Combined motor and somatosensory evoked potentials for intraoperative monitoring: intra- and postoperative data in a series of 69 operations

The primary objective of neurophysiologic monitoring during surgery is to avoid permanent neurological injury resulting from surgical manipulation. To prevent motor deficits, either somatosensory (SSEP) or transcranial motor evoked potentials (MEP) are applied. This prospective study was conducted to evaluate if the combined use of SSEP and MEP might be beneficial. Combined SSEP/MEP monitoring was attempted in 100 consecutive procedures, including intracranial and spinal operations. Repetitive transcranial electric motor cortex stimulation was used to elicit MEP from muscles of the upper and lower limb. Stimulation of the tibial and median nerves was performed to record SSEP. Critical SSEP/MEP changes were defined as decreases in amplitude of more than 50% or increases in latency of more than 10% of baseline values. The operation was paused or the surgical strategy was modified in every case of SSEP/MEP changes. Combined SSEP/MEP monitoring was possible in 69 out of 100 operations. In 49 of the 69 operations (71%), SSEP/ MEP were stable, and the patients remained neurologically intact. Critical SSEP/ MEP changes were seen in six operations. Critical MEP changes with stable SSEP occurred in 12 operations. Overall, critical MEP changes were recorded in 18 operations (26%). In 12 of the 18 operations, MEP recovered to some extent after modification of the surgical strategy, and the patients either showed no (n = 10) or only a transient motor deficit (n = 2). In the remaining six operations, MEP did not recover and the patients either had a transient (n = 3) or a permanent (n = 3) motor deficit. Critical SSEP changes with stable MEP were observed in two operations; both patients did not show a new motor deficit. Our data again confirm that MEP monitoring is superior to SSEP monitoring in detecting impending impairment of the functional integrity of cerebral and spinal cord motor pathways during surgery. Detection of MEP changes and adjustment of the surgical strategy might allow to prevent irreversible pyramidal tract damage. Stable SSEP/MEP recordings reassure the surgeon that motor function is still intact and surgery can be continued safely. The combined SSEP/ MEP monitoring becomes advantageous, if one modality is not recordable.     

The use of somtaosensory evoked potential (SSEP) and motor evoked potential (MEP) monitoring in a patient with Brugada syndrome

IntroductionWe report on the use of Somastosensory Evoked Potential (SSEP) and Motor Evoked Potential (MEP) monitoring in a patient with Brugada syndrome.ObjectivesThe concern in this case was that the amount of current/voltage generated by SSEP/MEP might trigger arrhythmias in a patient with underlying Brugada syndrome.MethodsA 42 year-old male patient with Brugada syndrome underwent excision of an intramedullary tumour with the use of SSEP and MEP monitoring. Preoperatively, he was not on antiarrhythmic medication, nor had an Implantable Cardioverter Device (ICD) in-situ.ResultsThe patient remained stable & in sinus rhythm throughout the operation and was successfully extubated postoperatively.ConclusionThis case report indicates that SSEP/MEP monitoring may be used in patients with Brugada syndrome.     

Somatosensory-evoked potential monitoring during instrumented scoliosis corrective procedures: validity revisited

BackgroundIntraoperative monitoring (IOM) using somatosensory-evoked potentials (SSEPs) plays an important role in reducing iatrogenic neurologic deficits during corrective pediatric idiopathic procedures for scoliosis. However, for unknown reasons, recent reports have cited that the sensitivity of SSEPs to detect neurologic deficits has decreased, in some to be less than 50%. This current trend, which is coincident with the addition of transcranial motor-evoked potentials, is surprising given that SSEPs are robust, reproducible responses that were previously shown to have sensitivity and specificity of >90%.PurposeOur primary aim was to assess whether SSEPs alone can detect impending neurologic deficits with similar sensitivity and specificity as originally reported. Our secondary aim was to estimate the potential predictive value of adding transcranial motor-evoked potentials to SSEP monitoring in idiopathic scoliosis procedures.DesignThis was a retrospective review to analyze the efficacy of SSEP monitoring in the group of pediatric instrumented scoliosis fusion cases.Patient sampleWe retrospectively reviewed all consecutive cases of patients who underwent idiopathic scoliosis surgery between 1999 and 2009 at Children’s Hospital of Pittsburgh. We identified 477 patients who had the surgery with SSEP monitoring alone. Exclusion criteria included any patients with neuromuscular disorders or unreliable SSEP monitoring. Patients who had incomplete neurophysiology data or incomplete postoperative records were also excluded.Outcome measuresMajor outcomes measured were clinically significant postoperative sensory or motor deficits, as well as significant intraoperative SSEP changes.MethodsContinuous interleaved upper- and lower-extremity SSEPs were obtained throughout the duration of all procedures. We considered a persistent 50% reduction in primary somatosensory cortical amplitude or a prolongation of response latency by >10% from baseline to be significant. Persistent changes represent significant deviation in SSEP amplitude or latency in more than two consecutive averaged trials. Patients were classified into one of four categories with respect to SSEP monitoring: true positive, false positive, true negative, and false negative. The sensitivity, specificity, positive predictive value, and negative predictive value were then calculated accordingly.ResultsOur review of 477 idiopathic scoliosis surgeries monitored using SSEPs alone revealed a new deficit rate of 0.63% with no cases of permanent injury. Sensitivity = 95.0%, specificity = 99.8%, positive predictive value = 95%, negative predictive value = 99.8%. Using evidence-based epidemiologic measures, we calculated that the number needed to treat was 1,587 patients for one intervention to be performed that would have been missed by SSEP monitoring alone. In addition, the number needed to harm, which represents the increase in false positives with the addition of transcranial electrical motor-evoked potentials, was 200.ConclusionSSEP monitoring alone during idiopathic scoliosis continues to be a highly reliable method for the detection and prevention of iatrogenic injury. Our results confirm the high sensitivity and specificity of SSEP monitoring alone published in earlier literature. As such, we suggest the continued use of SSEP alone in idiopathic scoliosis surgeries. At this time we do not believe there are sufficient data to support the addition of MEP monitoring, although more studies and revised criteria for the use of MEP may provide added value for its use in the future.     

Intra‐Operative Neurophysiological Monitoring in Patients with Intraspinal Abnormalities Undergoing Posterior Spinal Fusion

ObjectiveTo analyze the intraoperative neurophysiological monitoring (IONM) data of patients with intraspinal abnormalities undergoing posterior spinal fusion and to determine how intraspinal abnormalities influence IONM results.MethodsPatients with severe kyphoscoliosis and intraspinal abnormalities who underwent posterior spinal correction and fusion between September 2015 and January 2019 were retrospectively reviewed. Candidate intraspinal abnormalities included Chiari malformation, syringomyelia, split cord malformation, and tethered cord syndrome. Total intravenous anesthesia was administered, and no muscle relaxant or inhalation anesthesia was used for maintenance. IONM data, including somatosensory evoked potentials (SSEP) and motor evoked potentials (MEP), were recorded. The P37 and N50 latencies and amplitude were recorded for SSEP, whereas only the amplitude was recorded for MEP. The possible high‐risk factors for abnormal IONM results were analyzed.ResultsThe current study included 87 patients (40 men, 47 women) with an average age of 20.2 ± 10.4 years. The etiologies were neuromuscular in 45 patients, idiopathic in four, and congenital in 38. A total of 136 intraspinal abnormalities were detected, including Chiari malformation in 33 patients, syringomyelia in 55, split‐cord malformation in 25, and tethered cord syndrome in 23. Forty patients had one intraspinal abnormality, whereas 47 patients had two or three intraspinal abnormalities. The monitorabilities were 87.4% and 97.7% for the SSEP and MEP, respectively. SSEP alerts were reported in five patients and MEP alerts in four patients, and new neurological deficits were observed in three patients postoperatively. The sensitivity and specificity were 100% and 97.3% for SSEP, and 100% and 98.8% for MEP, respectively. A significant difference in MEP amplitude between the concave and convex sides was observed, while significantly higher SSEP latency was observed on the concave side in patients with preoperative neurological deficits. There were 52 (59.8%) patients with abnormal IONM data. Preoperative neurological deficits (χ² = 7.715, p = 0.005) and more than one intraspinal abnormality (χ² = 9.186, p = 0.004) indicated a higher risk of abnormal IONM data.ConclusionsIONM can be effectively used in patients with intraspinal abnormalities who undergo posterior spinal fusion. Patients with preoperative neurological deficits and more than one intraspinal abnormality have a higher risk of abnormal IONM monitoring.     

经颅刺激运动诱发电位联合体感诱发电位监测在特发性脊柱侧凸矫形手术中应用的研究

背景：特发性脊柱侧凸手术治疗中神经功能障碍是最应受到关注的并发症,术中神经功能监测可帮助早期发现可能的神经功能损伤。目的：分析联合应用经颅刺激运动诱发电位（TcMEP）和体感诱发电位（SEP）的多模式术中神经功能监测在特发性脊柱侧凸矫形手术中对预测医源性神经功能损害的作用。方法：在特发性脊柱侧凸矫形手术中,运用TcMEP和（或）SEP进行神经功能监测。MEP监测采用经颅刺激C3、C4,记录外周肌源性MEP,SEP监测采用刺激双侧胫后神经,记录电极采用Cz—CPz。阳性诊断标准：与基线相比,MEP波幅下降75％,SEP波幅下降50％。结果：112例特发性脊柱侧凸患者中,联合MEP、SEP监测的检出率为100％。MEP监测阳性6例,假阳性1例。1例出现一过性神经功能障碍。MEP的监测敏感性为100％,特异性为99％;SEP监测敏感性50％,特异性为100％;联合MEP、SEP监测的敏感性、特异性均为100％。结论：特发性脊柱侧凸矫形手术中MEP＋SEP的术中神经功能监测可提高监测敏感性及特异性,可预测术中神经功能损伤事件的发生。MEP是多模式监测的基础,SEP是重要补充。单独应用MEP监测在特发性脊柱侧凸患者手术中有应用前景。     

Operationsstrategieänderung durch somatosensorisch evozierte Potenziale (SSEP) bei der Karotis-TEA

The selective use of an intraluminal shunt during carotid endarterectomy (CEA) requires the reliable intraoperative monitoring of the cerebral blood flow. An intraoperative method for this monitoring is the registration of somatosensory evoked potentials (SSEP). Based on the following case we also want to emphasize the importance of intraoperative monitoring also during CEA with routine shunt placement. A 50-year-old male patient with an asymptomatic, 90% internal carotid artery (ICA) stenosis on the right side was admitted to our clinic. We performed a CEA under general anaesthesia and SSEP monitoring without shunt placement. During the operative procedure no technical complications occurred. After reconstruction of the ICA we performed an angiographic control of the endarterectomy site. During this control the amplitude of SSEPs decreased by 100% of the preclamping value. We therefore carried out another angiographic control of the distal ICA. This angiography showed a dissection of the ICA at the skull base. To examine sufficient collateral perfusion the general anaesthesia was interrupted for a few minutes after which the ICA was clamped. On being requested the patient was able to move his left arm and leg. In the presence of a sufficient collateral perfusion we excluded an embolic source by ligation of the ICA. The decrease of SSEPs occurred at a time when a routinely placed shunt would have already been removed. In this case it was an important clue to an embolic source. Therefore SSEP monitoring seems to be beneficial, even if an indwelling shunt is used routinely.     

Assessment of Early Brain Damage in Carotid Endarterectomy: Evaluation of S-100B Serum Levels and Somatosensory Evoked Potentials in a Pilot Study

The release of the neuronal protein S-100B into the circulation has been suggested as an early indication of cellular brain damage. The objective of this prospective pilot study was to determine S-100B serum levels in patients undergoing cross-clamping during carotid endarterectomy (CEA) and to correlate the results with the monitoring of somatosensory evoked potentials (SSEP) and the neurological short-term outcome. Arterial blood samples of 21 patients were drawn before oral intubation, cross-clamping, and unclamping, as well as before extubation and 6 hours later. Recording of SSEP was obtained during carotid occlusion and reperfusion. If loss of SSEP appeared, cerebral ischemia was assumed and an intraluminal shunt was placed. During cross-clamping, S-100B serum levels of 14 patients increased significantly from 0.05 ng/ml to 0.21 ng/ml, but returned to baseline levels after unclamping. In 5 cases, loss of SSEP amplitudes occurred but was reversed by the shunt insertion. No significant differences of S-100B serum values, neurological examination, and carotid duplex surveillance became obvious in this group when compared to the patients with undisturbed SSEP. However, 2 patients with complete disappearance of postcentral SSEP components suffered from neurological deficits in the postoperative period. S-100B serum levels remained highly elevated 6 hours after extubation (0.78 ng/ml and 0.41 ng/ml) compared to the baseline values (0.15 ng/ml and 0.07 ng/ml). During CEA a transitory increase of the S-100B serum levels appears to present an impairment of the blood–brain barrier integrity without any neurological deficits. In contrast, persistently elevated S-100B serum levels seem to be associated with transient loss of SSEP and development of neurological deficits.     

Monitoring of somatosensory evoked potentials during temporary arterial occlusion in cerebral aneurysm surgery

Somatosensory evoked potentials (SSEP) have been used during cerebral aneurysm surgery to monitor the integrity of neural pathways. The purpose of this study was to evaluate the effectiveness of SSEP monitoring as a predictor of neurological outcome during temporary arterial occlusion. In a series of 157 patients monitored, 97 patients had temporary occlusion of the feeding artery. Twenty-three patients developed a SSEP change during temporary occlusion, 15 reversible (recovery of the change after the release of occlusion), and 8 persistent (no recovery) changes. A persistent change predicted a postoperative neurological deficit in each case, whereas, of the 15 patients with reversible changes, only 5 had postoperative deficits. Seventy-four patients had no change on SSEP monitoring but 10 patients did have new neurological deficits postoperatively. The false positive rate was 43% and the false negative rate was 14%. SSEP was a better predictor of neurological deficits in patients with aneurysms of the carotid circulation than of the vertebral-basilar arteries. Despite these limitations, we find SSEP monitoring useful during temporary occlusion in cerebral aneurysm surgery.     

术中无肌松全静脉麻醉用于联合神经电生理监护脊柱手术的可行性

［摘要］ 目的 比较全静脉麻醉下术中使用或不使用肌松药对脊柱手术中联合神经电生理监测结果的影响,探讨安全有效的神经电生理监测麻醉方案。方法 选择拟行联合神经电生理监测的择期脊柱手术病人 40 例,分为A、B两组。两组病人均采用丙泊酚、瑞芬太尼和右美托咪定全凭静脉麻醉,A组病人术中使用小剂量阿曲库铵维持肌松,B组病人术中不使用肌松药。同时监测体感诱发电位（SEP）和运动诱发电位（MEP）评判脊髓功能。记录术中不同时间点两组病人的生命体征和SEP和MEP的波幅和潜伏期,同时记录经颅电刺激时病人是否出现剧烈体动和自主呼吸。比较两组病人术毕后麻醉苏醒时间和质量。结果 两组病人不同时间点的生命体征差异无统计学意义。两组病人的SEP的波幅和潜伏期差异无统计学意义,MEP的潜伏期差异无统计学意义,MEP的波幅差异有显著性统计学意义。两组病人在电刺激时均无自主呼吸和剧烈体动发生。结论 术中不使用肌松药的全静脉麻醉方案可安全有效地用于行神经电生理监测的脊柱手术,并且在电生理监测信号质量和术后苏醒方面具有明显优势。     

Intraoperative spinal cord monitoring during descending thoracic and thoracoabdominal aneurysm surgery

BACKGROUND: Postoperative paraplegia is one of the most dreaded complications after descending thoracic and thoracoabdominal aneurysm surgery. In this study, intraoperative monitoring was applied during resection of descending thoracic and thoracoabdominal aneurysms to detect spinal cord ischemia and help prevent paraplegia. METHODS: Fifty-six patients (descending thoracic, 25; thoracoabdominal, 31) were monitored intraoperatively with both motor- (MEP) and somatosensory- (SSEP) evoked potentials. MEPs were elicited with transcranial electrical stimulation and recorded from the spinal epidural space (D wave) or peripheral muscles (myogenic MEP). SSEPs were obtained with median and tibial nerve stimulation. RESULTS: A total of 16 patients (28.6%) showed MEP evidence of spinal cord ischemia, only 4 of whom had delayed congruent SSEP changes. In 13 patients (23.2%), ischemic changes in MEPs were reversed by reimplanting segmental arteries or increasing blood flow or blood pressure. None of these 13 patients suffered acute paraplegia regardless of the status of SSEP at the end of the procedure, but 1 of them developed delayed postoperative paraplegia after multisystem failure. Three patients (5.4%) who had persistent loss of MEPs despite of recovery of SSEPs awoke paraplegic. CONCLUSIONS: The results demonstrate that compared with SSEP, MEP, especially myogenic MEP, is more sensitive and specific in detection of spinal cord ischemia, and that intraoperative monitoring can indeed help prevent paraplegia.     

SSEP、MEP和DNEP在重度脊柱畸形截骨矫形术中同时联合监测的意义

目的探讨在重度脊柱畸形截骨矫形术中,体感诱发电位（somatosensory evoked potential,SSEP）、运动诱发电位（motor evoked potential,MEP）和下传神经源性诱发电位（descending neurogenic evoked potential,DNEP）同时联合监测的安全性和准确性。方法回顾性分析2010年8月～2011年7月采用3种诱发电位同时联合监测的重度脊柱畸形截骨矫形患者16例,所有患者均在全静脉麻醉并小剂量肌松剂泵注维持下行脊柱畸形截骨矫形术,术中均行SSEP、MEP和DNEP同时联合监测。结果 16例患者术中出现3种诱发电位皆阳性5例,唤醒试验也为阳性,术后均出现不同程度的神经并发症。单纯MEP阳性,而SSEP、DNEP正常者4例,术中唤醒试验均为阴性,术后无异常神经体征。单纯SSEP阳性,而MEP、DNEP正常者1例,术中唤醒阴性,术后查体正常。另外6例术中SSEP、MEP和DNEP皆正常,但其中1例考虑因神经根牵拉出现术后一过性股四头肌肌力下降,余5例术后查体均正常。结论术中DNEP与SSEP、MEP同时联合监测可减少传统SSEP和MEP监测产生假阳性对手术的干扰,对重度脊柱畸形截骨矫形术中脊髓损伤监测具有较好的敏感性和准确性,术中如有2种及以上诱发电位异常则出现脊髓损伤的可能性增大。     

Monitoring electrophysiologic function during carotid endarterectomy: a comparison of somatosensory evoked potentials and conventional electroencephalogram

There is no consensus as to the most appropriate monitor for detecting ischemia during carotid endarterectomy. Accordingly, simultaneous 16-channel continuous electroencephalogram (EEG) and somatosensory evoked potential (SSEP) monitoring were performed in 64 normocapnic patients undergoing carotid endarterectomy and anesthetized with isoflurane or halothane-nitrous oxide (supplemented with fentanyl). Recordings were obtained before, during, and for 15 min after cross-clamping of the internal carotid artery. Internal shunt was not used in any patient, regardless of EEG and SSEP changes. Significant amplitude reduction in the cortical component of the primary negative peak (greater than 50%) in SSEP occurred in 6 patients, and an increase in central conduction time (CCT) (greater than 1 ms) occurred in 5 patients. Major EEG changes occurred in 6 patients, 4 of whom also had SSEP changes. Two patients had transient neurologic deficits postoperatively, with both having SSEP changes (amplitude reduction greater than 50%), whereas one had EEG changes. Based on these observations, the relative sensitivity and specificity for EEG and SSEP (amplitude reduction greater than 50%) in detecting postoperative neurologic deficits were 50% and 92% for EEG and 100% and 94% for SSEP, respectively, differences that were not statistically significant. Regarding SSEP, the use of latency change (CCT) as a criterion was associated with a sensitivity of 0% (P = 0.046 from sensitivity of amplitude) and a specificity of 87% (P = 0.17 from specificity of amplitude).(ABSTRACT TRUNCATED AT 250 WORDS)     

Is transcranial Doppler useful in the detection of internal carotid artery cross-clamp intolerance?

The aim of this study was to test the hypothesis that a drop in the systolic blood flow velocity in the middle cerebral artery of 70% or more, measured by transcranial Doppler, is a better criteria in the detection of cross-clamp intolerance than electroencephalogram (EEG) and somatosensory evoked potential (SSEP) monitoring. After exclusion of patients with a recent stroke, urgent procedures and combined procedures, a transcranial Doppler with compression test was scheduled in 85 patients. In 13 patients the drop was 70% or more and in these patients a transcranial Doppler was also performed during the reconstruction of the internal carotid artery (the study group) under general anaesthesia. A shunt was used because of EEG and SSEP abnormality in one patient. No changes were observed in the remaining patients and no intraoperative strokes were seen. The transcranial Doppler monitoring was unreliable in three patients. During cross-clamp, the systolic blood flow velocity in the middle cerebral artery dropped less than 70% in four and 70% or more in six patients. It is concluded that using a drop of 70% or more of the systolic blood flow velocity in the middle cerebral artery during internal carotid artery cross-clamp, as an indicator of cross-clamp intolerance, will lead to unnecessary shunting.     

皮层体感诱发电位及经颅电刺激运动诱发电位联合监护在脊柱畸形矫正术中的应用

目的:探讨脊柱畸形矫正术中皮层体感诱发电位(CSEP)及经颅电刺激运动诱发电位(TES-MEP)联合监护在脊柱畸形矫正手术中的应用。方法:对我院收治的脊柱畸形患者根据术中监护方法分为两组:A组37例,其中男25例,女12例,年龄13～42岁,平均26.1岁,术中进行CSEP及TES-MEP联合监护;B组29例,其中男10例,女19例,年龄13～20岁,平均15.8岁,单纯采用CSEP监护作为对照组。术中持续观察CSEP及TES-MEP波幅及潜伏期变化,出现波幅下降50%、潜伏期延长10%或刺激强度高于初始刺激强度100V仍未引出者,停止手术并对症处理,术后给予激素治疗。结果:A组术中出现CSEP异常者4例(10.8%),TES-MEP异常者19例(60%)。术中CSEP及TES-MEP均异常者4例(10.8%),无术中CSEP异常而TES-MEP正常者。2例(陈旧性结核并后凸畸形1例,陈旧性骨折并后凸畸形1例)术中合拢截骨平面时,TES-MEP波形均消失,但仅1例出现CSEP异常,经术中积极处理,至手术结束时波形仍未恢复至术前水平,术后均出现神经功能障碍。余35例患者术后无神经功能损伤(假阴性率0%)。B组9例(21%)术中出现CSEP波形异常,其中2例虽经减少矫形角度及激素冲击治疗,术后仍出现双下肢瘫,余术后未出现神经功能障碍。3例术中监护未见异常者,术后出现重度不可逆性脊髓损伤(假阴性率10%)。结论:CSEP结合TES-MEP联合监护能较可靠、准确的反映术中脊髓功能状态,可降低监护假阴性率,为手术治疗过程提供参考。     

Concurrent recording of AEP, SSEP and EEG parameters during anaesthesia: a factor analysis

Background. Spontaneous EEG, mid-latency auditory evoked potentials(AEP) and somatosensory evoked potentials (SSEP) have been usedto monitor anaesthesia. This poses the question as to whetheror not EEG, AEP and SSEP vary in parallel with varying conditionsduring surgical anaesthesia. Methods. A total of 81 variables (31 EEG, 22 SSEP, 28 AEP) weresimultaneously recorded in 48 surgical patients during anaesthesia.A total of 307 cases of the 81 variables in stable anaestheticstates were recorded. A factor analysis was performed for thisdata set. Results. Sixteen variables were excluded because of multicollinearity.We extracted 13 factors with eigenvalues >1, representing78.3% of the total variance, from the remaining 65 x 307 matrix.The first three factors represented 12%, 11% and 10% of thetotal variance. Factor 1 had only significant loadings fromEEG variables, factor 2 only significant loadings from AEP variablesand factor 3 only significant loadings from SSEP variables. Conclusion. EEG, AEP and SSEP measure different aspects of neuralprocessing during anaesthesia. This gives rise to the hypothesisthat simultaneous monitoring of these quantities may give additionalinformation compared with the monitoring of each quantity alone.      

A combined urodynamic and electrophysiological study of diabetic cystopathy

AIMS: The aim of this study is to compare urodynamics and electrophysiological studies in the diagnosis of diabetic cystopathy. MATERIALS AND METHODS: In this prospective study are included twenty six patients with diabetes mellitus diagnosed at least since 5 years; 17 patients with diabetes type II and 9 with type I. They were divided in two groups in respect to lower urinary tract symptoms (LUTS) and signs suggestive of lower urinary tract dysfunction (LUTD) according to the ICS standardization. Patients with LUTS/LUTD were included in Group A and patients without LUTS/LUTD in Group B. Patients underwent different studies: urodynamic, somatosensory evoked potentials (SSEP) of tibial and pudendal nerves, bulbocavernosus reflex (BCR), bulbocavernosus muscles' electromyography and motor evoked potentials after transcranial magnetic stimulation to indirectly investigate bladder's innervation. RESULTS: Abnormal urodynamics were found in 13 patients of group A (92.9%) and in 5 of group B (47.1%). This difference was statistically significant (P=0.009). Abnormally prolonged latency of P40 of tibial SSEP was found in 11 patients of group A (78.6%) and in 4 of group B (33.3%) and this difference was also statistically significant (P=0.04). Differences between the two groups concerning: i) peripheral polyneuropathy; ii) pudendal SSEP, iii) dysfunction of central nervous system and iv) abnormal BCR were not statistically significant. CONCLUSION: The study of tibial SSEP is an easily performed test and it is well correlated to abnormal urodynamics in diabetic patients with and without LUTD/LUTS.     

Altered Excitability of the Motor Cortex after Minor Head Injury Revealed by Transcranial Magnetic Stimulation

Summary This study attempts to find out whether the motor evoked potential (MEP) elicited by single pulse and slow-rate (1 Hz) repetitive transcranial magnetic stimulation (TMS) can disclose concealed subclinical impairments in the cerebral motor system of patients with minor head injury. The motor response to single pulse TMS (STMS) of the patient groups was characterized by significantly higher threshold compared with that of the control group. The central motor conduction time, as well as the peripheral conduction time were normal in all patients pointing to cortical impairment. Two main patterns of MEP changes in response to repetitive TMS (RTMS) were observed in the patient group. A. – progressive decrease of the MEP amplitude throughout the stimulation session to a near complete abolition. B. – irregularity of the amplitude and the waveform of the MEP in a chaotic form. The MEP latency remained stable during the whole stimulation session. The MEP abnormalities recovered gradually over the period of a few months. The higher threshold of the motor response to STMS and the abnormal patterns of the MEP to RTMS seem to reflect transient impairment of cortical excitability or “cortical fatigue” in patients who sustained minor head injures. Further study is needed to evaluated the extent and the pathophysiological mechanisms of the central nervous system fatigue phenomenon following head injury.     

经颅磁刺激运动诱发电位监测脊髓创伤的实验研究

目的：观察脊髓创伤与运动诱发电位的关系，了解运动诱发电位在脊髓中的传导通路。方法：对３９只猫采用脊髓Ａｌｅｎ损伤模型和部分切断伤模型进行经颅磁刺激运动诱发电位（ＴＭＳ－ＭＥＰ）监测。结果：脊髓轻度打击伤时，ＭＥＰ潜伏期即有明显延长，但恢复良好；中度打击伤时，ＭＥＰ潜伏期延长更明显，且不能完全恢复；重度打击伤时，大部分动物ＭＥＰ不能引出，至２４ｈ不能恢复。ＭＥＰ的改变与后肢功能变化及镜下脊髓病理改变一致。ＴＭＳ－ＭＥＰ对脊髓前索和外侧索的损伤敏感，并可间接反应脊髓柱后索损伤。结论：ＴＭＳ－ＭＥＰ经脊髓前索和外侧索传导，可敏感而准确地反映脊髓损伤后功能改变，是一种有效的监测脊髓功能的手段     

Usefulness and Pitfalls of Intraoperative Spinal Motor Evoked Potential Recording by Direct Cortical Electrical Stimulation

Summary ? Objective. The aim of this study is to investigate the usefulness and problems with spinal motor evoked potential (MEP) recording, especially the reasons for failed recording. We report our personal experience over the last 8 years in patients with lesions adjacent to the primary motor cortex. Methods. MEP records of 50 consecutive patients were retrospectively reviewed. MEP was recorded by a catheter electrode inserted in the cervical epidural space. Stimulation electrodes were placed on the cortical surface during surgery. SEP recording was also performed in 29 of 50 patients. Results. MEP was obtained in 40 cases, and SEP was recorded in all 29 cases. The central sulcus was identified in 93% of patients in whom both MEP and SEP were performed, whereas in only 86% of patients who underwent only MEP. The main reason for MEP failure were inadequate exposure of the motor cortex, pre-existing hemiparesis and technical errors. Postoperative deterioration of motor function was closely related to intra-operative MEP changes. Conclusion. MEP is a useful tool to determine the motor cortex and to predict postoperative motor function. However, precise pre-operative craniotomy planning and combination with intra-operative SEP is essential to reduce the MEP failure.     

What is the predictive value of intraoperative somatosensory evoked potential monitoring for postoperative neurological deficit in cervical spine surgery?—a meta-analysis

BACKGROUND CONTEXTCervical decompression and fusion surgery remains a mainstay of treatment for a variety of cervical pathologies. Potential intraoperative injury to the spinal cord and nerve roots poses nontrivial risk for consequent postoperative neurologic deficits. Although neuromonitoring with intraoperative somatosensory evoked potentials (SSEPs) is often used in cervical spine surgery, its therapeutic value remains controversial.PURPOSEThe purpose of the present study was to evaluate whether significant SSEP changes can predict postoperative neurologic complications in cervical spine surgery. A subgroup analysis was performed to compare the predictive power of SSEP changes in both anterior and posterior approaches.STUDY DESIGNThe present study was a meta-analysis of the literature from PubMed, Web of Science, and Embase to identify prospective/retrospective studies with outcomes of patients who underwent cervical spine surgeries with intraoperative SSEP monitoring.PATIENT SAMPLEThe total cohort consisted of 7,747 patients who underwent cervical spine surgery with intraoperative SSEP monitoring.METHODSInclusion criteria for study selection were as follows: (1) prospective or retrospective cohort studies, (2) studies conducted in patients undergoing elective cervical spine surgery not due to aneurysm, tumor, or trauma with intraoperative SSEP monitoring, (3) studies that reported postoperative neurologic outcomes, (4) studies conducted with a sample size ≥20 patients, (5) studies with only adult patients ≥18 years of age, (6) studies published in English, (7) studies inclusive of an abstract.OUTCOME MEASURESThe sensitivity, specificity, diagnostic odds ratio (DOR), and likelihood ratios of overall SSEP changes, reversible SSEP changes, irreversible SSEP changes, and SSEP loss for predicting postoperative neurological deficit were calculated.RESULTSThe total rate of postoperative neurological deficits was 2.50% (194/7,747) and the total rate of SSEP changes was 7.36% (570/7,747). The incidence of postoperative neurological deficit in patients with intraoperative SSEP changes was 16.49% (94/570) while only 1.39% (100/7,177) in patients without. All significant intraoperative SSEP changes had a sensitivity of 46.0% and specificity of 96.7% with a DOR of 27.32. Reversible and irreversible SSEP changes had sensitivities of 17.7% and 37.1% and specificities of 97.5% and 99.5%, respectively. The DORs for reversible and irreversible SSEP changes were 9.01 and 167.90, respectively. SSEP loss had a DOR of 51.39, sensitivity of 17.3% and specificity 99.6%. In anterior procedures, SSEP changes had a DOR of 9.60, sensitivity of 34.2%, and specificity of 94.7%. In posterior procedures, SSEP changes had a DOR of 13.27, sensitivity of 42.6%, and specificity of 94.0%.CONCLUSIONSSSEP monitoring is highly specific but weakly sensitive for postoperative neurological deficit following cervical spine surgery. The analysis found that patients with new postoperative neurological deficits were nearly 27 times more likely to have had significant intraoperative SSEP change. Loss of SSEP signals and irreversible SSEP changes seem to indicate a much higher risk of injury than reversible SSEP changes.