Monitoring Of Evoked Potentials Research Articles

Predictive Value of Somatosensory Evoked Potential Monitoring during Resection of Intraparenchymal and Intraventricular Tumors Using an Endoscopic Port

Background and PurposeIntraoperative neurophysiological monitoring (IONM) using upper and lower somatosensory evoked potentials (SSEPs) is an established technique used to predict and prevent neurologic injury during intracranial tumor resections. Endoscopic port surgery (EPS) is a minimally-invasive approach to deep intraparenchymal and intraventricular brain tumors. The authors intended to evaluate the predictive value of SSEP monitoring during resection of intracranial brain tumors using a parallel endoscopic technique.MethodsA retrospective review was conducted of patients operated on from 2007-2010 utilizing IONM in whom endoscopic ports were used to remove either intraparenchymal or intraventricular tumors. Cases were eligible for review if an endoscopic port was used to resect an intracranial tumor and the electronic chart included all intraoperative monitoring data as well as pre- and post-operative neurologic exams.Results139 EPS cases met criteria for inclusion. Eighty five patients (61%) had intraparenchymal and fifty four (39%) had intraventricular tumors or colloid cysts. SSEP changes were seen in eleven cases (7.9%), being irreversible in three (2.2%) and reversible in eight cases (5.8%). Seven patients (5.0%) with intraparenchymal tumors had SSEP changes which met our criterea for significant changes while there were four (2.9%) with intraventricular (p-value=0.25). Five patients suffered post operative deficits, two reversible and two irreversible SSEP changes. Only one case exhibited post operative hemiparesis with no SSEP changes. The positive predictive value of SSEP was 45.4% and the negative predictive value was 99.2%.ConclusionsBased on the high negative and low positive predictive values, the utility of SSEP monitoring for cylindrical port resections may be limited. However, the use of SSEP monitoring can be helpful in reducing the impact of endoscopic port manipulation when the tumor is closer to the somatosensory pathway.

The clinical practice of intraoperative neurophysiological monitoring in Shanghai Huashan Hospital

Intraoperative neurophysiological monitoring (IONM) is the gold standard of the intraoperative functional brain mapping. It employs various electrophysiological methods such as awake craniotomy, intraoperative somatosensory and motor evoked potentials monitoring, intraoperative cortical stimulation and sub⁃cortical stimulation to accurately map the cortical and sub⁃cortical nervous pathways so that the continuous assessment and real ⁃ time protection of the functional integrity of certain neural structures can be achieved during surgery. Based on decades of clinical practice, the Department of Neurosurgery of Shanghai Huashan Hospital has set up an clinical practice used in the institute. The clinical practice guideline covers technical and operation standards of IONM in all kinds of common neurosurgery diseases and does improve the clinical efficacy in neurosurgical procedures. DOI：10.3969/j.issn.1672⁃6731.2012.06.007

Effects of propofol and fentanil compounded different doses of dexmedetomidine on hymodynamics and intraoperative somatosensory and motor evoked potentials monitoring of senile patient

Objective To evaluate the effects of different doses of dexmedetomidine compounded propofol and fentanil on hymodynamics and intraoperative somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) monitoring on the senile people.Methods Forty-five patients undergoing selected anterior spinal fusion surgery were randomly divided into three groups by the dose of dexmedetomidine: group C (normal saline,NS); group D1 (dexmedetomidine injected by 0.3 μg·kg-1·h-1);group D2(dexmedetomidine injected by 0.8 μg·kg-1·h-1).The induction of all patients in three groups:midazolam 2 mg-3 mg,propofol Cp 1.5 mg/L (Marsh model),fentanil 1.5 μg/kg-2 μg/kg.When the patient's consciousness disappeared,a LMA was intubated and mechanical ventilation was made.In group D1 and group D2,dexmedetomidine (0.5 μg/kg over 10 min) was administered and then followed by an infusion of 0.3 μg·kg-1 ·h-1 or 0.8 μg ·kg-1 ·h-1 until the end of surgery.In group C,the same dose of NS instead of dexmedetomidine was administered.Anesthesia was maintained by target controlled injection of propofol.Bispectral index (BIS) were kept in the range of 45-55 by adjusting the concentration of propofol.Muscle relaxant wasn't be used in whole operation.SEPs and MEPs were monitored by a specialist during the operation.Results Heart rate were lower in group D1 and D2 than group C,but mean arterial pressure (MAP) were no different in three groups.The latency and the amplitude of SEPs P15-N20 were also no different in three groups (P＞0.05).Three patients's amplitudes of MEPs were disappeared in different degrees among the group D2.The positive rate is 3/15.There was a significant difference from the cases of group D1 (0/14) and C (0/14).After dexmedetomidine was stopped about 20 min-30 min,the amplitudes of MEPs recoveried in all the three patients.Conclusions In scnile paticnts,dexmedetomidine possibly prolonged analepsia time and decreased heart rate.Dexmedetomidine does not significantly influence the SEPs,but higher dose of dexmedetomidine depressed MEPs. Key words: Anesthesia, general; Senile; Anesthetics, intravenous; Evoked potentials; Medetomidine; Propofol

Improvement of motor evoked potentials monitoring is required during thoracic or thoracoabdominal aortic aneurysm surgery under hypothermic cardiopulmonary bypass

Keywords Motor evoked potential Thoracoabdominalaortic aneurysm HypothermiaMonitoring of motor evoked potentials (MEPs) can provideinformation about the functional integrity of a motorpathway and, therefore, has been widely used during sur-gery in which a motor pathway is at risk of injury,including craniotomy, spine/spinal surgery, and thoracic orthoracoabdominal aortic aneurysm (TAA or TAAA) sur-gery [1, 2]. Because myogenic MEPs are very sensitive tosuppression by anesthetic agents and neuromuscularblockade, careful attention should be paid to anestheticmanagement during monitoring of MEPs. In general, totalintravenous anesthesia with propofol and opioids is used,although ketamine-based anesthesia may be applied incases in which recording of myogenic MEPs is not reliablebecause of suppression by anesthetic agents or influence bypreoperative motor dysfunction.Of the cases in which MEPs monitoring is required,TAA/TAAA surgery is the most challenging for reliableMEP monitoring. In addition to the effects of anesthetics,a variety of factors can affect the recording of MEPs,including hypothermia, aortic clamp, and induction ofcardiopulmonary bypass (CPB). Hypothermia may havedirect effects on the MEP itself and also indirect effects onMEPs by changing the pharmacokinetics and pharmaco-dynamics of anesthetic agents, modified by the effects ofaortic clamp and the induction of CPB. Leslie et al. [3]demonstrated that a temperature reduction of 3 C increasedblood propofol concentration by 30 C during a constantrate infusion. Kakinohana et al. [4] reported that plasmapropofol concentration increased and bispectral indexvalues decreased rapidly after aortic cross-clamping inthoracic aortic aneurysm repair surgery during propofolanesthesia. Yoshitani et al. [5] demonstrated that, in patientsreceiving propofol infusion at a rate of 5 or 6 mg/kg/h,plasma propofol concentration increased and burst sup-pression rate on electroencephalogram increased after theinduction of normothermic CPB, compared with thosevalues before CPB. These findings suggest that interpre-tation of MEP changes could be difficult because anestheticlevel can easily fluctuate during TAAA surgery withhypothermic CPB.Data regarding the effects of hypothermia on myogenicMEPs have been limited to animal experiments. Meylaertset al. [6] investigated the effects of regional spinal cordhypothermia on myogenic MEPs induced by transcranialtrain-pulse stimulation in pigs anesthetized with ketamine,sufentanil, clonidine, and nitrous oxide. They demonstratedthat progressive cooling resulted in an increase of MEPs at28 –30 C and was followed by a progressive decrease inMEP amplitude. MEP amplitude decreased below 25% atapproximately 14 C. Sakamoto et al. [7] also investigatedthe effects of systemic hypothermia on myogenic MEPsinduced by a single pulse and a train of pulses under

Efficacy of combined monitoring with TES-MEP and CSEP during anterior or posterior surgery for cervical spondylitic myelopathy

Objective To evaluate of the efficacy of transcranial electrical stimulation motor evoked potential (TES-MEP)in combination with cortical somatosensory evoked potential (CSEP) monitoring during the anterior or posterior approach spinal surgery for cervical spondylitie myelopathy (CSM).Methods TES-MEP on the bilateral anterior tibial muscle and flexor hallucal brevis and thenar muscles and CSEP on the bilateral posterior tibial nerve and ulnar nerve were observed simultaneously in 135 patients during spinal surgery.Intravenous anesthesia was employed in all the patients.The results of TES-MEP,CSEP and combined monitoring were analyzed statistically.Pre-oporative and post-operative motor and sensory functions of the spinal cord were compared. Result Success rate of TES-MEP,CSEP and the combined monitoring was 87.4%.97.8%and 100%,respectively.Out of 135 patients,nine patients (6.7%) were detected with the positive evoked potentials due to surgical operation.The sensitivity of TES-MEP and CSEP in assessing the spinal cord motor function was 100%and 83.3%,respectively,while that in assessing the spinal cord sensory function was 77.8%and 100%,respectively.The sensitivity and specificity of the combined monitoring was both 100%. Conclusion The successful detection rate and accuracy of the combined monitoring for spinal cord function are apparently higher than that of simple TES-MEP or CSEP.The causes for operative maneuvers evoking a positive evoked potential include complete anterior decompression of the spinal canal,intervertebral bone graft,laminoplasty for OPLL and hematoma compression caused by a failed drainage in a posterior-anterior approach surgery. Key words: Cervical spondylosis,myelopathy; Electrical stimulation; Evoked potentials,motor; Evoked potentials,somatosensory; Combined monitoring

FK506 promotes repair of injured spinal cord pathway after neural stem cell transplantation

Objective To observe the effect of tacrolimus(FK506)in promoting repair of the injured spinal cord pathway after neural stem cell transplantation in rats. Methods A neurysm clip was used to compress the T8 spinal cord segment of SD rats under microscope to establish model of spinal cord injury.The rats were randomly divided into three groups seven days after injury,ie,control group (injection of normal saline at the injury center),transplantation group(injection of neural stem cells,NSCs,at the injury center),FK506 group(injection of NSCs at the injury center plus 7 days of intrapernerve conduction was compared by using the Basso-Beatfle-Bresnahan (BBB) scale,BDA tracing,somatosensory evoked potential(SEP)and motor evoked potentials(MEP)monitoring at 1,2,4 and 8weeks. Results The motor function of the hind limb after injury was recovered in various degrees with time,with the most significant recovery at 4 weeks.The BBB score reached 6,the maximum at 8 weeks.BDA tracing showed that some nerve fibers were found crossing the injured center of the spinal cord one week later in FK506 group and cell transplantation group,that BDA-positive labeled corticospinal tract fibets were seen across the injury site in all groups by the end ofthe eight weeks.In the FKS06 group,the regeneration could be observed even as 1.7 cm away from tlle injury center.SEP latency was significantly shorter in the FK506 group after two weeks(P<0.05)and the MEP latency in the FK506 group was shortened significantly at four weeks compared with the other groups(P<0.05),indicating that the immunosuppressants could promote the recovery of the injured spihal cord,shorten the latency of SEP and MEP，improve SEP at early stage and MEP at late stage．Conclusions Systemic application immunosuppressive agents FK506 plays an important role in neuroprotection and neurotrophy，which promotes the repair of the injured spinal cord after neural stem cell transplantation． Key words: Spinal cord injuries; FK506; Stem cell transplantation; Evoked potentials

Evaluation of the role of combined TES-MEP and CSEP monitoring during the spinal surgery

To evaluate of the role of transcranial electrical stimulation motor evoked potential (TES-MEP) in combination with cortical somatosensory evoked potential (CSEP) monitoring during the spinal surgery. TES-MEP on bilateral anterior tibial muscle and flexor hallucal brevis and CSEP on bilateral posterior tibial nerve were observed simultaneously on 293 patients during spinal surgery from July 2006 to April 2009. Intravenous anesthesia was employed in all the patients, a part of which were added low dose of sevoflurane or muscle relaxant. The results of TES-MEP, CSEP and combined monitoring were analyzed statistically. Pre-operative and post-operative motor and sensory functions of spinal cord were compared. Success rate of TES-MEP, CSEP and combined monitoring was 90.8%, 96.9% and 100% respectively. For the judgment of motor function of spinal cord, the sensitivity of TES-MEP and CSEP was 100% and 89.3% respectively and the specificity of 98.4% and 96.9%. The Youden index of the two methods was 0.984 and 0.862. For sensory function, the sensitivity of them was 76.7% and 93.3% respectively and the specificity of 98.7% and 98.0%. The Youden index was 0.754 and 0.913. The sensitivity of combined monitoring was 100%, with the specificity of 96.9%. The Youden index was 0.969. The precision of monitoring motor function of spinal cord with TES-MEP is higher than that with CSEP, however, for sensory function, CSEP is more precise. The sensitivity and precision of combined monitoring for spinal cord function were apparently better than that of unitary TES-MEP or CSEP. The combined TES-MEP and CSEP monitoring is a relatively ideal method.

Target-Controlled Infusion Of Remifentanil Using Orchestratm During Motor Evoked Potential Monitoring.

We performed anesthetic management for removal of a brain tumor, during which motor evoked potential (MEP) monitoring was performed. In addition to target-controlled infusion (TCI) of propofol, TCI of remifentanil, which was preinstalled in the Orchestra, was used for anesthetic induction and maintenance. Remifentanil was administered at the effect-site concentration of 10 μg/mL during surgery, and hemodynamics was stable and MEP was well elicited. Since TCI of remifentanil was easily performed by using Orchestra and it could provide stable hemodynamics and good conditions for MEP monitoring, Orchestra is thought to be suitable for MEP monitoring during craniotomy.

Therapeutic extradural cortical stimulation for Parkinson's Disease: Report of six cases and review of the literature

Objectives We report our experience and results with extradural cortical stimulation (ECS) in the surgical treatment of Parkinson's Disease (PD). Besides, we review the literature supporting the use of this technique. Materials and methods Six patients with advanced PD and exclusion criteria for Deep Brain Stimulation (DBS) were included in our ECS protocol. With the aid of functional MRI and somato-sensory evoked potentials monitoring, the motor cortex projection over the scalp was drawn. Finally, under local anesthesia a stimulation lead was placed in the epidural space overlying the central sulcus. Results Patients showed mild daily life activities improvement with a slightly lower levodopa equivalent dose, but UPDRS part III scores showed no significant modification. Conclusions Despite ECS is a minimally invasive surgical technique, our results only support its use in selected patients with advanced PD, in whom this therapy may be modestly effective. More experimental studies regarding the neuromodulation of the basal ganglia-cortex loops are required to optimize its clinical application.

Intramedullary cavernous malformations: Clinical features and surgical technique via hemilaminectomy

Objective The purpose of this study was to define the clinical features and the surgical technique of unilateral hemilaminectomy for treating intramedullary cavernous malformations. Materials and methods Retrospective chart was performed in 16 patients with histologically diagnosed intramedullary cavernous malformations. All patients were treated with unilateral hemilaminectomy and microsurgical resection of the malformations. The pre- and postoperative neurological state was evaluated using Frankel scale. Results There were nine females and seven males (mean age 38 years) harbouring symptomatic intramedullary cavernous malformations. The annual retrospective haemorrhage rate was 3.1% per patient/year. All cavernous malformations were completely resected. Twelve of 16 patients experienced the improvement of the neurological state and in four patients, clinical features remained unchanged during the follow-up period. Static and dynamic plain radiograph film showed none of them had spinal deformity or spinal instability. Conclusion According to the defined bleeding risk, symptomatic and MRI-morphologically growing intramedullary cavernous malformations should be totally surgically removed, to avoid the recurrence and rebleeding of the residue. A least traumatic myelotomy, as well as a meticulous microsurgical technique and the intraoperative somatosensory evoked potentials monitoring, together with selection of a minimally invasive microsurgical approach (hemilaminectomy), leads to a favourable outcome and prevents additional morbidity.

Observation of combined application of TES-MEP and CSEP monitoring during the surgery of scoliosis

Objective To investigate the feasibility and applied value of transcranial electrical stimulation motor evoked potential (TES-MEP) combined with cortical somatosensory evoked potential (CSEP) monitoring during the surgery of scoliosis.Methods From July 2006 to April 2008, 76 patients were simultaneously recorded the TES-MEP on bilateral anterior tibial muscle and flexor hallucal brevis and the CSEP on bilateral posterior tibial nerve during the surgery of scoliosis.Forty -night of these patients received total intravenous anesthesia and the other 27 patients were anesthetized by propofol and sevoflurane (inhalant concentration <1%).The results of TES-MEP in both groups were analyzed by X2 analysis and related index about the true positive, false positive and true negative, false negative results were calculated.Results Success rates of TES-MEP and CSEP recording were both 96.1%.There was no statistics difference of the success rate of TES-MEP in the two different anesthesia groups.Evoked potentials changes occurred in 11 cases, in which 9 cases were true positive results in direct relation to an incorrect operative maneuver.The sensitivity of the CSEP, TES -MEP and muitimodality recording was 75.0%, 87.5% and 100%, respectively.The specificity of the three methods was 98.5%, 98.5% and 97.0%, respectively.The Youden index of the three methods was 0.74, 0.86 and 0.97, respectively.Conclusion The anesthesia by intravenous propofol and sevoflurane (inhalant concentration <1%) was a feasible method for muitimodality recording.The sensitivity and precision of muitimodality recording for detecting spinal cord function were apparently higher than that of unitary TES-MEP or CSEP monitoring. Key words: Scoliosis; Electric stimulation; Evoked potentials,motor; Evoked potentials, somatosensory

Comparison between Sevoflurane/Remifentanil and Propofol/Remifentanil Anaesthesia in Providing Conditions for Somatosensory Evoked Potential Monitoring during Scoliosis Corrective Surgery

Somatosensory evoked potential (SSEP) monitoring is an important tool in spinal corrective surgery. Anaesthesia has a significant influence on SSEP monitoring and a technique which has the least and shortest suppressant effect on SSEP while facilitating a fast recovery from anaesthesia is ideal. We compared the effect of sevoflurane/ remifentanil and propofol/remifentanil anaesthesia on SSEPs during scoliosis corrective surgery and assessed patients' clinical recovery profiles. Twenty patients with idiopathic scoliosis receiving surgical correction with intraoperative SSEP monitoring were prospectively randomised to receive sevoflurane/remifentanil anaesthesia or propofol/remifentanil anaesthesia. During surgery, changes in anaesthesia dose and physiological variables were recorded, while SSEP was continuously monitored. A simulated 'wake-up' test was performed postoperatively to assess speed and quality of recovery from anaesthesia. The effects of propofol and sevoflurane resulted in SSEP amplitude variability between 18.0% +/- 3.5% to 28.7% +/- 5.9% and SSEP latency variability within 1.3% +/- 0.4% to 2.6% +/- 1.2%. Patients receiving sevoflurane had faster suppression and faster recovery of SSEP amplitude compared to propofol (P < 0.05), although propofol anaesthesia showed less within-patient variability in Cz amplitude and latency (P < 0.05). On cessation of anaesthesia, time to eye-opening (5.2 vs. 16.5 minutes) and toe movement (5.4 vs. 17.4 minutes) was shorter following sevoflurane (all P < 0.05). These findings indicate that propofol produces a better SSEP signal than sevoflurane. However adjustments in sevoflurane concentration result in faster changes in the SSEP signal than propofol. Assessment of neurological function was facilitated more rapidly after sevoflurane anaesthesia.

Friedreich's Ataxia and Scoliosis

Friedreich's ataxia is a genetically transmitted, progressive spinocerebellar degenerative disease characterized by ataxia. The purpose of this study is to evaluate the demographics, progression, nonoperative, and operative treatment of spinal deformities in patients with Friedreich's ataxia at 2 tertiary pediatric orthopaedic hospitals. After institutional review board approval, chart review of Friedreich's ataxia patients identified those having scoliosis. Demographic data, length of follow-up, brace treatment, operative treatment, and complications were determined. Radiographic review was also performed. Seventy-seven patients were identified as having Friedreich's ataxia, of which 49 (63%) were diagnosed with scoliosis. Twenty-seven were male; 22 were female. Mean age at diagnosis of scoliosis was 12.8 years (4.9-20 years). Mean follow-up was 3.7 years (0-13 years). There were 16 (33%) double major curves, with 8 (22%) of the thoracic curves being left sided. Hyperkyphosis was present in 12 (24.5%).Twenty-four (49%) of patients progressed > or =6 degrees. Using a chi-square analysis, there was no association, with a curve magnitude of 10 degrees before the age of 10 years and progression of the curve (P = 0.4386). Ten (20%) patients were treated in braces, with average progression in brace of 15 (0-44) degrees. Sixteen (33%) patients were treated with spinal fusion (15 posterior spinal fusion and 1 anterior spinal fusion). Thirteen (81%) of 16 patients who underwent operative intervention were wheelchair dependent. Somatosensory evoked potentials monitoring was attempted in 11 patients but was effective in only 1. Immediate postoperative correction averaged 49% in the thoracic spine (24%-87%) and 51% in the lumbar spine (26%-82%). This correction decreased to 39% in the thoracic (-22% to 85 %) and 30% in the lumbar spine (-35% to 82%) at final follow-up. The average postoperative follow-up was 3.6 years (2-6.5). One patient (6.2%) developed an infection and was the only patient who underwent reoperation. Scoliosis in Friedreich's ataxia is common (63%). Curve patterns are variable and do not necessarily resemble idiopathic curves. Although few patients were braced, results were poor. Fusion using modern segmental constructs was effective in creating substantial intraoperative correction and maintaining correction postoperatively. SSEP monitoring was usually ineffective, so preparation for a wake-up test is recommended. Patients with Friedreich's ataxia need to be carefully screened for scoliosis and counseled about the high rate of surgical fusion. Using modern implants, correction can be achieved and maintained.

Poster 12: Somatosensory Evoked Potentials Monitoring During Restoration Functions of Spinal Cord and Peripheral Nerves

Poster 12: Somatosensory Evoked Potentials Monitoring During Restoration Functions of Spinal Cord and Peripheral Nerves

Combined monitoring of evoked potentials during microsurgery for lesions adjacent to the brainstem and intracranial aneurysms

Neurophysiologic monitoring during surgery is to prevent permanent neurological injury resulting from surgical manipulation. To improve the accuracy and sensitivity of intraoperative neuromonitoring, combined monitoring of transcranial electrical stimulation motor evoked potentials (TES-MEPs), somatosensory evoked potentials (SSEPs) and brainstem auditory evoked potentials (BAEPs) was attempted in microsurgery for lesions adjacent to the brainstem and intracranial aneurysms. Monitoring of combined TES-MEPs with SSEPs was attempted in 68 consecutive patients with lesions adjacent to the brainstem as well as intracranial aneurysms. Among them, 31 patients (31 operations, 28 of posterior cranial fossa tumors, 3 of posterior circulation aneurysms) were also subjected to monitoring of BAEPs. The correlation of monitoring results and clinical outcome was studied prospectively. Combined monitoring of evoked potentials (EPs) was done in 64 (94.1%) of the 68 patients. MEPs monitoring was impossible for 4 patients (5.9%). No complication was observed during the combined monitoring in all the patients. In 45 (66.2%) of the 68 patients, EPs were stable, and they were neurologically intact. Motor dysfunction was detected by MEPs in 8 patients, SSEPs in 5, and BAEPs in 4, respectively. A close relationship exists between postoperative motor function and the results of TES-MEPs monitoring. TES-MEPs are superior to SSEPs and BAEPs in detecting motor dysfunction, but combined EPs serve as a safe, effective and invasive method for intraoperative monitoring of the function of the motor nervous system. Monitoring of combined EPs during microsurgery for lesions adjacent to the brainstem and intracranial aneurysms may detect potentially hazardous maneuvers and improve the safety of subsequent procedures.

Hemifacial Spasm: A Neurosurgical Perspective

Hemifacial spasm (HFS) is characterized by tonic clonic contractions of the muscles innervated by the ipsilateral facial nerve. Compression of the facial nerve by an ectatic vessel is widely recognized as the most common underlying etiology. HFS needs to be differentiated from other causes of facial spasms, such as facial tic, ocular myokymia, and blepharospasm. To understand the overall craniofacial abnormalities and to perform the optimal surgical procedures for HFS, we are to review the prevalence, pathophysiology, differential diagnosis, details of each treatment modality, usefulness of brainstem auditory evoked potentials monitoring, debates on the facial EMG, clinical course, and complications from the literature published from 1995 to the present time.

The Utility of Somatosensory Evoked Potential Monitoring During Cervical Spine Surgery: How Often Does It Prompt Intervention and Affect Outcome?

Study DesignRetrospective review of the results of somatosensory evoked potentials (SSEP) performed in cervical spine surgery.PurposeTo evaluate the utility of spinal cord monitoring during cervical spine surgery in a single surgeon's practice, based on how often it prompted an intraoperative intervention.Overview of LiteratureIntraoperative monitoring during cervical spine surgery is not a universally accepted standard of care. This is due in part to the paucity of literature regarding the impact of monitoring on patient management or outcome.MethodsSSEP for tibial, median, and ulnar nerves were monitored in 809 consecutive cervical spine operations performed by a single surgeon. The average patient age was 52 years (range, 2 to 88 years), with 472 males and 339 females. Cases were screened for significant degradation or loss of SSEP data. Specific attention was paid to 1) what interventions were performed in response to the SSEP degradation with subsequent improvement, and 2) whether SSEP changes corresponded with postoperative neurological deficits.ResultsSeventeen of 809 patients (2.1%) had SSEP degradation that met warning criteria and therefore prompted intervention. Release of shoulder tape (8) or traction (4) most often resulted in SSEP improvement. Failure of SSEP data to return to within acceptable limits of baseline was associated with neurological deficit (p=0.04). Two patients awoke with new postoperative neurological deficits, which resolved in 6 hours and 2 months respectively. Patients with ossification of the posterior longitudinal ligament (OPLL) were at seven-fold greater risk of intraoperative SSEP degradation.ConclusionsSSEP monitoring in this surgical population proved sensitive to perioperative factors which may increase the risk of postoperative neurologic deficit, and probably prevented neurological deficits in 15 of 809 patients (1.9%). Improvement in data following intervention appears to correlate well with unchanged neurologic status. Experience with intraoperative monitoring in this patient series has led to incorporation of these techniques as a standard of care in cervical spine surgeries performed by this surgeon.

Immediate ischemic preconditioning based on somatosensory evoked potentials seems to prevent spinal cord injury following descending thoracic aorta cross-clamping

Delayed ischemic preconditioning has demonstrated neuroprotective effects in spinal cord ischemia. We investigated the effects of immediate ischemic preconditioning based on somatosensory evoked potentials monitoring in a model of spinal cord injury due descending thoracic aorta occlusion in dogs. Twenty-one dogs were submitted to spinal cord ischemia induced by descending thoracic aorta cross-clamping for 45 min. Control group underwent only the aortic cross-clamping (n=7), group A underwent one cycle of ischemic preconditioning (n=7) and group B underwent three equal cycles of ischemic preconditioning (n=7), immediately before the aortic cross-clamping. Ischemic preconditioning cycles were determined by somatosensory evoked potentials monitoring. Neurologic evaluation was performed according to the Tarlov score at 72 h of follow-up. The animals were then sacrificed and the spinal cord harvested for histopathology. Aortic pressures before and after the occluded segment were similar in the three groups. Ischemic preconditioning periods corresponded to a mean ischemic time of 3+/-1 min and a mean recovery time of 7+/-2 min. Severe paraplegia was observed in three animals in Control group, in four in group A and in none in group B. Tarlov scores of group B were significantly better in comparison to the Control group (P=0.036). Histopathologic examination showed severe neuronal necrosis in the thoracic and lumbar gray matter in animals who presented paraplegia. Immediate repetitive ischemic preconditioning based on somatosensory evoked potentials monitoring seems to protect spinal cord during descending aorta cross-clamping, reducing paraplegia incidence.

Cerebellar-evoked potentials and nitrous oxide in healthy subjects

INTRODUCTION: Evoked Potential monitoring has become common practice during major spinal surgery. The aim is to alert the surgical team to impending ischaemic damage and avoid permanent neurological injury. The most common modality used is Somatosensory Evoked Potential (SSEP) monitoring. However, SSEPs have some important limitations. They are known to be influenced by commonly used anaesthetic agents.(1). SSEPs are carried via the dorsal columns so monitoring of SSEPs alone may allow a ventral cord defect to go undetected. Cerebellar Evoked Potentials (CEPs) have been reported as a potential monitor of ventral cord integrity. (2,3). A pilot study in the intraoperative setting has suggested that CEPs are robust during general anaesthesia.(4). The purpose of this study is to characterize these evoked potentials and to determine the effect of nitrous oxide in healthy volunteers.

An experimental study of cell apoptosis and correlative gene expression after tractive spinal cord injury in rats

To observe the cell apoptosis after tractive spinal cord injury in rats, determine expression of apoptosis correlative genes, and study the molecular mechanism of cell apoptosis. The T(13)-L(2) spinal cord of rats was injured by traction after the amplitude of P1-N1 wave decreased to 70% in postoperation than in preoperation through cortical somatosensory evoked potential (CSEP) monitor. Then rats were killed in 30 min, 6 h, 1, 4, 7, 14 and 21 d respectively after operation (n = 4). Cell apoptosis was examined by the flow cytometer and terminal deoxynucleotidyl transferase-mediated DUTP-biotin nick end labeling (TUNEL) reaction, the expression of p53, bax and bc1-2 genes was tested with immunohistochemistry. The flow cytometer test and TUNEL method showed that the apoptosis cell ratio raised in 6 h and reached at peak in 7 d after injury, and then declined till 21 d, they showed significant difference (P < 0.05, 0.01). TUNEL method showed that injured group had a large number of apoptosis glial cells in white matter. Immunohistochemical staining showed that the positive expression of p53, bax and bc1-2 protein raised at 6 h, expression of p53 protein reached at peak in 4 d, bax and bc1-2 protein reached at peak in 7 d after injury. Compared with control group and laminectomy group, the injured group showed significant difference (P < 0.05, 0.01). There is cell apoptosis phenomenon after tractive spinal cord injury in rats. Morphology indicates that apoptosis includes neurons and glialcytes, which is an important form of cell death and pathological changes in secondary lesion period after tractive spinal cord. There exist high expression of apoptosis correlative gene p53 and bax after spinal cord injury, they may play an important role in reduction of cells to apoptosis.