial injury).This subject studied the signal changes of brainstem motor evoked potential before and after injury.The characteristic values of motor evoked potentials were analyzed and studied in time domain,frequency domain and time-frequency domain respectively.Combined with the known finite element simulation experiments,the corresponding strain rates during impact at different strike heights(1.25 m and 2.25m)were obtained,and the relationship between the value of strain rate and signal change was explored.Conclusion: under the impact of 1.25 m height(strain 13.8%,strain rate 285s-1),the amplitude of motor evoked potential decreased by 40.1% ± 2.1%,and the latency increased by 42.03% ± 2.44%.Under the impact of height of 2.25m(strain of 16.8%,strain rate of283s-1),the amplitude of motor evoked potential decreased by 53.01% ± 4.5%,and the latency increased by 53.85% ± 3.85%.Through frequency domain analysis,it can be seen that the spectral peak of motor evoked potential amplitude decreases after injury.Through time-frequency domain analysis,the action time of high-frequency signal after damage is significantly reduced.The experimental results show that with the increase of strain rate,the amplitude of motor evoked potential decreases and the latency increases significantly,which reflects the increase of the functional damage of rat brainstem,that is,after brainstem injury,MEP signal changes significantly in time domain,frequency domain and time-frequency domain.To sum up,this paper established the detection model of mechanical injury and neuroelectrophysiology of brain stem in SD rats,analyzed the relationship between MEP signal changes and mechanical parameters of brain injury,explored the relationship between PSSR(production of strain and strain rate)and MEP amplitude changes,and preliminarily established their mathematical model.It is expected that the degree of brain stem function injury can be quantitatively evaluated through MEP value and this mathematical model in the future.This topic is expected to provide experimental basis and data support for further exploring the evaluation indexes of craniocerebral functional injury and the biomechanical mechanism of craniocerebral injury caused by traffic injury. |
PDF Full Text Request