Intraoperative Neuromonitoring Signal Research Articles

Determinants influencing intraoperative neuromonitoring quality during cervical spine treatment: A systematic review

The functional integrity of the nervous system is monitored using a method known as Intraoperative Neuromonitoring (IONM) during surgical operations. Utilizing devices positioned on the patient's skin or within their muscles, IONM normally entails monitoring the electrical activity of nerves or muscles. The surgical technique used during the cervical spine treatment can influence the quality of IONM. Surgeons who are experienced in IONM and have a good understanding of the anatomy and physiology of the cervical spine are more likely to obtain accurate and reliable IONM signals. The signals are transmitted to a monitoring system that provides real-time feedback to the surgical team. This feedback can alert the team to potential nerve damage, allowing them to make adjustments to the surgical technique or take other steps to protect the nerves. Patient factors such as age, medical history, and comorbidities can influence the quality of IONM. For instance, patients with pre-existing neurological conditions or those who are elderly may have a higher risk of neurological damage during the surgery, which can affect the quality of IONM. The use of IONM for Anterior Cervical Spinal Surgery (ACSS) has been widely researched across a number of medical reference sources. Research on behind cervical surgery were neglected to take into consideration.

Abstract 036: Diagnostic Accuracy of IONM for Perioperative Strokes during Endovascular Treatment of Ruptured Intracranial Aneurysms

Introduction Ruptured aneurysmal SAH accounts up to 80% of nontraumatic SAH, with more than 80% located in the anterior circulation and a mortality rate upwards of 50%.1‐3 Endovascular treatment (EVT) of ruptured intracranial aneurysms (rIA) is increasingly being recognized as a standard treatment that may result in better early outcomes and independency when compared with open neurosurgical clipping in cases of appropriate equipoise.1,2,4–6 Despite this, EVT of intracranial aneurysms has its own risk of complications including intraoperative rupture and thromboembolic events.7 The complication rate is found to be higher in cases of rIA than that seen in cases of unruptured intracranial aneurysms.8 The use of somatosensory evoked potentials (SSEP) and electroencephalography (EEG) intraoperative neuromonitoring (IONM) have proven their efficacy in identifying iatrogenic neurological complications in vascular surgeries including carotid endarterectomy 9–11, EVT and microsurgical treatment of intracranial aneurysms. 11,12 rIA have their own unique challenges due to preoperative neurological deficits and perioperative vasospasm making it more difficult to identify new neurological deficits after the procedure. They are also associated with decreased vasoreactivity secondary to bleeding, and a higher rate of procedural complications that can alter the IONM signals.13,14 IONM in the form of SSEP and EEG can be utilized in anesthetized patients to indirectly monitor intraoperative cerebral perfusion as well as central and peripheral neuronal integrity.15,16 Changes in one or both modalities indicate a change in cerebral perfusion that can be related to EVT directly, for example, aneurysm perforation or coil herniation and embolism, or indirectly secondary to anesthesia and hemodynamic changes.17 (Figure1) Methods We reviewed the medical records of 323 patients who underwent EVT of ruptured aneurysms with IONM utilizing SSEP and EEG. We included all patients who had endovascular management of ruptured aneurysm and completed IONM records until the end of the procedure and excluded those with no IONM records or incomplete records. Patients were divided into 2 groups, one group with postprocedural neurological deficits (PPND) and one group without PPND. Results Total of 323 patients undergoing EVT, significant IONM changes were noted in 71 patients (21.98%) and 46 (14.24%) who experienced PPND. 22 out of 71 (30.98%) patients who had significant IONM changes experienced PPND. Univariable analysis demonstrated that persistent changes in SSEP and EEG were associated with PPND (p‐values: <0.001 and <0.001). Multivariable analysis showed that persistent IONM changes were significantly associated with PPND (OR: 8.28 (95%CI:2.92‐24.66, p‐value: <0.001). Simultaneous changes in both modalities had a specificity of 95% (95% CI: 0.92, 0.97%) and sensitivity of 48% (95% CI: 0.33, 0.63) to predict PPND when either modality had a change. Out of 46 patients with PPND, 29 (63.04%) experienced periprocedural complications. PPND was associated with periprocedural complications with a p‐value <0.001. Also, multivariable analysis showed an association between IONM changes and persistent IONM changes with PPND with OR of 7.35 (95% CI; 3.68, 15.03) and 7.25 (95% CI; 3.58, 15.00), respectively. Conclusion Significant IONM changes during EVT for rIA are associated with an increased risk of PPND.

A practical example of an integrated interoperable neuromonitoring system based on IEEE 11073 SDC and HL7

Abstract Purpose: With the ongoing work on the Health Level Seven (HL7) standards and the IEEE 11073 Serviceoriented Device Connectivity (SDC) family, the demand for open integration of medical devices in the operating room (OR) has become clear. Nevertheless, there are very few interoperable medical devices available to date. This work describes a practical example of connecting an intraoperative neuromonitoring (IONM) device with a radiofrequency (RF) surgical device based on SDC and with the hospital information system (HIS) based on HL7. Methods: Before starting the surgery, patient-related data must be entered into the neuromonitoring system. To minimize manual input, we integrated an automized patient data query based on HL7, which completes all other necessary data provided by the HIS after entering the patient identification number. During the surgery, while mapping neural structures in the situs using IONM, the parallel operation of RF devices for coagulation generates artifacts in the neuromonitoring signals, which makes a reliable interpretation of the IONM signals impossible. Therefore, we developed an IEEE 11073 SDC interface for the neuromonitoring device and implemented an SDC-based OR control panel. While placing the hand probe for mapping neural structures in the situs, the OR control panel suppresses the coagulation of the electrosurgical instrument and only reenables it, after the mapping has been terminated. After the surgery, the generated IONM report can be uploaded into the HIS using HL7. Therewith it is assigned automatically to the previously selected patient. Result: With the SDC- and HL7-enabled neuromonitoring system, we showed a practical use case of interoperable medical devices to optimize surgical workflow.

Thoracic pediculectomy for acute spinal cord decompression in high-risk spinal deformity correction: illustrative case.

Neurological complications are higher in patients with severe spinal deformities (Cobb angle >100°). The authors highlight a known technique for thoracic concave apical pedicle resection that is useful for spinal cord decompression in patients with high-risk spinal deformities in the setting of intraoperative neuromonitoring (IONM) changes. A 14-year-old female with progressive idiopathic scoliosis presented for evaluation of her clinical deformity. Scoliosis radiographs showed a double major curve pattern comprising a 107° right main thoracic curve and a compensatory 88° left thoracolumbar curve. She underwent 2 weeks of halo-gravity traction that reduced her major thoracic curve to 72°. During thoracic posterior column osteotomies, the authors were alerted to decreases in IONM signals that were not responsive to increases in mean arterial pressure, traction weight reduction, and convex compression maneuvers. The dural surface was tightly draped over the two thoracic apical pedicles of T7 and T8, so emergent pediculectomies were performed at both levels for spinal cord decompression. IONM signals gradually improved and eventually became even better than baseline. The patient woke up without any neurological deficits. Pediculectomy of the concave apical pedicle(s) should be considered for spinal cord decompression if there are IONM changes during high-risk spinal deformity surgery.

Intraoperative Neuromonitoring during Peripheral Arteriovenous Malformation Embolization

PurposeTo evaluate whether intraoperative neuromonitoring (IONM), including pre-embolization lidocaine injection challenge (“provocative testing”) is associated with reduced risk of irreversible nerve injury during embolization of peripheral arteriovenous malformations (AVMs). Materials and MethodsMedical records of patients with peripheral AVMs who underwent embolotherapy with IONM with provocative testing between 2012 and 2021 were reviewed retrospectively. Data collected included patient demographic characteristics, AVM location and size, embolic agent used, IONM signal changes after lidocaine and embolic agent injections, postprocedural adverse events, and clinical outcomes. Decisions regarding whether embolization would proceed at specific locations were based on IONM findings after the lidocaine challenge and as embolization proceeded. ResultsA cohort of 17 patients (mean age, 27 years ± 19; 5 women) who underwent 59 image-guided embolization procedures with adequate IONM data was identified. No permanent neurologic deficits occurred. Transient neurologic deficits were observed in 3 patients (4 sessions), comprising skin numbness (2 patients), extremity weakness (1 patient), and extremity weakness and numbness (1 patient). All neurologic deficits resolved by postoperative day 4 without additional treatment. ConclusionsIONM, including provocative testing, during AVM embolization may minimize potential nerve injury.

Deformity angular ratio is associated with neuromonitoring changes without a vertebral column resection: spinal deformity is more influential than type of surgery

PurposeThe purpose of this study is to investigate the effect of the deformity angular ratio (DAR) on intra-operative neuromonitoring (IONM) signal changes during posterior spinal fusion (PSF) without vertebral column resection (VCR).MethodsRetrospective review of severe pediatric spinal deformity patients treated with PSF without VCR or three-column osteotomy from 2008 to 2018. Exclusion criteria were prior instrumentation, lack of IONM, and incomplete radiographic data. Coronal DAR (C-DAR), sagittal DAR (S-DAR), and total DAR (T-DAR) were calculated and compared between patients with IONM signal loss and those without.ResultsTwo hundred and fifty-three patients met inclusion criteria. Forty-seven of two hundred and fifty-three (19%) patients had IONM signal loss. Intra-operative wake-up test was performed in seven cases; three of seven (43%) had a neurological deficit on wake-up test. All neurological deficits resolved at a mean of 41 days postop. IONM loss was associated with increased kyphosis (p = 0.003) and was not associated with Cobb angle (p = 0.16). S-DAR (p = 0.03) and T-DAR (p = 0.005) were associated with IONM signal loss but C-DAR was not (p = 0.06). Increased incidence of IONM signal loss was seen with S-DAR > 7 (p = 0.02) or T-DAR > 27 (p = 0.02). Twenty-four of ninety-two (26%) patients with S-DAR > 7 had IONM signal loss compared to twenty-three of one hundred and sixty-one (14%) with S-DAR ≤ 7 (OR, 2.1; 95% CI, 1.1–4.0). Seven of sixteen (44%) patients with T-DAR > 27 had signal loss compared to forty of two hundred and thirty-seven (17%) patients with T-DAR ≤ 27 (OR, 3.8; 95% CI, 1.3–10.9).ConclusionPatients with S-DAR > 7 or T-DAR > 27 have a higher risk of IONM loss during pediatric PSF even in the absence of a VCR or three-column osteotomies.Level of evidence II.

Intraoperative neuromonitoring for pediatric Chiari decompression: when is it useful?

Surgical treatment for symptomatic Chiari I malformation involves surgical decompression of the craniovertebral junction. Given the proximity of critical brainstem structures, intraoperative neuromonitoring (IONM) is employed for safe decompression in some institutions. However, IONM adds time and cost to the operation, and the benefit to the patient has not been defined. Given the diversity in surgical practices, there is no evidence-based standard of care regarding when to use IONM and which modalities are most helpful. The purpose of this study was to review a single-surgeon experience with IONM in order to determine the sensitivity, specificity, and predictive values of various IONM modalities routinely used in pediatric Chiari I decompression; to examine the associations between patient, clinical, and radiographic characteristics and IONM alerts; and to obtain data regarding the usefulness of these modalities during the surgical process to improve patient outcomes. A retrospective review was performed for 300 consecutive pediatric patients who underwent suboccipital craniectomy and C1 laminectomy for Chiari decompression performed by a single surgeon over a 15-year period. Clinical, radiographic, and IONM data were collected. Radiographic measurements of the skull base morphological abnormalities, including clival angle, Chamberlain's line, and Grabb-Oakes line, were compared between patients with and without true IONM signal changes. A total of 291 cases were included, with an age range of 6 months to 19 years. Among 291 cases, somatosensory evoked potentials (SSEPs) were monitored in 291, motor evoked potentials (MEPs) in 209, cranial nerve spontaneous electromyography (sEMG) in 290, and brainstem auditory evoked potentials (BAEPs) in 110. Sensitivity, specificity, positive predictive value, and negative predictive value, respectively, were as follows: 1.00, 1.00, 1.00, and 1.00 for SSEPs; 1.00, 0.99, 0.67, and 1.00 for MEPs; 0.00, 0.88, 0.00, and 1.00 for sEMG; and not appliable, 1.00, not applicable, and 1.00 for BAEPs. Six patients had true IONM signal changes. These patients had radiographic evidence of more severe concomitant craniocervical instability and basilar invagination, with steeper clival angles (124° vs 146°, p = 0.02) and larger Grabb-Oakes lines (10.1 mm vs 6.7 mm, p = 0.02), when compared with the patients without any true IONM changes. Intraoperative neuromonitoring may be best utilized for patients who show radiographic features of abnormal skull base morphology, defined as a clival angle < 135° or Grabb-Oakes line > 9 mm. When IONM is employed, SSEP and MEP monitoring are the most useful modalities.

Utility of intraoperative neuromonitoring for decompression of Chiari type I malformation in 93 adult patients.

There is currently a lack of consensus on the utility of intraoperative neuromonitoring (IONM) for decompression of Chiari type I malformation (CM-I). Commonly used monitoring modalities include somatosensory evoked potentials (SSEPs), motor evoked potentials (MEPs), and brainstem auditory evoked potentials (BAEPs). The purpose of this study was to evaluate the utility of IONM in preventing neurological injury for CM-I decompression. The authors conducted a retrospective study of a population of adult patients (ages 17-76 years) diagnosed with CM-I between 2013 and 2021. IONM modalities included SSEPs, MEPs, and/or BAEPs. Prepositioning baseline signals and operative alerts of significant signal attenuation were recorded. Ninety-three patients (average age 38.4 ± 14.6 years) underwent a suboccipital craniectomy for CM-I decompression. Eighty-two (88.2%) of 93 patients underwent C1 laminectomy, 8 (8.6%) underwent C1 and C2 laminectomy, and 4 (4.3%) underwent suboccipital craniectomy with concomitant cervical decompression and fusion in the setting of degenerative cervical spondylosis. Radiographically, the average cerebellar tonsillar ectopia/descent was 1.1 ± 0.5 cm and 53 (57.0%) of 93 patients presented with a syrinx. The average number of vertebral levels traversed by the syrinx was 5.3 ± 3.5, and the average maximum width of the syrinx was 5.8 ± 3.3 mm. There was one instance (1/93, 1.1%) of an MEP alert, which resolved spontaneously after 10 minutes in a patient who had concomitant stenosis due to pannus formation at C1-2. No patient developed a permanent neurological complication. There were no permanent complications related to intraoperative neurological injury. Transient fluctuations in IONM signals can be detected without clinical significance. The authors suggest that CM-I suboccipital decompression surgery may be performed safely without IONM. The use of IONM in patients with additional occipitocervical pathology should be left as an option to the performing surgeon on a case-by-case basis.

A comparison between cisatracurium and rocuronium-induced neuromuscular block on laryngeal electromyography recovery after neostigmine reversal in a porcine model.

BackgroundInducing and reversing neuromuscular block is essential to a positive outcome of thyroid surgery, with intraoperative neuromonitoring (IONM) being used to decrease recurrent and superior laryngeal nerve injuries and improve vocal outcome. Neostigmine is a non-specific broad-spectrum and inexpensive reversal agent for neuromuscular blocking agents (NMBAs). The aim of this porcine study was to explore the effect of neostigmine on electromyography (EMG) signal recovery profile following the commonly used NMBAs, cisatracurium and rocuronium.MethodsTwelve piglets were allocated into two groups with six piglets in each group. When stable baseline EMG signals were obtained, a neuromuscular block was induced by intravenous cisatracurium 0.2 mg/kg (group C) or rocuronium 0.6 mg/kg (group R) for each piglet. We compared laryngeal EMG tracing with spontaneous recovery (control) and neostigmine (0.04 mg/kg) reversal for each group. The time course of real-time laryngeal EMG signals was observed for 30 min from NMBA injection. Effects of neostigmine on EMG signal were assessed at 50% EMG recovery and by the maximum neuromuscular block recovery degree from the baseline value.ResultsNeostigmine shortened the recovery time to 50% EMG amplitude in both group C (16.5 [2.5] vs. 29.0 [2.0] min, P<0.01) and group R (16.5[2.5] vs. 26.5 [1.5] min, P<0.05) compared to spontaneous recovery, respectively. Neostigmine reversal also enhanced the maximum degree of EMG amplitude recovery in both group C (83.6 [5.1] vs. 47.2 [6.1] %, P<0.01) and group R (85.6 [18.2]vs. 57.1 [6.3] %, P<0.05) compared to spontaneous recovery, respectively. The reversal effect of neostigmine did not differ significantly between cisatracurium and rocuronium.ConclusionsThis porcine model demonstrated that neostigmine provides an adequate and timely IONM signal suppressed by both cisatracurium and rocuronium. These results can potentially expand the options for precision neuromuscular block management during IONM to improve vocal outcomes in thyroid surgery patients.

Surgical management of giant calcified thoracic disc herniation and the role of neuromonitoring. The outcome of large mono centric series

PurposeGiant thoracic disc herniations (GTDH) are considered a subgroup of TDHs with worse functional outcomes, a high calcification rate, and a considerable risk of complications. We aimed to determine whether there is a relationship between the extent of calcification of GTDH and outcomes concerning the risk of complications, the surgical technique, and changes in neuromonitoring signals. MethodsWe present a retrospective analysis of 76 patients undergoing surgery for calcific GTDH. We introduced and defined a radiological definition of the calcified disc into“fully calcified” and “partially calcified.” We performed a statistical analysis between clinical and radiological variables, type of surgical procedure, the extent of excision, neuro-monitoring signals, and outcome, comparing a group of 58 “fully-calcified TDH” patients and 18 “partially-calcified TDH” patients. ResultsFully calcified TDHs, compared with partially calcified TDHs, do not have significant differences in outcome (worse outcome 4/58–6.9% versus 0/18, p = 0.25) and complications (10/58–17.24% versus 4/18–22.2%, p = 0.63); Fully calcified TDH is associated with a higher risk of alterations in neurophysiological potentials (14/58–24.1% versus 0/18, p = 0.02) and subtotal excision (18/58–31% versus 2/18–11%, p = 0.15), without significant differences between the approaches used. ConclusionFully calcified TDH group has a similar outcome and complication rate as the partially calcified TDH group, but they are associated with higher intraoperative neuromonitoring signal changes. We introduced a new classificationsystem that guides the approach and helps tocounsel the patients.

Long-term Neurologic Outcome After Spinal Ependymoma Resection With Multimodal Intraoperative Electrophysiological Recording: Cohort Study and Review of the Literature.

ObjectiveTo evaluate how multimodal intraoperative neuromonitoring (IONM) changes during spinal ependymoma (SE) resection correlate with long-term neuro-functional outcomes. MethodsA retrospective analysis of patients aged 18 years or older who underwent surgical resection for SE over a 10-year period was conducted. IONM changes were defined as sustained transcranial motor evoked potential (TcMEP) and/or somatosensory evoked potential (SSEP) signal decrease of 50% or greater from baseline. Primary endpoints were postoperative modified McCormick Neurologic Scale (MNS) scores at postoperative day (POD) < 2, 6 weeks, 1 year, and 2 years. Univariate and multivariate analyses were performed.ResultsTwenty-nine patients were identified. Average age was 44.2±15.4 years. Sixteen (55.2%) were male and 13 (44.8%) were female. Tumor location was 10 cervical-predominant (34.5%), 13 thoracic-predominant (44.8%), and 6 lumbar/conus-predominant (20.7%). A majority (69.0%) were World Health Organization grade 2 tumors. Twentyfour patients (82.8%) achieved gross total resection. Thirteen patients (44.8%) had a sustained documented IONM signal change and 10 (34.5%) had a TcMEP change with or without derangement in SSEP. At POD < 2, 6 weeks, 1 year, and 2 years, MNS was significantly higher for those when analyzing subgroups with either any sustained IONM or TcMEP±SSEP signal attenuation > 50% below baseline (all p<0.05). ConclusionSustained IONM derangements > 50% below baseline, particularly for TcMEP, are significantly associated with higher MNS postoperatively out to 2 years. Intraoperative and postoperative management of these patients warrant special consideration to limit neurologic morbidity.

Transcutaneous Laryngeal Ultrasonography for Assessing Vocal Cord Twitch Response in Thyroid Operation during Predissection Vagus Nerve Stimulation.

BACKGROUNDIn this study, we aimed to report our experience with the use of intraoperative transcutaneous laryngeal ultrasonography (TLUSG) to evaluate the vocal cord twitch response during predissection vagus nerve stimulation in thyroid surgeries and examine the reliability of this technique when compared with that of laryngeal twitch palpation (LTP).STUDY DESIGNThe prospective data collection of consecutive patients who underwent open thyroidectomy with intraoperative neuromonitoring (IONM) was reviewed retrospectively. We recorded the electromyographic activity and assessed the vocal cord twitch response on LTP, TLUSG. We compared the accessibility, sensitivity, and specificity of the techniques.RESULTSA total of 110 patients (38 men and 72 women) with 134 nerves at risk were enrolled. The vocal cord was assessable by TLUSG in 103 (93.6%) patients and by LTP in 64 (59.1%) patients. Two patients showed negative predissection IONM signal but positive on TLUSG and the presence of laryngeal twitch response confirmed by laryngoscopy. Fourteen patients showed positive IONM signals and presence of the vocal cord twitch response on TLUSG but not on LTP. The sensitivity and specificity were 70.21% and 100%, respectively, for LTP, and those both were 100% for TLUSG. For patients who could be assessed using both techniques, TLUSG had better accuracy than LTP (100% vs 80.33%, p = 0.0005).CONCLUSIONSThe innovative intraoperative application of TLUSG is better for evaluating the laryngeal twitch response than LTP. This technique provides practical troubleshooting guidance for patients with no IONM signals during predissection vagus nerve stimulation.

Surgical Causes of Significant Intraoperative Neuromonitoring Signal Changes in Three-Column Spinal Surgery.

Study DesignRetrospective case series.PurposeTo evaluate the risks and causes of neurologic complications in three-column spinal surgery by analyzing intraoperative neurophysiological monitoring (IONM) data. Overview of LiteratureThree-column spinal surgery, which may be required to correct complex spinal deformities or resection of spinal tumors, is known to carry a high risk of neurologic complications. However, few studies reported a specific surgical procedure related to a significant IONM signal change during surgery.MethodsMultimodality IONM data, including somatosensory-evoked potentials (SSEP) and motor-evoked potentials (MEP), were reviewed in 64 patients who underwent three-column spinal surgery from 2011 to 2015. Surgical procedures included posterior vertebral column resection, pedicle subtraction osteotomy, total en bloc spondylectomy, piecemeal spondylectomy, and corpectomy with laminectomy (n=27) in three cervical, 34 thoracic, and 31 lumbar procedures.ResultsSignificant IONM signal changes occurred in 11 of 64 (17.1%) patients. SSEP and MEP were changed in 11 patients. Postoperative neurologic deterioration occurred in 54.5% (6 of 11) of the patients, and two of them were permanent. There was no postoperative neurologic deterioration in patients without significant signal change. Suspected causes of IONM data changes are as follows: adhesion/tethering, translation, contusion, and perfusion.ConclusionsBased on the results of this study, to enhance neurologic safety in three-column spinal surgery, surgeons should pay attention to protect the spinal cord from mechanical insult, especially when the spinal column was totally destabilized during surgery, and not to compromise perfusion to the spinal cord in close cooperation with a neurologist and anesthesiologist.

The Effect of Patient Positioning on Intraoperative Neuromonitoring During Thyroid and Parathyroid Surgery.

Intraoperative neuromonitoring (IONM) has been accepted as a routine adjunct among surgeons who perform thyroid and parathyroid surgeries. Thyroid and parathyroid surgeries use various patient positioning strategies that have poorly understood effects on IONM. The aim of this study was to compare IONM signals between the transaxillary and transcervical approaches. In this retrospective cohort study, we evaluated 463 adult patients who underwent a total of 502 procedures. The procedures performed included total thyroidectomy, right or left hemithyroidectomy, and parathyroidectomy. Vagus nerve and recurrent laryngeal nerve (RLN) latency and amplitude measurements were analyzed intra-operatively. The distances between the vagus nerve and the trachea were measured via ultrasound during transaxillary procedures. Compared to the transcervical approach, the right vagus nerve latency was significantly decreased in the transaxillary approach. Transaxillary surgery was not associated with increased latency or decreased amplitude on IONM. The distance between the vagus nerve and trachea was significantly decreased post-positioning during transaxillary approaches. Despite differences in patient positioning, a transaxillary approach was not associated with increased stress on the vagus nerve or RLN, according to IONM data. The decreased right vagus nerve latency associated with a transaxillary approach highlights the importance of considering patient positioning and laterality while interpreting IONM data.

P118. Establishing baseline motor and somatosensory evoked potentials (MEPs and SSEPs) prior to cervical spine surgery: Association with diagnosis, demographics, comorbidities, and patient-reported measures

<h3>BACKGROUND CONTEXT</h3> During cervical spine procedures, motor evoked potentials (MEPs) and somatosensory evoked potentials (SSEPs) are the main modalities used for intraoperative neuromonitoring (IONM). Although MEPs and SSEPs monitoring have been recommended in cervical procedures, there is little research regarding risk factors for unmonitorable signals. <h3>PURPOSE</h3> To determine diagnosis, health history, demographic, and patient-reported symptom variables associated with attainability of monitorable baseline MEPs and SSEPs. <h3>STUDY DESIGN/SETTING</h3> Retrospective cohort review. <h3>PATIENT SAMPLE</h3> Records of adult patients who underwent elective surgery for cervical radiculopathy or myelopathy with IONM between January 2017 and December 2019 at a high-volume, single center were retrospectively reviewed. Patients with tumor or trauma were excluded. <h3>OUTCOME MEASURES</h3> Short Form-12 Physical (PCS-12), modified Japanese Orthopaedic Association (mJOA) survey, MEP and SSEP monitorability. <h3>METHODS</h3> Demographic data included age at time of procedure, sex, body mass index (BMI) and race. Health history data included 18 health conditions of the circulatory system, joints and other chronic disorders. Patient reported outcome measures (PROM) were derived from the SF-12 survey and the modified Japanese Orthopaedic Association (JOA) survey. All surveys and data were collected preoperatively. The baseline response of each muscle MEP and nerve SSEP was reported as monitorable or unmonitorable and documented in the electronic record during the procedure. Patients were separated into two cohorts based on the primary diagnosis of radiculopathy or myelopathy. Odds ratios were used to compare baseline monitorability of SSEPs and MEPs between cohorts, and within cohort comparisons utilized T-tests, Mann-Whitney U, and chi-squared tests, as appropriate, and logistic regression models. <h3>RESULTS</h3> Baseline MEPs were established in all myotomes in 93.5% of radiculopathic patients but just 87.6% of myelopathic patients, and for just lower extremity myotomes, baselines were established in 97.9% of radiculopathic patients but just 89.2% of myelopathic patients. Relative to radiculopathic patients, the odds ratios for unmonitorable baseline MEPs were significantly increased in myelopathic patients for all myotomes and lower extremity myotomes in particular (2.04 [1.52;2.78], and 2.68 [1.89, 3.82], p<0.001, respectively). For the myelopathic group, unmonitorable MEP signals were associated with age (p < 0.001), being male (p = 0.002) having high blood pressure (p < 0.001), peripheral vascular disease (p < 0.001), rheumatoid arthritis (p = 0.018), and type II diabetes (p < 0.001). For the radiculopathic group, unmonitorable MEP signals were only associated with gout (p < 0.001). For both groups, the majority of patients with unmonitorable lower extremity MEPs reported modest to moderate to major ambulatory dysfunction. Regarding SSEPs, the odds ratios for unmonitorable baselines were also increased in the myelopathic group relative the radiculopathic group (2.72 [1.86, 4.09], P<0.001), and for both groups, unmonitorable SSEPs were significantly associated with age, male sex, BMI, and type II diabetes (p values <0.005). <h3>CONCLUSIONS</h3> Baseline IONM signals are less likely to be established in myelopathic patients than radiculopathic patients. Age, male gender, and elevated BMI, and a history of a chronic circulatory or metabolic disorder such as high blood pressure, peripheral vascular disease, thyroid disorder, or type II diabetes were predictive of unmonitorable signals. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.

Intraoperative Neuromonitoring in Patients with Intradural Extramedullary Spinal Cord Tumor: A Single-Center Case Series

Intradural extramedullary spinal cord tumors (ID-EMSCT) make up 40% of all spinal neoplasms. Resection of these tumors is mostly conducted using intraoperative neuromonitoring (IONM). However, the literature shows heterogenous data on its added value for ID-EMSCT. The aim of this study is to define sensitivity and specificity of IONM in ID-EMSCT resection and to study possible correlations between preoperative, intraoperative, and postoperative variables and neurologic outcomes after ID-EMSCT resection. Data of patients undergoing ID-EMSCT surgeries with IONM from January 2012 until July 2019 were examined. Using neurologic status 6 weeks and 1 year postoperatively, sensitivity and specificity for IONM were calculated. IONM test results and neurologic outcomes were paired to preoperative, intraoperative, and postoperative parameters. Data of 78 patients were analyzed. 6 weeks postoperatively, 14.10% of patients had worse neurologic status, decreasing to 9.84% 1 year postoperatively. Multimodal IONM showed a sensitivity of 0.73 (95% confidence interval [CI], 0.39-0.94) and a specificity of 0.78 (95% CI, 0.66-0.87) after 6 weeks, and a sensitivity of 1.00 (95% CI, 0.54-1.00) and a specificity of 0.71 (95% CI, 0.57-0.82) after 1 year. IONM yielded high to perfect sensitivity and high specificity. However, IONM signals did not always determine the extent of resection, and false-positive results did not always result in incomplete tumor resections, because of surgeons overruling IONM. Therefore, IONM cannot fully replace clinical judgment and other perioperative information.

Neuromonitoring in Cervical Spine Surgery: When Is a Signal Drop Clinically Significant?

Study DesignRetrospective cohort study.PurposeTo identify the clinical significance of different patterns of intraoperative neuromonitoring (IONM) signal alerts.Overview of LiteratureIONM is a long-established valuable adjunct to complex spine surgeries. IONM for cervical spine surgery is in the form of somatosensory evoked potential (SSEP) and motor evoked potential (MEP). The efficacy of both modalities (individually or in combination) to detect clinically significant neurological compromise is constantly being debated and requires conclusive suggestions.MethodsClinical and neuromonitoring data of 207 consecutive adult patients who underwent cervical spine surgeries at multiple surgical centers using bimodal IONM were analyzed. Signal changes were divided into three groups. Group 0 had transient signal changes in either MEPs or SSEPs, group 1 had sustained unimodal changes, and group 2 had sustained changes in both MEPs and SSEPs. The incidences of true neurological deficits in each group were recorded.ResultsA total of 25% (52/207) had IONM signal alerts. Out of these signal drops, 96% (50/52) were considered to be false positives. Groups 0 and 1 had no incidence of neurological deficits, while group 2 had a 29% (2/7) rate of true neurological deficits. The sensitivities of both MEP and SSEP were 100%. SSEP had a specificity of 96.6%, while MEP had a lower specificity at 76.6%. C5 palsy rate was 6%, and there was no correlation with IONM signal alerts (p=0.73).ConclusionsThis study shows that we can better predict its clinical significance by dividing IONM signal drops into three groups. A sustained, bimodal (MEP and SSEP) signal drop had the highest risk of true neurological deficits and warrants a high level of caution. There were no clear risk factors for false-positive alerts but there was a trend toward patients with cervical myelopathy.

Laryngeal paralysis detected in preoperative laryngoscopy in malignant and benign thyroid disease. Systematic review and meta-analysis

There is controversy regarding the performance of preoperative laryngoscopy (LP) in thyroid surgery, with different recommendations being made, based on observational studies, in various publications.The aim of the study was to know the prevalence of laryngeal paralysis found in the LPs of patients who underwent thyroidectomy in benign and malignant pathology.A systematic review was carried out with 29 articles included for the qualitative study and a meta-analysis of 13 articles in which the data could be obtained to evaluate the same effect (in all patients in which an LP was carried out, those with preoperative laryngeal paralysis were included, and assigned to malignant or benign postoperative histology groups).The pooled prevalence of preoperative paralysis in benign pathology was 1.1% (95% CI 0.7 to 1.7%, 71% I2) and in 6.3% malignant pathology (95% CI 3.8 to 9.4%; I2 85%). The prevalence was significantly higher among patients with malignant pathology with an estimated effect RR 5.66, 95% CI [2.48, 12.88].The studies analyzed present biases that will need to be corrected in future research, eliminating blinding biases in the selection and allocation of patients or in the laryngoscopy technique used. The LP in thyroid surgery evaluates possible disorders of laryngeal motility. The prevalence of laryngeal paralysis in thyroid pathology found in LPs in patients with a postoperative diagnosis of malignant pathology was higher than in the benign pathology group. This information is necessary for interpreting the intraoperative neuromonitoring signal and for making informed decisions.

Association Between Recurrent Laryngeal Nerve Calibre and Body Figure: A Preoperative Tool to Assess Thin-Diameter Nerves in Thyroidectomy.

Inadvertent recurrent laryngeal nerve (RLN) injury is a major complication of thyroidectomy. This study aimed to investigate the association between preoperative clinical parameters and RLN size prediction. Total thyroidectomy and thyroid lobectomy data were collected between January 2014 and April 2017. Routine identification of the recurrent laryngeal nerves was performed, while intraoperative findings (nerve diameter, thyroid gland weight, intraoperative neuromonitoring (IONM) use, and signal recording) and demographic data were collected for analysis. A total of 848 patients with 1357 RLNs at risk were enrolled in this study. RLN diameter was thinner in females, those with body height <160cm, and those with a BMI <25 (all p < 0.001). RLN diameter was directly proportional to age, body weight, height, and BMI. RLN diameter was thinner (1.71mm vs. 1.55mm, p = 0.039) and branched nerve incidence was higher (18.5% vs. 29.7%, p = 0.09) in the postoperative RLN injury group. Branched nerves were more frequently encountered in female patients (female vs. male: 28.8% vs. 18.7%, p = 0.004). The risk of RLN palsy in intraoperative IONM loss patients was 27 times higher compared to that in IONM normal patients (1.55% vs. 30%, p < 0.001). Thinner nerves did not yield a higher rate of IONM signal loss. Thinner nerves and higher palsy rates could be anticipated in females, younger age groups, those with shorter stature, and those with low BMI. RLN diameter was not associated with the rate of IONM signal loss.

Role of intraoperative neuromonitoring in spine surgery: A retrospective study

Background: Iatrogenic neurological injury resulting during surgical intervention is a devastating complication not only for patient but also for the operating surgeon. Even with best efforts, the risk remains approximately 5%. Aims: This study aims to study the role of intraoperative neuromonitoring (IONM) in non-deformed spine surgeries and to find out the sensitivity and specificity. Settings and Design: Tertiary health-care centre. Retrospective study with data of the patients operated from January 2019 to January 2020 was reviewed and evaluated. Materials and Methods: Patients with spinal fractures, spondylodiscitis, bony tumours of spine and degenerative spinal disorders without neurological deficit were included. The patients with spinal deformity and with prior neurological deficits were excluded. Group A: the patients with no IONM signal drop during procedure, Group B: the patients who experienced significant drop in signal during surgery. Statistical Analysis Used: Data entry-MS Excel, Data analysis-SPSS 23.0 version for windows, descriptive statistics-mean ± numerical variable, null hypothesis-paired test-two sample for mean (