Intraoperative Neural Monitoring Research Articles

Intermittent Intraoperative Neural Monitoring Technology in Minimally Invasive Video-Assisted Thyroidectomy: A Preliminary Study

ABSTRACTPurpose: Intraoperative neural monitoring (IONM) technology was applied in minimally invasive video-assisted thyroidectomy (MIVAT) to explore its safety and effectiveness. Materials and Methods: Data were collected retrospectively from October 2009 to August 2011. Inclusion criteria included the following: (1) benign thyroid nodule with maximum diameter less than 4.0 cm by preoperative ultrasound evaluation; (2) no previous thyroid surgeries; (3) no cervical radiation history; (4) normal function of recurrent laryngeal nerve (RLN) examined by preoperative laryngoscopy; (5) patients who did not accept to take a “wait and see” follow-up strategy. Enrolled patients were randomly allocated into NIM group and control group. Results: 46 patients were enrolled in NIM group, and 51 patients were enrolled in control group. All surgeries in NIM group were performed successfully, and majority of tracheal intubations were placed with one attempt. 47 RLNs in NIM group and 60 RLNs in control group were exposed. The time of RLN locating was 6.06 ± 1.48 min in NIM group and 6.92 ± 1.34 min in control group (p = .02). The time of RLN tracing and exposing was 28.96 ± 4.75 min in NIM group and 32.17 ± 5.56 min in control group (p = .02). 1 case of temporary RLN paralysis was observed in both groups, and no permanent RLN paralysis was reported. Conclusions: The application of intermittent IONM in MIVAT is feasible. Intermittent IONM can help reduce the time of RLN locating and the time of RLN tracing and exposing.

Revision neural monitored surgery for recurrent thyroid cancer: Safety and thyroglobulin response.

To evaluate the quantitative biochemical response, recurrence rate, and rate of surgical complications for thyroid cancer revision surgery. Retrospective review. This is a single institution analysis of a prospective database of 181 patients undergoing reoperation for local recurrent thyroid cancer by the same surgeon from 2004 to 2013 with intraoperative neural monitoring. Main outcome measures included pathologic findings, surgical complications, effect of reoperation on thyroglobulin (Tg) levels, and recurrence rate. We defined biochemical complete remission as postoperative stimulated Tg of 0.2 ng/mL or less. Fourteen percent of the patients presented with permanent vocal cord palsy (VCP), and 20% of the patients presented with hypocalcemia prior to surgery. Among them, 70% of the patients underwent first revision surgery; whereas in 30% the surgery represented second or higher revision surgery, with 8% being a third or higher revision. None developed temporary or permanent VCP. Temporary hypocalcemia occurred in 9% of the patients, and permanent hypocalcemia occurred in 4.2%. The rate of cervical node recurrence was 5% at a median follow-up of 3.4 years. There were no disease-specific deaths. Mean preoperative basal Tg was 22.3 ng/mL and mean postoperative Tg was 5.7 ng/mL, a decline of 74% (P = 0.023, paired t test). Biochemical complete remission was achieved in 58% of all revision cases. Reoperative neural monitored surgery for recurrent thyroid cancer is a safe and effective procedure with limited morbidity in experienced hands, even in the setting of multiple prior revision surgeries and existing comorbidities such as VCP and hypocalcemia. 4.

The Overwhelming Majority but not All Motor Fibers of the Bifid Recurrent Laryngeal Nerve are Located in the Anterior Extralaryngeal Branch.

BackgroundFew small studies reported that motor fibers are located exclusively in the anterior branch of the bifid recurrent laryngeal nerve (RLN). The aim of this study was to investigate the location of the motor fibers to the intrinsic muscles of the larynx among the bifid RLNs, and assess the prevalence of RLN injury with respect to nerve branching in a pragmatic trial.MethodsThis was a prospective cohort study of 1250 patients who underwent total thyroidectomy with intraoperative neural monitoring. The primary outcome was the position of the motor fibers in the bifid nerves. Adduction of the vocal folds was detected by the endotracheal tube electromyography and abduction by finger palpation of muscle contraction in the posterior cricoarytenoid. The secondary outcomes were the prevalence of the RLN branching and the prevalence of RLN injury in bifid versus non-bifid nerves.ResultsThe bifid RLNs were identified in 613/2500 (24.5 %) nerves at risk, including 92 (7.4 %) patients with bilateral bifurcations. The motor fibers were present exclusively in the anterior branch in 605/613 (98.7 %) bifid nerves, and in both the RLN branches in 8/613 (1.3 %) bifid nerves. Prevalence of RLN injury was 5.2 versus 1.6 % for the bifid versus non-bifid nerves (p < 0.001), odds ratio 2.98 (95 % confidence interval 1.79–4.95; p < 0.001).ConclusionsThe motor fibers of the RLN are located in the anterior extralaryngeal branch in the vast majority of but not in all patients. In rare cases, the motor fibers for adduction or abduction are located in the posterior branch of the RLN. As the bifid nerves are more prone to injury than non-branched nerves, meticulous dissection is recommended to assure preservation of all the branches of the RLN during thyroidectomy.

Prospective validation study of Cernea classification for predicting EMG alterations of the external branch of the superior laryngeal nerve.

Cernea classification is applied to describe the external branch of the superior laryngeal nerve (EBSLN). Using intraoperative neural monitoring we evaluated whether or not this classification is useful for predicting which EBSLN subtype has an increased risk of injury. An analysis of 400 EBSLN. The identification of EBSLN was achieved with both cricothyroid muscle twitch and the glottis evoked electromyography response. We defined S1 initial EBSLN stimulation at identification and S2 final nerve stimulation achieved in the most cranial aspect of the nerve exposed above the area of surgical dissection after superior artery ligation. The mean S1 amplitude acquired was 259+/67 (180-421), 321+/79 (192-391), 371+/38 (200-551) μV, respectively, for type 1, 2A, 2B (p=0.08). The S1 and S2 amplitudes were similar in type 1 (p=0.3). The S1 and S2 determinations changed significantly in type 2A and 2B (p=0.04 and 0.03). EBSLN which demonstrated a >25% decreased amplitude in S2 increased significantly from Type 1 (4.9%) to Type 2A (11.2%) and 2B (18%) (p=0.01). None of type 1, 2.8% type 2A and 3% type 2B showed a loss of EBSLN conductivity. The latency determinations did not vary significantly for any parameter compared. The Cernea classification was, therefore, found to predict the risk of EBSLN stress. We identified amplitude differences between S1 and S2 determinations in type 2A and 2B, thus confirming that surgical dissection in these subtypes is, therefore, extremely difficult to perform.

Consensus statements in surgery: intra-operative neural monitoring for thyroid surgery.

Consensus statements in surgery: intra-operative neural monitoring for thyroid surgery.

Superior laryngeal nerve quantitative intraoperative monitoring is possible in all thyroid surgeries

To report normative electromyography (EMG) data on the external branch of the superior laryngeal nerve (EBSLN) and to compare this to analogous data of the recurrent laryngeal nerve (RLN) and vagus nerve (VN) during intraoperative neural monitoring (IONM) using both the standard monopolar stimulator probe and a novel bipolar stimulator probe. Prospective multiple tertiary care center study. A prospective study of EBSLN, RLN and VN EMG data in 22 thyroid surgeries was performed. Subjects with preoperative vocal fold paralysis were excluded. Postoperative laryngoscopy was normal in all subjects. Normative EMG data were acquired using both a standard monopolar and a novel bipolar stimulator probe, as well as a novel endotracheal tube. Cricothyroid muscle (CTM) twitch response during EBSLN stimulation was analyzed. In 100% of cases, EBSLN was identified and quantifiable EMG response was observed. EMG amplitude did not change despite extensive nerve dissection and multiple nerve stimulations. EBSLN amplitude was similar for left and right sides for patients under age 50 and aged 50 or older, for both genders, and with monopolar and bipolar stimulators. Intraoperative neural monitoring may be used to safely assist in EBSLN identification during thyroid surgery in 100% of patients. A novel endotracheal tube allows for quantifiable EBSLN EMG activity in 100% of cases. Monopolar and bipolar stimulator probes produce similar EMG data. 4.

The value of neuromonitoring in cervical spine surgery.

Dear Editor, We read with interest the paper by Epstein entitled: The need to add motor evoked potential monitoring to somatosensory and electromyographic monitoring in cervical spine surgery.[1] The paper reviews the spine surgery literature regarding the use of intraoperative neural monitoring (IONM). Theoretically, IONM should alert the operative team that impending neurological injury is possible and a corrective maneuver performed to prevent such. IONM may be problematic in that it might alarm and result in an abandonment or alteration of the surgical procedure when no true neurological deficit is subsequently demonstrated (false positive). More worrisome, however, is the situation when no alert is observed and neurological injury ensued (false negative). Debate may be held with regard to the most appropriate surgical procedures for the use of IONM. Ideally, this should involve procedures in which potentially harmful maneuvers can be reversed. A classic example is deformity correction, which can be reversed if IONM suggests such. In cases in which “surgical reversal” is not possible, IONM has been shown to demonstrate true and false positives, however, studies have not demonstrated improved outcomes.[7] Many infer that IONM is associated with improved clinical results. However, it should be noted that the referenced studies compared outcomes with historical cohorts. Epstein et al.[2] reported 100 cases of IONM monitored cervical surgeries with no new neurological deficit. The historical cohort of this study included 218 patients operated in years 1985-1989, 8 of which became quadriplegic. This control population is clearly an outlier, as quadriplegia following elective cervical spine surgery for degenerative conditions is, indeed, a rarity and the rate is far less than the nearly 4% reported in the referenced study. Other studies cited by Epstein[1] show a high rate of false positives or false negatives with IONM, and low rate of true positives.[3,5,6] During degenerative cervical spine surgery, neurological injury may occur any of several phases. It may occur during induction of anesthesia with resultant hypotension, during positioning (flexion or extension) of the cervical spine in either prone or supine position, from intraoperative hypotension, and/or from direct surgical trauma. With the exception of hypotension and positioning, none of these potential causes of neurological injury are reversible. IONM, therefore can only signal that a neurological injury may have occurred, but does not afford the surgeon an enhanced opportunity to remedy or mitigate the neurological injury. When spinal cord injury occurs from direct surgical trauma, IONM serves only to document the timing of the trauma and cannot assist with altering the clinical outcome. There may then be little utility for IONM in degenerative cervical spine surgery. This conclusion has been borne out in the literature. Resnick et al.[7] reviewed the literature regarding IONM for degenerative cervical spine surgery. Their published guidelines concluded that relying on IONM changes as an indication for altering surgical procedure or administration of steroids has not been shown to reduce the incidence of neurological deterioration. The addition of IONM to degenerative cervical surgery has financial implications, however, cost-benefit analysis has not demonstrated benefit.[4] IONM is also often used for medico-legal reasons. Epstein reviewed the cervical spine surgery verdicts and determined the causes for verdicts were negligent surgery, lack of informed consent, failure to diagnose/treat, and failure to brace. She speculated that failure to adequately perform IONM may become the fifth reason for verdicts in cervical spine surgery. As the guidelines for cervical spinal surgery do not include the use of IONM,[7] and no clear algorithm for intraoperative action when IONM changes are observed, the routine use of IONM cannot serve as protection against a plaintiffs’ verdict. In the authors’ opinion, IONM in spine surgery has a definite role. This role includes intradural tumor surgery, deformity surgery, and cases in which patient positioning in and of itself poses neurological risk. IONM, however, has not been proven effective as a neuroprotective maneuver in the majority of cervical degenerative surgical procedures.

Intraoperative neuro-monitoring corner editorial: The need for preoperative sep and mep baselines in spinal surgery: Why can't we and our monitoring colleagues get this right?

Background:The majority of spinal surgeons now utilize intraoperative neurophysiological monitoring (IONM) during spinal procedures to limit the risk of inadvertent injury. Nevertheless, probably the most frequent error is the failure of the surgeon and IONM to obtain adequate preoperative baselines (e.g. before intubation or positioning).Methods:Intraoperative neural monitoring should begin with the spinal surgeon, anesthesiologist, and monitoring technician/neurologist reviewing the patient's neurological deficits, the operative approach, the most anticipated risks and complications as well as the type of monitoring to be used (e.g. somatosensory evoked responses [SEP], motor evoked potential [MEP] monitoring, and electromyography [EMGs]). Baseline data should accurately reflect the preoperative status of the patient, and provide the appropriate data to be monitored and maintained throughout surgery.Results:Significant but transient changes from the established preoperative baseline SEP and MEP often reflect alterations in the anesthetic technique (e.g. hypotension/hypoperfusion). However, when these changes persist, and resuscitative maneuvers have been exhausted (e.g. removing an oversized graft to avoid ischemia, utilizing total intravenous anesthesia [TIVA] correctly, reversing hypotension, changing the patient's cervical position, checking the electrode placement, checking the position of the limbs, and other factors), significant MEP/SEP changes may signal a major impending neural injury.Conclusion:IONM is only as good as how competently it is implemented by the technologist/neurologist, and understood by the surgeon and anesthesiologist. If any team member does not understand what and how the monitoring should be performed, then it becomes a useless adjunct to spinal surgery.

Intraoperative neural monitoring in thyroid cancer surgery

Intraoperative neural monitoring (IONM) has increasingly garnered the attention of the surgeons performing thyroid and parathyroid surgery around the world. Current studies suggest a majority of general and head and neck surgeons utilize neural monitoring in their thyroid surgical case load in both the US and Germany. We aim to present an up-to-date review of the application of IONM specifically focusing on its utility in thyroid cancer surgery. Neural monitoring is discussed particularly as it relates to neural prognosis, the issues of staged thyroid surgery for thyroid cancer, and new horizons in the monitoring of the superior laryngeal nerve (SLN) and prevention of neural injury through continuous vagal neural monitoring. IONM, as it relates to thyroid surgery, has obtained a widespread acceptance as an adjunct to the gold standard of visual nerve identification. The value of IONM in prognosticating neural function and in intraoperative decision making regarding proceeding to bilateral surgery is also well-known. Initial data on recent extensions of IONM in the form of SLN monitoring and continuous vagal nerve monitoring are promising. Continuous vagal nerve monitoring expands the utility of IONM by providing real-time electrophysiological information, allowing surgeons to take a corrective action in impending neural injury.

Pediatric Anesthesiology 2013 Meeting Review

Pediatric Anesthesiology 2013 Meeting Review

Electrophysiologic Monitoring Characteristics of the Recurrent Laryngeal Nerve Preoperatively Paralyzed or Invaded with Malignancy

To elucidate electrophysiologic responses of the recurrent laryngeal nerves that were preoperatively paralyzed or invaded by malignancy and to use this information as an added functional parameter for intraoperative management of recurrent laryngeal nerves with malignant invasion. Case series with chart review. Academic, tertiary care center. All consecutive neck surgeries with nerve monitoring performed by senior author (GWR) between December 1995 and January 2007 were reviewed after obtaining Institutional Review Board approval from Massachusetts Eye and Ear Infirmary Human Subjects Committee and the Partners Human Research Committee. Electrophysiologic parameters in all cases with preoperative vocal cord paralysis/paresis, and the recurrent laryngeal nerve invasion by cancer, were studied. Of the 1138 surgeries performed, 25 patients (2.1%) had preoperative vocal cord dysfunction. In patients with preoperative vocal cord dysfunction, recognizable recurrent laryngeal nerve electrophysiologic activity was preserved in over 50% of cases. Malignant invasion of the recurrent laryngeal nerve was found in 22 patients (1.9%). Neural invasion of the recurrent laryngeal nerve was associated with preoperative vocal cord paralysis in only 50% of these patients. In nerves invaded by malignancy, 60% maintained recognizable electrophysiologic activity, which was more commonly present and robust when vocal cord function was preserved. Knowledge of electrophysiologic intraoperative neural monitoring provides additional functional information and, along with preoperative vocal cord function information, aids in constructing decision algorithms regarding intraoperative management of the recurrent laryngeal nerve, in prognosticating postoperative outcomes, and in patient counseling regarding postoperative expectations.

External branch of the superior laryngeal nerve monitoring during thyroid and parathyroid surgery: International Neural Monitoring Study Group standards guideline statement

Intraoperative neural monitoring (IONM) during thyroid surgery has gained widespread acceptance as an adjunct to the gold standard of visual identification of the recurrent laryngeal nerve (RLN). Contrary to routine dissection of the RLN, most surgeons tend to avoid rather than routinely expose and identify the external branch of the superior laryngeal nerve (EBSLN) during thyroidectomy or parathyroidectomy. IONM has the potential to be utilized for identification of the EBSLN and functional assessment of its integrity; therefore, IONM might contribute to voice preservation following thyroidectomy or parathyroidectomy. We reviewed the literature and the cumulative experience of the multidisciplinary International Neural Monitoring Study Group (INMSG) with IONM of the EBSLN. A systematic search of the MEDLINE database (from 1950 to the present) with predefined search terms (EBSLN, superior laryngeal nerve, stimulation, neuromonitoring, identification) was undertaken and supplemented by personal communication between members of the INMSG to identify relevant publications in the field. The hypothesis explored in this review is that the use of a standardized approach to the functional preservation of the EBSLN can be facilitated by application of IONM resulting in improved preservation of voice following thyroidectomy or parathyroidectomy. These guidelines are intended to improve the practice of neural monitoring of the EBSLN during thyroidectomy or parathyroidectomy and to optimize clinical utility of this technique based on available evidence and consensus of experts. 5

Trends in intraoperative neural monitoring for thyroid and parathyroid surgery amongst otolaryngologists and general surgeons

The role of intraoperative neural monitoring (IONM) in thyroid and parathyroid surgery remains a controversial subject for surgeons regardless of surgical training and background. This study aims to compare usage patterns and motivations behind IONM among otolaryngologist-head and neck surgeons (OTO-HNS) and general surgeons (GS) performing thyroid and parathyroid surgery. The study is a multi-institution survey of 103 otolaryngology and affiliated 103 GS programs in the US. 206 surveys were sent to OTO-HNS and GS academic program directors with a response rate of 44.7 %. Of those who performed thyroid surgery, 80.6 % of OTO-HNS and 48.0 % of GS surgeons reported using IONM. 44.3 % of OTO-HNS and 30.8 % of GS respondents used IONM in all thyroid cases. For thyroid surgery, as surgical volume increased, surgeons were more likely to use IONM more frequently. Fourteen percent (14 %) of the OTO-HNS and 41.7 % of the GS respondents used IONM primarily to locate the RLN. Forty percent (40 %) of the OTO-HNS and 8.3 % of the GS used IONM for medicolegal reasons. The majority of OTO-HNS programs use IONM for thyroid and parathyroid surgery, whereas less than half of GS programs regularly use IONM for these surgeries. Thyroid surgeons, with larger thyroid surgery volume, regardless of discipline, tend to use IONM more. The motivations for using IONM differ significantly between OTO-HNS and general surgeons in that more GS use it for locating the RLN, and more OTO-HNS use it for continuous monitoring of the nerve during resection and for medicolegal purposes.

The need to add motor evoked potential monitoring to somatosensory and electromyographic monitoring in cervical spine surgery.

Intraoperative neural monitoring (IONM), utilizing somatosensory evoked potentials (SEP) and electromyography (EMG), was introduced to cervical spine surgery in the late 1980's. However, as SEP only provided physiological data regarding the posterior cord, new motor deficits were observed utilizing SEP alone. This prompted the development of motor evoked potential monitoring (MEP) which facilitated real-time assessment of the anterior/anterolateral spinal cord. Although all three modalities, SEP, EMG, and MEP, are routinely available for IONM of cervical spine procedures, MEP are not yet routinely employed. The purpose of this review is to emphasize that MEP should now routinely accompany SEP and EMG when performing IONM of cervical spine surgery. Interestingly, one of the most common reasons for malpractice suits involving the cervical spine, is quadriparesis/quadriplegia following a single level anterior cervical diskectomy and fusion (ACDF). Previously, typical allegations in these suits included; negligent surgery, lack of informed consent, failure to diagnose/treat, and failure to brace. Added to this list, perhaps, as the 5th most reason for a suit will be failure to monitor with MEP. This review documents the value of MEP monitoring in addition to SEP and EMG monitoring in cervical spine surgery. The addition of MEP0 should minimize major motor injuries, and more accurately and reliably detect impending anterior cord deterioration that may be missed with SEP monitoring alone.

Visualization versus Neuromonitoring of Recurrent Laryngeal Nerves during Thyroidectomy: What About the Costs?

The objective of the present study was to evaluate costs for thyroidectomy performed with the aid of intraoperative neural monitoring (IONM), which has gained widespread acceptance during thyroid surgery as an adjunct to the gold standard of visual nerve identification. Through a micro-costing approach, the thyroidectomy patient-care process (with and without IONM) was analyzed by considering direct costs (staff time, consumables, equipment, drugs, operating room, and general expenses). Unit costs were collected from hospital accounting and standard tariff lists. To assess the impact of the IONM technology on hospital management, three macro-scenarios were considered: (1) traditional thyroidectomy; (2) thyroidectomy with IONM in a high-volume setting (5 procedures per week); and (3) thyroidectomy with IONM in a low-volume setting (1 procedure per week). Energy-based devices (EBD) for hemostasis and dissection in thyroidectomy were also evaluated, as well as the reimbursement made by the Italian Healthcare System on the basis of diagnosis related groups (DRGs), about €2,600. Comparison between costs and the DRG fee shows an underfunding of total hospitalization costs for all thyroidectomies, regardless of IONM use (scenario 1: €3,471). The main cost drivers are consumables and technologies (25%), operating room (16%), and staff (14%). Hospitalization costs for a thyroidectomy with IONM range from €3,713 to €3,770 (scenarios 2 and 3), 5–7% higher than those for traditional thyroidectomy. Major economic differences emerge when an EBD is used (€3,969). The regional DRG tariff for thyroid surgery is barely sufficient to cover conventional surgery costs. Intraoperative neural monitoring accounts for 5–7% of the hospitalization costs for a thyroidectomy.

Vestibular Monitoring via Abducens EMG: Observations on a Single Case

Advancement in skull base surgery has occurred due to the improved ability to remove larger and less accessible tumors while minimizing morbidity. Petroclival meningiomas represent a particular challenge due to their proximity to and involvement with multiple cranial nerves. Intraoperative neural monitoring has become routine in assisting the surgeon to avoid injury to these structures. We present a case of a large petroclival meningioma removed by a transpetrosal approach with intent of hearing preservation in which an interesting finding was obtained from neural monitoring. In addition to facial, trigeminal, SSEP, and BAER monitoring, continuous EMG monitoring of the abducens nerve was performed. During the transmastoid approach, an opening was inadvertently made in the lateral semicircular canal. With the membranous labyrinth intact, it was decided to pack the canal to prevent further injury. The cupular deflection caused by the packing resulted in a rhythmic repeated firing of the ipsilateral abducens, representing the correcting saccades of the induced nystagmus. This confirmed that the vestibular apparatus, local brainstem, and nerve were intact and functional, as ablative nystagmus would have been in the opposite direction. This was confirmed further by there being no change in the wave I or V of the BAER. For the remainder of the case, the rhythmic firing of the abducens nerve served as a monitor of the health of both the VI and VIII nerves. Tumor involvement at the brainstem insertion of the VIII nerve eventually resulted in the loss of this phenomenon, mirroring the findings on BAER. It is felt that this phenomenon may be exploited in future selected cases to provide real-time feedback on the health of the vestibular nerve during skull base surgery.

Intraoperative Monitoring of the Recurrent Laryngeal Nerve during Thyroidectomy: A Standardized Approach Part 2

ABSTRACT This is the second of two articles on intraoperative neural monitoring. The aim of part one was to provide a concise overview of intraoperative nerve monitoring in thyroid surgery and its effectiveness. Part 1 included a brief review of the surgical anatomy of the recurrent laryngeal nerve and described the surgical landmarks which can be used to identify the nerve during surgery. Part 2 will describe in detail a standardized approach to intraoperative nerve monitoring during thyroid surgery. A brief review of the nerve monitoring procedure and all its requirements will be discussed. The article concludes with the description of a troubleshooting algorithm for intraoperative loss of signal. How to cite this article Poveda MCD, Dionigi G, Sitges- Serra A, Barczynski M, Angelos P, Dralle H, Phelan E, Randolph G. Intraoperative Monitoring of the Recurrent Laryngeal Nerve during Thyroidectomy: A Standardized Approach Part 2. World J Endocr Surg 2012;4(1):33-40.

Electrophysiologic recurrent laryngeal nerve monitoring during thyroid and parathyroid surgery: International standards guideline statement

Intraoperative neural monitoring (IONM) during thyroid and parathyroid surgery has gained widespread acceptance as an adjunct to the gold standard of visual nerve identification. Despite the increasing use of IONM, review of the literature and clinical experience confirms there is little uniformity in application of and results from nerve monitoring across different centers. We provide a review of the literature and cumulative experience of the multidisciplinary International Neural Monitoring Study Group with IONM spanning nearly 15 years. The study group focused its initial work on formulation of standards in IONM as it relates to important areas: 1) standards of equipment setup/endotracheal tube placement and 2) standards of loss of signal evaluation/intraoperative problem-solving algorithm. The use of standardized methods and reporting will provide greater uniformity in application of IONM. In addition, this report clarifies the limitations of IONM and helps identify areas where additional research is necessary. This guideline is, at its forefront, quality driven; it is intended to improve the quality of neural monitoring, to translate the best available evidence into clinical practice to promote best practices. We hope this work will minimize inappropriate variations in monitoring rather than to dictate practice options.

Neural Complications in the Surgical Treatment of Adolescent Idiopathic Scoliosis

Multicenter, prospective, consecutive clinical series. To report on neural complications in a prospective cohort study of 1301 children undergoing spinal fusion and instrumentation for adolescent idiopathic scoliosis (AIS). The incidence of neural complications for spinal deformity surgery has been reported to be 0.26% to 17%. However, most studies have relied on retrospective voluntary reporting of nonconsecutive cases. A review of 1301 consecutive surgical cases was conducted using the Prospective Pediatric Scoliosis Study database, which is maintained by the Spinal Deformity Study Group. There were 9 neural complications. There were 3 thecal penetrations, none of which required repair, and none of which demonstrated intraoperative neural monitoring changes or postoperative clinical sequelae. There were 2 nerve root injuries. In 1 nerve root injury, a positional compression femoral neurapraxia resolved over 6 months. The other was an L4 neurapraxia despite lowest instrumented vertebra L1, and resolved spontaneously by 3 months' follow-up. There were 4 spinal cord injuries. One required removal of implants and fusion in situ, 1 required relaxation of correction and in situ fusion with instrumentation, while the other 2 were observed after fusion and instrumentation with reduction. All resolved spontaneously within 3 months after operation. The neural complication rate was 0.69%. Two thecal penetrations were due to medial placement of pedicle screws, and 1 was due to dissection during spine exposure. If these are eliminated, as they imply intraspinal entry but not direct neural injury, together with 1 positional neurapraxia, which is remote from the surgical field, our complication rate is 0.38%. This is consistent with other studies in the North American Literature, including multiple reports from the Scoliosis Research Society. Common themes are significant curve correction producing neural stretch and the use of sublaminar wires. None of the neural injuries was permanent. These results reaffirm that surgical treatment of adolescent idiopathic scoliosis has a low but real neural complication rate.

Magnetic Resonance Imaging Abnormalities of Neural Axis in Lenke Type 1 Idiopathic Scoliosis

Patients with Lenke type 1 single thoracic idiopathic scoliosis were included in this prospective study. All patients had preoperative magnetic resonance imaging (MRI). To examine the frequency of neural axis abnormalities and the need for preoperative MRI in this group of patients. Because of the increasing use of MRI, neural axis abnormalities have been reported in association with certain clinical and radiologic findings in idiopathic scoliosis cases. A total of 104 patients (49 juvenile onset and 55 adolescent onset), older than 10 years, were included in the study. The association of neural axis abnormalities with pes cavus, abnormal deep tendon reflexes, age of onset, presence of pain, severity of the frontal plane deformity, and sagittal contours were investigated. All 7 patients with a neural axis abnormality on MRI had an early onset disease, and 6 of them had back pain. Thus, age of onset and back pain seem to be predictive of these abnormalities. Frequency of MRI abnormalities was as high as 45% for patients with back pain in addition to a type IC curve. In patients with juvenile idiopathic scoliosis and back pain, preoperative MRI should be performed to eliminate the risk of postoperative neurologic deficits, even if the scoliosis is Lenke type 1. However, in patients with Lenke type 1 idiopathic scoliosis, preoperative MRI studies seem unnecessary if intraoperative neural monitoring is to be performed.