Value Of Intraoperative Neurophysiological Monitoring Research Articles

Bilateral C5 Palsy Following A Circumferential Surgery for Cervical Spondylotic Myelopathy: A Case Report and Review

Background and Importance: The development of C5 root palsy is a well-known potential complication of cervical spine surgeries for the correction of cervical spondylotic myelopathy. It typically occurs unilaterally, but on extremely rare occasions, bilaterally. The value of intraoperative neurophysiologic monitoring in detecting iatrogenic acute versus delayed onset C5 palsy, the rarity of bilateral C5 palsy, and its optimal management require further discussion. Case Presentation: A 49-year-old woman with quadriparesis due to cervical spondylotic myelopathy is presented. She underwent circumferential 360° cervical spine surgery. This operation was subsequently complicated by a delayed bilateral C5 palsy, despite normal transcranial motor evoked potentials (MEPs). With the utilization of conservative treatment, the complete resolution of this complication took roughly eight months. Conclusion: Bilateral C5 palsy is an infrequent consequence of multilevel cervical spine surgeries. Although intraoperative monitoring of transcranial electrical stimulation-induced MEPs has high sensitivity and specificity in foreseeing the acute-onset C5 palsy, it cannot predict delayed-onset palsy. Including the current case, only seven cases have been reported in the medical literature. Overall, conservative management in adherence to rigorous physical therapy may be an acceptable treatment.

Neurophysiological monitoring during anterior cervical discectomy and fusion for ossification of the posterior longitudinal ligament

ObjectiveThis study aimed to investigate the value of intraoperative neurophysiological monitoring (IONM) in anterior cervical spine discectomy with fusion (ACDF) for ossification of the posterior longitudinal ligament (OPLL). MethodsPatients who underwent multimodal IONM (transcranial electrical motor-evoked potentials [tcMEP], somatosensory-evoked potentials, and continuous electromyography) for ACDF from 2009 to 2019 were compared to historical controls from 2003 to 2009. The rates of postoperative neurological deficits, neurophysiological warnings, and their characteristics were analyzed. ResultsAmong 196 patients, postoperative neurological deficit rates were 3.79% and 14.06% in the IONM and historical control (non-IONM) groups, respectively (p < 0.05). The use of IONM (OR: 0.139, p = 0.003) and presence of myelopathy (OR: 8.240, p = 0.013) were associated with postoperative neurological complications on multivariate regression. In total, 23 warnings were observed during IONM (17 tcMEP and/or electromyography; six electromyography). Sensitivity and specificity of IONM warnings for detecting neurological complications were 84.2% and 93.7%, respectively. ConclusionsIONM, especially multimodal IONM, may be a useful tool to detect neurological damage in ACDF for high-risk conditions such as OPLL with pre-existing myelopathy. SignificanceThe utility of IONM in ACDF for OPLL has not been evaluated due to its rarity. This study supports the use of IONM in cervical OPLL with myelopathy.

Intraoperative neurophysiological monitoring during scoliosis surgery in patients with Duchenne muscular dystrophy

PurposeLittle is known about the reliability and value of intraoperative neurophysiological monitoring (IONM) in patients with Duchenne muscular dystrophy (DMD) undergoing scoliosis correction surgery. The aim of this study was to investigate the feasibility of IONM and the cortical excitability in these patients.MethodsFifteen patients with DMD and scoliosis and 15 patients with adolescent idiopathic scoliosis (AIS) underwent scoliosis correction surgery with the use of IONM. IONM consisted of transcranial electrical stimulation motor evoked potential (Tc-MEP) and somatosensory evoked potential (SSEP) monitoring. The highest Tc-MEP amplitudes were collected to test the feasibility. Preoperative compound muscle action potentials (CMAPs) and transcranial magnetic stimulation (TMS)-MEPs were recorded to test the cortical excitability. SSEPs were scored as elicitable or not elicitable.ResultsTc-MEP amplitudes were significantly lower in the DMD group for both the gastrocnemius and tibialis anterior muscles. However, the abductor hallucis muscle had similar amplitudes in both the DMD as the AIS group. TMS/CMAP and Tc-MEP/CMAP ratios were similar in the DMD and AIS group (P = 0.126 and P = 0.792 respectively).ConclusionsTc-MEP and SSEP monitoring is feasible, particularly when Tc-MEPs are recorded from the abductor hallucis muscle in patients with DMD. Similar TMS/CMAP and Tc-MEP/CMAP ratios show that there were no differences observed in cortical excitability between the groups. IONM seems a feasible and valuable neurophysiological tool to signal possible surgically induced damage to the spinal cord during scoliosis correction surgery in patients with DMD.

Intraoperative electrophysiology during single-level selective dorsal rhizotomy: technique, stimulation threshold, and response data in a series of 145 patients.

Selective dorsal rhizotomy (SDR) is effective at permanently reducing spasticity in children with spastic cerebral palsy. The value of intraoperative neurophysiological monitoring in this procedure remains controversial, and its robustness has been questioned. This study describes the authors' institutional electrophysiological technique (based on the technique of Park et al.), intraoperative findings, robustness, value to the procedure, and occurrence of new motor or sphincter deficits. The authors analyzed electrophysiological data of all children who underwent SDR at their center between September 2013 and February 2019. All patients underwent bilateral SDR through a single-level laminotomy at the conus and with transection of about 60% of the L2-S2 afferent rootlets (guided by intraoperative electrophysiology) and about 50% of L1 afferent roots (nonselectively). One hundred forty-five patients underwent SDR (64% male, mean age 6 years and 7 months, range 2 years and 9 months to 14 years and 10 months). Dorsal roots were distinguished from ventral roots anatomically and electrophysiologically, by assessing responses on free-running electromyography (EMG) and determining stimulation thresholds (≥ 0.2 mA in all dorsal rootlets). Root level was determined anatomically and electrophysiologically by assessing electromyographic response to stimulation. Median stimulation threshold was lower in sacral compared to lumbar roots (p < 0.001), and 16% higher on the first operated (right) side (p = 0.023), but unrelated to age, sex, or functional status. Similarly, responses to tetanic stimulation were consistent: 87% were graded 3+ or 4+, with similar distributions between sides. This was also unrelated to age, sex, and functional status. The L2-S2 rootlets were divided (median 60%, range 50%-67%), guided by response to tetanic stimulation at threshold amplitude. No new motor or sphincter deficits were observed, suggesting sparing of ventral roots and sphincteric innervation, respectively. This electrophysiological technique appears robust and reproducible, allowing reliable identification of afferent nerve roots, definition of root levels, and guidance for rootlet division. Only a direct comparative study will establish whether intraoperative electrophysiology during SDR minimizes risk of new motor or sphincter worsening and/or maximizes functional outcome.

Intramedullary spinal cord tumors: the value of intraoperative neurophysiological monitoring in a series of 57 cases from two Italian centers.

Intramedullary spinal cord tumors are rare lesions of the central nervous system. Anatomical, molecular and radiological features are well defined, but correct management is still matter of debate. Pertinent literature has reported conflicting opinions regarding the use of intraoperative electrophysiological monitoring (IONM) in the surgical treatment of this kind of lesions, recently. We report a retrospective study from two Italian centers, in order to highlight the usefulness of IONM in the management of intramedullary lesions. We performed a retrospective review of patients with intramedullary spinal tumor who underwent surgical resection from February 2011 to February 2018 in two different institutions. Clinical and radiological data, lesion features, timing of symptom onset and IONM findings were recorded. The IONM included somatosensory-evoked potentials (SSEP), motor-evoked potentials (MEP) and D-Wave whenever possible. We evaluated the outcome according to the Modified McCormick scale. We also evaluated the accuracy and relevance of surgical outcomes for each evoked potential (SSEP, MEP, D-Wave). A total of 57 patients were included. A gross total removal was achieved in 46 cases. Neurological follow-up was assessment at 3 days, and 3 and 6 months after surgery. Comparing the preoperative status and 6 months follow-up: the modified McCormick scale showed a neurological stability for 30 patients (52.63%), a worsening of neurological status for 7 patients (12.28%) and an improvement for 20 patients (35.08%). IONM presented high accuracy (sensibility of 100% and specificity of 95.65%) and significantly predicted postoperative permanent motor deficits (P<0.0001; AUC=0.978). D-Wave appeared to have significant greater predictive value than MEP and especially SSEP alone (0.967 vs 0.722 vs 0.542; P=0.044 and P<0.001 respectively). The gold standard in the intramedullary lesion treatment is maximal safe resection with good neurological outcome, as shown in our patients. The use of IONM is helpful in intramedullary tumors resection in order to minimize postoperative neurological deficits and our analysis suggests that the use of D-Wave presents a statistically significant higher accuracy for predicting postoperative deficits than SSEP and MEP alone.

Value of intraoperative neurophysiological monitoring for clinical outcome of deep brain stimulation of subthalamic nucleus in Parkinson’s disease

Value of intraoperative neurophysiological monitoring for clinical outcome of deep brain stimulation of subthalamic nucleus in Parkinson’s disease

33. The role of intraoperative neurophysiology in scoliosis surgery

The onset of neurological deficit is the most feared complications in surgical correction of spine deformities. Aim of this study is to assess the value of intraoperative neurophysiologic monitoring during scoliosis surgery. 173 scoliosis surgeries in 164 patients were monitored with muscle-motor evoked potentials (m-MEPs) and peripheral and cortical upper and lower limb Somatosensory Evoked Potentials (SEPs). In 45 surgeries, thoracic and lumbar pedicle screws were neurophysiologically tested by triggered-EMG. The overall monitor ability was 98.3%. Significant intraoperative modification occurred in 26 surgeries (15%). In 11 cases (6.4%) changes were consistent with spinal cord damage, in 6 (6.9%) with brachial plexopathy. Finally, three patients (1.7%) presented transient disappearance of four limbs MEPs and SEPs due to a pharmacological effect. 2 patients (1.2%) awaked with a brachial plexopathy: they all completely recovered within 3 months. In one patients, an intraoperative persistent disappearance of unilateral lower limb MEPs and SEPs was associated with a postoperative severe monoparesis: therefore, the rate of new neurological deficit was 0.6%. Intraoperative neurophysiology may provide a valuable biomarker in detection of impending central and/or peripheral nervous system injury at a reversible stage.

Spinal intradural extramedullary tumors: the value of intraoperative neurophysiologic monitoring on surgical outcome

Nerve sheath tumors and meningiomas account for most intradural extramedullary (IDEM) tumors. These tumors are benign and amenable to complete surgical resection. In recent years, these surgeries are performed with intraoperative neurophysiologic monitoring (IONM) in order to minimize neurological injury, but the evidence for the statistical efficacy of this utility is lacking. This paper evaluates IONM benefits in IDEM tumor resection. Data of patients treated surgically for spinal intradural tumors from 1998 to 2003 was previously collected and analyzed. We retrospectively evaluated patients' charts operated in the years 2011 to 2013. Patients' medical files were reviewed including radiological examinations and electrophysiological reports. The data was collected and evaluated. Forty-one cases of meningioma or nerve sheath tumor resection surgery were performed in the study period. The surgical results were compared to 70 cases of historical controls. Demographic data was similar in these two groups. Sensitivity, specificity, and positive and negative predicted values of IONM were 75, 100, 100, and 97%, respectively. New neurological deficit rate was evident in 10 and 14% for the study and control groups, respectively (not significant). While IONM predicts neurological deficits with high accuracy level, this study does not suggest that there is a significant global benefit of IONM in these cases. As reported by others, in this series, the rate of new neurological deficits in non-monitored cases is similar to the monitored cases series; hence, IONM role in preventing new neurological deficits has yet to be proven.

Commentary : The value of intraoperative neurophysiological monitoring: evidence, equipoise and outcomes.

The use of intraoperative neurophysiological monitoring (IONM) has grown despite an absence of randomized controlled trials that might unequivocally demonstrate improved outcomes. At issue is how to demonstrate value when other evidence indicates patient harms (opportunity cost) if IONM is withheld for the sake of randomization. In this article we review other non-randomized methods to assess the effects of IONM on post-operative outcomes. We also examine how clinical equipoise may resolve whether (or not) an anticipated controlled study is ethical. We conclude that the value of IONM in a particular surgical setting should be determined by a benefits/harms analysis based on all the available evidence.

319 Predictive Value of Intraoperative Neurophysiological Monitoring During Spine Surgery

INTRODUCTION: A single-center study to define the sensitivity and specificity of intraoperative neurophysiological monitoring in detecting new neurological deficits. METHODS: A cohort of 4989 consecutive (2962 male and 2027 female) patients operated on over 3 years was evaluated. Subgroup analysis was performed for patients undergoing posterior cervical intervention (n = 1373) and posterior lumbar fusion surgery (n = 2420). Sensitivity and specificity were determined using Bayesian techniques. Impact of length of surgery and of variables, including age, sex, body mass index, diabetes mellitus, hypertension, coronary artery disease, cerebrovascular disease, and history of smoking, on the development of a new neurodeficit was defined. RESULTS: Of 4489 patients, 426 patients (9.4%) had significant intraoperative somatosensory evoked potential (SSEP) changes. New postoperative neurological deficits occurred in 121 (2.7%) patients. Twenty-five of 426 patients (5.8%) with neuromonitoring changes developed a new neurodeficit. Ninety-six of 4063 patients (2.3%) with no changes developed a new neurodeficit. In posterior cervical interventions, 98 of 1373 (7.1%) developed SSEP changes and 13 of 98 (13.2%) patients developed a new neurodeficit, whereas 49 (3.8%) developed a new neurodeficit without any changes in intraoperative monitoring (IOM). In posterior lumbar fusion SSEPs, electromyographs (EMGs), and pedicle screw stimulation was utilized. Two hundred forty-nine of 2420 (10.2%) patients developed IOM changes and 8 of 249 (3.2%) patients developed a new neurodeficit, while 37 (1.7%) developed a new neurodeficit without changes in IOM. In the entire cohort SSEPs had sensitivity 20.7% and specificity of 90.8%. In the posterior cervical cohort, SSEPs had s sensitivity of 20.9% and a specificity of 93.7%. In the lumbar fusion cohort, multimodality monitoring including SSEPs, EMGs, and pedicle screw stimulation had a sensitivity of 17.8% and a specificity of 88.6%. Neither the length of surgery nor did any analyzed patient-related variable have a statistically significant impact on the development of a new neurodeficit. CONCLUSION: The strength of SSEPs is their negative predictive value. A cost-utility analysis for IOM in spine surgery should be undertaken.

Intraoperative neurophysiological monitoring during endoscopic endonasal surgery for pediatric skull base tumors

OBJECT The aim of this study was to evaluate the value of intraoperative neurophysiological monitoring (IONM) using electromyography (EMG), brainstem auditory evoked potentials (BAEPs), and somatosensory evoked potentials (SSEPs) to predict and/or prevent postoperative neurological deficits in pediatric patients undergoing endoscopic endonasal surgery (EES) for skull base tumors. METHODS All consecutive pediatric patients with skull base tumors who underwent EES with at least 1 modality of IONM (BAEP, SSEP, and/or EMG) at our institution between 1999 and 2013 were retrospectively reviewed. Staged procedures and repeat procedures were identified and analyzed separately. To evaluate the diagnostic accuracy of significant free-run EMG activity, the prevalence of cranial nerve (CN) deficits and the sensitivity, specificity, and positive and negative predictive values were calculated. RESULTS A total of 129 patients underwent 159 procedures; 6 patients had a total of 9 CN deficits. The incidences of CN deficits based on the total number of nerves monitored in the groups with and without significant free-run EMG activity were 9% and 1.5%, respectively. The incidences of CN deficits in the groups with 1 staged and more than 1 staged EES were 1.5% and 29%, respectively. The sensitivity, specificity, and negative predictive values (with 95% confidence intervals) of significant EMG to detect CN deficits in repeat procedures were 0.55 (0.22-0.84), 0.86 (0.79-0.9), and 0.97 (0.92-0.99), respectively. Two patients had significant changes in their BAEPs that were reversible with an increase in mean arterial pressure. CONCLUSIONS IONM can be applied effectively and reliably during EES in children. EMG monitoring is specific for detecting CN deficits and can be an effective guide for dissecting these procedures. Triggered EMG should be elicited intraoperatively to check the integrity of the CNs during and after tumor resection. Given the anatomical complexity of pediatric EES and the unique challenges encountered, multimodal IONM can be a valuable adjunct to these procedures.

Predictive value of intraoperative neurophysiologic monitoring in assessing long-term facial function in grade IV vestibular schwannoma removal.

Despite routine use of intraoperative neuromonitoring in acoustic neuroma removal, its application in predicting long-term facial function is limited. Prospective recording of facial nerve function and subsequent review of intraoperative neurophysiologic data. Stimulation of the facial nerve was performed proximal and distal to the tumor locus after tumor removal with measurement of amplitude and latency responses in the orbicularis oculi and oris muscles. Prospective review of current facial nerve function was performed using the House-Brackmann (HB) scoring system. Good facial function was determined as HB I/II and HB III-VI was considered poor facial function. Minimum follow-up time was 15 months, and averaged 40 months. Twenty-four grade IV acoustic neuromas (54 % larger than 4 cm) were completely removed from October 2008 to November 2013. Nine patients (37.5 %) had HB I/II and 15 (62.5 %) had HB III-VI. The poor prognosis group had a higher latency than the good prognosis group (p = 0.045). Lower proximal amplitude was detected in the poor prognosis group (p = 0.046). Lower proximal-to-distal amplitude ratio was also detected in the poor prognosis group (p = 0.052). Amplitude ratio cut-offs of 0.44 and 0.25 were able to predict poor prognosis with sensitivity of 0.73 and 0.4 and specificity of 0.78 and 1, respectively (p = 0.046). Lower proximal amplitude and proximal-distal amplitude ratio were previously reported as predictors of poor facial function in different sizes of vestibular schwannomas. We observed that the same applies specifically for large-sized, completely removed, grade IV tumors. Additionally, we describe a difference in proximal latency time between the good and poor prognosis groups, which was not previously reported.

The value of intraoperative neurophysiological monitoring for microsurgical removal of conus medullaris lipomas: a 12-year retrospective cohort study.

BackgroundLipomas in the lower spinal canal can lead to progressive neurological deficits, so they may have to be surgically removed. Intraoperative neurophysiological monitoring serves to minimize the morbidity of the surgical procedure. However, so far there are no evidence-based recommendations which type of monitoring procedure or combination of procedures to choose.MethodsThe aim of this study was to evaluate the feasibility and value of various intraoperative monitoring techniques: motor and sensory evoked potentials (MEP, SEP), free-running and triggered electromyography (EMG). Thirty cases of spinal lipomas of the Conus medullaris (dorsal Type A: 20.0%; caudal Type B: 33.3%; transitional Type C: 46.7%) were retrospectively evaluated over a 12-year period.ResultsThe patients were mostly pediatric and suffered from persistent pain (73.3%), pareses (56.7%), sensory deficits (43.4%), and/or urogenital dysfunctions (60.0%). SEPs were successfully evoked in 66.7% of cases, MEPs in 86.7% of cases, and EMGs in 100%. MEP alterations correlated with direct mechanical maneuvers in the operating site. SEP changes correlated mostly with physiological events, such as rinsing/cooling of the operating site. Spike-, burst- or tonic train-activity was found in the free-running EMG that occurred only with certain manipulation patterns. Irreversible MEP changes and signal loss in the triggered EMG correlated with post-operative deficits.ConclusionsThe results of this study showed, that intraoperative monitoring could be considered a helpful tool during lipoma tumor surgery near the Conus medullaris. Most reliable results were obtained from transcranial MEPs, free-running EMGs, and triggered EMGs. That’s why the authors favor a routine set-up consisting of at least these three techniques, as this enables mapping at the beginning of the operation, continuous functional testing during surgery, and prognosis of the post-operative symptomology.

The value of intraoperative neurophysiological monitoring for microsurgical removal of conus medullaris lipomas: a 12-year retrospective cohort study

BackgroundLipomas in the lower spinal canal can lead to progressive neurological deficits, so they may have to be surgically removed. Intraoperative neurophysiological monitoring serves to minimize the morbidity of the surgical procedure. However, so far there are no evidence-based recommendations which type of monitoring procedure or combination of procedures to choose.MethodsThe aim of this study was to evaluate the feasibility and value of various intraoperative monitoring techniques: motor and sensory evoked potentials (MEP, SEP), free-running and triggered electromyography (EMG). Thirty cases of spinal lipomas of the Conus medullaris (dorsal Type A: 20.0%; caudal Type B: 33.3%; transitional Type C: 46.7%) were retrospectively evaluated over a 12-year period.ResultsThe patients were mostly pediatric and suffered from persistent pain (73.3%), pareses (56.7%), sensory deficits (43.4%), and/or urogenital dysfunctions (60.0%). SEPs were successfully evoked in 66.7% of cases, MEPs in 86.7% of cases, and EMGs in 100%. MEP alterations correlated with direct mechanical maneuvers in the operating site. SEP changes correlated mostly with physiological events, such as rinsing/cooling of the operating site. Spike-, burst- or tonic train-activity was found in the free-running EMG that occurred only with certain manipulation patterns. Irreversible MEP changes and signal loss in the triggered EMG correlated with post-operative deficits.ConclusionsThe results of this study showed, that intraoperative monitoring could be considered a helpful tool during lipoma tumor surgery near the Conus medullaris. Most reliable results were obtained from transcranial MEPs, free-running EMGs, and triggered EMGs. That's why the authors favor a routine set-up consisting of at least these three techniques, as this enables mapping at the beginning of the operation, continuous functional testing during surgery, and prognosis of the post-operative symptomology.

Value of multimodality monitoring using brainstem auditory evoked potentials and somatosensory evoked potentials in endoscopic endonasal surgery

Objectives: To evaluate the value of intraoperative neurophysiological monitoring (IONM) using brainstem auditory evoked potential (BAEP) and somatosensory evoked potential (SSEP) monitoring to predict and/or prevent postoperative neurological deficits during endoscopic endonasal surgery (EES).Methods: We retrospectively identified 138 consecutive patients who had BAEP monitoring in addition to SSEP monitoring during EES at our institution. We reviewed the postoperative clinical outcomes and neurophysiological changes independently.Results: The total of number of patients with any IONM changes was 10. The incidence of BAEP changes was 3·62%. The incidence of SSEP changes was 3·62% as well. One patient had changes in both BAEPs and SSEPs. Majority of the changes were observed during changes in mean arterial pressure (MAP) without any postoperative neurological deficits. There were two postoperative neurological deficits.Discussion: BAEPs and SSEPs provide unique information about integrity of brainstem function during EES procedures involving tumors in the and around clival region. We advocate a comprehensive multimodality approach to IONM during EESs including BAEPs and SSEPs depending on the location of the neural structures at risk.

Does intraoperative neurophysiological monitoring have predictive value for functional recovery following spinal cord injury? A case report

To present a case report of a patient with an ASIA B spinal cord injury with partially intact baseline IONM who made a complete functional recovery postoperatively. A thirty-three year old male presented after a motor vehicle accident. Imaging studies revealed a C4-C5 bilateral facet dislocation. On presentation the patient had 4/5 strength in bilateral biceps and wrist extensors, 3/5 strength in bilateral triceps, and 0/5 strength in the finger flexors, intrinsics and all lower extremity muscles. Motor level was C7. Sensation was grossly intact to light touch throughout all extremities, intact to pinprick from C2 to T7, and absent to pinprick caudal to T7. Rectal tone and contraction were absent. After attempts at closed reduction failed the patient underwent an open reduction and posterior C4-C5 fusion. Intraoperative neurophysiologic monitoring (IONM) revealed the presence of baseline responses to the posterior tibial nerve using somatosensory evoked potentials and to the right abductor hallucis using transcranial motor evoked potentials. At the 6 weeks postoperative visit the patient had full 5/5 motor strength to all muscles except the left deltoid that was 4/5 due to a rotator cuff injury. This case illustrates a potential prognostic value of IONM. Despite lack of clinical motor function at the time of surgery, IONM was able to illicit a motor response in the right lower extremity. Further prospective studies are needed for further investigation.

Evidence-based guideline update: Intraoperative spinal monitoring with somatosensory and transcranial electrical motor evoked potentials: Report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology and the American Clinical Neurophysiology Society

Editors' Note: We are publishing all previously posted dialogue about intraoperative spinal monitoring. Evidence-based medicine (EBM) is a laudable goal, but it is clear that well-intentioned authorities will have strongly held opinions based on their review of the same evidence. The concluding letter by Gronseth, arguably our specialty's leading figure in EBM, does not “give the answer” but does suggest a way forward. Robert C. Griggs, MD, and Megan Alcauskas, MD # {#article-title-2} Nuwer et al.1 consolidated the best evidence available on the use of evoked potentials during spinal operations. However, focusing on the value of intraoperative neurophysiological monitoring (IOM) alerts in predicting postoperative motor deficits does not offer new answers to the question “Why use IOM?” The guideline authors agree with the results of a review2 that supported IOM as a predictive diagnostic tool with a high level of evidence. Prediction alone is insufficient to warrant use of IOM especially when actual outcomes will be revealed almost immediately following the surgery. Also, short-term prediction is insufficient to justify the costs of the specialized equipment, technicians, and professional oversight necessary for proper IOM performance. The evidence for IOM to alter outcomes is weak with only one nonrandomized study3 showing a 52% rate of preventing neurologic deficits from acting on IOM alerts. In the absence of randomized controlled trials, outcomes research from large observational datasets may clarify the utility of IOM as cost-effectiveness becomes a greater factor in medical decision-making.4 # Author Response: {#article-title-3} IOM raises warnings early enough to allow for interventions during spinal cord surgery. We believe clinical experience and animal experiments establish unequivocally that IOM warns of spinal cord injury, and interventions reverse impairment and prevent paraplegia. Our assessment1 discussed this rationale and cited literature. The assessment process was constrained narrowly …

Cost-effectiveness of intraoperative neurophysiological monitoring for spinal surgeries: Beginning steps

highlights Cost-effectiveness modeling of multimodal intraoperative neurophysiologic monitoring (IONM) for spinal surgery relies on assumptions based on pooled results of uncontrolled observational studies, with uncertainty evaluated through probabilistic sensitivity analysis of Monte Carlo simulation results. Multimodal IONM reduces the relative risk of post-operative neurological complications by an estimated 49.4% (p < 0.001) at a cost of $63,387 (95%CI $61,939–$64,836) per neurological deficit averted. 2012 Published by Elsevier Ireland Ltd. on behalf of International Federation of Clinical Neurophysiology. The use of evoked potentials (EPs) and electromyograms (EMGs) in the operating room has increased in popularity over the past several decades, beginning with brainstem auditory EPs for acoustic neuroma resections to the most common usage today, neck and back surgeries. Intraoperative neurophysiologic monitoring (IONM) holds the promise of prevention of neurological complications by detecting evolving abnormalities and alerting the operating team to take actions to normalize the electrodiagnostic abnormality, including repositioning the patient, taking a different surgical approach, adjusting anesthesia, giving blood pressure support or waking the patient. By monitoring motor and somatosensory EPs with free run and triggered EMG, multimodal IONM may have greater diagnostic sensitivity than any single modality. However, the evidence for efficacy of IONM in spinal surgeries is scant, as seen in a recent systematic review (Fehlings et al., 2010), which concluded that IONM may be more helpful for complicated surgeries and recommended usage based on the discretion of the operating surgeon. Furthermore, multimodal IONM adds cost to already expensive procedures (average US cost of spinal fusion in 2007 was $24,600 (Elixhauser and Andrews, 2010)). The value of IONM in spinal procedures is in the avoidance of neurological deficits, based on IONM diagnostic characteristics, likelihood of preventing a post-operative injury following an IONM alert, and the baseline (a priori) rate of neurological complications from a given spinal operation. We created an economic decision model which incorporates the available evidence for these parameters. To account for uncertainty inherent in observational, nonrandomized data, the diagnostic characteristics of IONM and neurological complication rates for the eleven studies using multimodal IONM in spinal surgeries identified by Fehlings et al. (n = 2162) were pooled in a random effects meta-analysis to give estimates of average effect size and standard errors. This yielded a 5.0% baseline neurological complication rate for spinal surgeries (95% CI, 3.0– 7.0%), 94.3% sensitivity (95% CI, 92.3–96.3%) and 95.6% specificity (95% CI, 93.3–97.4%). The rate of prevention of post-operative deficits given an IONM alert has only been evaluated in a single study (Wiedemayer et al., 2002), which reported a 52.4% prevention rate (95%CI 37.3–67.3%) when actions were taken subsequent to IONM alerts compared to no actions taken. The per-operation cost of multimodal IONM for four-limb EMG, upper and lower extremity motor and somatosensory EPs and continuous IONM was calculated from 2009 Medicare reimbursement rates (national rating, global fee) for corresponding Current Procedure Terminology codes totaled $1535. The cost-effectiveness outcome was the cost per undesirable consequence avoided, calculated as the mean expense of IONM divided by the difference in post-operative neurological deficit rates in spinal surgeries using IONM compared with those not using IONM. In the IONM usage arm of the model, the likelihood of preventing a neurological deficit is the baseline risk of neurological deficit for the surgery X diagnostic sensitivity of IONM X probability of prevention of neurological deficit given an IONM alert, where the post-operative neurological deficit rate in the non-IONM arm is equal to the baseline risk of neurological complications for the surgery. To incorporate uncertainty, we conducted a probabilistic sensitivity analysis (PSA) with Monte Carlo simulation. Probability

P12.3 Guiding or confirming value of intraoperative neurophysiological monitoring in intramedullary spinal cord mass lesion surgery

P12.3 Guiding or confirming value of intraoperative neurophysiological monitoring in intramedullary spinal cord mass lesion surgery

The value of intraoperative neurophysiological monitoring in tethered cord surgery

PurposeThe value of intraoperative neurophysiological monitoring (IONM) with surgical detethering in dysraphic patients has been questioned. A retrospective analysis of our series of 65 patients is presented with special focus on technical set-up and outcome.MethodsAll patients were diagnosed with a tethered cord (TC) due to spinal dysraphism. A high-risk group (HRG) was determined consisting of 40 patients with a lipomyelomeningocele and/or a split cord malformation sometimes in combination with a tight filum terminale. The surgical procedure was a detethering operation in all cases performed by a single surgeon during a 9-year period (1999–2008). A standard set-up of IONM was used in all patients consisting of motor-evoked potentials (MEP) evoked by transcranial electrical stimulation (TES) and electrical nerve root stimulation. In young patients, conditioning stimulation was applied in order to improve absent or weak MEPs.ResultsIONM responses could be obtained in all patients. Postoperative deterioration of symptoms was found in two patients of whom one patient belonged to the HRG. Mean maximal follow-up of all 65 patients was 4.6 years (median 4.1 years). Long-term deterioration of symptoms was found in 6 of 65 patients with a mean follow-up of 5 years (median 5.3 years).ConclusionThe use of IONM is feasible in all TC patients. The identification of functional nervous structures and continuous guarding of the integrity of sacral motor roots by IONM may contribute to the safety of surgical detethering.