Identification of injury type using somatosensory and motor evoked potentials in a rat spinal cord injury model

The spinal cord is at risk of injury during spinal surgery.If intraoperative spinal co rd injury is identified early,irreve rsible impairment or loss of neurological function can be prevented.Different types of spinal cord injury result in damage to diffe rent spinal cord regions,which may cause diffe rent somatosensory and motor evoked potential signal res ponses.In this study,we examined electrophysiological and histopathological changes between contusion,distra ction,and dislocation spinal cord injuries in a rat model.We found that contusion led to the most severe dorsal white matter injury and caused considerable attenuation of both somatosensory and motor evoked potentials.Dislocation resulted in loss of myelinated axons in the lateral region of the injured spinal cord along the rostrocaudal axis.The amplitude of attenuation in motor evoked potential responses caused by dislocation was greater than that caused by contusion.After distraction injury,extracellular spaces were slightly but not significantly enlarged;somatosensory evoked potential res ponses slightly decreased and motor evoked potential responses were lost.Correlation analysis showed that histological and electrophysiological findings we re significantly correlated and related to injury type.Intraope rative monitoring of both somatosensory and motor evoked potentials has the potential to identify iatrogenic spinal cord injury type during surgery.

Correlation study between the changes of motor evoked potential and the improvement of spinal canal volume in minimally invasive transforaminal lumbar interbody fusion

Objective:To analyze the correlation between the amplitude changes of motor evoked potential(MEP),the 3D volume changes of spinal canal measuring by postoperative CT and the improvement rate of clinical symptoms after the spinal canal decompression in minimally invasive transforaminal lumbar interbody fusion(MIS-TLIF),and to explore the predictive value of the changes of both MEP amplitude and spinal canal volume in the assessment of long-term clinical prognosis in MIS-TLIF.Methods:A retrospective study of 68 patients with L4/5 spinal stenosis treated with MIS-TLIF was performed.The changes of both intraoperative MEP amplitude and 3D spinal canal volume during the spinal canal decompression,as well as the visual analogue scale(VAS)and Oswestry dysfunction index(ODI)scores in the long-term follow-up were all recorded.Results:The values of intraoperative MEP amplitude was 159.04%higher in 68 patients with MIS-TLIF after spinal canal decompression(P<0.01).The 3 postoperative 3D spinal canal volume(4.89±1.27)cm increased by 31.22%in comparison 3 with preoperative date(3.78±1.08)cm(P<0.01).The VAS and ODI scores were improved to 78.55%and 80.60%,respectively at the last follow-up(P<0.01).The improvement rate of MEP amplitude on the decompression side was positively correlated with the improvement rate of postoperative spinal canal volume(r=0.272,P=0.025).The improvement rate of postoperative spinal canal volume was positively correlated with the improvement rate of VAS and ODI at the last follow-up(r=0.656,r=0.490,P<0.01).Moreover,the improvement rate of MEP amplitude on the decompression side was also positively correlated with the improvement rate of VAS and ODI at the last follow-up(r=0.322 and 0.235,respectively,P<0.05).Conclusion:The increase of MEP amplitude after spinal canal decompression in patients with lumbar spinal stenosis treated by MIS-TLIF was closely correlated with both of the increase of spinal canal volume and the improvement of clinical symptoms.Therefore,MEP amplitude monitoring was not only the one of the important monitoring methods for predicting the prognosis of MIS-TLIF but also the reliably predictive value in the long-term clinical prognosis in MIS-TLIF.

Cortical evoked potential changes in a rat model of acute ischemic stroke Detection of somatosensory evoked potential and motor evoked potential

BACKGROUND： Studies have shown that latency changes of some elements in a somatosensory evoked potential （SEP） and motor evoked potential （MEP） can reflect electrical activity of cerebral cortical neurons and conduction of white matter nerve fibers. However, there is a paucity of information regarding the dynamic observation of SEP and MEP following cerebral ischemic injury. OBJECTIVE： To explore SEP and MEP changes following acute ischemic stroke, and investigate the role of evoked potentials in monitoring brain function in stroke. DESIGN, TIME AND SETTING： A randomized, controlled, animal experiment was performed at the Chongqing Key Laboratory of Neurology, Affiliated Hospital of Chongqing Medical University from September 2007 to August 2008. MATERIALS＂ Hydrogen blood flow detector was purchased from Soochow University Medical Instrument Co., China, and Power lab system was purchased from AD Instruments, Inc., USA. METHODS A total of 36 healthy, adult, male, Sprague Dawley rats were randomly assigned to four groups （n = 9）, including three ischemia groups （12, 24 and 72 hours of ischemia） and a sham-surgery group. The rat model of acute ischemic stroke was established by middle cerebral artery occlusion （MCAO） in the left hemisphere. MAIN OUTCOME MEASURES＂ SEP and MEP of the left limbs were detected, and cerebral blood flow was measured by the hydrogen cleaning method. RESULTS： The latency of positive wave 1 （P1）, negative wave 1 （N1） and positive wave 2 （P2） waves in SEP, and latency of negative wave 1,2 （N1, N2） waves in MEP were significantly prolonged with increasing ischemic duration following MCAO （P 〈 0.01）, but cerebral blood flow was significantly decreased （P 〈 0.05, or P 〈 0.01）. CONLUSION： Ischemic stroke prolongs the latency of SEP waves （P1, N1, P2） and MEP waves （N1, N2）, and cerebral cortical evoked potential may correlate with cerebral blood flow changes. This indicates that SEP and MEP can be used to evaluate brain function following acute ischemic stroke.

Why do stroke patients with negative motor evoked potential show poor limb motor function recovery?

Negative motor evoked potentials after cerebral infarction, indicative of poor recovery of limb motor function, tend to be accompanied by changes in fractional anisotropy values and the cerebral pe-duncle area on the affected side, but the characteristics of these changes have not been reported. This study included 57 cases of cerebral infarction whose motor evoked potentials were tested in the 24 hours after the first inspection for diffusion tensor imaging, in which 29 cases were in the negative group and 28 cases in the positive group. Twenty-nine patients with negative motor evoked potentials were divided into two groups according to fractional anisotropy on the affected side of the cerebral peduncle： a fractional anisotropy 〈 0.36 group and a fractional anisotropy 〉 0.36 group. All patients underwent a regular magnetic resonance imaging and a diffusion tensor imaging examina- tion at 1 week, 1, 3, 6 and 12 months after cerebral infarction. The FugI-Meyer scores of their hemiplegic limbs were tested before the magnetic resonance and diffusion tensor imaging exami-nations. In the negative motor evoked potential group, fractional anisotropy in the affected cerebral peduncle declined progressively, which was most obvious in the first 1-3 months after the onset of cerebral infarction. The areas and area asymmetries of the cerebral peduncle on the affected side were significantly decreased at 6 and 12 months after onset. At 12 months after onset, the area asymmetries of the cerebral peduncle on the affected side were lower than the normal lower limit value of 0.83. FugI-Meyer scores in the fractional anisotropy ≥0.36 group were significantly higher than in the fractional anisotropy 〈 0.36 group at 3-12 months after onset. The fractional anisotropy of the cerebral peduncle in the positive motor evoked potential group decreased in the first 1 month after onset, and stayed unchanged from 3-12 months; there was no change in the area of the cerebral peduncle in the first 1-12 months after cerebral infarction. These findings confirmed that if the fractional anisotropy of the cerebral peduncle on the affected side is 〈 0.36 and the area asym-metries 〈 0.83 in patients with negative motor evoked potential after cerebral infarction, then poor hemiplegic limb motor function recovery may occur.

MOTOR EVOKED POTENTIAL OF MAGNETIC STIMULATION IN THE DETERMINATION OF S_1 RADICULOPATHY

Motor evoked potentlal (MEP) elicited by magnetic stimulation was utilised to diagnose S1 radiculopathy non-invasively. Magnetic stimulation estimated motor nerve conduction time (MNCT), which was used in combination with F response recorded from soleus, allowed calculation of motor root conduction time (MRCT). 50 healthy controls and 30 patients with S1 radiculopathy were studied- The results showed that no difference was seen in MNCT in all patients, but MRCT were markedly prolonged in 87% of the patients, which was higher than the prolongation of F wave latency in 71% or the patients. it is concluded that MEP of magnetic stimulation is a useful technique for non-invasive diagnosis of S, radiculopathy.

Involuntary muscle spasm expressed as motor evoked potential after olfactory mucosa autograft in patients with chronic spinal cord injury and complete paraplegia

Object: The efficacy of olfactory mucosa autograft (OMA) for chronic spinal cord injury has been reported. New activity in response to voluntary effort has been documented by electromyography (EMG), but the emergence of motor evoked potential (MEP) reflecting electrophysiological conductivity in the central nervous system, including the corticospinal pathway, after OMA, and the best indications for OMA, have not been clarified. Here, we report the emergence of MEPs after OMA and offer recom-mendations for appropriate indications based on the presence of involuntary muscle spasm (IMS). We used analysis of MEP to examine the efficacy of OMA for patients with complete paraplegia due to chronic spinal cord injury. To clarify the indications for OMA, we investigated the association of IMS and efficacy of OMA. Methods: Four patients, 3 men and 1 woman, were enrolled. The mean age of the cases was 30.3 ± 9.5 years (range, 19 to 40 years). All 4 cases were American Spinal Injury Association (ASISA) grade A. The mean duration from injury to OMA was 95.8 ± 68.2 months (range, 17 to 300 months). Samples of olfactory mucosa were removed, cut into smaller pieces, and grafted into the sites of spinal cord lesions after laminectomy. Postoperative subcutaneous fluid collection, postoperative meningitis, postoperative nosebleed, postoperative infection in the nasal cavity, impaired olfaction, neoplastic tissue overgrowth at the autograft site, new sensory disturbance, and involuntary muscle spasm were investigated as safety issues. Improvements in ASIA grade, variations in ASIA scores, EMG, SSEP, and improved urological function were evaluated as efficacy indicators. Results: There were no serious adverse events in this series. In 2 of the 4 cases, an improvement in motor function below the level of injury was recognized. In one, the motor score was 50 until 16 weeks after surgery, and it increased to 52 from 20 weeks after surgery. In the other, the motor score was 50 until 20 weeks after surgery, and it increased to 52 at 24 weeks after surgery with a further increase to 54 at 48 weeks after surgery. The emergence of MEP was recognized in the latter case at 96 weeks after surgery. The other 2 cases had no improvement in ASIA motor score. Both of these cases who showed improvements in the ASIA motor scores exhibited relative IMS compared with those who had no ASIA motor score recovery. Conclusions: We recognized the emergence of MEPs in a case with complete paraplegia due to chronic spinal cord injury after OMA. IMS might be a candidate of indication of OMA.

CLINICAL STUDY OF MOTOR EVOKED POTENTIALS BY MAGNETIC STIMULATION IN CERVICAL SPONDYLOTIC MYELOPATHY

The combined use of motor .yoked pot'ntlais (MEPs) with F way, recording was cornpared with somatesemory evoked potentials (SEPs) in order to evaluate the clinical value or MEPs incervical spondylotic myelopathy. Magnetic stimulation of motor cortex with F wave recording was used assess central motor conduction. time, (CMCT). and central somatoseusory conduction time(CSCT)was evaluated by SEPs in 20 pailents surffring from myeloP8thy of cervical spondylosis. Theresults were comapared with 20 control subjects. The results showed that CMCT of Patients was obviously prolonged then that of contral subjects, the sbnormal rate was 80% which was higher than70K of SEPs slid that the prolongation or CMCT had a good correlation with the severe degree ofmyelopathy. The Painless and noninvasive .magnetic stimulation of PEPs could figure out the compressed degree of motor descending pathway and was. useful technique for diagnosis of cervicalspondylotic myelopathy.

Intraoperative facial motor evoked potentials monitoring with transcranial electrical stimulation for preservation of facial nerve function in patients with large acoustic neuroma

Background Although various monitoring techniques have been used routinely in the treatment of the lesions in the skull base, iatrogenic facial paresis or paralysis remains a significant clinical problem. The aim of this study was to investigate the effect of intraoperative facial motor evoked potentials monitoring with transcranial electrical stimulation on preservation of facial nerve function. Method From January to November 2005, 19 patients with large acoustic neuroma were treated using intraoperative facial motor evoked potentials monitoring with transcranial electrical stimulation （TCEMEP） for preservation of facial nerve function. The relationship between the decrease of MEP amplitude after tumor removal and the postoperative function of the facial nerve was analyzed. Results MEP amplitude decreased more than 75% in 11 patients, of which 6 presented significant facial paralysis （H-B grade 3）, and 5 had mild facial paralysis （H-B grade 2）. In the other 8 patients, whose MEP amplitude decreased less than 75%, 1 experienced significant facial paralysis, 5 had mild facial paralysis, and 2 were normal. Conclusions Intraoperative TCEMEP can be used to predict postoperative function of the facial nerve. The decreased MEP amplitude above 75 % is an alarm point for possible severe facial paralysis.

VALUE OF MOTOR EVOKED POTENTIALS BY MAGNETIC STIMULATION IN DIAGNOSIS OF LUMBOSACRAL RADICULOPATHY

Motor root conduction time(MRCT) was calculated by combining the magnetic stimulatiou eliciting motor evoked poentials (MEP)in lumbosacral region with F wave in popliteal rossa.Motor nerve conduction time(MNCT)and MRCT were calculated reliably from the tibialis and the soleal MEPS in 40 patients suffering from L5 or S1 radlculopathies owing to disc protrusion,and in 50 healthy controls.Meanwhile,corticals somatosensory evoked potentials(SEP)were recorded by segmental cutaneous nerve stimulation for comparison.The results showed that no differences were seen in MNCT in all patients,but MRCT was markedly prolonged in 85%or the patients,which was higher than the prolongation of SEP in 45% or the patients.It is concluded that magnetic stimulation of MEP is a useful technique ror non-invasive diagnosis of lumbosacral radlculopathies.

CORRELATION OF THE MAGNETIC MOTOR EVOKED POTENTIAL TECHNIQUE WITH PATHOLOGICAL CHANGES ASSOCIATED WITH SPINAL CORD INJURY IN ADULT CATS

To determine whether the pathological changes caused by injury to the spinal cord can be correlated with values obtained by the Magnetic Motor Evoked Potential (MEPs) technique, we studied spinal cords from 41 adult cats who were divided into 4 groups. The groups ranged from normal cats whose spinal cords were not compressed, to slightly, moderately and severely injured. MEPs were recorded before compression and in 30 minutes, 6 hours, 1 week, 2 week and 4 week after the compression unit was installed. Pathological changes with increased pressure were seen in blood vessels, nerve cells and fibers, Nissl substance and the central canal. A reversal of pathological changes was observed in slight or moderate injury during the 4 weeks of the experiment. Extensive injury, however, caused irreversible changes in the nerve cells with loss of motor function. The latency of MEPs at 30 minutes and 6 hours in the slightly injured group was 037 and 038 times greater than the baseline and returned to normal levels in 4 weeks. In the moderately injured group, the latency was increased 077 and 081 times and in the severely injured 132 and 136 times over the baseline. Recovery in the second group was partial and not at all in the severely injured. Thus, there appears to be good correlation between observed pathological changes, motor functions and MEPs.

Local injection of bone morphogenetic protein 7 promotes neuronal regeneration and motor function recovery after acute spinal cord injury

After spinal cord injury,the number of glial cells and motor neurons expressing bone morphogenetic protein 7（BMP7）increases,indicating that upregulation of BMP7 can promote nerve repair.We,therefore,tested whether direct injection of BMP7 into acutely injured ratalalo createrywith 50 ng BMP7（BMP7 group）or physiological saline（control group）for 7 consecutive days.Electrophysiological examination showed that the amplitude of N1 in motor evoked potentials（MEP）decreased after spinal cord injury.At 8 weeks post-operation,the amplitude of N1 in the BMP7 group was remarkably higher than that at 1 week post-operation and was higher than that of the control group.Basso,Beattie,Bresnahan scale（BBB）scores,hematoxylin-eosin staining,and western blot assay showed that at 1,2,4 and 8 weeks post-operation,BBB scores were increased;Nissl body staining was stronger;the number of Nissl-stained bodies was increased;the number of vacuoles gradually decreased;the number of synapses was increased;and the expression of neuronal marker,neurofilament protein 200,was increased in the hind limbs of the BMP7 group compared with the control group.Western blot assay showed that the expression of GFAP protein in BMP7 group and control group did not change significantly and there was no significant difference between the BMP7 and control groups.These data confirmed that local injection of BMP7 can promote neuronal regeneration after spinal cord injury and promote recovery of motor function in rats.

Effects of cortical intermittent theta burst stimulation combined with precise root stimulation on motor function after spinal cord injury: a case series study

Activation and reconstruction of the spinal cord circuitry is important for improving motor function following spinal cord injury.We conducted a case series study to investigate motor function improvement in 14 patients with chronic spinal cord injury treated with 4 weeks of unilateral(right only)cortical intermittent theta burst stimulation combined with bilateral magnetic stimulation of L3-L4 nerve roots,five times a week.Bilateral resting motor evoked potential amplitude was increased,central motor conduction time on the side receiving cortical stimulation was significantly decreased,and lower extremity motor score,Berg balance score,spinal cord independence measure-III score,and 10 m-walking speed were all increased after treatment.Right resting motor evoked potential amplitude was positively correlated with lower extremity motor score after 4 weeks of treatment.These findings suggest that cortical intermittent theta burst stimulation combined with precise root stimulation can improve nerve conduction of the corticospinal tract and lower limb motor function recovery in patients with chronic spinal cord injury.

Corticospinal excitability during motor imagery is diminished by continuous repetition-induced fatigue

Application of continuous repetition of motor imagery can improve the performance of exercise tasks.However,there is a lack of more detailed neurophysiological evidence to support the formulation of clear standards for interventions using motor imagery.Moreover,identification of motor imagery intervention time is necessary because it exhibits possible central fatigue.Therefore,the purpose of this study was to elucidate the development of fatigue during continuous repetition of motor imagery through objective and subjective evaluation.The study involved two experiments.In experiment 1,14 healthy young volunteers were required to imagine grasping and lifting a 1.5-L plastic bottle using the whole hand.Each participant performed the motor imagery task 100 times under each condition with 48 hours interval between two conditions:500 mL or 1500 mL of water in the bottle during the demonstration phase.Mental fatigue and a decrease in pinch power appeared under the 1500-mL condition.There were changes in concentration ability or corticospinal excitability,as assessed by motor evoked potentials,between each set with continuous repetition of motor imagery also under the 1500-mL condition.Therefore,in experiment 2,12 healthy volunteers were required to perform the motor imagery task 200 times under the 1500-mL condition.Both concentration ability and corticospinal excitability decreased.This is the first study to show that continuous repetition of motor imagery can decrease corticospinal excitability in addition to producing mental fatigue.This study was approved by the Institutional Ethics Committee at the Nagasaki University Graduate School of Biomedical and Health Sciences(approval No.18121302)on January 30,2019.

Combining Motor Imagery and Action Observation with Vibratory Stimulation Increases Corticomotor Excitability in Healthy Young Adults

Vibratory stimulation but also motor imagery and action observation can induce corticomotor modulation, as a bottom-up stimulus and top-down stimuli, respectively. However, it remains unknown whether the combination of motor imagery, action observation, and vibratory stimulation can effectively increase corticomotor excitability. This study aimed to investigate the effect of motor imagery and/or action observation, in the presence or absence of vibratory stimulation, on the corticomotor excitability of healthy young adults. Vibratory stimulation was provided to the palm of the right hand. Action observation consisted in viewing a movie of someone else’s finger flexion and extension movements. The imagery condition required the participants to imagine they were moving their fingers while viewing the movie and attempting to move their fingers in accordance with the movie. Eleven right-handed healthy young adults were asked to perform six conditions randomly: 1) vibratory stimulation, imagery, and action observation, 2) vibratory stimulation and action observation, 3) vibratory stimulation and viewing of a blank screen, 4) imagery and action observation, 5) action observation, and 6) viewing of a blank screen. Single-pulse transcranial magnetic stimulation was conducted to assess corticomotor excitability and the peak-to-peak amplitude of the motor evoked potentials. The results showed that vibratory stimulation increases corticospinal excitability. The findings further revealed that performing motor imagery while viewing finger movement is more effective at inducing an augmentation of corticomotor excitability compared to action observation alone. Thus, the combination of motor imagery, action observation, and vibratory stimulation can effectively augment corticomotor excitability.

Combined monitoring of evoked potentials during microsurgery for lesions adjacent to the brainstem and intracranial aneurysms

Background Neurophysiologic monitoring during surgery is to prevent permanent neurological injury resulting from surgical manipulation. To improve the accuracy and sensitivity of intraoperative neuromonitoring, combined monitoring of transcranial electrical stimulation motor evoked potentials （TES-MEPs）, somatosensory evoked potentials （SSEPs） and brainstem auditory evoked potentials （BAEPs） was attempted in microsurgery for lesions adjacent to the brainstem and intracranial aneurysms. Methods Monitoring of combined TES-MEPs with SSEPs was attempted in 68 consecutive patients with lesions adjacent to the brainstem as well as intracranial aneurysms. Among them, 31 patients （31 operations, 28 of posterior cranial fossa tumors, 3 of posterior circulation aneurysms） were also subjected to monitoring of BAEPs. The correlation of monitoring results and clinical outcome was studied prospectively. Results Combined monitoring of evoked potentials （EPs） was done in 64 （94.1%） of the 68 patients. MEPs monitoring was impossible for 4 patients （5.9%）. No complication was observed during the combined monitoring in all the patients. In 45 （66.2%） of the 68 patients, EPs were stable, and they were neurologically intact. Motor dysfunction was detected by MEPs in 8 patients, SSEPs in 5, and BAEPs in 4, respectively. Conclusions A close relationship exists between postoperative motor function and the results of TES-MEPs monitoring TES-MEPs are superior to SSEPs and BAEPs in detecting motor dysfunction, but combined EPs serve as a safe, effective and invasive method for intraoperative monitoring of the function of the motor nervous system. Monitoring of combined EPs during microsurgery for lesions adjacent to the brainstem and intracranial aneurysms may detect potentially hazardous maneuvers and improve the safety of subsequent procedures.

Collagen/heparan sulfate porous scaffolds loaded with neural stem cells improve neurological function in a rat model of traumatic brain injury

One reason for the poor therapeutic effects of stem cell transplantation in traumatic brain injury is that exogenous neural stem cells cannot effectively migrate to the local injury site,resulting in poor adhesion and proliferation of neural stem cells at the injured area.To enhance the targeted delivery of exogenous stem cells to the injury site,cell therapy combined with neural tissue engineering technology is expected to become a new strategy for treating traumatic brain injury.Collagen/heparan sulfate porous scaffolds,prepared using a freeze-drying method,have stable physical and chemical properties.These scaffolds also have good cell biocompatibility because of their high porosity,which is suitable for the proliferation and migration of neural stem cells.In the present study,collagen/heparan sulfate porous scaffolds loaded with neural stem cells were used to treat a rat model of traumatic brain injury,which was established using the controlled cortical impact method.At 2 months after the implantation of collagen/heparan sulfate porous scaffolds loaded with neural stem cells,there was significantly improved regeneration of neurons,nerve fibers,synapses,and myelin sheaths in the injured brain tissue.Furthermore,brain edema and cell apoptosis were significantly reduced,and rat motor and cognitive functions were markedly recovered.These findings suggest that the novel collagen/heparan sulfate porous scaffold loaded with neural stem cells can improve neurological function in a rat model of traumatic brain injury.This study was approved by the Institutional Ethics Committee of Characteristic Medical Center of Chinese People’s Armed Police Force,China(approval No.2017-0007.2)on February 10,2019.

脊柱矫形术中神经监测研究进展

脊柱侧凸矫形手术是治疗脊柱侧凸畸形最常用的治疗方式之一,而术后神经功能缺损是脊柱侧凸手术术后最严重的并发症。针对这种难以承受的风险,自上世纪以来,临床上陆续出现了很多监测检查神经功能完整性的方法,如术中唤醒试验、肌电图、体感诱发电位、运动诱发电位等。近年来,术中多模式结合的神经监测方案被逐渐推广和使用,其特异性及准确率较单一神经监测方式有再一次提升。本文通过对多种术中神经电生理监测技术原理、优劣势、影响因素、准确性等进行多方面介绍,旨在指导临床医师在不同病例中选择最佳监测手段。