Evoked-potential monitoring during dorsal root entry zone surgery. Patients with chronic pain

Somatosensory evoked potentials (SEP) were monitored intraoperatively in 15 patients who underwent spinal cord radiofrequency thermal dorsal root entry zone (DREZ) lesion procedures to treat chronic deafferentation pain. We found a significant correlation between transient latency shifts (recovery to prelesion values in the postlesioning period) of the first positive peak of the SEP (P1) during lesion production and the patients' subsequent postoperative neurological status (p less than 0.01). Transient increases in P1 latency above 2 ms were associated with detectable but transient postoperative sensorimotor deficits that resolved weeks to months after surgery. In 1 patient, the intraoperative P1 latency failed to return to baseline values; this patient had irreversible postoperative sensorimotor dysfunction. In 9 patients, we confirmed the value of recording bilateral SEP, using the contralateral side of the spinal cord (with no lesions) as a control. This experience has resulted in an improved SEP monitoring strategy: we now reconsider the risk-benefit ratio of additional DREZ lesions if early lesion production results in increased P1 latency. Rapid normalization of the P1 latency indicates that any postoperative deficits likely will resolve. Failure of P1 latency to return to control levels during the surgical wound closure period (approximately 1 h) indicates the high probability of permanent neurological deficits.     

Comparison of the Interference Effects on Somatosensory Evoked Potential from Tonic,Burst, and High-dose Spinal Cord Stimulations

Spinal cord stimulations have been used widely to treat intractable neuropathic pain. The conventional spinal cord stimulation paradigm, the “tonic” type, suppresses excessive activation of wide dynamic range neurons in the dorsal horn via the collateral branch from the dorsal column. Therefore, preserved dorsal column function is an important prerequisite for tonic spinal cord stimulations. A tonic spinal cord stimulation requires eliciting paresthesia in the painful area due to stimulation of the dorsal column and dorsal root. Recent spinal cord stimulation paradigms, including burst and high-dose, are set below the paresthesia threshold and are proposed to have different pain reduction mechanisms. We conducted an interference study of these different stimulation paradigms on the somatosensory evoked potential (SEP) to investigate differences in the sites of action between tonic and new spinal cord stimulations. We recorded posterior tibial nerve-stimulated SEP in seven patients with neuropathic pain during tonic, burst, and high-dose stimulations. The total electrical energy delivered was calculated during SEP-spinal cord stimulation interference studies. High-dose stimulations could not reduce the SEP amplitude despite higher energy delivery than tonic stimulation. Burst stimulation with an energy similar to the tonic stimulation could not reduce SEP amplitude as tonic stimulation. The study results suggested different sites of action and effects on the spinal cord between the conventional tonic and burst or high-dose spinal cord stimulations.     

脊髓急性牵拉损伤动物模型机理研究

目的对犬脊髓(神经根)急性牵拉损伤的病理机制进行初步探讨。方法12只健康成年杂种犬，随机分为对照组和不同程度牵拉损伤组。前后路联合手术离断脊柱后施加纵向牵拉损伤，对牵拉应变率、体感诱发电位(SEP)、神经源性脊髓运动诱发电位(NMEP)、硬膜下压力(SP)、硬膜血流量(EBF)等进行持续观察。伤后取脊髓及神经根标本进行HE、髓鞘神经中丝(NF)及胶原纤维酸性蛋白(GFAP)抗体免疫组织化学染色及电镜超微结构观察。结果牵拉损伤涉及牵拉节段和其上下脊髓及神经根的损伤。牵拉后出现硬膜下压力的显著增高和硬膜血流的显著降低。SEP异常的出现较NMEP更早。结论牵拉后脊髓内压力的增加导致脊髓血流减少。以及直接的机械性牵拉损伤可能是脊髓牵拉损伤的重要机制。     

体感诱发电位在椎体后凸成形术中的脊髓监测

目的探讨体感诱发电位（SEP）在椎体后凸成形术（PKP）中的脊髓监测作用。方法33例46个椎体行PKP,术中均予SEP监护。结果46个椎体疼痛均好转,椎体复位良好,2例出现波幅降低,1例出现潜伏期延长,无重大并发症。结论SEP在PKP中对脊髓有良好的监测作用。     

Somatosensory and Motor Evoked Potentials in Patients with Tumours in the Spinal Canal

Summary  Motor and sensory evoked potentials were recorded in 27 patients with expanding spinal tumour. The patients were divided into 2 groups: I. tumours at the level of the spinal cord [18] and II. at the level of the cauda equina [9]. On the basis of the localization of the tumour, midline and lateral subgroups were distinguished.  The latencies of motor evoked potentials were prolonged in most of the patients, even those without paresis, in both groups. The motor evoked potentials detected subclinical motor lesions in 7 patients. All patients but one manifested sensory deficits, which could not be shown with the somatosensory evoked potentials.  Significantly more prolonged cortical motor latencies were found in most of the patients with a laterally located tumour on the tumour side than contralaterally, whereas in somatosensory evoked potentials this difference was not apparent.  On the basis of these observations, we concluded that motor evoked potentials, 1. could more reliably detect the neural deficit than somatosensory evoked potentials; 2. could show the side where the tumour was located; 3. proved useful in the detection of subclinical motor lesions. The general conclusion may be drawn that this electrophysiological method can provide useful information for the surgeon.     

常压及控制性降压下脊髓急性牵拉损伤比较研究

目的 评价控制性降压是否增加脊髓对牵拉损伤的易感性。材料与方法健康成年杂种犬6只，随机分为常压和控制性降压脊髓牵拉损伤组。观察常压及控制性降压水平下相同程度牵拉损伤后脊髓血流(SCBF)、体感诱发电位(SEP)、神经源性运动诱发电位(NMEP)改变的差异。结果 外周血有创动脉压(MABP)平均下降幅度为40．5％。经SSPS统计软件独立样本t检验，不同牵拉水平下，常压组及低压组的SCBF(％)、SEP波幅(Asep)(％)及NMEP波幅(％)无显著差异。结论 尼卡地平控制性降压不增加脊髓对牵拉损伤的易感性。     

体感诱发电位评价家兔脊髓冲击伤模型的神经机能变化

目的 探讨脊髓冲击伤前后的体感诱发电位的变化,评价家兔神经机能的改变程度.方法 应用改良霍普金森杠杆设备根据冲击波的压力不同(0.40 MPa,0.60 MPa,0.80 MPa)建立不同损伤程度的胸T9-T10脊髓冲击伤模型,12 h后用体感诱发电位仪分别计测家兔脊髓冲击伤前后的体感诱发电位,利用分析软件对诱发电位P...     

Motor evoked potential monitoring during neurosurgical operations on the spinal cord

In order to monitor descending pathways during neurosurgical operations on the spinal cord, motor evoked potentials (MEP) were recorded from the epidural space of the spinal cord and the cauda equina following transcranial electrical cortex stimulation in a total of 40 patients. It was the aim of our study to test this invasive recording technique with regard to recordability of potentials as well as correlation to post-operative neurological conditions. In 15 of 23 patients (65.2%) intraoperative potentials were obtained from the spinal cord and in 33 of 40 patients (82.5%) they were obtained from the cauda equina. On the basis of acceptable changes in amplitudes of up to 50% at the end of the operation, 13 of 15 (86.7%) recordings from the spinal cord and 28 of 33 (84.8%) from the cauda equina correlated correctly with the post-operative motor status. At the same time, there were false positive results in 2 (13.3%) and 5 (15.2%) recordings, respectively. False negative results were not observed. Post-operative deterioration of the motor status as observed in 3 patients coincided in 2 patients with a permanent reduction in amplitudes of more than 50% of the baselines and in 1 patient with an intra-operative loss of potentials. Thus both spinal cord and cauda equina recording of MEP clicited by transcranial electrical stimulation were proven to be sensitive methods for detection of impending neucological complications. Cauda equina recording, however, seems to allow recording in more cases.     

Experimental study of spinal cord evoked potentials in cats

Assessment of function of the spinal cord utilizing spinal cord evoked potentials (SEP) has become a useful diagnostic tool. In the present study, various aspects of characteristics of SEP were analyzed. The basic waveform of conductive SEP consisted of two major components, namely, N1 and N2, whose conduction velocities along the dorsal surface of the cord were 74 m/s and 55 m/s, respectively. Halothane inhalation caused reduction of N2 amplitude, whereas asphyxia caused latency delay of N2. Significant amplitude reduction of N1, N2 (p less than 0.005) and considerable latency delay of N1 were noted in ventral epidural recording. Although there was no relationship between severity of injury and the appearance of positive potentials, N2 tended to be positive-going in heavy injury. Findings of positive potentials showed that N1 originated in the area of ventral gray matter through the ventro-lateral column and N2 through the dorsal column.     

Direct spinal versus peripheral nerve stimulation as monitoring techniques in epidurally recorded spinal cord potentials

Summary We recorded spinal cord evoked potentials (SCEPs) and spinal somatosensory evoked potentials (spinal SEPs) in 30 operations following stimulation of the epidural spinal cord and the peripheral nerve, respectively, to compare their feasibility as an intraoperative technique for spinal cord monitoring. SCEPs produced quicker responses and had larger amplitudes with simpler waveforms. SCEPs could reflect residual function of the pathological spinal cord and predict the postoperative clinical outcome, findings which are not observed with spinal SEPs. Moreover, SCEPs had a much higher sensitivity to spinal cord insult. Therefore, we conclude that the SCEPs were more appropriate indicator than the spinal SEPs as an intra-operative monitoring method for spinal cord function.     

Motor versus somatosensory evoked potential changes after acute experimental spinal cord injury in rats

Summary In this study, averaged cortical somatosensory evoked potentials (SEP) after sciatic nerve stimulation, and lower extremity muscle responses after motor cortex stimulation (MEP) were compared in rats. 10 animals served as light (25g-cm) and 10 animals as severe (80g-cm) acute spinal cord injury group after weight dropping trauma. After the initial loss of components, both SEP and MEP recovered in most cases in the light injury group. In the severe injury group, however, no recovery was observed in cortical SEPs, while the muscle MEP recovered in some animals. Light spinal cord injury had little effect on muscle MEPs and caused a paradoxical amplitude increase in some MEP recordings. Latency values of muscle MEPs did not show great changes after either kind of injury, while cortical SEP latency was considerably delayed.In this model cortical SEPs were more sensitive to light spinal cord injury than muscle MEPs after single electrical cortical stimuli. Severe spinal cord injury caused amplitude changes or loss of waves from both SEP and MEP.This work was partly presented in the poster sections at 39. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie, Köln (F. R. G., May 8-1, 1988 and Congress of the International Medical Society of Motor Disturbances, Rome, Italy, June 2–4, 1988.     

体感诱导电位在可逆性脊髓损伤和根性病损中的应用

为了弄清脊髓损伤的发展规律，我们对动物模型从Ａｌｌｅｎ的背侧撞击改用腹侧撞击，使其更接近于脊髓损伤的模式。在一定功率下可使动物模型产生可逆性单侧损伤，从而观察脊髓损伤后的病理变化。用０．０１５８Ｊ／ｃｍ的力，制成不全截瘫的动物模型，并用ＳＥＰ波型及其潜伏值来进行定量分析，了解伤后的发展进程，同时通过病理观察；与ＳＥＰ检查匹配，对脊髓损伤的程度和变化有一个比较清楚的概念。对脊髓损伤，完全性操作不会出现ＳＥＰ波，一旦ＳＥＰ波出现，说明脊髓功能已存在，单从波形角度考虑，不能说明可以恢复，应看其发展过程中潜伏值的变化，比较上、下肢的潜伏值系数，才具有显著的评估意义。可以看出潜伏值的变化与临床表现有密切关联。ＳＥＰ只能代表脊髓的感觉功能，而不能代表运动功能。     

躯体感觉诱发电位在脊柱手术监护中的应用

目的 探讨躯体感觉诱发电位（SEP）在脊柱手术监护中的应用价值。方法 分析４５８例脊柱手术中SEP监护的结果,特征,适用范围,其中颈部手术275例,胸椎,腰椎部手术183例,刺激电极为手指、足趾的环状电极或腕、踝的表面电极,记录电极为头皮针电极。结果 大部分患者的肌电图改变在器质性改变的范围内。409例（89．3％）,术中SEP有波幅轻度下降,潜伏期轻度延长,术后又恢复后近手术开始时水平;32例（7．1％）,SEP波幅有一定程度的提高,潜伏期部分缩短;12例（2．6％）有术中SEP明显恢复;2例（0．4％）术中未见SEP明显改变,术后有功能障碍;3例（0．7％）,术中出现SEP的波幅明显下降,潜伏期轻度延长,术持恢复欠佳。结论 SEP在脊柱手术监护中的作用是肯定的,但有一定的局限性。     

Intraoperative somatosensory evoked potential monitoring in scoliosis

During surgical correction of scoliosis, 63 patients had somatosensory evoked potential (SEP) monitoring of the spinal cord. Tibial nerves were unilaterally stimulated, and the potentials were recorded from the midcervical spine with surface and epidural needle electrodes. Over 85% had no significant change in their SEP and no postoperative neurologic deficits. Eleven percent had a significant change in their potential (amplitude decrease of greater than 60% and/or latency increase of greater than 2.5 msec) with no neurologic complications. One patient had a significant potential change and temporary postoperative sensory deficits did occur. One additional patient experienced postoperative neurologic complications but had no SEP change. This single false negative case, however, was clinically significant only for motor dysfunction, which is not monitored by the SEP. When changes in patient core temperature were compared to changes in SEP amplitude and latency, an intraoperative decrease in core temperature increased SEP latency and decreased amplitude, which may explain in part the false positive rate of the procedure.     

脊髓损伤后早期减压对诱发电位影响的实验研究

[目的]观察脊髓损伤后早期减压对体感诱发电位及经颅磁刺激运动诱发电位的影响，以探讨诱发电位在判断手术时机及预后中的应用价值。[方法]日本大耳兔32只随机分4组。A组为对照组，不造成脊髓损伤。B、C、D组为脊髓损伤组。对每组动物于不同时间分别检测SEP、MEP。分析波形的潜伏期、峰问波幅。用后肢的Tarlov分级法作伤后运动功能评分。取脊髓标本，行组织学观察。[结果]随着脊髓压迫时间的延长，SEP、MEP的潜伏期逐渐延长，波幅逐渐减小．波幅变化较潜伏期更为敏感。在恢复过程中，脊髓受压时间越短，诱发电位恢复越早。潜伏期恢复早于波幅，而且SEP恢复早于MEP，MEP的恢复早于功能评分。[结论]SEP与TMS-MEP对脊髓损伤十分敏感，能较早反映脊髓损伤程度，可用于指导临床手术治疗和判断预后。     

Effects of dorsal root entry zone lesion on spinal cord potentials evoked by segmental,ascending and descending volleys

Summary The spinal cord potentials (SCPs) were recorded from the dorsal root entry zone (DREZ) and posterior epidural space in patients before and after dorsal root entry zone lesion (DREZL) during general anaesthesia. The SCPs from the DREZ activated by segmental, ascending and descending volleys were basically the same in fundamental waveform as those recorded from the posterior epidural space. Segmentally activated slow negative (N₁) wave, reflecting synchronized activities of dorsal horn neurones, and positive (P₂) wave, thought to indicate primary afferent depolarization, were affected by DREZL in all 4 subjects tested, even by contralateral stimulation, suggesting that these components of the segmental SCPs in man partly reflect the activities of the contralateral dorsal horn. The spike-like potentials activated by ascending volleys were not affected by DREZL, while the subsequent slow components were decreased in the lesioned level. This may indicate that ascending spinal cord tracts are not affected by the operation, and suggests that the origin of the slow components by ascending volleys lies at least in part in the segmental dorsal horn. The slow negative and positive components, recorded at a remote segment from DREZL, in response to the descending volleys, were augmented after DREZL, suggesting that activation of ascending or descending inhibition through a feedback loop via the supraspinal structures might occur at least transiently following DREZL. All components of the SCPs activated by descending volleys were decreased or disappeared in recording from the lesioned level, as expected. Thus, intra-operative recording of the SCPs during DREZL might be beneficial for monitoring and studying human spinal cord function.     

定量半横断刀改进大鼠脊髓半横断块状缺损模型

目的研究自制定量半横断刀对大鼠脊髓半横断块状缺损模型的改进效果。方法清洁级健康成年雄性SD大鼠48只,体重220～250 g。将实验动物随机分为实验组和对照组,每组24只。实验组采用自制定量半横断刀制作脊髓半横断块状缺损模型,对照组采用眼科手术刀制作模型。观察两组大鼠术后并发症;模型制备前及制备后21 d行电生理检测;模型制备后6 h及5、28 d,光镜下观察各组脊髓半横断块状缺损边缘的组织结构;模型制备后1、3、5、7、14、21、28、35、42、56、84 d,对两组实验动物行健、患侧后肢BBB运动功能评分。结果实验组和对照组实验动物死亡率分别为0和26.67%,比较差异有统计学意义(P=0.028)。电生理检测:两组术前健侧感觉诱发电位(sensory evokedpotentials,SEP)及运动诱发电位(motor evoked potentials,MEP)潜伏期和波幅比较差异均无统计学意义(P>0.05);术后21 d,对照组MEP及SEP潜伏期明显延长,波幅降低,与术前及实验组术后21 d比较差异均有统计学意义(P<0.05);实验组组内术前及术后21 d比较差异无统计学意义(P>0.05)。组织学观察:对照组健侧脊髓损伤后6 h可观察到小血肿,5 d时见脊髓组织间隙疏松及嗜神经现象,28 d时见脊髓块状缺损边缘组织明显小空洞形成,未见正常形态神经元;而实验组5 d时未见神经元不可逆损伤,28 d时块状缺损边缘可见正常形态神经元及部分空泡样改变。运动功能评分:除实验组与对照组患侧BBB评分差异无统计学意义(P>0.05)外,其余组间或健、患侧间BBB评分比较差异均有统计学意义(P<0.05)。结论定量半横断刀制备大鼠脊髓半横断损伤模型,制作过程重复性好且制成的模型稳定,是研究脊髓半横断损伤的理想模型。     

皮导节段性脊髓诱发电位在脊髓型颈椎病中的应用

本文通过对１０只成兔、 ２０名神经功能正常看、 ３例椎管狭窄症不伴有脊髓功能障碍和 ３０例脊髓型颈椎病者经皮导出的皮导节段性脊髓诱发电位 （ｐｅｒｃｕｔａｎｅｏｕｓ ｓｅｇｍｅｎｔａｌ ｓｐｉｎａｌ ｃｏｒｄ ｅｖｏｋｅｄｐｏｔｅｎｔｉａｌ，ＰＳＳＣＥＰ）进行对比分析研究后，证实了从颈背侧中线皮下导出的Ｐ１、Ｎ１和Ｐ２波不仅能对脊髓型颈椎病做出脊髓功能定位诊断，而且对估计预后和制定正确手术方案都有一定参考和实用价值。     

Somatosensory spinal cord evoked potentials in the evaluation of the effect of dexamethasone in experimental spinal cord injury

We studied the effects of high-dose dexamethasone on amplitude and latency values of spinal cord evoked potentials. Thirty-three rabbits were divided into three equal groups. The first group served as the control group, the others received high-dose (2.5 mg/kg) dexamenthasone, the second group 1 hour prior to and the third group immediately after the induction of a spinal cord trauma in segment T12. The spinal cord evoked potentials were recorded epidurally from T12 segment 5 min before and 5, 30, 60, 90,120 and 150 min after trauma. Pretreatment with dexamethasone (group II) prevented the latency delay, and later treatment with dexemethasone (group III) prevented the latency delay partially.Our results suggest that when dexamethasone is given prophylactially it prevents latency alteration, while treatment with dexamethasone after lesioning prevents latency alteration partially. From our results we conclude that pre-treatment with dexamethasone may involve different mechanisms than were activated in the posttreatment group.     

早期手术减压对损伤脊髓caspase-3表达的影响

目的探讨大鼠脊髓损伤后不同减压时间对大鼠脊髓细胞caspase-3表达的影响。方法将动物分为:大鼠脊髓挫伤即刻手术减压组(A组),大鼠脊髓挫伤2小时手术减压组(B组),大鼠脊髓挫伤8小时手术减压组(C组),大鼠脊髓挫伤24小时手术减压组(D组)。手术后1、3、7、14、28天对脊髓损伤区进行细胞凋亡caspase-3蛋白表达的测定(免疫组化法),采用计算机图像分析技术,进行定量分析。并用行为学和电生理检查观察大鼠功能恢复情况。结果A、B、C、D四组中均发现凋亡caspase-3蛋白阳性表达细胞,图象分析发现,各组凋亡细胞caspase-3免疫反应阳性细胞表达顺序为D>C>B>A,与大鼠后肢功能恢复有平行的变化趋势。结论大鼠脊髓损伤早期手术减压能抑制脊髓损伤后的细胞凋亡,促进大鼠后肢功能恢复。