Spinal Cord Monitoring Research Articles

Spinal Cord Monitoring in Neuromuscular Scoliosis

This article reviews the use of spinal cord monitoring in neuromuscular scoliosis, a condition having a higher incidence of true positive results than idiopathic scoliosis. While somatosensory cortical evoked potentials (SCEP) are unreliable, somatosensory spinal evoked potentials (SSEP) are possible to obtain in most cases and a method using an epidural electrode is described. The '50% rule' is satisfactory having good specificity and sensitivity with it rare for post-operative paralysis to have occurred undetected. The spinal cord in these cases appears to have increased susceptibility particularly during the passage of sublaminar wires with the incidence of complications reduced using modern instrumentation.

Room E, 10/16/2000 9: 00 AM - 11: 00 AM (PS) Spinal Cord Monitoring during Thoracic Neurosurgical Procedures

<b>Room E, 10/16/2000 9: 00 AM - 11: 00 AM (PS) Spinal Cord Monitoring during Thoracic Neurosurgical Procedures</b>

Safety of sublaminar wires with Isola instrumentation for the treatment of idiopathic scoliosis.

To investigate the incidence of acute neurologic complications of use of sublaminar wires with third-generation spine instrumentation for the treatment of idiopathic scoliosis. To assess the safety of sublaminar wires in the surgical treatment of idiopathic scoliosis. The use of sublaminar wires in spine deformity for neuromuscular scoliosis and the Luque system has been reported. Use of sublaminar wires is an integral part of the technique in the surgical treatment of spine deformity with Isola instrumentation (AcroMed, Cleveland, OH). To date, the safety of this technique has not been documented. The average age of the patients was 37 years (range, 11-74 years). Preoperative diagnosis was adolescent idiopathic scoliosis in 75 patients and adult idiopathic scoliosis in 66. One hundred nine were primary surgeries, and 32 were revision. Detailed evaluation of the curve type, curve magnitude, number of vertebrae instrumented, level of vertebrae wired, postoperative neurologic deficit, and the findings of intraoperative spinal cord monitoring was performed. Wires were always passed just before corrective maneuvers were performed. A total of 1366 wires were placed, 65% (n = 888) in the thoracic region, 22% (n = 300) in the thoracolumbar, and 13% (n = 178) in the lumbar. No permanent change in intraoperative spinal cord monitoring was detected. Stagnara wake-up test was performed in all patients. No patient with adolescent idiopathic scoliosis had neurologic complication. Two adults underwent revision surgery and had transient dysesthesia in the leg, which completely resolved with observation. Despite the increasing complexity of spinal instrumentation systems, sublaminar wire placement is a safe and useful adjunct in the surgical treatment of neurologically intact patients with idiopathic scoliosis.

Intra-operative spinal cord monitoring in orthopaedics.

The surgical correction of spinal deformities carries a small but significant risk of injury to the spinal cord. To detect the onset and possibly reverse the effects of surgical complication, a variety of neurophysiological monitoring procedures can be employed. The purpose of this review is to provide information regarding the various methodologies available for monitoring spinal cord and nerve root function during orthopaedic procedures. Intra-operative monitoring of cortically recorded somatosensory evoked potentials (SEPs) by peripheral nerve stimulation is of value during orthopaedic surgery and is the state-of-the-art in terms of non-invasiveness, versatility, time requirement, lateral discrimination, and ease of electrode placement. Monitoring of motor evoked potentials (MEPs) is useful particularly in combination with SEPs but is still considered investigational. Root function monitoring has limited application and requires more clinical research.

Evaluation of motor- and sensory-evoked potentials for spinal cord monitoring during thoracoabdominal aortic aneurysm surgery.

To assess the utility of spinal cord monitorings for prediction of spinal cord ischemia, we investigated the role of both motor evoked potentials and sensory evoked potentials during thoracoabdominal aortic aneurysm surgeries. We monitored two kinds of sensory evoked potentials; descending evoked spinal cord potentials from the lumbar enlargement after cervical spinal cord stimulation and segmental evoked spinal cord potentials at the lumbar enlargement elicited by peroneal nerve stimulation, and motor evoked potentials from the lumbar enlargement elicited by direct subcranial stimulation in 9 thoracoabdomonal aortic aneurysm surgeries. Postoperative paraplegia occurred in one case in which the patients died during the perioperative period. One case showed transient paraparesis, but recovered following rehabilitatation. These cases showed a decrease in the amplitude of descending evoked spinal cord potentials and motor evoked potentials. The recovery of the amplitude of the motor evoked potentials and the descending evoked spinal cord potentials after declamping correlated with the neurologic outcome.

Spinal cord monitoring

Spinal cord monitoring

Anaesthesia for spinal surgery

Patients with and without spinal disease are at risk of neurological damage during anaesthesia, even when the surgery is not directed at the spine. Certain types of spinal surgery carry a substantial risk. Reports of spinal cord damage due to direct laryngoscopy are unconvincing. Evoked potential spinal cord monitoring is used increasingly during anaesthesia, and successful recording of potentials requires the co-operation of the anaesthetist. Airway problems are common in cervical spine disease, particularly if the disease affects the upper three vertebrae. Anterior surgical approaches to the craniocervical junction involve extensive surgery, with implications for airway management and nutrition.

Spinal cord monitoring.

Over the past two decades, intraoperative spinal cord monitoring has matured into a widely used clinical tool. It is used when the spinal cord is at risk for damage during a surgical procedure. This includes orthopedic, neurosurgical, and certain cardiothoracic procedures. Both somatosensory evoked potential (SEP) and direct motor pathway stimulation techniques are available. The SEP techniques are used most widely, are generally accepted, and have been shown to reduce surgical morbidity. A large multicenter study has shown that SEP monitoring reduces postoperative paraplegia by more than 50-60%. Techniques and literature on clinical applications are reviewed in this report.

Successful monitoring of neurogenic mixed evoked potentials elicited by anterior spinal cord stimulation through thoracoscopy during spine surgery.

Neurogenic mixed evoked potentials were recorded after thoracoscopic spinal cord stimulation in patients undergoing video-assisted spine surgery. To demonstrate the feasibility and value of thoracoscopic spinal cord monitoring. Video-assisted thoracic surgery recently has been proposed as a new technique for thoracic spine surgery. It can be used for anterior spinal release of patients with severe spinal deformities and for thoracic hernia removal. Five patients undergoing video-assisted thoracic surgery for spinal fusion were studied. Neurogenic mixed evoked potentials were elicited by electrodes seated into intervertebral discs through thoracoscopy and recorded from peripheral nerves of the lower limbs. Moreover, the study included the case of a patient with a thoracic hernia who underwent video-assisted thoracic surgery with combined thoracoscopic neurogenic mixed evoked potential and standard somatosensory evoked potential monitoring. Neurogenic mixed evoked potentials were recorded consistently after spinal cord stimulation in all patients. For the patient with a thoracic hernia, neurogenic mixed evoked potentials suddenly disappeared, whereas somatosensory evoked potentials were not significantly modified, leading to surgery interruption. Neurogenic mixed evoked potentials progressively reappeared after a 30-minute delay. Postoperation examination revealed a Brown-Sequard's syndrome with incomplete right motor deficit. Neurogenic mixed evoked potentials evoked by anterior stimulation through thoracoscopy are of interest for spinal cord monitoring when posterior electrical stimulation is impossible, and they provide reliable information regarding spinal motor pathways.

SPINAL CORD MONITORING: Current State of the Art

The intraoperative application of evoked potential and electromyographic (EMG) monitoring has increased significantly over the last 2 decades. Cranial nerve monitoring is widely accepted and used by otologists, neurologic surgeons, and ophthalmologists. Direct and indirect techniques for assessing the peripheral nervous system are used by plastic and orthopedic surgeons when performing intraoperative nerve grafting. Myriad techniques and applications for monitoring the spinal cord and peripheral nervous system have been developed, evaluated, and used by orthopedic and neurologic surgeons involved in spinal surgery.

Spatial facilitation of motor evoked responses in monitoring during spinal surgery

During spinal cord monitoring, motor responses in the tibialis anterior muscles were recorded on transcranial electrical stimulation of the motor cortex. In order to facilitate the responses, the cortical stimulus was preceded by a train of stimuli to the foot sole within the receptive field of the withdrawal reflex of the tibialis anterior muscle. This cutaneous input provides a spatial facilitation of the cortically elicited response. When the stimulus interval was 50–100 ms, large and reliable responses were seen in most cases.

Convergence characteristics of two algorithms in non-linear stimulus artefact cancellation for electrically evoked potential enhancement

Somatosensory evoked potentials (SEPs) are a sub-class of evoked potentials (EPs) that are very useful in diagnosing various neuromuscular disorders and in spinal cord and peripheral-nerve monitoring. Most often, the measurements of these signals are contaminated by stimulus-evoked artefact. Conventional stimulus-artifact (SA) reduction schemes are primarily hardware-based and rely on some form of input blanking during the SA phase. This procedure can result in partial SEP loss if the tail of the SA interferes with the SEP. Adaptive filters offer an attractive solution to this problem by iteratively reducing the SA waveform while leaving the SEP intact. Owing to the inherent non-linearities in the SA generation system, non-linear adaptive filters (NAFs) are most suitable. SA reduction using NAFs based on truncated second-order Volterra expansion series is investigated. The focus is on the performance of two main adaptation algorithms, the least mean square (LMS) and recursive least squares (RLS) algorithms, in the context of non-linear adaptive filtering. A comparison between the convergence and performance characteristics fo these two algorithms is made by processing both simulated and experimental SA data. It is found that, in high artefact-to-noise ratio (ANR) SA cancellation, owing to the large eigenvalue spreads, the RLS-based NAF is more efficient than the LMS-based NAF. However, in low-ANR scenarios, the RLS-and LMS-based NAFs exhibit similar convergence properties, and the computatioal simplicity of the LMS-based NAFs makes them the preferred option.

Within-Patient Variability of Myogenic Motor-Evoked Potentials to Multipulse Transcranial Electrical Stimulation During Two Levels of Partial Neuromuscular Blockade in Aortic Surgery

Intraoperative recording of myogenic motor responses evoked by transcranial electrical stimulation (tcMEPs) is a method of assessing the integrity of the motor pathways during aortic surgery.To identify conditions for optimal spinal cord monitoring, we investigated the effects of manipulating the level of neuromuscular blockade (T1 response of the train-of-four (TOF) stimulation 5%-15% versus T1 response 45%-55% of baseline), as well as the number of transcranial pulses (two versus six stimuli) on the within-patient variability and amplitude of tcMEPs. Ten patients (30-76 yr) scheduled to undergo surgery on the thoracic and thoracoabdominal aorta were studied. After achieving a stable anesthetic state and before surgery, 10 tcMEPs were recorded from the right extensor digitorum communis muscle and the right tibialis anterior muscle in response to two-pulse and six-pulse transcranial electrical stimulation with an interstimulus interval of 2 ms during two levels of neuromuscular blockade. The right thenar eminence was used for recording the level of relaxation. The tcMEP amplitude using the six-pulse paradigm was larger (P < 0.01; leg and arm) compared with the amplitude evoked by two-pulse stimulation during both levels of relaxation. The within-patient variability, expressed as median coefficient of variation, was less when six-pulse stimulation was used. At a T1 response of 45%-55% of baseline, larger, less variable tcMEPs were recorded than at a T1 response of 5%-15%. Our results suggest that the best quality of tcMEP signals (tibialis anterior muscle) is obtained when the six-pulse paradigm is used with a stable level of muscle relaxation (the first twitch of the TOF-thenar eminence-at 45%-55% of baseline). Implications: This study shows that six-pulse (rather than two-pulse) transcranial electrical stimulation during a stable anesthetic state and a stable neuromuscular blockade aimed at 45%-55% (rather than 5%-15%) of baseline provides reliable and recordable muscle responses sufficiently robust for spinal cord monitoring in aortic surgery. (Anesth Analg 1999;88:22-7)

Protocolo de monitorizacion neurofisiológica intraoperatoria de la médula espinal

The consequences derived from medullar harm caused during several spinal cord surgical interventions can often be catastrophic for the patient, even more taking into consideration that many of them are young. This problem is observed specially at interventions of spinal malformations (kyphoscoliosis), but also during other surgical techniques like fractures, degenerations, spinal tumors and aortic lesions. The use of somatosensory evoked potentials (SEP) began at late 70's, as a method to monitorize spinal cord function during surgery; years later, motor evoked potentials (MEP) joined this option, giving us direct information about the functioning of posterior spinothalamic tract (posterior column) and lateral corticospinal tract (pyramidal tract), respectively. This has motivated that, although the degree of surgical difficulty and complexity of spinal instrumentation have raised, the actual percentage of neurological complications derived from them has decreased. This article describes the intraoperative spinal cord monitoring protocol followed at Hospital Clínico San Carlos of Madrid, Spain, which includes the making of SEP and MEP, the latest according to the translaminar stimulation technique.

Ｔ‐ｓａｗを用いたきょく突起縦割式脊柱管拡大術中における脊髄モニタリングの変化例について

Ｔ‐ｓａｗを用いたきょく突起縦割式脊柱管拡大術中における脊髄モニタリングの変化例について

Le monitorage des potentiels évoqués mixtes neurogènes au cours de la chirurgie du rachis: une bonne solution?

Spinal deformity surgery carries a risk of rare but dramatic neurological complications. Intraoperative spinal cord monitoring has been initially performed using somatosensory evoked potentials (SEP). However, false-negative cases have been reported and neurophysiologists supplement SEPs with concurrent motor evoked potentials. The so-called neurogenic mixed evoked potentials (NMEPs) represent an alternate choice, allowing combined monitoring of motor and somatosensory central pathways. They are recorded from a peripheral nerve after spinal cord stimulation. NMEPs have been experimentally and clinically shown to be sensible for detecting spinal cord injury. They are easily and rapidly recorded, and NMEP monitoring may be continuously performed during the critical steps of surgery.

Spinal cord monitoring.

Spinal cord monitoring.

Spinal cord monitoring with somatosensory techniques.

Spinal cord monitoring with somatosensory techniques.

Convergence characteristics of two algorithms in non-linear stimulus artefact cancellation for electrically evoked potential enhancement.

Somatosensory evoked potentials (SEPs) are a sub-class of evoked potentials (EPs) that are very useful in diagnosing various neuromuscular disorders and in spinal cord and peripheral-nerve monitoring. Most often, the measurements of these signals are contaminated by stimulus-evoked artefact. Conventional stimulus-artifact (SA) reduction schemes are primarily hardware-based and rely on some form of input blanking during the SA phase. This procedure can result in partial SEP loss if the tail of the SA interferes with the SEP. Adaptive filters offer an attractive solution to this problem by iteratively reducing the SA waveform while leaving the SEP intact. Owing to the inherent non-linearities in the SA generation system, non-linear adaptive filters (NAFs) are most suitable. SA reduction using NAFs based on truncated second-order Volterra expansion series is investigated. The focus is on the performance of two main adaptation algorithms, the least mean square (LMS) and recursive least squares (RLS) algorithms, in the context of non-linear adaptive filtering. A comparison between the convergence and performance characteristics of these two algorithms is made by processing both simulated and experimental SA data. It is found that, in high artefact-to-noise ratio (ANR) SA cancellation, owing to the large eigenvalue spreads, the RLS-based NAF is more efficient than the LMS-based NAF. However, in low-ANR scenarios, the RLS- and LMS-based NAFs exhibit similar convergence properties, and the computational simplicity of the LMS-based NAFs makes them the preferred option.

Anesthesia for Surgery of the Spine

Division of Neurosurgical Anesthesia and Neurocritical Care Medicine (Ulatowski).Fellow in Neurosurgical Anesthesia, Department of Anesthesiology/Critical Care Medicine, The Johns Hopkins Medical Institutions, Meyer 8–140, 600 N. Wolfe Street, Baltimore, Maryland 21287 (Breder).James C. Eisenach, M.D., EditorAnesthesia for Surgery of the Spine. Edited by Susan S. Porter. New York, McGraw Hill, Inc., 1995. Pages: 390. Price:$65.00.It is with pleasure that I review this compact but reasonably comprehensive textbook. It is multi-authored, containing 12 chapters, 15–60 pages in length. Contributors are respected experts in the field of anesthesia and neurosurgery of the spine. The combination makes for an informative base for discussion of topics shared in common between anesthesiologist and surgeon. Each chapter begins with an outline, providing the reader an opportunity to scan the content for the desired topic.The early chapters cover anatomy, functional organization, and physiology of the spinal cord. Herein are descriptions of bony and ligamentous vertebral anatomy, followed in sequence by a neuroanatomic review of the spinal cord, and, all important to the anesthesiologist, a review of spinal cord blood flow and responses of the vascular system to metabolic stimulation and anesthetic agents. In these preliminary chapters, the reader is introduced to wonderful drawings, which for the most part are in grey scale. They are simple and adequately labeled and can serve as templates for teaching slides. One of the highlights of the early chapters is a comprehensive review of acute and chronic cervical spinal cord injury that is well referenced and written by noted experts in the field of neurosurgical anesthesia.The core of the book, some five chapters, proceeds through an anatomically based review of surgical procedures and anesthetic management of spine operations. These deal with cervical and thoracic, thoracolumbosacral, and surgery for radiculopathy and discectomy. Interspersed within this scheme are chapters dealing with intrinsic lesions of the spinal cord and considerations to special aspects for surgery and anesthesia of the arthritides. Although these two chapters interrupt the flow of the anatomic review, they are nonetheless valuable components of the book. Of special note in this section is a chapter covering the anesthesia and surgery for pediatric spine, an extremely well-referenced compendium of current practice on this topic.The final chapters span electrophysiologic monitoring of spinal cord, intensive care management, and treatment and diagnosis of pain syndromes after spinal cord injury. These also are up-to-date and adequately annotated for later reference by the reader.There are, however, some disappointing aspects of the book that deserve comment. Although each chapter obviously was designed to be comprehensive and to stand alone, the degree of overlap is excessive. Reading more than one chapter at a sitting, one discovers significant duplication especially regarding general diagnosis and in particular patient positioning. Because perioperative comanagement of patients and positioning are of such importance in spine surgery, a chapter devoted to this would be an outstanding reference. Also, my initial enthusiasm for the illustrations in the early chapters soon found similar disappointment. Mislabeling of a figure and failure to consider that a multicolored graph would not show differences in grey scale were rare and forgivable. However, less acceptable was the reproduction quality of radiographs, magnetic resonance imaging scans, and tissue specimens. These were suboptimal as a result of poor lighting or dark reproductions. On many, labeling with arrows, which would have been helpful, was unclear or absent. One cervical radiograph was positioned upside down. Anesthesiologists increasingly need expertise in reading radiographs, including magnetic resonance imaging scans, for appropriate evaluation of the patient with scoliosis, evidence of cord compression before intubation, and placement of intraoperative monitoring, for example. Reason enough for a second edition!Despite minor drawbacks, this textbook still has considerable value for the price. The anesthesiologist who only occasionally does anesthesia for spine surgery will find the concise chapter, which can be read the evening before a case, very useful. Even the expert neuroanesthesiologist will find particular chapters on physiology, acute and chronic spinal cord injury, and pediatric spine surgery valuable collections for distribution to fellows and residents.John A. Ulatowski, M.D., Ph.D.Division of Neurosurgical Anesthesia and Neurocritical Care MedicineChris Breder, M.D.Fellow in Neurosurgical Anesthesia; Department of Anesthesiology/Critical Care Medicine; The Johns Hopkins Medical Institutions; Meyer 8–140; 600 N. Wolfe Street; Baltimore, Maryland 21287