Transcranial electrical motor evoked potential monitoring for brain tumor resection

OBJECTIVE: This study was designed to examine whether transcranial electrical motor evoked potential (MEP) monitoring is safe, feasible, and valuable for brain tumor surgery. METHODS: Fifty consecutive patients undergoing brain tumor resection were studied, using nitrous oxide/propofol anesthesia. MEPs were continuously recorded throughout surgery, using a Sentinel 4 evoked potential system (Axon Systems, Inc., Hauppauge, NY). The MEPs were elicited by transcranial electrical stimulation (train of 5; stimulation rate, 0.5-2 Hz; square wave pulse with a time constant of 0.5 ms; stimulation intensity, 40-160 mA) through spiral electrodes placed over the primary motor cortex and were recorded by needle electrodes inserted into the contralateral orbicularis oris, biceps, abductor pollicis brevis, and anterior tibialis muscles. When MEP amplitudes decreased by more than 50%, MEP stimulation was repeated, with increased stimulation intensity, and MEP changes were reported to the surgeon. The motor function of each patient was examined before and after surgery, using a reproducible scale. The relationship between MEP amplitude decreases and worsening motor status was analyzed using linear regression. RESULTS: Preoperative neurological examinations revealed mild to moderate motor deficits (2/5 to 4/5) for 38% of patients (19 of 50 patients). Most of the patients (96%) exhibited recordable baseline MEPs. Persistent MEP decreases of more than 50% were noted for eight patients (16%) (11 muscles). The MEPs were completely abolished in two patients (three muscles). The degree of postoperative worsening of motor status was correlated with the degree of intraoperative MEP amplitude reduction (r = -0.864; P < 0.001). CONCLUSION: Persistent intraoperative MEP reductions of more than 50% were associated with postoperative motor deficits. The degree of MEP amplitude reduction was correlated with postoperative worsening of motor status. Transcranial electrical MEP monitoring is feasible, safe, and valuable for brain tumor surgery.     

Intraoperative somatosensory evoked potential monitoring during anterior cervical discectomy and fusion in nonmyelopathic patients--a review of 1,039 cases.

BACKGROUND CONTEXT: Intraoperative somatosensory evoked potential (SSEP) monitoring has been shown to reduce the incidence of new postoperative neurological deficits in scoliosis surgery. However, its usefulness during cervical spine surgery remains a subject of debate. PURPOSE: To determine the utility of intraoperative SSEP monitoring in a specific patient population (those with cervical radiculopathy in the absence of myelopathy) who underwent anterior cervical discectomy and fusion (ACDF) surgery. STUDY DESIGN: Retrospective review. PATIENT SAMPLE: A total of 1,039 nonmyelopathic patients who underwent single or multilevel ACDF surgery. The control group (462 patients) did not have intraoperative SSEP monitoring, whereas the monitored group (577 patients) had continuous intraoperative SSEP monitoring performed. OUTCOME MEASURE: A new postoperative neurological deficit. METHODS: SSEP tracings were reviewed for all 577 patients in the monitored group and all significant signal changes were noted. Medical records were reviewed for all 1,039 patients to determine if any new neurological deficits developed in the immediate postoperative period. RESULTS: None of the patients in the control group had any new postoperative neurological deficits. In the monitored group there were six instances of transient SSEP changes (1 due to suspected carotid artery compression; 5 thought to be due to transient hypotension) which resolved with the appropriate intraoperative intervention (repositioning of retractors; raising the arterial blood pressure). Upon waking up from anesthesia, one patient in the monitored group had a new neurological deficit (partial central cord syndrome) despite normal intraoperative SSEP signals. CONCLUSIONS: ACDF appears to be a safe surgical procedure with a low incidence of iatrogenic neurological injury. Transient SSEP signal changes, which improved with intraoperative interventions, were not associated with new postoperative neurological deficits. An intraoperative neurological deficit is possible despite normal SSEP signals.     

Variability of somatosensory evoked potential monitoring during scoliosis surgery

OBJECTIVE: Somatosensory evoked potentials (SEPs) of 65 patients undergoing scoliosis surgery were monitored by stimulation of posterior tibial nerve to observe variations in latencies and amplitudes. METHODS: Monitoring was divided into five stages: pre incision, spine exposure, instrumentation loading, deformity correction, and wound closure (stages 1-5, respectively). RESULTS: We found the latency showed significant increase and the amplitude significant reduction from stages 1 to 2. There was no significant variability from stages 2, 3, and 4, but both latency and amplitude recovered significantly from stage 4 to 5. This variability correlated with the changes in mean arterial pressure and end-tidal concentrations of isoflurane and was not dependent on the type of surgical procedure. If either 50% amplitude reduction or 10% latency prolongation of SEP compared with baseline recordings at stage 1 (pre incision) was used as warning criterion, the overall false-positive rate was 23.1%. It was significantly reduced to 7.7% if stage 2 (spine exposure) recordings were used as the baseline (P < 0.05). The false-positive rate decreased to 0% if a combined 50% amplitude reduction and 10% latency prolongation of SEP compared with the stage 2 baseline were used (P < 0.001). CONCLUSION: Based on these findings, we concluded that the time to obtain SEP baseline data should be adjusted to be post incision instead of pre incision.     

Variability of somatosensory cortical evoked potential monitoring during spinal surgery

The intraoperative variability of somatosensory cortical evoked potentials (SCEPs) has been measured for 320 consecutive spinal surgeries and found to be a function of patient diagnosis, neuromuscular status, age, and procedural factors. In many cases, it is likely that this variability severely limits the reliability and usefulness of spinal cord monitoring in detecting early cord compromise. Patients with idiopathic scoliosis, spondylolisthesis, and pseudarthrosis have the smallest spontaneous variability and strongest amplitudes, while those with congenital, paralytic scoliosis, stenosis, or tumor have very variable, weak SCEPs. Patients with neurologic disorders, particularly cerebral palsy, myelomeningocele, Friedreich's ataxia, and peripheral deficits, also have high variability and weak amplitudes. A monitoring quality scoring system is proposed that may be useful during surgery in judging how well the SCEPs can discern surgically related changes in cord function from background variations.     

Continuous monitoring of short-latency somatosensory evoked potentials during cardiac and aortic surgery

The effectiveness of monitoring somatosensory evoked potentials (SEPs) intraoperatively to detect brain damage early remains controversial. To assess the diagnostic accuracy of this modality, a study was conducted between 1991 and 1994, recording SEPs in 287 consecutive patients undergoing cardiac and aortic surgery using cardiopulmonary bypass (CPB) with moderate hypothermia or deep hypothermic circulatory arrest. From P1 to N2 of the SEPs occurring within 50 ms latency in response to electrical stimulation of the median nerve were recorded over the contralateral postcentral cortex at 5-min intervals using a Neuropack-2 (Nihon Koden, Tokyo, Japan). Normal SEPs were recovered in 247 patients postoperatively; however, 2 of these patients had suffered a cerebral infarction and 1, a transient stroke intraoperatively, demonstrating a false-negative incidence of 1.2%. On the other hand, three different types of abnormal SEPs were recorded postoperatively. P1 and N1 absence, probably caused by a subcortical lesion, was observed in 4 patients; P2 and N2 absence, probably caused by a cortical lesion, was observed in 8 patients; and a flat SEP, representing diffuse damage, was observed in 2 patients. Among these 14 patients with abnormal SEPs, 7 showed no neurologic disturbance at all, demonstrating a false-positive incidence of 50%. Thus, we concluded that when normal SEPs are recovered during weaning from CPB, the incidence of brain damage could be predicted at below 5%. Conversely, when abnormal SEPs are demonstrated, the incidence of brain dysfunction impeding a return to active life is estimated to be about 70%.     

Cerebral monitoring of somatosensory evoked potentials during carotid surgery: a review of 100 cases

The purpose of this study was to evaluate immediate and middle-term results of surgical carotid artery revascularization (CAR) with cerebral monitoring of intraoperative somatosensory evoked potentials (SEPs). Between 1998 and 2004, a total of 100 CARs in 86 patients were performed under general anesthesia with SEP monitoring. A shunt was inserted if SEP amplitude decreased by 50% or latency time increased by 10%. Immediate and middle-term results were analyzed retrospectively. The shunt insertion rate was 5%. Two transient ischemic attacks were observed, and one patient died postoperatively due to myocardial infarction. The cumulative stroke and death rate was 1% at 30 days. Intraoperative SEP monitoring with selective shunt placement can be used safely for carotid surgery. Randomized studies will be necessary to determine the respective indications for various cerebral monitoring techniques.     

Intraoperative somatosensory evoked potential monitoring of pelvic and acetabular fractures.

The efficacy of intraoperative somatosensory evoked potential (SSEP) monitoring was evaluated in the surgical management of 82 patients with pelvic and acetabular fractures. The injuries consisted of 45 acetabular fractures, 30 pelvic ring disruptions, and seven combined injuries. Preoperative neurological deficits were recorded in 34% of the study group (29% of those with an acetabular fracture and 47% of those with a pelvic ring injury). Three patients sustained an iatrogenic sciatic nerve injury during the study period (all of which were documented in the first 40 cases). Two patients sustained an exacerbation of an existing sciatic nerve injury. In the group of pelvic fractures, hazardous parts of the exposure, reduction, and fixation were identified by the SSEP monitoring. Removal of the provocative stimulus by the surgeon led to reversal of the SSEP abnormalities, and none of this group of patients sustained an iatrogenic injury. When the intraoperative SSEP changes were noted during an acetabular fracture fixation, immediate attempts were made to relieve the excessive tension on the sciatic nerve by replacing or removing a retractor, flexing the knee, extending the hip, or dividing the femoral insertion of the gluteus maximus. None of the SSEP changes were associated with the lacerative injury to the sciatic nerve. For the method to be clinically effective in reducing the incidence of neurological deficit, even subtle changes in the SSEP tracing must be recognized immediately by the neurophysiologist so that a corresponding corrective measure can be rapidly undertaken by the surgeon to remove the offending stimulus.     

围脑干手术中体感诱发电位监测的临床研究

目的 研究体感诱发电位（ＳＥＰ）神经生理监测在围脑干手术中的可行性。方法 选择静脉麻醉下围脑干手术４３例,对两侧正中神经分别进行刺激,记录相应的ＳＥＰ Ｎ２０波形,术中Ｎ２０发生明显变化,即通知桩得调整操作。结果 在静脉麻醉维持过程,波形基本保护稳定;４３例手术中ＳＥＰ发生显著变化的有８例,其中５例逐渐恢复,术后未出现新的神经功能障碍,另外３例至术终未恢复。术后均出现了相应的神经系统并发症。研究中     

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。     

颈椎病前路手术中体感诱发电位监护临床研究

目的探讨体感诱发电位监护(SSEP)在颈椎病前路手术中的应用价值。方法收治颈椎病前路手术患者142例,年龄37~75岁,男96例,女46例。神经根型颈椎病35例,脊髓型颈椎病107例。对照组83例无SSEP监护,监护组59例。在麻醉诱导后和摆放体位前确立SSEP基线,波幅降低50%或潜伏期延长10%为报警标准。记录SSEP报警因素及改善措施,术后明确有无医源性神经损伤。结果对照组无医源性神经损伤。监护组:真阳性2例出现报警,采取措施后解除报警;假阳性0例;真阴性56例SSEP无报警,无医源性神经损伤;假阴性1例SSEP无报警,术后右侧三角肌麻痹;SSEP监护医源性神经损伤的敏感性和特异性分别为66.7%和100%。结论 SSEP在颈椎病前路手术中监护脊髓损伤方面较敏感,对神经根损伤不敏感。     

Laryngeal melanosis: Report of four cases and literature review

OBJECTIVE: Laryngeal melanosis is a rare condition defined by the presence of melanocytes within the laryngeal epithelial lining. Our aims were (1) to review our cases together with those in the literature, and (2) to determine whether melanocyte incidence is increased with exposure to irritant stimuli such as tobacco.METHODS: A retrospective study of all cases diagnosed with laryngeal melanosis in our hospital from January 1, 1990, to December 31, 1996, was accomplished. To determine the melanocyte incidence in the normal larynx as well as the influence of tobacco in development of laryngeal melanosis, 16 age-matched controls, 8 of whom were smokers and 8 of whom were not, were chosen, and a histochemical and immunohistochemical study was performed. The following antibodies were used: S-100 protein, CD1a, and HMB-45. A comparative study of the melanocyte incidence between patients with laryngeal melanosis and the controls was carried out. Also, a comparative study between smoking and nonsmoking patients was performed.RESULTS: Laryngeal melanosis was diagnosed in 4 patients at our hospital during this period of time. In the comparative study, the number of melanocytes in the 4 patients with laryngeal melanosis was higher than in the 8 smoking ( p < 0.01, Mann-Whitney U test) and 8 nonsmoking ( p < 0.01) controls, and there was a trend toward a higher number of melanocytes in the 8 smoking patients than in the 8 nonsmoking ( p = 0.064) controls.CONCLUSIONS: Laryngeal melanosis was more frequent in smoking men older than 50 years. Our observations underline the association of LM with larynx carcinoma and its relation to a stimulus such as tobacco. In fact, we have found activated melanocytes in our cases of laryngeal melanosis. They were identified by immunoreactivity for HMB-45. (Otolaryngol Head Neck Surg 1997;117:708-12.)     

体感诱发电位在脊柱手术中的监测作用

目的：探讨脊柱外科手术中体感诱发电位监护技术的准确性。方法：对78例颈、胸椎手术患者术中采用皮层体感诱发电位(cortical somatosensory evoked potential，CSEP)术中监测，记录术前、术中、术后各个重要手术步骤的CSEP变化，根据不同阶段诱发电位的变化与术后临床脊髓功能改变相结合，判断CSEP的准确性。结果：78例患者中，CSEP未达到监护界值71例，术后无脊髓损伤；5例患者术中CSEP达到预警标准，告诫手术医生，注意手术操作，术后无脊髓损伤；另外，出现假阳性和假阴性各1例，术后恢复亦良好。结论：排除各种干扰因素后体感诱发电位可较准确地对脊髓的功能状况进行监测，是较准确的脊柱外科手术监护技术。     

Hemangiopericytomas of the spinal canal. Report of four cases and review of literature

The Authors report four cases of spinal hemangiopericytomas. The diagnosis has been ascertained by electron microscopy. Despite the malignant nature, the association of surgery and radiotherapy is interesting in that it prolongs the survival rate. Clinical, neuroradiological, microscopic and ultrastructural features of intraspinal hemangiopericytomas are evaluated in the light of the review of the relevant literature.