Intraoperative neurophysiological monitoring in spinal surgery

Recently, many surgeons have been using intraoperative neurophysiological monitoring(IOM) in spinal surgery to reduce the incidence of postoperative neurological complications, including level of the spinal cord, cauda equina and nerve root. Several established technologies are available and combined motor and somatosensory evoked potentials are considered mandatory for practical and successful IOM. Spinal cord evoked potentials are elicited compound potentials recorded over the spinal cord. Electrical stimulation is provoked on the dorsal spinal cord from an epidural electrode. Somatosensory evoked potentials assess the functional integrity of sensory pathways from the peripheral nerve through the dorsal column and to the sensory cortex. For identification of the physiological midline, the dorsal column mapping technique can be used. It is helpful for reducing the postoperative morbidity associated with dorsal column dysfunction when distortion of the normal spinal cord anatomy caused by an intramedullary cord lesion results in confusion in localizing the midline for the myelotomy. Motor evoked potentials(MEPs) consist of spinal, neurogenic and muscle MEPs. MEPs allow selective and specific assessment of the functional integrity of descending motor pathways, from the motor cortex to peripheral muscles. Spinal surgeons should understand the concept of the monitoring techniques and interpret monitoring records adequately to use IOM for the decision making during the surgery for safe surgery and a favorable surgical outcome.     

Intraoperative Monitoring Using Somatosensory Evoked Potentials

Objective: To provide an educational service to the intraoperative neurophysiologist community by publishing a position statement by the American Society of Neurophysiological Monitoring on the recommended appropriate and correct use of somatosensory evoked potentials as an intraoperative neurophysiological monitoring tool to protect patient well-being during surgery. This position statement presents the somatosensory evoked potential utilization basis, relevant anatomy, patient preparation, important systemic factors, anesthesia considerations, safety and technical considerations, documentation requirements, neurophysiologist credentials and staffing practice patterns, and monitoring applications for protecting brain, spinal nerve root, peripheral nerve, plexus and spinal cord function. In conclusion, a summary of major recommendations regarding the use of somatosensory evoked potentials in intraoperative neurophysiological monitoring is presented.     

Intraoperative Applications Of The H-Reflex And F-Response: A Tutorial

Traditional intraoperative monitoring of spinal cord function involves the use of three techniques: 1. Orthodromic ascending somatosensory evoked potentials (SSEPs) and 2. antIDromic descending neurogenic somatosensory evoked potentials (DNSSEPs) monitor long-tract sensory function. SSEPs and DNSSEPs do not monitor interneuronal gray matter function. 3. Transcranial motor evoked potentials (TMEPs) monitor descending long-tract motor function and measure interneuronal gray matter function by activating motor neurons. TMEPs activate from 4–5% of the motor neuron pool. When using TMEPs 95–96% of the motor spinal cord systems activating the motor neurons are not monitored. Our ability to interact with our environment involves not only intact sensation and strength, but also complex coordinated motor behavior. Complex coordinated motor behavior is controlled by groups of electrically-coupled spinal cord central pattern generators (CPGs). The components of CPGs are: descending and propriospinal systems, peripheral input, and segmental interneurons. The point-of-control is the level of excitation of interneurons, which is determined by the integrated activity of the other components. Spinal cord injury (SCI) changes segmental reflex gain by uncoupling these components. Changes in gain are detected by recordings from muscles. SSEPs, DNSSEPs and TMEPs provIDe limited information about the status of CPGs. H-reflexes measure the function of from 20–100% of the motor neuron pool. F-responses measure the function of from 1–5% of the motor neuron pool. H-reflexes and F-responses provIDe information about the degree of coupling between CPG components. Recording H-reflexes and F-responses together with SSEPs and TMEPs not only monitors spinal cord long-tract function, but also provIDes a multiple-systems approach that monitors those spinal cord systems that are responsible for the control of complex coordinated motor behavior. The objective of this paper is to describe how H-reflexes and F-responses can be used to monitor complex coordinated motor behavior.     

Monitoring des potentiels évoqués moteurs neurogènes lors de la chirurgie correctrice de la scoliose

Neurogenic motor evoked potentials in association with somatosensory evoked potentials were used to assess the functional integrity of spinal cord during scoliosis surgery. They were elicited by a spinal electrical stimulation and recorded from peripheral nerves in 23 patients. Reproductible responses were obtained in every patient under anesthesia. In three patients a modification of neurogenic motor evoked responses occurred: in one case, loss of potentials associated with a postoperative tetraplegia; in two cases, transient amplitude decrease without major neurological complications. Although the real origin of these potentials remains to be determined (possible involvement of antidromic sensory pathway conduction), this technique seems to be easy to perform, reproductible, fast and sensible for assessment of spinal cord during scoliosis surgery.     

精确显微技术条件下构建脊髓损伤模型的脊髓离断状态

背景：弥散张量成像是一项常用于大脑临床研究中的技术,但很少用于脊髓损伤的诊断或预后。 目的：采用显微技术建立大鼠脊髓损伤模型,用弥散张量成像技术评测脊髓离断情况,这为进一步的干预治疗提供良好的动物损伤模型。 方法：健康SD大鼠12只在精确显微技术下制备脊髓损伤模型,6只假手术组作为对照。用核磁弥散张量成像技术观察实验组大鼠造模后脊髓离断情况,用运动诱发电位和感觉诱发电位检测大鼠神经电生理改变情况,利用斜坡实验和BBB评分评价大鼠造模后的神经功能的变化。 结果与结论：实验组大鼠苏醒后双下肢全瘫、尾巴不能摆动、尿潴留;弥散张量成像图像显示其T 10段脊髓完全离断;运动及感觉诱发电位波形较对照组均未引出;造模后1 d、造模后1,2,4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。说明精确显微技术能成功构建大鼠脊髓损伤模型,并且在弥散张量成像图像上清晰可见T 10段脊髓完全离断。     

脊髓损伤实验动物模型评价：诱发电位的应用与研究进展

背景：随着工业社会的发展和交通的发达,脊髓损伤的发病率也逐年升高。脊髓损伤的辅助检查手段除了影像学以外,神经电生理技术的应用也越来越广泛。其中诱发电位因其准确率高、操作简便应用较多。目的：综述躯体感觉诱发电位及运动诱发电位在兔脊髓损伤中的应用情况。方法：通过检索中国知网、PubMed数据库,输入“脊髓损伤,诱发电位,动物模型,Spinal cord injury,evoked potential,animal model”等关键词进行检索,最终纳入文章33篇进入结果分析。结果与结论：详细阐述了体感诱发电位与运动诱发电位在动物实验中的操作方法、波形分析、应用价值、影响因素及诱发电位与动物预后功能评价。其中体感诱发电位是反应脊髓后索功能的很好指标,操作简便,对检测患者感觉功能的变化有很好的指导作用。运动诱发电位能为各种脊髓疾病提供敏感而精确的诊断,尤其在患者治疗和康复期间可作为重要的评估手段。而两者连用效果更精确。     

Electrophysiological evaluation of the patient with acute spinal cord injury

This article reviews basic principles, equipment and techniques, and clinical applications of electrophysiologic monitoring in patients with spinal cord injuries. Four groups of electrophysiologic measurements are considered: Somatosensory evoked potentials (SEPs); motor evoked potentials (MEPs); electromyography (EMG) and nerve conduction studies; and late responses, including H reflex, M response, and F wave. Reports of SEP recordings in spinal cord injury, as drawn from the literature, are tabulated in detail.     

Neurophysiological Identification of Position-Induced Neurologic Injury During Anterior Cervical Spine Surgery

This study was a retrospective review of 3,806 patients who underwent anterior cervical spine surgery with multi-modality neurophysiological monitoring consisting of transcranial electric motor evoked potentials, somatosensory evoked potentials and spontaneous electromyography between 1999–2003. The objectives of this study were twofold: (1) to evaluate the role of transcranial electric motor evoked potential tceMEP and ulnar nerve somatosensory evoked potential (SSEP) monitoring for identifying impending position-related stretch brachial plexopathy, peripheral nerve entrapment/compression or spinal cord compression and (2) to estimate the point-prevalence of impending neurologic injury secondary to surgical positioning effects. Sixty-nine of 3,806 patients (1.8% showed intraoperative evidence of impending neurologic injury secondary to positioning, prompting interventional repositioning of the patient. The brachial plexus was the site of evolving injury in 65% of these 69 cases. Impending brachial plexopathy was most commonly noted immediately following shoulder taping and the application of counter-traction. Brachial plexus stretch upon neck extension for optimal surgical access and visualization was second in frequency-of-occurrence. Evolving traction injury to the ulnar nerve attributed to tightly-wrapped or malpositioned arms was observed in 16% of alerted cases, whereas evolving spinal cord injury following neck extension accounted for an additional 19%. This study highlights the role of tceMEP and ulnar nerve SSEP monitoring for detecting emerging peripheral nerve injury secondary to positioning in preparation for and during anterior cervical spine surgery.     

Nondepolarizing neuromuscular blockade does not alter sensory evoked potentials

Objective. The objective of this study was to determine whether changes in nondepolarizing neuromuscular blockade (NMB) alter the latency or amplitude of visual, brain stem auditory, or median nerve somatosensory evoked potentials.Methods. Ten adult cynomologousMacaca fascicularis monkeys were studied during continuous ketamine anesthesia infusion. The NMB was incrementally adjusted between no block and complete block using infusions of vecuronium or atracurium. The NMB was measured by observing the mechanical response of the hand muscles to train-of-four stimulation of the median nerve and by quantification of the peak-to-peak electromyographic activity of the thenar muscles to supramaximal median nerve stimulation. The following variables were measured: the latencies of the three major peaks of the brain stem auditory evoked potential, the latency and amplitude of the cortical visual evoked potential, the latency of the spinal cord response, and the latency and amplitude of the cortical median nerve somatosensory evoked response.Results. No statistically significant changes were observed for any evoked response variable measured at any degree of NMB when compared with values obtained in the unblocked control state.Conclusions. The results suggest that fluctuating degrees of NMB may contribute little to changes in these evoked potentials during intraoperative monitoring, given the testing parameters used.This project was partially funded by gifts from Burrows-Wellcome, Research Triangle Park, NC, and Organon, Inc, West Orange, NJ.     

持续脊髓压迫与神经功能恢复的相关性研究

目的:探讨组织压迫时间与脊髓损伤程度及神经功能恢复的关系。方法:20只犬随机分为两组,应用水囊压迫造成脊髓损伤,分别压迫30min和180min。在压迫期间和去除压迫后不同时间监测躯体感觉诱发电位(SSEP)和脊髓灰质血流量。去除压迫后不同时间进行后肢运动功能评价,去除压迫后28天处死动物进行组织学评价。结果:脊髓压迫期间SSEP波幅迅速下降并消失。30min组去除压迫后SSEP波幅缓慢恢复,180min组始终无恢复(P<0.05)。加压后两组血流量迅速下降,去除压迫即刻两组血流量差异有显著性(P<0.05)。后肢运动功能检查30min组恢复较快,180min组较慢(P<0.05)。180min组较30min组组织损伤重(P<0.05)。结论:脊髓压迫时间越长组织破坏程度越重,神经功能恢复时间越长,效果越差。脊髓受压后尽早行减压术有利于神经功能恢复。     

Canal lombaire étroit, explorations neurophysiologiques: électromyographie et potentiels évoqués

A number of electrophysiological tests are used in the diagnosis of nerve root defects. Practitioners must select the most appropriate tests based on the clinical presentation of each case. Needle EMG is the most reliable method because of its high sensitivity and specificity, and it is the only technique capable of demonstrating the clinical course of lesions over time. Proximal conduction is assessed by examining late responses (H-reflex and F-wave). If negative or inconsistent, motor evoked potentials and dermatomal somatosensory evoked potentials can reveal the extent of the nerve root lesion. In the case of lumbar spinal stenosis, spinal function is assessed using somatosensory evoked potentials.     

大鼠脊髓半横切损伤动物模型的建立与神经功能评价

目的:建立一种稳定可靠、操作简单的脊髓半横切损伤动物模型,并对其神经功能进行初步评价。方法:将18只SD大鼠随机分为正常对照、假手术组和T10段脊髓半切组。术后不同时间点分别采用BBB运动功能评分及足迹法检测其脊髓功能的变化情况,同时检测其运动诱发电位(MEP)和体感诱发电位(SEP),记录N1及P1波潜伏期。结果:损伤组BBB运动功能评分显著低于正常对照及假手术组(P<0.01),且足迹法检测结果也存在统计学意义(P<0.01)。神经电生理检测结果表明,SEP和MEP潜伏期均具有统计学意义(P<0.01)。结论:成功制备了大鼠脊髓半切损伤动物模型,为研究脊髓损伤相关机制及药物治疗奠定了基础。     

后路一期全脊椎切除并脊柱重建术中高发风险因素分析及护理对策

总结和分析了13例脊柱恶性肿瘤患者行后路一期全脊椎切除并钛网植骨、椎弓根钉系统重建脊柱手术的术中高发风险因素和护理配合要点.术中容易引起脊髓神经损伤、椎旁静脉丛破裂大出血、肿瘤细胞局部播散种植等风险,采取的护理配合措施包括改良手术器械、联合诱发电位监护脊髓功能、控制性降压、严格无瘤技术操作等.本组手术过程顺利,未发生医源性脊髓损伤和重要血管、脏器损伤等并发症.术后随访3～13个月,近期疗效满意,未发现肿瘤局部复发.     

电刺激对大鼠脊髓损伤后神经生长因子表达的影响

目的探讨电刺激对成年大鼠脊髓损伤后脊髓灰质神经元神经生长因子(NGF)表达的影响。方法健康成年SD大鼠72只,随机分为正常组、损伤对照组、电刺激组。采用Allen法,将后两组复制为脊髓T9损伤模型。术后对电刺激组大鼠进行电刺激治疗7 d。于术后l d、3 d、5 d、7 d对3组进行BBB评分,免疫组化和Western blot法检测NGF的表达情况。结果 BBB评分结果显示大鼠脊髓损伤后有自行恢复功能,从第5天开始电刺激组与损伤对照组有显著性差异(P<0.05)。脊髓损伤后,电刺激组和损伤对照组NGF表达均持续升高(P<0.05),电刺激组表达多于损伤对照组(P<0.05)。结论脊髓损伤后电刺激诱导损伤区NGF表达,从而创造了有利于神经再生的微环境。     

Concomitant hypertension,bradycardia, and loss of transcranial electric motor evoked potentials during pedicle hook removal: report of a case

Neurophysiologic monitors in the form of transcranial electric motor evoked potentials (tceMEPs) and somatosensory evoked potentials (SSEPs) have become widely used modalities to monitor spinal cord function during major orthopedic spine procedures. In combination with invasive and non-invasive clinical monitoring and an anesthesia information management system (AIMS), we promptly recognized an acute change in hemodynamic and neurophysiologic parameters, managed intraoperative spinal cord contusion, and successfully minimized iatrogenic injury to the spinal cord during corrective spine surgery.     

Intraoperative monitoring of sensory evoked potentials may be neither a proven nor an indicated technique

Excluding specific neurosurgical indications for cortical localization or peripheral nerve surgery, the use of sensory evoked potentials as a monitor in the operating room should be controversial at this time. Whether appropriate or not, legal and medical forces have largely established the use of somatosensory evoked potential monitoring as a standard during procedures that threaten the integrity of the spinal cord. The author believes that such monitoring should not replace the use of a wake-up test during these procedures because of the recognized possible occurrence of false negative results (i.e., normal evoked potentials despite abnormal spinal cord function). Another apparent established practice is monitoring of brainstem auditory evoked potentials to recognize the onset of disturbance in the auditory system. It has not been established that other recommended evoked potential monitoring practices, such as somatosensory evoked potential monitoring for such purposes as recognizing cerebral ischemia, or brainstem auditory evoked potential monitoring for recognizing untoward medullary stimulation, are as good as or better for these purposes than currently recognized and simpler monitors.     

自体富血小板血浆对大鼠脊髓损伤后神经功能的影响

目的 研究自体富血小板血浆对大鼠脊髓损伤后神经功能恢复的影响。方法 SD大鼠30只,随机分为PRP组(A组)和对照组(B组)各15只。采用改良Nystr?m法后路压迫大鼠胸段脊髓模型,A组予自体富血小板血浆灌注于损伤脊髓处,B组予自体血浆灌注于损伤脊髓处。术后第3、7、14天采用斜板试验和BBB运动功能评分观察大鼠后肢运动功能恢复情况、检测体感诱发单位(SSEP)检测神经传导功能。结果 大鼠脊髓损伤后7、14天,A组后肢运动功能评分明显高于B组,两者间差别有统计学意义(p<0.05)。SSEP潜伏期及波幅值变化：术后14天A组潜伏期12.37±1.689ms、波幅0.54±0.056mv；B组潜伏期14.14±1.553ms、波幅0.32±0.031mv,两组差别有统计学意义(P<0.05)。结论 自体富血小板血浆能促进大鼠神经功能的早期恢复。     

Compound action potentials recorded in the human spinal cord during neurostimulation for pain relief

Electrical stimulation of the spinal cord provides effective pain relief to hundreds of thousands of chronic neuropathic pain sufferers. The therapy involves implantation of an electrode array into the epidural space of the subject and then stimulation of the dorsal column with electrical pulses. The stimulation depolarises axons and generates propagating action potentials that interfere with the perception of pain. Despite the long-term clinical experience with spinal cord stimulation, the mechanism of action is not understood, and no direct evidence of the properties of neurons being stimulated has been presented. Here we report novel measurements of evoked compound action potentials from the spinal cords of patients undergoing stimulation for pain relief. The results reveal that Aβ sensory nerve fibres are recruited at therapeutic stimulation levels and the Aβ potential amplitude correlates with the degree of coverage of the painful area. Aβ-evoked responses are not measurable below a threshold stimulation level, and their amplitude increases with increasing stimulation current. At high currents, additional late responses are observed. Our results contribute towards efforts to define the mechanism of spinal cord stimulation. The minimally invasive recording technique we have developed provides data previously obtained only through microelectrode techniques in spinal cords of animals. Our observations also allow the development of systems that use neuronal recording in a feedback loop to control neurostimulation on a continuous basis and deliver more effective pain relief. This is one of numerous benefits that in vivo electrophysiological recording can bring to a broad range of neuromodulation therapies.     

Usefulness of epidurally evoked cortical potential monitoring during cervicomedullary glioma surgery

This report describes a patient with an intramedullary ependymoma at the region of the cervicomedullary junction in whom there was an abolition of somatosensory evoked potentials following median nerve stimulation. During intraoperative monitoring of cortical potentials elicited by epidural cervical cord stimulation, the tumor was removed. Posterior epidural stimulation appeared to depolarize more ascending fibers than did stimulation of a single peripheral nerve. We recommend that, in cases of operations in this vital area, epidurally evoked cortical potentials be monitored intraoperatively.     

Spinal NMDA-receptor dependent amplification of nociceptive transmission to rat primary somatosensory cortex (SI)

The role of NMDA mechanisms in spinal pathways mediating acute nociceptive input to the somatosensory cortex is not clear. In this study, the effect of NMDA-antagonists on nociceptive C fibre transmission to the primary somatosensory cortex (SI) was investigated. Cortical field potentials evoked by CO(2)-laser stimulation of the skin were recorded in the halothane/nitrous oxide anaesthetized rat. The SI nociceptive evoked potential (EP) amplitudes were dependent on the frequency of noxious heat stimulation. The amplitudes of SI potentials evoked by CO(2)-laser pulses (duration 15-20 ms, stimulation energy 21-28 mJ/mm(2)) delivered at a frequency of 0.1 Hz were approximately 40% of the amplitudes of potentials evoked by 1.0 Hz stimulation. After intrathecal lumbar application of either of the NMDA-antagonists CPP or MK-801, the amplitudes of nociceptive SI potentials, evoked by 1.0 Hz stimulation of the contralateral hindpaw, were reduced to approximately 40% of controls. By contrast, field potentials evoked by 0.1 Hz stimulation of the hindpaw were unaffected by MK-801. SI potentials evoked by 1.0 Hz stimulation of the contralateral forepaw did not change after lumbar application of CPP or MK-801, indicating that the depression of hindpaw EPs was due to a segmental effect in the spinal cord. It is concluded that spinal NMDA-receptor mechanisms amplify the acute transmission of nociceptive C fiber input to SI in a frequency-dependent way.