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 co...     

Simple and reproducible model of rat spinal cord injury induced by a controlled cortical impact device.

Consistently reproducible experimental trauma was inflicted on the rat spinal cord (L3-L4) employing a controlled cortical impact device. The spinal cord was injured with one of three sizes of chips; thick (3 mm diameter), medium (2 mm diameter), thin (1 mm diameter). Each chip was applied at 1, 2 and 3 mm deformation depths. The correlations of the magnitude of the primary trauma were examined histopathologically. It was found that the extent and intensity of the trauma could be changed by altering the depth of deformation and the chip diameter at a fixed velocity of 4.6 m per sec. The injury caused by the 2 mm diameter chip at 0.5 mm-deformation damaged one to two segments of the perifocal spinal cord. In the surviving animals, the histological changes could be classified as primary, secondary, and late phase changes, and finally the lesion became a cavity. This study reports the application of a controlled cortical impact device to morphological research on a spinal cord injury. We found that the injury by the 2 mm chip at 0.5 mm deformation was the most advantageous and reproducible model for further investigations.     

大鼠脊髓完全性损伤模型的建立

背景：建立有效的完全性脊髓损伤动物模型是深入研究脊髓损伤的前提,只有建立标准的、可重复性高的实验动物模型才能择优选出治疗脊髓损伤的可行方案。 目的：实验拟建立一种稳定的大鼠完全性脊髓损伤动物模型。 设计、时间及地点：对照观察动物实验,于2007-11/2008-10在石河子大学药学院动物试验中心完成。 材料：30只健康Wistar大鼠随机分成假手术组6只、实验组24只。 方法：显露实验组大鼠T8~T12棘突及椎板,切除T9~10棘突及椎板,暴露相应脊髓段作为损伤区,采用大鼠脑定位仪自主设计改良Allen模型打击装置,予15 g×20 cm=2.94×10-2N 重力打击大鼠T10节段脊髓,动物模型保证硬脊膜完整。假手术组仅同法暴露相应脊髓段,但不做打击。 主要观察指标：造模后2,4,8周以斜板试验及BBB评分观察大鼠双后肢运动功能,以苏木精-伊红染色观察大鼠脊髓组织的变化。 结果：假手术组大鼠苏醒后能站立行走,斜板试验角度均大于70°,BBB评分21分,脊髓结构正常。实验组大鼠造模后双下肢全瘫,2只大鼠表现为痉挛性瘫痪,5只大鼠表现出不同程度的自残现象。造模后2,4,8周斜板试验角度均小于30°,BBB评分均少于10分,随时间延长,部分大鼠可见后肢刺激性反射,但无主动性功能活动,局部脊髓结构破坏严重。 结论：以2.94×10-2N 重力打击大鼠脊髓可保证硬脊膜的完整,并获得稳定的完全性脊髓损伤动物模型。     

Simple and reproducible model of rat spinal cord injury induced by a controlled cortical impact device

Abstract

Consistently reproducible experimental trauma was inflicted on the rat spinal cord (L3-L4) employing a controlled cortical impact device. The spinal cord was injured with one of three sizes of chips; thick (3 mm diameter), medium (2 mm diameter), thin (1 mm diameter). Each chip was applied at ), 2 and 3 mm deformation depths. The correlations of the magnitude of the primary trauma were examined histopathologically. It was found that the extent and intensity of the trauma could be changed by altering the depth of deformation and the chip diameter at a fixed velocity of 4.6 m per sec. The injury caused by the 2 mm diameter chip at 0.5 mm deformation damaged one to two segments of the perifocal spinal cord. In the surviving animals, the histological changes could be classified as primary, secondary, and late phase changes, and finally the lesion became a cavity. This study reports the application of a controlled cortical impact device to morphological research on a spinal cord injury. We found that the injury by the 2 mm chip at 0.5 mm deformation was the most advantageous and reproducible model for further investigations. [Neurol Res 1999; 21: 313–323]     

体感诱发电位在脊髓损伤后药物疗效观察中的应用

目的观察大鼠脊髓损伤后药物对体感诱发电位（ＳＥＰ）的影响。方法４８只Ｗｉｓｔａｒ大鼠脊髓损伤术后立即给小檗胺或尼莫地平１次，术后２、４、８小时各给同样药１次，以后每日２次给药，至术后２周。分别于术前及术后４周在麻醉状态下进行ＳＥＰ检查。结果脊髓损伤后４周各组实验动物的ＳＥＰ潜伏期都有一定程度的延长，脊髓传导速度明显下降。大剂量小檗胺组与对照组相比其潜伏期及损伤部位的传导时间均明显缩短，损伤部位的传导速度明显加快，与对照组相比差异有极显著性意义（Ｐ＜０．０１）。结论ＳＥＰ能客观评价脊髓的神经传导功能，对脊髓损伤后药物疗效观察有一定的客观意义。     

Motor and somatosensory evoked potentials in a primate model of experimental spinal cord injury

Motor and somatosensory evoked potentials (MEP and SSEP) were compared after experimental spinal cord injury in Bonnet monkeys (macaca radiata). The MEP and SSEP changes following graded injuries were related to clinical outcome. Eight healthy mature monkeys with a mean weight of 4.2 + 0.9 Kg were chosen for the study. Graded spinal cord injury was caused using 50, 100, 200, 300 gm-cm force by modified Allens' weight drop device. MEP and SSEP recordings were done before injury and at 0, 2, 4 and 6 hours after injury and on the 7th postoperative day. Neurological assessment was done at 24 hours and on the 7th day following injury. 50, 100, 200 gm-cm force caused partial injuries and 300 gm-cm force caused severe spinal cord injury. The predictive value of MEP and SSEP following partial injuries was 80% and 66.67% respectively. Both MEP and SSEP were 100% predictive in severe injury. MEP and SSEP monitoring can therefore be complementary to each other in predicting the neurological outcome in partial injuries to the spinal cord.     

Huangqin flavonoid extraction for spinal cord injury in a rat model

Flavonoids from Huangqin(dried roots of Scutellaria baicalensis Georgi) have anti-inflammatory effects, and are considered useful for treatment of spinal cord injury. To verify this hypothesis, the T9–10 spinal cord segments of rats were damaged using Allen's method to establish a rat spinal cord injury model. Before model establishment, Huangqin flavonoid extraction(12.5 g/kg) was administered intragastrically for 1 week until 28 days after model establishment. Methylprednisolone(30 mg/kg) was injected into the tail vein at 30 minutes after model establishment as a positive control. Basso, Beattie, and Bresnahan locomotor scale scores were used to assess hind limb motor function. Hematoxylin-eosin staining was used to detect pathological changes in the injured spinal cord. Immunofluorescence and western blot assays were performed to measure immunoreactivity and expression levels of brain-derived neurotrophic factor, neuronal marker neurofilament protein, microglial marker CD11 b and astrocyte marker glial fibrillary acidic protein in the injured spinal cord. Huangqin flavonoid extraction markedly reduced spinal cord hematoma, inflammatory cell infiltration and cavities and scars, and increased the Basso, Beattie, and Bresnahan locomotor scale scores; these effects were identical to those of methylprednisolone. Huangqin flavonoid extraction also increased immunoreactivity and expression levels of brain-derived neurotrophic factor and neurofilament protein, and reduced immunoreactivity and expression levels of CD11 b and glial fibrillary acidic protein, in the injured spinal cord. Overall, these data suggest that Huangqin flavonoid extraction can promote recovery of spinal cord injury by inducing brain-derived neurotrophic factor and neurofilament protein expression, reducing microglia activation and regulating reactive astrocytes.     

Cortical somatosensory evoked potentials in spinal cord injury patients.

The amplitude and latency of somatosensory evoked potentials (SEPs) in healthy subjects depend on intensity of stimulation. The effect of this parameter on SEPs in patients with neurologic disorders has not been systematically studied, although it could have a profound impact if SEPs are to be used for prognostication. We have compared the latency and amplitude of SEPs in healthy subjects and patients with spinal cord injury (SCI). Stimulation intensity was standardized at two different biologically calibrated levels. Cortical SEPs in patients with SCI showed greater decrease in latency and increase in amplitude with increased intensity of stimulation in comparison to healthy subjects. These phenomena were observed in the majority of patients with incomplete SCI who subsequently showed improvement in cortical SEPs. We observed situations in which the SEP was absent with the usual intensity of stimulation and present only with the stronger stimulation intensity. Furthermore, SEP latencies often changed dramatically with different intensities of stimulation, potentially making any calculation of central conduction velocity meaningless without precise standardization of stimulation. These findings demonstrate a necessity for a biological calibration of stimulation intensity to improve the repeatability of SEPs. We suggest the use of two different standardized intensities of stimulation for SEP studies in SCI patients, one of which should be stronger than the intensity presently recommended.     

Intraoperative spinal cord monitoring during surgery for aortic aneurysm: application of spinal cord evoked potential.

Spinal cord evoked potentials elicited by direct stimulation of the spinal cord were monitored in 21 patients during thoracic or thoraco-abdominal aortic aneurysm surgery. Flexible catheter-type electrodes were used for both stimulating and recording. The basic pattern of the spinal cord evoked potential consisted of an initial spike and a subsequent polyphasic component. The earliest and most frequent alterations after cross-clamping of the aorta were changes in the configuration or amplitude of the polyphasic component. In 13 patients who exhibited no change except minor alterations of the polyphasic component during the initial test clamping for 15 or 20 min, subsequent graft replacements were safely performed without reimplantation of intercostal vessels. In 2 patients who had sudden cardiac arrests, the evoked potential completely disappeared. The polyphasic component disappeared first, followed by the initial spike. Another patient developed acute loss of the potential after the aneurysm was incised, presumably due to distal aortic hypoperfusion. In this case, prolonged distal hypotension resulted in flaccid paraplegia. Intraoperative monitoring of the spinal cord evoked potential is a useful method for the early detection of spinal cord ischemia during surgery requiring aortic occlusion.     

人参皂甙对损伤脊髓诱发电位的影响

目的　研究猫急性脊髓损伤 (SCI)后脊髓诱发电位 (SCEP)的变化规律及人参皂甙 (GS)对其的影响 ,探讨 GS对 SCI的作用 ,旨在寻求治疗 SCI的新方法。方法　采用改良 Allen氏重量打击法制作猫急性脊髓损伤模型 ,动物随机分组 ,通过电生理及病理学方法 ,研究 SCEP的变化规律及 GS对其的影响 ,脊髓形态学的改变作为进一步的佐证。结果　 (1)损伤组伤后 SCEP辐值随时间延长逐渐变小 ,潜伏期逐渐延长 ;治疗组波形则逐渐恢复 ,6 h全部恢复 ,差异显著。(2 )光镜下两组均有水肿、中心性出血 ,神经元空泡变性 ,核溶解或固缩 ,尼氏小体消失 ,部分神经纤维脱髓鞘或断裂 ,损伤组最重 ,治疗组均有不同程度的恢复。结论　 GS对 SCI有治疗作用。     

Topiramate as a neuroprotective agent in a rat model of spinal cord injury

Topiramate(TPM) is a widely used antiepileptic and antimigraine agent which has been shown to exert neuroprotective effects in various experimental traumatic brain injury and stroke models. However, its utility in spinal cord injury has not been studied extensively. Thus, we evaluated effects of TPM on secondary cellular injury mechanisms in an experimental rat model of traumatic spinal cord injury(SCI). After rat models of thoracic contusive SCI were established by free weight-drop method, TPM(40 mg/kg) was given at 12-hour intervals for four times orally. Post TPM treatment, malondialdehyde and protein carbonyl levels were significantly reduced and reduced glutathione levels were increased, while immunoreactivity for endothelial nitric oxide synthase, inducible nitric oxide synthase, and apoptotic peptidase activating factor 1 was diminished in SCI rats. In addition, TPM treatment improved the functional recovery of SCI rats. This study suggests that administration of TPM exerts neuroprotective effects on SCI.     

BDA皮质脊髓束神经顺行示踪在大鼠脊髓损伤模型中的应用

目的本研究采用生物素标记葡聚糖(Biotin Dextran Amine,BDA)顺行示踪技术来观察大鼠皮质脊髓束(CST)在中枢神经系统中的走行及脊髓损伤后的表现特征。方法20只雌性成年Sprague-Dawley大鼠,分为脊髓损伤组(n=10)和损伤对照组(n=10)。在相当于T7椎板水平用做好标记的显微剪刀剪断脊髓的后2/3。对照组动物术中仅咬除棘突、椎板,不切断脊髓。术后第15 d,所有动物通过立体定向开颅,将10％BDA溶液注入右侧的感觉运动区皮质内。BDA注射2周后,取出大脑和脊髓组织,采用自由漂浮法行BDA染色显影。实验动物于脊髓损伤术前、术后3d、1周、2周、4周采用Basso、Beatlie、Bresnahan(BBB)评分法测量运动功能,所得数据采用两组均数比较t检验进行统计学处理。结果1.脊髓损伤组动物双后肢瘫痪,BBB运动功能评分明显低于损伤对照组,统计学比较差异十分显著(P<0.01);2.BDA顺行示踪显示大脑皮层BDA注射区内见大脑皮层的锥体细胞及其发出的轴突呈阳性染色,BDA阳性染色的皮质脊髓束神经纤维在中脑、桥脑及延髓的腹侧面行走,但在锥体交叉后皮质脊髓束主要(约99％)在对侧脊髓白质的后索中行走。在致伤组动物中,位于脊髓白质后索中的皮质脊髓束纤维在脊髓损伤处终止;在对照组皮质脊髓束纤维染色可一直延伸至L1水平。结论BDA顺行神经     

Effects of selective spinal cord lesions on the spinal motor evoked potential (MEP) in the rat

The effects of selective spinal cord lesions on the motor evoked potential (MEP) in 21 rats were investigated. No significant change in peak amplitude was observed following lesions of the pyramidal tract. There was a significant decrease in peaks 1 and 2 with ventral funiculi lesions. All 4 peaks of the MEP were significantly reduced following lesions of the lateral funiculus. The most marked decrease in peak amplitude followed lateral funiculi lesions that involved the lateral grey of the spinal cord. In one animal where the lesion was confined to the grey matter in the cord there was a marked decrease in all peaks of the MEP. In 3 additional animals interruption of the descending tracts of the spinal cord via bilateral hemisections of the spinal cord failed to completely abolish the MEP. Increases in peak latency were also noted following spinal lesions. In some animals the increase in latency occurred in the absence of significant peak amplitude changes. The findings in this study refute the previously held position that the MEP in the rat arises from pyramidal tract activation. The role of the reticulospinal and propriospinal tracts in the generation and propagation of the MEP are discussed.     

皮层体感诱发电位术中监护脊髓损伤的实验研究

目的：为开展皮层体感诱发电位（ＣＳＥＰ）术中监护脊髓损伤，判断损伤程度及确定脊髓损伤的警戒线。方法：采用４２只家犬，分别造成静压型和加速压迫型脊髓损伤，术中ＣＳＥＰ动态监测，并观察术后１～３个月脊髓功能恢复情况。结果：静压３０分钟所造成的脊髓损伤，虽然波幅较术前下降１００％，并无危险，若能及时彻底解除压迫，脊髓功能日后可基本恢复正常。加速压迫型脊髓损伤ＣＳＥＰ术中监护安全范围是Ｐ１潜伏期较术前延长不超过１．５倍，波幅下降＜５０％。结论：ＣＳＥＰ术中监护脊髓损伤准确可靠，为成功地用于临床提供了依据。     

Three-dimensional alteration of microvasculature in a rat model of traumatic spinal cord injury

Acute spinal cord injury (SCI) always leads to severe destruction of the microvascular networks. To investigate the three-dimensional (3D) alterations of microvasculature following SCI, we utilized an established rat SCI model. Based on the hypothesis that the spinal cord would undergo reorganization and postinjury modification of the vascular networks after SCI, we reconstructed the normal and injured angioarchitecture using micro-CT images of silicone rubber microsphere-perfused specimens. Several morphometric parameters were used to study the 3D vascular alterations in the SCI rat model, including the casting-based vessel volume fraction, connectivity density, separation, thickness and thickness distribution. Our results indicated that the microvascular spatial conformations were significantly different between the normal and injured spinal cord segments. The morphometric changes showed an increase of the vessel volume fraction and separation and a decrease of vessel connectivity density during the vascular healing process after SCI. Our results may contribute to elucidation of the mechanisms of compensatory vascular reconstitution in traumatized spinal cord. The method used here has the potential to improve our understanding of changes in the spatial architecture of vascular networks after SCI compared to the conventional histomorphology techniques. In summary, we developed a new methodology to analyze neurovascular pathology based on 3D vascular network patterns and features in an experimental rat SCI model. This technique could be used as a complementary tool to investigate the efficacy and side effects of therapeutic drugs or rehabilitation regimens.     

Deferoxamine improves neurological function in a rat model of experimental spinal cord injury

A rat model of spinal cord injury was established using modified Allen's method and treated with the ferric iron-chelating agent,deferoxamine.Hematoxylin-eosin,Nissl and Perl's Prussian blue staining,at 7-14 days following spinal cord injury,showed that following deferoxamine treatment,glial cells proliferation increased significantly,nerve cell morphology was improved and hemosiderin was significantly reduced in the injury region.At 1-56 days following injury,Basso,Beattie,and Bresnahan Locomotor Rating Sc...     

Alterations in the corticomotor evoked potential following spinal cord ischemia

A simple yet reliable model of spinal cord ischemia has been previously developed by inserting a Swan-Ganz catheter into the abdominal aorta of rabbits and inflating the balloon just inferior to the renal arteries. Recent investigations have shown that paraplegia is consistently reproduced if the balloon remains inflated for 20 min after loss of the N3 component of the somatosensory evoked potential. Because of its high reliability, this model has been frequently and successfully used to determine the efficacy of pharmacological agents thought to provide protection against spinal cord ischemia. Results from the present report demonstrate that a similar degree of reliability can be achieved in this model for testing motor activity. A simple method of evoking highly reproducible motor potentials, that can be percutaneously recorded from the spinal cord in response to cortical stimulation, was developed. Predictable and repeatable changes in the configuration of the corticomotor evoked potential were found during spinal cord ischemia and reperfusion. With this added dimension of functional assessment, future application of the current spinal cord ischemia model have been greatly expanded.     

Effects of spinal cord ischemia on the refractory period of descending spinal cord evoked potential

The recovery cycle, following the conduction of action potentials along a nerve fiber, consists of the absolute refractory period (ARP), the relative refractory period (RRP) and the supernormal period (SNP). The recovery cycle of the descending conductive spinal cord evoked potential (SCEP) was shown during normal state, ischemia and after ischemia using paired stimuli in cats. During ischemia the refractory period revealed a trend towards increment. Five minutes after reperfusion the refractory period decreased transiently compared with the normal level and within 30 min the refractory period returned to the normal level. The recovery curve of the 2nd potential showed different pattern compared with that of the 1st potential. Moreover, during ischemia, firstly the 3rd potential and secondly the 2nd potential of the SCEP elicited by the 2nd stimulus were disturbed. These results demonstrated that there is increased excitability of the spinal cord to the second stimulus after a brief period of ischemia, and that the 2nd and 3rd potentials are evoked synaptically and easily disturbed during ischemia. Measuring the SCEP elicited by paired stimuli or constructing the recovery curve of the SCEP is useful for the electrophysiological assessment of spinal cord function.     

Nestin-positive cells in the spinal cord: a potential source of neural stem cells

Some literatures have reported neural precursor cells (NPCs) exist in spinal cord of adult mammal, however, the NPCs distribution feature in spinal cord of adult mice so far is not described in detail. In order to observe and compare the distribution feature of NPCs in various spinal cord regions of adult mice, to research a potential source of neural stem cells (NSCs), we obtained NPCs distribution feature by analyzing the distribution of the nestin-containing cells (NCCs) in spinal cord of adult nestin second-intron enhancer controlled LacZ reporter transgenic mice (pNes-Tg) with LacZ staining and positive cell quantification. The results showed that: NCCs were observed in various regions of spinal cord of adult mice, but amount of NCCs was different in distinct region, the rank order of NCCs amount in various spinal cord regions was dorsal horn region greater than central canal greater than the ventral and lateral horn. NCCs in dorsal horn region mainly distributed in substantia gelatinosa, NCCs in central canal mainly distributed in ependymal zone, on the contrary, NCCs in ventral, lateral horn, medullae, nucleus regions of spinal cord were comparatively less. The rank order of NCCs amount in various spinal cord segments was cervical segment greater than lumbar sacral segment greater than thoracic segment. There was no significantly difference between NCCs amount in the left and right sides, and within cervical 1–7, thoracic 1–12, lumbar 1–5, sacral segment of spinal cord in adult mice. These data collectively indicate that NPCs extensively distribute in various regions of spinal cord of adult mice, especially in substantia gelatinosa and ependymal zone. NPCs in cervical segment are abundant, NPCs in thoracic segment are the least while compared the different spinal cord segment, the NPCs in various regions of spinal cord of adult mice are a potential source of NSCs.     

Monitoring somatosensory evoked potentials in spinal cord ischemia-reperfusion injury

It remains unclear whether spinal cord ischemia-reperfusion injury caused by ischemia and other non-mechanical factors can be monitored by somatosensory evoked potentials. Therefore, we monitored spinal cord ischemia-reperfusion injury in rabbits using somatosensory evoked potential detection technology. The results showed that the somatosensory evoked potential latency was significantly prolonged and the amplitude significantly reduced until it disappeared during the period of spinal cord ischemia. After reperfusion for 30-180 minutes, the amplitude and latency began to gradually recover; at 360 minutes of reperfusion, the latency showed no significant difference compared with the pre-ischemic value, while the somatosensory evoked potential amplitude in- creased, and severe hindlimb motor dysfunctions were detected. Experimental findings suggest that changes in somatosensory evoked potentia~ ~atency can reflect the degree of spinat cord ischemic injury, while the amplitude variations are indicators of the late spinal cord reperfusion injury, which provide evidence for the assessment of limb motor function and avoid iatrogenic spinal cord injury.