急性脊髓损伤后磁刺激运动诱发电位及体感诱发电位的诊断意义

目的 研究磁刺激运动诱发电位（ｍｏｔｏｒ ｅｖｏｋｅｄ ｐｏｔｅｎｔｉａｌｓ,ＭＥＰ）对脊髓损伤（ｓｐｉｎａｌ ｃｏｒｄ ｉｎｊｕｒｉｅｓ,ＳＣＩ）后运动传导功能的诊断价值。方法 采用Ｍａｇ－２型磁刺激仪对３２例ＳＣＩ患者进行经颅磁刺激ＭＥＰ检查,分别在双侧外展拇短肌（ａｂｄｕｃｔｏｒ ｐｏｌｌｉｃｉｓ ｂｒｅｖｉｓ,ＡＰＢ）和胫前肌（ａｎｔｅｒｉｏｒ ｔｉｂｉａｌｉｓ,ＡＴ）进行记录。同时检测Ｆ     

Recording of spinal somatosensory evoked potentials for intraoperative spinal cord monitoring

The authors' experience with intradural and epidural recording of spinal somatosensory evoked potentials (SSEP's) during 26 cases of spinal surgery is described. The techniques of monitoring spinal cord function provided good quality SSEP waveforms in patients both with and without neurological deficits. The SSEP configuration and peak latencies remained stable for up to 5 hours during anesthesia with nitrous oxide, halothane, and fentanyl. Patterns of baseline SSEP's were characteristic of different spinal segments. Distortion and asymmetry of these baseline patterns were seen in several patients with spinal neoplasms. Loss of waveform components during surgery occurred with profound hypotension, overdistraction of the vertebral axis, dorsal midline myelotomy, and removal of intramedullary tumors. Persistent loss of waveform components was associated with an acquired neurological deficit. Fluctuations in the amplitude of the SSEP's were common but were not associated with postoperative neurological deficits. Spinal cord monitoring by means of SSEP recording would appear to be useful during extradural spinal surgery, but there are limitations associated with this technique during some types of intradural surgery.     

术中体感诱发电位监测在椎管内肿瘤手术中的预测价值

[目的]评价体感诱发电位(somatosensory evoked potential,SEP)术中单独监测在椎管内肿瘤切除手术中对术后脊髓功能状态的预测作用。[方法]回顾性分析42例椎管内肿瘤病例,评价单独SEP术中监测与术后患者感觉和运动功能变化的关系。[结果]42例监测对象中,术中SEP报警25例,7例发生不可逆波形改变;以感觉变化为结局,SEP敏感性67%,特异性87%;以肌力变化为结局,敏感性50%,特异性87%;以上述任一功能改变为结局,敏感性57%,特异性91%。[结论]本研究为椎管内肿瘤手术中单独使用SEP监测的预后价值提供循证医学数据,支持SEP作为替代监测方式用于椎管内肿瘤术后运动功能的评估。     

Dissociation of muscle action potentials and spinal somatosensory evoked potentials after ischemic damage of spinal cord

In patients undergoing spinal fusion and Cotrel-Dubousset instrumentation we recorded compound muscle action potentials (CMAP) from the lower limb and spinal somatosensory evoked potentials (SSEP) from the caudal epidural space after direct stimulation of rostral spinal cord via epidural electrodes. In three of 30 patients tested, the derotation maneuver altered CMAP but not SSEP. In ten dogs, we observed similar dissociation with decrease or disappearance of CMAP amplitude and unchanged SSEP after ligation of the thoracoabdominal aorta or intercostal arteries at each level. In contrast, both CMAP and SSEP were unchanged by clamping the artery at the lumbar level. This is likely due to the lack of collateral vascular flow at the thoracic cord level, the anterior cord in particular, which is mainly supplied by a single large radicular artery (Adamkiewicz artery). These findings support that the CMAP and SSEP are mediated through two independent pathways located in the anterior and posterior spinal cord, respectively. We postulate that the dissociate alteration of CMAP and SSEP by derotation maneuver is due to greater vulnerability of the anterior cord or motor tract to ischemia caused by the displacement of anterior spinal or radiculomedullary artery. Therefore, the patients requiring major derotation procedure would benefit from CMAP monitoring, which provides more sensitive measure of anterior cord function that the conventional SSEP monitoring.     

Spinal cord monitoring using intraoperative somatosensory evoked potentials for spinal trauma

BACKGROUND: Intraoperative spinal cord monitoring is commonplace in scoliosis surgery as an adjunct to evaluate functional integrity of the cord; however, limited information is available on its applicability in spinal trauma. METHODS: We investigated the efficacy of somatosensory evoked potential (SEP) recording during reconstructive procedures in 82 patients who sustained 20 cervical, 8 thoracic, 6 thoracolumbar, and 48 lumbar vertebral fractures or fractures-dislo-cations. Seventy-one patients underwent single anterior or posterior operations and 11 combined anterior-posterior procedures. Forty patients had incomplete injuries, and 42 had no preoperative neurologic deficit. SEP trace amplitude at insertion of electrode was considered as the baseline value and was compared with the lowest intraoperative signal amplitude and the amplitude at completion of operation. RESULTS: Fifty-nine patients had a depression in wave amplitude of >25% during surgery; in 25 patients, the trace fell by >50%, and in 7 cases, a >75% diminution was recorded. A loss of 50% in SEP signal amplitude showed 67% sensitivity and 71% specificity in predicting neurologic outcome. Increasing trace deterioration threshold from 50% to 60% improved specificity to 81% without compromising sensitivity. A loss of >50% in SEP amplitude occurred with significantly increased incidence during the anterior compared with the posterior spinal procedures. More than 20% recovery in signal amplitude at the conclusion of the procedure in patients with incomplete injuries was correlated with favorable neurologic function. CONCLUSION: Persistent intraoperative decrement in SEP amplitude and poor restitution at completion of surgery increase the risk for postoperative neurologic compromise.     

Intra-operative spinal cord monitoring during surgery for scoliosis using somatosensory evoked potentials

The method of intra-operative monitoring of spinal cord function by spinal somatosensory evoked potentials (SEP), as used at the Royal Alexandra Hospital for Children during surgery for scoliosis is described. Using a non-polarisable platinum spinal epidural electrode, SEP elicited by tibial and peroneal nerve stimulation in the popliteal fossa are recorded proximal to the level of spinal correction. The large amplitude and discrete waveform of the SEP enable rapid signal acquisition and easy interpretation. The spinal SEP is stable under both therapeutic hypotension and general anaesthesia. Electrophysiological monitoring has now superceded the 'wake-up' test as an index of spinal cord function during corrective surgery for scoliosis.     

Effects of spinal cord lesioning on somatosensory and neurogenic-motor evoked potentials

Somatosensory (SEPs) and neurogenic-motor evoked potentials (NMEPs) were elicited from 16 hogs and two humans before, during, and after spinal cordotomy, dorsal, or ventral root rhizotomy. Results indicated that SEPs appear to be insensitive to the effects of motor tract lesioning in hogs and humans. In every case of motor paraplegia, SEPs remained unchanged in the presence of abnormal ischiatic/sciatic NMEPs. These results suggest that SEPs are not adequately sensitive to the functional status of the motor system in hogs and humans. Ischiatic/sciatic NMEPs remained unchanged after sensory tract lesioning, suggesting that these NMEPs are insensitive to the functional status of the sensory system. These results suggest that SEPs and NMEPs should be used in combination when monitoring spinal cord function during surgeries that place that structure at risk.     

Optical imaging of somatosensory evoked potentials in the rat cerebral cortex after spinal cord injury

Optical imaging techniques have made it possible to monitor neural activity and to determine its spatiotemporal patterns. Traumatic spinal cord injury (SCI) results in both the death of gray matter neurons and the disruption of ascending and descending white matter tracts at the injury site, leading to the loss of motor and sensory functions. In this study, we monitored and compared cortical responses to the stimulation of sensory tracts in normal control and spinal-cord-injured rats using an optical imaging technique based on a voltage-sensitive dye (VSD). The sciatic nerve was stimulated with a platinum bipolar electrode, and the exposed cortical surface was stained with Di-2-ANEPEQ. Optical signals were recorded from the cerebral cortex using the MiCAM02 optical imaging system. Characteristic spatiotemporal patterns were observed in response to electrical stimulation of the sciatic nerve in normal control rats. In spinal-cord-injured rats, the optical signals were dramatically reduced compared to those of normal rats. Four weeks after SCI, however, the activation area increased in the vicinity of the focal sensory area compared to that of the rats 1 week after SCI. These results suggest that optical imaging with VSD may be useful to map functional changes after SCI.     

Prevention of spinal cord ischemia after cross-clamping of the thoracic aorta--monitoring of spinal cord perfusion pressure and somatosensory evoked potentials

The pressure difference between the mean distal aortic pressure (MDAP) and the cerebrospinal fluid pressure (CSFP), defined as the spinal cord perfusion pressure (SCPP), as well as somatosensory evoked potentials (SEP) were monitored intraoperatively to detect and prevent intraoperative spinal cord ischemia in 24 patients who required cross-clamping of the descending thoracic aorta. A temporary axillo-femoral shunt, utilizing a 10 mm woven Dacron tube graft, was employed in 10 patients and partial cardiopulmonary bypass was employed in fourteen. Ischemic SEP changes were seen in six patients. Two patients, whose SCPPs were 32 and 35 mmHg, showed a complete loss of SEP and subsequently developed paraplegia. In the other four cases, increase of the MDAP and/or withdrawal of cerebrospinal fluid were performed to increase the SCPP to more than 60 mmHg when ischemic SEP changes occurred. The SEP gradually recovered in two of these cases. The ischemic SEP changes seen in one patient, who had the longest aortic cross-clamping time, (175 minutes) returned to normal immediately after unclamping. In another case, who had a thoracoabdominal aortic aneurysm, the intercostal arteries were reimplanted since the ischemic SEP changes did not revert. These four patients recovered without any neurological deficit. In the other 18 cases without ischemic SEP change, SCPP was kept at more than 40 mmHg during aortic cross-clamping. We conclude that the SCPP should be maintained at more than 40 mmHg during aortic occlusion, and increased to more than 60 mmHg when ischemic SEP changes occur, by increasing MDAP and/or withdrawing cerebrospinal fluid in order to prevent postoperative paraplegia.     

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。     

Comparison of spinal cord evoked potentials and peripheral nerve evoked potentials by electric stimulation of the spinal cord under acute spinal cord compression in cats

STUDY DESIGN: Spinal cord evoked potentials and peripheral nerve evoked potentials after spinal cord stimulation were recorded under acute spinal cord compression in 19 cats. OBJECTIVES: To investigate the effects of acute compression upon grey matter and white matter by comparing both potentials. METHODS: We compared peripheral nerve evoked potentials, recorded at the biceps brachii branch of the musculocutaneous nerve, with descending spinal cord evoked potentials, recorded from the lumbar spinal cord, by stimulation to the C2 level, under compression of the C6 segment. RESULTS: The amplitude of both potentials decreased with increased compression. The second wave of peripheral nerve evoked potentials, which are motor fibre action potentials, decreased sooner than those of the spinal cord evoked potentials. CONCLUSION: These findings indicate that peripheral nerve evoked potentials are sensitive to acute damage of the segmented compression. This suggests that grey matter is more vulnerable to compression than white matter.     

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。     

Somatosensory evoked potentials in acute spinal cord injury: prognostic value

The somatosensory evoked potential is absent in patients with complete motor and sensory loss below the level of spinal cord injury. When spinal cord injury is incomplete, these alterations in potential may be elicited from stimulation of a nerve entering the cord below the level of injury. The presence of such potentials soon after injury, or their early return, and progressive normalization of the wave form are sensitive early indications of favorable prognosis. Indeed, recovery of the somatosensory evoked potentials frequently precedes major clinical improvement and may occur in advance of clinical recovery or posterior column function.     

Acute changes in somatosensory evoked potentials following graded experimental spinal cord compression

Amplitude and latency of cortical somatosensory potentials evoked in cats by peripheral nerve stimulation were measured before, during, and for 5 hours after injury of spinal cord segment L-7 by a predetermined degree and duration of compression. An amplitude decrease, slight and transitory, was first observed after compression reduced the segmental cross section by 60%. After an 80% compression, amplitude reduction was initially larger and lasted longer, but recovered 2.5 hours after injury to a level that did not differ statistically from control values. After total (100%) compression, evoked responses disappeared abruptly and did not recover significantly. Latency was unaltered at all degrees of compression. Structural damage increased with the degree of compression. In this model, evoked potential changes neither reflect nor predict the magnitude of acute incomplete spinal cord injury.     

体感诱发电位用于脊柱手术中脊髓功能的监测

目的评估体感诱发电位(SEP)用于脊柱手术中脊髓监测的可行性，以及皮质体感诱发电位(CSEP)与皮质下体感诱发电位(Sub—CSEP)监测的适应证。方法42例脊柱手术患者，年龄6～68岁，咪唑安定、丙泊酚及维库溴铵静脉诱导，安氟醚吸入维持麻醉．术中均应用CSEP和Sub—CSEP监测脊髓功能。结果CSEP受麻醉影响较大，Sub—CSEP波形稳定，全组7例诱发电位出现异常，其中3例与临床相符，4例为假阳性，无假阴性发生，准确率为90．5％。结论CSEP适于麻醉深度的监测，Sub—CSEP是脊柱手术中脊髓功能监测较为理想的方法。     

Effect of epidural bupivacaine on somatosensory evoked potentials after dermatomal stimulation

The effect of lumbar epidural analgesia with plain bupivacaine, 0.5%, on early (less than 0.5 sec) somatosensory evoked potentials (SEP) to electrical stimulation of the T-10, L-1, and S-1 dermatomes and the posterior tibial nerve was examined in eight patients. A decrease of the cortical amplitude and an increase in latency were seen, most pronounced at the L-1 level, but with only minor effect on the S-1 dermatome. No correlation was found between segmental level of analgesia and decrease in amplitude of the evoked potentials. Thus despite clinically adequate surgical anesthesia, the neural pathways as assessed by SEP were incompletely blocked except at the L1 dermatome near the epidural injection site.     

Utilization of somatosensory evoked cortical potentials in spinal cord injury. Prognostic limitations

The prognostic value of somatosensory evoked cortical potentials (SECP) for clinical recovery was studied in 71 patients with complete (28) and incomplete (43) spinal injuries. While the absence of an SECP was associated with no clinical recovery, the presence of an SECP was of little value in predicting the clinical state at the time of examination or the potential for recovery.     

SEP与MEP对脊髓功能的监测作用

随着影像学技术的快速发展,磁共振成像可准确提供更多的信息,直接评价脊髓损伤范围和程度,从而提高了脊髓型颈椎病(CSM)确诊率。但颈椎退变引起脊髓受压并不一定伴随脊髓病变,且大部分MRI显示椎管狭窄的患者既无脊髓损伤的临床症状也无电生理的改变[1]。王新家等[2]发现脊髓电生理特性的改变与病理变化以及功能变化相一致;并发现躯体感觉诱发电位(SEP)与运动诱发电位(MEP)的潜伏期与椎管侵占率、CBS功能评分呈正相关。Maertens等[3]发现MEP与SEP在脊髓型颈椎病的异常率分别为93%和73%。因此MEP与SEP是比影像学诊断和临床检查脊…