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A prospective multicenter observational study.The aim was to investigate the validity of transcranial motor-evoked potentials (Tc-MEP) in cervical spine surgery and identify factors associated with positive predictive value when Tc-MEP alerts are occurred.The sensitivity and specificity of Tc-MEP for detecting motor paralysis are high; however, false-positives sometimes occur.The authors examined Tc-MEP in 2476 cases of cervical spine surgeries and compared patient backgrounds, type of spinal disorders, preoperative motor status, surgical factors, and the types of Tc-MEP alerts. Tc-MEP alerts were defined as an amplitude reduction of more than 70% from the control waveform. Tc-MEP results were classified into two groups: false-positive and true-positive, and items that showed significant differences were extracted by univariate analysis and detected by multivariate analysis.Overall sensitivity was 66% (segmental paralysis: 33% and lower limb paralysis: 95.8%) and specificity was 91.5%. Tc-MEP outcomes were 33 true-positives and 233 false-positives. Positive predictive value of general spine surgery was significantly higher in cases with a severe motor status than in a nonsevere motor status (19.5% vs . 6.7%, P =0.02), but not different in high-risk spine surgery (20.8% vs . 19.4%). However, rescue rates did not significantly differ regardless of motor status (48% vs . 50%). In a multivariate logistic analysis, a preoperative severe motor status [ P =0.041, odds ratio (OR): 2.46, 95% confidence interval (95% CI): 1.03-5.86] and Tc-MEP alerts during intradural tumor resection ( P0.001, OR: 7.44, 95% CI: 2.64-20.96) associated with true-positives, while Tc-MEP alerts that could not be identified with surgical maneuvers ( P =0.011, OR: 0.23, 95% CI: 0.073-0.71) were associated with false-positives.The utility of Tc-MEP in patients with a preoperative severe motor status was enhanced, even in those without high-risk spine surgery. Regardless of the motor status, appropriate interventions following Tc-MEP alerts may prevent postoperative paralysis.

A prospective, multicenter study.This study clarified the uses and limitations of transcranial motor-evoked potentials (Tc-MEPs) for nerve root monitoring during adult spinal deformity (ASD) surgeries.Whether Tc-MEPs can detect nerve root injuries (NRIs) in ASD surgeries remains controversial.We prospectively analyzed neuromonitoring data from 14 institutions between 2017 and 2020. The subjects were ASD patients surgically treated with posterior corrective fusion using multichannel Tc-MEPs. An alert was defined as a decrease of ≥70% in the Tc-MEP's waveform amplitude from baseline, and NRI was considered as meeting the focal Tc-MEP alerts shortly following surgical procedures with postoperative nerve root symptoms in the selected muscles.A total of 311 patients with ASD (262 women and 49 men) and a mean age of 65.5 years were analyzed. Tc-MEP results revealed 47 cases (15.1%) of alerts, including 25 alerts after 10 deformity corrections, six three-column osteotomies, four interbody fusions, three pedicle screw placements or two decompressions, and 22 alerts regardless of surgical maneuvers. Postoperatively, 14 patients (4.5%) had neurological deterioration considered to be all NRI, 11 true positives, and three false negatives (FN). Two FN did not reach a 70% loss of baseline (46% and 65% loss of baseline) and one was not monitored at target muscles. Multivariate logistic regression analysis revealed that risk factors of NRI were preexisting motor weakness ( P0.001, odds ratio=10.41) and three-column osteotomies ( P =0.008, odds ratio=7.397).Nerve root injuries in our ASD cohort were partially predictable using multichannel Tc-MEPs with a 70% decrease in amplitude as an alarm threshold. We propose that future research should evaluate the efficacy of an idealized warning threshold (e.g., 50%) and a more detailed evoked muscle selection, in reducing false negatives.

To measure the neuromagnetic fields of carpal tunnel syndrome patients after electrical digital nerve stimulation and evaluate median nerve function with high spatial resolution.A superconducting quantum interference device magnetometer system was used to record neuromagnetic fields at the carpal tunnel after electrical stimulation of the middle digital nerve in 10 hands of nine patients with carpal tunnel syndrome. The patients were diagnosed based on symptoms (numbness, tingling, and pain) supported by a positive Phalen or Tinel sign. A novel technique was applied to remove stimulus-induced artifacts, and current distributions were calculated using a spatial filter algorithm and superimposed on X-ray.In 6 of the 10 hands, the amplitude of the inward current waveform attenuated to70% or the nerve conduction velocity was40 m/s. The results of conventional nerve conduction studies were normal for two of these six hands. All four hands that could not be diagnosed by magnetoneurography had severe carpal tunnel syndrome superimposed on peripheral neuropathy secondary to comorbidities.Technical improvements enabled magnetoneurography to noninvasively visualize the electrophysiological nerve activity in carpal tunnel syndrome patients.Magnetoneurography may have the potential to contribute to the detailed diagnosis of various peripheral nerve disorders.

An adjustable helmet-style magnetoresistive (MR) sensor array, a room-temperature magnetic flux sensor, was developed to demonstrate simultaneous multipoint measurement of the somatosensory evoked magnetic field (SEF). The SEF was measured in three healthy subjects using an array of 30-channel MR sensors placed on the left hemisphere of the head with median nerve stimulation in the right wrist and averaged over 8,000 measurements. An M20 component (maximum amplitude of 725 ± 257 fT, peak latency of 20.5 ± 0.45 ms), considered to originate from the primary somatosensory cortex, was observed at an approximate latency of 20 ms of the magnetic field waveform in all cases. The phase inversion observed around C3 corresponded to the palmar area of the primary somatosensory cortex on the contour map of the magnetic field at the M20 peak. The MR sensor, a relatively inexpensive and easy-to-use magnetic sensor that does not require a zero-field environment, was successfully used for simultaneous multipoint SEF measurements in humans and may be a promising option to realize a reasonable magnetoencephalography application device.

Lumbar canal stenosis due to degenerative lumbar spondylolisthesis is one of the most common indications for lumbar spinal surgery. However, from a long-term perspective, it is still unclear which of these procedures should be performed: decompression, decompression plus fusion, or decompression plus stabilization.This study aimed to present the long-term results of a randomized controlled trial of surgery for degenerative spondylolisthesis.This is a long-term follow-up of a previously reported randomized controlled trial.Patients aged ≤75 years with single L4/5 level lumbar canal stenosis caused by degenerative lumbar spondylolisthesis were enrolled at two hospitals from May 1, 2003, to April 30, 2012; the final follow-up was on May 20, 2021.The following data were collected: modified Japanese Orthopedic Association (JOA) score, visual analog scale (VAS) score for lower back pain, leg pain, and numbness, and scores from eight Short-Form 36 (SF-36) subscales preoperatively, 1 year postoperatively, 5 years postoperatively, and at the final follow-up.Patients were randomized to undergo decompression alone, decompression plus fusion, or decompression plus stabilization. The primary outcome measure was the change in VAS for lower back pain with secondary outcomes including the modified JOA score, VAS for leg pain, VAS for leg numbness, eight SF-36 subscale scores, and occurrence of reoperation at the last follow-up.Among 85 patients who were randomized, 66 responded to the current survey. The mean follow-up period was 12.3 years. The VAS score for low back pain improvement was not significantly different between the decompression and fusion groups at the mean follow-up of 12.3 years. Of the 12 secondary outcomes, 8 showed no significant difference between decompression and fusion, 12 showed no significant difference between decompression and stabilization, and 10 showed no significant difference between fusion and stabilization.Although additional instrumentation surgery did not significantly improve low back pain at the mean follow-up of 12.3 years compared with decompression alone, fusion surgery provided clinically meaningful improvements in patient-reported vitality, social functioning, role limitations due to personal or emotional problems, and mental health compared with decompression alone.UMIN000028114.

Study design A prospective, multicenter study. Objective To evaluate the usefulness of transcranial motor-evoked potentials (Tc-MEPs) during supine-to-prone position change for thoracic ossification of the posterior longitudinal ligament (T-OPLL). Summary of background data Supine-to-prone position change might be a risk of spinal cord injury in posterior decompression and fusion surgeries for T-OPLL. Methods The subjects were 145 patients with T-OPLL surgically treated with posterior decompression and fusion using Tc-MEPs in 14 institutes. Tc-MEPs were monitored before surgery from supine-to-prone position and intraoperatively in 7 institutes and only intraoperatively in the other 7 institutes because of disapproval of the anesthesia department. In cases of Tc-MEP alert after position change, we adjusted the cervicothoracic posture. When the MEP did not recover, we reverted the position to supine and monitored the Tc-MEPs in supine position. Results There were 83 and 62 patients with/without Tc-MEP before position change to prone (group A and B). The true-positive rate was lower in group A than group B, but without statistical significance (8.4% vs 16.1%, p = 0.12). In group A, 5 patients who had Tc-MEP alert during supine-to-prone position change were all female and had larger body mass index values and upper thoracic lesions. Among the patients, 3 underwent surgeries after cervicothoracic alignment adjustment, and 2 had postponed operations to 1 week later with halo-vest fixation because of repeated Tc-MEP alerts during position change to prone. The Tc-MEP alert at exposure was statistically more frequent in group B than in group A (p = 0.033). Conclusion Tc-MEP alert during position change is an important sign of spinal cord injury due to alignment change at the upper thoracic spine. Tc-MEP monitoring before supine-to-prone position change was necessary to prevent spinal cord injury in surgeries for T-OPLL.Level of Evidence: 4.

Intraoperative neuromonitoring (IONM) is important for detecting neurological dysfunction, allowing for intervention and reversal of neurological deficits before they become permanent. Of the several IONM modalities, transcranial electrical stimulation of motor-evoked potential (TES-MEP) can help monitor the activity in the pyramidal tract. Surgery- and non-surgery-related factors could result in a TES-MEP alert during surgery. Once the alert occurs, the surgeon should immediately intervene to prevent a neurological complication. However, TES-MEP monitoring does not provide sufficient data to identify the non-surgery-related factors. Therefore, this study aimed to identify and describe these factors among TES-MEP alert cases.In this multicenter study, data from 1934 patients who underwent various spinal surgeries for spinal deformities, spinal cord tumors, and ossification of the posterior longitudinal ligament of the spine from 2017 to 2019 were collected. A 70% amplitude reduction was set as the TES-MEP alarm threshold. All surgeries with alerts were categorized into true-positive (TP) and false-positive (FP) cases according to the assessment of immediate postoperative neurological deficits.In total, TES-MEP alerts were observed in 251 cases during surgery: 62 TP and 189 FP IONM cases. Overall, 158 cases were related to non-surgery-related factors. We observed 22 (35.5%) TP cases and 136 (72%) FP cases, which indicated cases associated with non-surgery-related factors. A significant difference was observed between the two groups regarding factors associated with TES-MEP alerts (p 0.01). The ratio of TP and FP cases (related to non-surgery-related factors) associated with TES-MEP alerts was 13.9% (22/158 cases) and 86.1% (136/158 cases), respectively.Non-surgery-related factors are proportionally higher in FP than in TP cases. Although the surgeon should examine surgical procedures immediately after a TES-MEP alert, surgical intervention may not always be the best approach according to the results of this study.

We developed a superconducting quantum interference device (SQUID)-based biomagnetometer system for magnetoneurograms. The system was improved from a previously reported prototype magnetospinograph (MSG)/neurograph (MNG) system to satisfy the additional requirements that arose when we investigated practical clinical applications of the MSG/MNG in a hospital. The dimensions of the vector-type SQUID flux sensor array were increased to 150 mm × 188 mm, and the shape of the cryostat was modified so that the peripheral nerves at different body parts of a subject who assumed various postures, including positions provoking neurological symptoms, could be examined. In this paper, the improved MNG system is described in detail. Functional imaging of the brachial plexuses of subjects whose arms were in the abduction and external rotation position, which is one of the typical symptom-provocative positions for the shoulder, was achieved using the improved MNG system.

Study design A prospective multicenter observational study. Objective To elucidate the efficacy of transcranial motor-evoked potentials (Tc(E)-MEPs) in degenerative cervical myelopathy (DCM) surgery by comparing cervical spondylotic myelopathy (CSM) to cervical ossification of the posterior longitudinal ligament (OPLL) and investigate the timing of Tc(E)-MEPs alerts and types of interventions affecting surgical outcomes. Summary of background data Although CSM and OPLL are the most commonly encountered diseases of DCM, the benefits of Tc(E)-MEPs for DCM remain unclear and comparisons of these two diseases have not yet been conducted. Methods We examined the results of Tc(E)-MEPs from 1176 DCM cases (840 CSM /336 OPLL) and compared patients background by disease, preoperative motor deficits, and the type of surgical procedure. We also assessed the efficacy of interventions based on Tc(E)-MEPs alerts. Tc(E)-MEPs alerts were defined as an amplitude reduction of more than 70% below the control waveform. Rescue cases were defined as those in which waveform recovery was achieved after interventions in response to alerts and no postoperative paralysis. Results Overall sensitivity was 57.1%, and sensitivity was higher with OPLL (71.4%) than with CSM (42.9%). The sensitivity of acute onset segmental palsy including C5 palsy was 40% (OPLL/CSM: 66.7%/0%) whereas that of lower limb palsy was 100%. The most common timing of Tc(E)-MEPs alerts was during decompression (63.16%), followed by screw insertion (15.79%). The overall rescue rate was 57.9% (OPLL/CSM: 58.3%/57.1%). Conclusion Since Tc(E)-MEPs are excellent for detecting long tract injuries, surgeons need to consider appropriate interventions in response to alerts. The detection of acute onset segmental palsy by Tc(E)-MEPs was partially possible with OPLL, but may still be difficult with CSM. The rescue rate was higher than 50% and appropriate interventions may have prevented postoperative neurological complications.Level of Evidence: 3.

Study Design: Multicenter prospective study. Objectives: Although intramedullary spinal cord tumor (IMSCT) and extramedullary SCT (EMSCT) surgeries carry high risk of intraoperative motor deficits (MDs), the benefits of transcranial motor evoked potential (TcMEP) monitoring are well-accepted; however, comparisons have not yet been conducted. This study aimed to clarify the efficacy of TcMEP monitoring during IMSCT and EMSCT resection surgeries. Methods: We prospectively reviewed TcMEP monitoring data of 81 consecutive IMSCT and 347 EMSCT patients. We compared the efficacy of interventions based on TcMEP alerts in the IMSCT and EMSCT groups. We defined our alert point as a TcMEP amplitude reduction of ≥70% from baseline. Results: In the IMSCT group, TcMEP monitoring revealed 20 true-positive (25%), 8 rescue (10%; rescue rate 29%), 10 false-positive, a false-negative, and 41 true-negative patients, resulting in a sensitivity of 95% and a specificity of 80%. In the EMSCT group, TcMEP monitoring revealed 20 true-positive (6%), 24 rescue (7%; rescue rate 55%), 29 false-positive, 2 false-negative, and 263 true-negative patients, resulting in a sensitivity of 91% and specificity of 90%. The most common TcMEP alert timing was during tumor resection (96% vs. 91%), and suspension surgeries with or without intravenous steroid administration were performed as intervention techniques. Conclusions: Postoperative MD rates in IMSCT and EMSCT surgeries using TcMEP monitoring were 25% and 6%, and rescue rates were 29% and 55%. We believe that the usage of TcMEP monitoring and appropriate intervention techniques during SCT surgeries might have predicted and prevented the occurrence of intraoperative MDs.

STUDY DESIGN Prospective multicenter study. OBJECTIVE To examine transcranial motor evoked potential (Tc-MEP) waveforms in intraoperative neurophysiological monitoring (IONM) in surgery for intradural extramedullary (IDEM) tumors, focused on the characteristics for cervical, thoracic and conus lesions. SUMMARY OF BACKGROUND DATA IDEM tumors are normally curable after resection, but neurological deterioration may occur after surgery. IONM using Tc-MEPs during surgery is important for timely detection of possible neurological injury. METHODS The subjects were 233 patients with IDEM tumors treated surgically with Tc-MEP monitoring at 9 centers. The alarm threshold was ≥70% waveform deterioration from baseline. A case with a Tc-MEP alert that normalized and had no new motor deficits postoperatively was defined as a rescue case. A deterioration of manual muscle test (MMT) score ≥1 compared to the preoperative value was defined as postoperative worsening of motor status. RESULTS The 233 patients (92 males, 39%) had a mean age of 58.1 ± 18.1 years, and 185 (79%), 46 (20%) and 2 (1%) had schwannoma, meningioma, and neurofibroma. These lesions had cervical (C1-7), thoracic (Th1-10), and conus (Th11-L2) locations in 82 (35%), 96 (41%) and 55 (24%) cases. There were no significant differences in preoperative motor deficit among the lesion levels. Thoracic lesions had a significantly higher rate of poor baseline waveform derivation (0% cervical, 6% thoracic, 0% conus, p

STUDY DESIGN Prospective multicenter study. OBJECTIVE The purpose of the study is to examine cases with poor baseline waveform derivation for all muscles in multichannel monitoring of transcranial motor-evoked potentials (Tc-MEPs) in spine surgery. SUMMARY OF BACKGROUND DATA Intraoperative neuromonitoring (IONM) is useful for identifying neurologic deterioration during spinal surgery. Tc-MEPs are widely used for IONM, but some cases have poor waveform derivation, even in multichannel Tc-MEP monitoring. METHODS The subjects were 3625 patients (mean age 60.1 years, range 4-95; 1886 females, 1739 males) who underwent Tc-MEP monitoring during spinal surgery at 16 spine centers between April 2017 and March 2020. Baseline Tc-MEPs were recorded from the deltoid, abductor pollicis brevis, adductor longus, quadriceps femoris, hamstrings, tibialis anterior, gastrocnemius, and abductor hallucis (AH) muscles after surgical exposure of the spine. RESULTS The 3625 cases included cervical, thoracic, and lumbar lesions (50%, 33% and 17%, respectively) and had preoperative motor status of no motor deficit, and motor deficit with manual muscle testing (MMT) ≥3 and MMT

To visualize impulse conduction along the brachial plexus through simultaneous electromagnetic measurements.Neuromagnetic fields following median nerve stimulation were recorded above the clavicle with a superconducting quantum interference device biomagnetometer system in 7 healthy volunteers. Compound nerve action potentials (CNAPs) were obtained from 12 locations. Pseudocolor maps of equivalent currents reconstructed from magnetic fields and isopotential contour maps were superimposed onto X-ray images. Surface potentials and current waveforms at virtual electrodes along the brachial plexus were compared.In magnetic field analysis, the leading axonal current followed by a trailing backward current traveled rostrally along the brachial plexus. The spatial extent of the longitudinal intra-axonal currents corresponded to the extent of the positive-negative-positive potential field reflecting transmembrane volume currents. The peaks and troughs of the intra-axonal biphasic current waveforms coincided with the zero-crossings of triphasic CNAP waveforms. The amplitudes of CNAPs and current moments were linearly correlated.Reconstructed neural activity in magnetic field analysis visualizes not only intra-axonal currents, but also transmembrane volume currents, which are in good agreement with the surface potential field.Magnetoneurography is a novel non-invasive functional imaging modality for the brachial plexus whose performance can surpass that of electric potential measurement.

Study Design Retrospective multicenter cohort study Objectives We aimed to clarify the efficacy of multimodal intraoperative neuromonitoring (IONM), especially in transcranial electrical stimulation of motor-evoked potentials (TES-MEPs) with spinal cord-evoked potentials after transcranial stimulation of the brain (D-wave) in the detection of reversible spinal cord injury in high-risk spinal surgery. Methods We reviewed 1310 patients who underwent TES-MEPs during spinal surgery at 14 spine centers. We compared the monitoring results of TES-MEPs with D-wave vs TES-MEPs without D-wave in high-risk spinal surgery. Results There were 40 cases that used TES-MEPs with D-wave and 1270 cases that used TES-MEPs without D-wave. Before patients were matched, there were significant differences between groups in terms of sex and spinal disease category. Although there was no significant difference in the rescue rate between TES-MEPs with D-wave (2.0%) and TES-MEPs (2.5%), the false-positivity rate was significantly lower (0%) in the TES-MEPs-with-D-wave group. Using a one-to-one propensity score-matched analysis, 40 pairs of patients from the two groups were selected. Baseline characteristics did not significantly differ between the matched groups. In the score-matched analysis, one case (2.5%) in both groups was a case of rescue ( P = 1), five (12.5%) cases in the TES-MEPs group were false positives, and there were no false positives in the TES-MEPs-with-D-wave group ( P = .02). Conclusions TES-MEPs with D-wave in high-risk spine surgeries did not affect rescue case rates. However, it helped reduce the false-positivity rate.

Study design Prospective, multicenter, observational study. Objective The aim of this study was to investigate the efficacy of intervention after an alert in intraoperative neurophysiological monitoring (IONM) using transcranial motor-evoked potentials (Tc-MEPs) during surgery for thoracic ossification of the posterior longitudinal ligament (T-OPLL). Summary of background data T-OPLL is commonly treated with posterior decompression and fusion with instrumentation. IONM using Tc-MEPs during surgery reduces the risk of neurological complications. Methods The subjects were 79 patients with a Tc-MEP alert during posterior decompression and fusion surgery for T-OPLL. Preoperative muscle strength (manual muscle testing [MMT]), waveform derivation rate at the start of surgery (baseline), intraoperative waveform changes; and postoperative motor paralysis were examined. A reduction in MMT score of ≥1 on the day after surgery was classified as worsened postoperative motor deficit. An alert was defined as a decrease in Tc-MEP waveform amplitude of ≥70% from baseline. Alerts were recorded at key times during surgery. Results The patients (35 males, 44 females; age 54.6 years) had OPLL at T1-4 (n = 27, 34%), T5-8 (n = 50, 63%), and T9-12 (n = 16, 20%). The preoperative status included sensory deficit (n = 67, 85%), motor deficit (MMT ≤4) (n = 59, 75%), and nonambulatory (n = 26, 33%). At baseline, 76 cases (96%) had a detectable Tc-MEP waveform for at least one muscle, and the abductor hallucis had the highest rate of baseline waveform detection (n = 66, 84%). Tc-MEP alerts occurred during decompression (n = 47, 60%), exposure (n = 13, 16%), rodding (n = 5, 6%), pedicle screw insertion (n = 4, 5%), posture change (n = 4, 5%), dekyphosis (n = 2, 3%), and other procedures (n = 4, 5%). After intraoperative intervention, the rescue rate (no postoperative neurological deficit) was 57% (45/79), and rescue cases had a significantly better preoperative ambulatory status and a significantly higher baseline waveform derivation rate. Conclusion These results show the efficacy of intraoperative intervention following a Tc-MEP alert for prevention of neurological deficit postoperatively.Level of Evidence: 2.

Introduction Anterior decompression and fusion have shown favorable neurologic outcomes in patients with cervical myelopathy. However, implant migration sometimes occurs immediately after multilevel anterior cervical corpectomy with fusion (ACCF). Risk factors associated with early bone graft migration have not been precisely documented. The study aimed to investigate how frequently bone graft subsidence occurs after ACCF and to determine the factors affecting implant migration. Methods Forty-seven consecutive patients who underwent ACCF for ossification of the posterior longitudinal ligament at our hospital between 2007 and 2015 and were able to complete 1 year of follow-up were enrolled. Patients treated with hybrid fixation were excluded. Data on demographics and radiographic findings, namely, fused segment angle and fused segment height (FSH), were collected. Implant migration was defined as subsidence of >3 mm. The patients were divided into 2-segment (2F), 3-segment (3F), and ≥4-segment (4F) groups. Results were compared between the groups using one-way analysis of variance, the Mann-Whitney U test, and the chi-square test. Results Mean age was 61.6 years in the 2F group (n = 17), 62.1 years in the 3F group (n = 21), and 69 years in the 4F group (n = 9). There were no significant between-group differences in demographics or clinical characteristics. Implant subsidence occurred in 3 cases (17.6%) in the 2F group, 4 (19%) in the 3F group, and 3 (33.3%) in the 4F group. Revision surgery was required in 2 cases (1 patient each in the 3F and 4F groups). Logistic regression analysis showed a significant association of increased FSH and increased risk of postoperative implant subsidence. Conclusions A postoperative increase in FSH may affect graft stability and lead to early implant migration.

Objective Magnetospinography (MSG) has been developed for clinical application and is expected to be a novel neurophysiological examination. Here, we used an MSG system with sensors positioned in three orthogonal directions to record lumbar canal evoked magnetic fields (LCEFs) in response to peripheral nerve stimulation and to evaluate methods for localizing spinal cord lesions. Methods LCEFs from the lumbar area of seven rabbits were recorded by the MSG system in response to electrical stimulation of a sciatic nerve. LCEFs and lumbar canal evoked potentials (LCEPs) were measured before and after spinal cord compression induced by a balloon catheter. The lesion positions were estimated using LCEPs and computationally reconstructed currents corresponding to the depolarization site. Results LCEFs were recorded in all rabbits and neural activity in the lumbar spinal cord could be visualized in the form of a magnetic contour map and reconstructed current map. The position of the spinal cord lesion could be estimated by the LCEPs and reconstructed currents at the depolarization site. Conclusions MSG can visualize neural activity in the spinal cord and localize the lesion site. Significance MSG enables noninvasive assessment of neural activity in the spinal canal using currents at depolarization sites reconstructed from LCEFs.

Objective To visualize neural activity in the brachial plexus using magnetoneurography (MNG). Methods Using a 124- or 132-channel biomagnetometer system with a superconducting quantum interference device, neuromagnetic fields above the clavicle and neck region were recorded in response to electrical stimulation of the median and ulnar nerves in five asymptomatic volunteers (four men and one woman; age, 27–45 years old). Equivalent currents were computationally reconstructed from neuromagnetic fields and visualized as pseudocolor maps. Reconstructed currents at the depolarization site and compound nerve action potentials (CNAPs) at Erb’s point were compared. Results Neuromagnetic fields were recorded in all subjects. The reconstructed equivalent currents propagated into the vertebral foramina, and the main inflow levels differed between the median nerve (C5/C6–C7/T1 vertebral foramen) and the ulnar nerve (C7/T1–T1/T2). The inward current peaks at the depolarization site and CNAPs showed high linear correlation. Conclusions MNG visualizes neural activity in the brachial plexus and can differentiate the conduction pathways after median and ulnar nerve stimulations. In addition, it can visualize not only the leading and trailing components of intra-axonal currents, but also inward currents at the depolarization site. Significance MNG is a novel and promising functional imaging modality for the brachial plexus.

Prospective observational single-center study.To evaluate anterior decompression and fusion (ADF) or posterior surgery (PS) for patients with cervical spondylotic myelopathy (CSM) using the modified K-line (mK-line) and to compare clinical and radiologic outcomes between these 2 techniques.The authors have previously reported that insufficient posterior decompression is often seen after laminoplasty for CSM in patients with preoperative anterior clearance of the spinal cord4 mm on the basis of the mK-line. However, to our knowledge, no study has investigated the role, if any, of the mK-line in surgical decision making for patients with CSM.A total of 87 patients were enrolled who underwent surgery for treatment of CSM between 2011 and 2015 at our hospital and who could be followed up for at least 2 years. ADF was selected as a more favorable procedure than PS in patients with anterior spinal clearance of4 mm on preoperative midsagittal magnetic resonance imaging. On the basis of the Japanese Orthopedic Association (JOA) scoring system for cervical myelopathy, the rate of recovery of the JOA scores at 2 years after surgery was investigated as a clinical outcome to compare these 2 groups.Mean age was 65.1 (±12.9) years in the ADF group (n=26) and 70.5 (±8.6) years in the PS group (n=61). In the PS group, 10 patients underwent posterior decompression with fusion. Mean preoperative and postoperative JOA scores were 10.5 and 14.1 points in the ADF group and 9.8 and 13.1 points in the PS group, respectively, showing no significant difference in recovery rate of JOA score between the ADF (58.9%) and PS (47.1%) groups. However, patients with a minimum interval between the mK-line and the anterior compression factor on the midsagittal image (minimum interval of the spinal cord)4 mm tended to have unsatisfactory outcomes (recovery rate 29.6%) compared with patients with minimum interval of the spinal cord4 mm (53.6%, P=0.07) in the PS group.Preoperative intervention using the mK-line is useful to predict residual cord compression and might homogenize postoperative clinical outcomes in both anterior surgery and PS.

Biomagnetic field measurement is a promising tool for the investigation of electrical activities in a living body. Room temperature (RT) magnetic sensors with an improved resolution such as magnetoresistance (MR) devices have been recently employed for the detection of weak magnetic fields, which were earlier detected solely using superconducting interference device magnetic sensors. The position, orientation, and sensitivity of each magnetic sensor in a sensor array must be precisely determined for accurate magnetic source analysis. We proposed a calibration method using an array of multiple coils, which is applicable to an RT magnetic sensor array. To demonstrate the validity of the proposed calibration method, we applied it to an MR device-based magnetocardiography (MCG) system equipped with an L-shaped planar sensor array, which was newly developed for the simultaneous observation of both anterior and lateral sides of the body. The deviation of the sensor parameters from the designed values was estimated via calibration. The result of the marker coil localization test indicated that the calibration considerably improved the accuracy of the magnetic source analysis. Finally, we demonstrated a preliminary MCG measurement using the calibrated magnetic sensor array.

STUDY DESIGN Prospective multicenter study. OBJECTIVE The aim of this study was to evaluate transcranial motor evoked potential (Tc-MEP) waveform monitoring in spinal surgery for patients with severe obesity. SUMMARY OF BACKGROUND DATA Spine surgeries in obese patients are associated with increased morbidity and mortality. Intraoperative Tc-MEP monitoring can identify neurologic deterioration during surgery, but has not been examined for obese patients. METHODS The subjects were 3560 patients who underwent Tc-MEP monitoring during spine surgery at 16 centers. Tc-MEPs were recorded from multiple muscles via needle or disc electrodes. A decrease in Tc-MEP amplitude of ≥70% from baseline was used as an alarm during surgery. Preoperative muscle weakness with manual muscle test (MMT) grade ≤4 was defined as a motor deficit, and a reduction of one or more MMT grade postoperatively was defined as deterioration. RESULTS The 3560 patients (1698 males, 47.7%) had a mean age of 60.0 ± 20.3 years. Patients with body mass index >35 kg/m2 (n = 60, 1.7%) were defined as severely obese. Compared with all other patients (controls), the rates of preoperative motor deficit (41.0% vs. 29.6%, P

Spinal schwannoma recurs after initial surgery at a rate of 4%-6%, with known risk factors including subtotal resection, multilevel involvement, large tumor size, and malignant histopathology. This study examined risk factors for schwannoma recurrence and residual tumor regrowth.Sixty-five patients who underwent resection of spinal schwannoma in our department between July 2010 and December 2018 and were followed up for more than 1 year were retrospectively analyzed for age, sex, follow-up duration, imaging and surgical data, recurrence, reoperation, and Japanese Orthopaedic Association scores before and 1 year after surgery. Patients with postoperative recurrence or residual tumor regrowth of10% at the final visit (R+ group) were compared with patients without recurrence or regrowth (R- group). Multivariate logistic regression analysis was performed to analyze concurrent effects of risk factors on recurrence and regrowth.The 65 patients (mean age 52.4 years at surgery) had schwannomas involving cervical (n = 14), thoracic (n = 25), and lumbar (n = 26) spinal levels. Mean follow-up duration was 58 months. Location was intradural in 65%, extradural in 17%, and both intradural and extradural in 18%. There were 4 recurrences (6.2%), and the mean interval between surgery and recurrence was 18.8 months. Seven patients (10.8%) experienced regrowth. Comparing group R+ (n = 11) and group R- (n = 54), univariate analysis showed significant differences in Sridhar tumor classification, giant tumor (Sridhar classification II, IVb, and V), left-right and cranial-caudal tumor size, largest diameter, operative time, blood loss, subtotal resection, reoperation, fusion surgery, and follow-up duration. Multivariate logistic regression analysis revealed giant tumor (Sridhar classification types II, IVb, and V) as an independent risk factor for recurrence and regrowth.This retrospective review of 65 consecutive patients with spinal schwannoma in a single institution demonstrated that 16.9% had recurrence or regrowth, demonstrating that this potential risk should be kept in mind.

Objective Noninvasive and detailed visualization of electrophysiological activity in the thoracic spinal cord through magnetoneurography. Methods In five healthy volunteers, magnetic fields around current flowing in the thoracic spinal cord after alternating unilateral and synchronized bilateral sciatic nerve stimulation were measured using a magnetoneurograph system with superconductive quantum interference device biomagnetometers. The current distribution was obtained from the magnetic data by spatial filtering and visualized by superimposing it on the X-ray image. Conduction velocity was calculated using the peak latency of the current waveforms. Results A sufficiently high magnetic signal intensity and signal-to-noise ratio were obtained in all participants after synchronized bilateral sciatic nerve stimulation. Leading and trailing components along the spinal canal and inward components flowing into the depolarization site ascended to the upper thoracic spine. Conduction velocity of the inward current in the whole thoracic spine was 42.4 m/s. Conclusions Visualization of electrophysiological activity in the thoracic spinal cord was achieved through magnetoneurography and a new method for synchronized bilateral sciatic nerve stimulation. Magnetoneurography is expected to be a useful modality in functional assessment of thoracic myelopathy. Significance This is the first report to use magnetoneurography to noninvasively visualize electrophysiological activity in the thoracic spinal cord in detail.

Study design Prospective multicenter observational study. Objective To evaluate transcranial motor-evoked potentials (Tc-MEPs) baseline characteristics of lower limb muscles and to determine the accuracy of Tc-MEPs monitoring based on preoperative motor status in surgery for high-risk spinal disease. Summary of background data Neurological complications are potentially serious side effects in surgery for high-risk spine disease. Intraoperative spinal neuromonitoring (IONM) using Tc-MEPs waveforms can be used to identify neurologic deterioration, but cases with preoperative motor deficit tend to have poor waveform derivation. Methods IONM was performed using Tc-MEPs for 949 patients in high-risk spinal surgery. A total of 4454 muscles in the lower extremities were chosen for monitoring. The baseline Tc-MEPs was recorded immediately after exposure of the spine. The derivation rate was defined as muscles detected/muscles prepared for monitoring. A preoperative neurological grade was assigned using the manual muscle test (MMT) score. Results The 949 patients (mean age 52.5 ± 23.3 yrs, 409 males [43%]) had cervical, thoracic, thoracolumbar, and lumbar lesions at rates of 32%, 40%, 26%, and 13%, respectively. Preoperative severe motor deficit (MMT ≤3) was present in 105 patients (11%), and thoracic ossification of the posterior longitudinal ligament (OPLL) was the most common disease in these patients. There were 32 patients (3%) with no detectable waveform in any muscles, and these cases had mostly thoracic lesions. Baseline Tc-MEPs responses were obtained from 3653/4454 muscles (82%). Specificity was significantly lower in the severe motor deficit group. Distal muscles had a higher waveform derivation rate, and the abductor hallucis (AH) muscle had the highest derivation rate, including in cases with preoperative severe motor deficit. Conclusion In high-risk spinal surgery, Tc-MEPs collected with multi-channel monitoring had significantly lower specificity in cases with preoperative severe motor deficit. Distal muscles had a higher waveform derivation rate and the AH muscle had the highest rate, regardless of the severity of motor deficit preoperatively.Level of Evidence: 3.

To visualize the neural activity of the ulnar nerve at the elbow using magnetoneurography (MNG).Subjects were asymptomatic volunteers (eight men and one woman; age, 26-53 years) and a male patient with cubital tunnel syndrome (age, 54 years). The ulnar nerve was electrically stimulated at the left wrist and evoked magnetic fields were recorded by a 132-channel biomagnetometer system with a superconducting quantum interference device at the elbow. Evoked potentials were also recorded and their correspondence to the evoked magnetic fields was evaluated in healthy participants.Evoked magnetic fields were successfully recorded by MNG, and computationally reconstructed currents were able to visualize the neural activity of the ulnar nerve at the elbow. In the affected arm of the patient, reconstructed intra-axonal and inflow currents attenuated and decelerated around the elbow. Latencies of reconstructed currents and evoked potentials were correspondent within an error of 0.4 ms in asymptomatic participants.Neural activity in the ulnar nerve can be visualized by MNG, which may be a novel functional imaging technique for ulnar neuropathy at the elbow, including cubital tunnel syndrome.MNG permits visualization of evoked currents in the ulnar nerve at the cubital tunnel.

Several postoperative problems have been reported in conventional cervical laminoplasty (C-LAMP), such as loss of cervical curvature, sagittal imbalance, and loss of range of motion (ROM). Selective laminectomy (S-LAM) is a less invasive procedure that may prevent the problems associated with conventional C-LAMP. In this study, the authors prospectively compared neurological outcomes and radiological parameters in C-LAMP and S-LAM for the treatment of cervical spondylotic myelopathy. Fifty-three patients were enrolled, with 25 patients receiving conventional double-door C-LAMP and 28 patients receiving S-LAM. Measured outcomes included operative time, intraoperative blood loss, Japanese Orthopaedic Association score for neurological recovery, cervical sagittal alignment at C2-7, cervical sagittal vertical axis from occiput to C7, C7 slope, and cervical ROM at C2-7. No difference was found in operative time, whereas intraoperative blood loss was significantly less in the S-LAM group ( P P P P Orthopedics . 2020;43(4);e311–e315.]

OBJECTIVE To obtain magnetic recordings of electrical activities in the cervical cord and visualize sensory action currents of the dorsal column, intervertebral foramen, and dorsal horn. METHODS Neuromagnetic fields were measured at the neck surface upon median nerve stimulation at the wrist using a magnetospinography system with high-sensitivity superconducting quantum interference device sensors. Somatosensory evoked potentials (SEPs) were also recorded. Evoked electrical currents were reconstructed by recursive null-steering beamformer and superimposed on cervical X-ray images. RESULTS Estimated electrical currents perpendicular to the cervical cord ascended sequentially. Their peak latency at C5 and N11 peak latency of SEP were well-correlated in all 16 participants (r = 0.94, p

To clarify whether there is any difference in mid-term clinical and radiologic outcomes between bone-grafted laminoplasty (BG LAMP) and non-bone-grafted laminoplasty (non-BG LAMP) when used to treat cervical spondylotic myelopathy.Conventional BG LAMP includes bone grafting at the lamina hinge site to prevent closure of the lamina postoperatively, but it often results in segmental fusion and sometimes causes loss of cervical mobility and lordotic alignment. Non-BG LAMP can now be performed to address this problem and preserve mobility postoperatively. However, there have been no studies comparing BG LAMP and non-BG LAMP to date.Forty-one patients who underwent BG LAMP (n = 24) or non-BG LAMP (n = 17) and had 5 years of follow-up were enrolled in the study. Neurological status was assessed preoperatively and postoperatively using the Japanese Orthopedic Association (JOA) scoring system. The Numeric Rating Scale (NRS) was used to assess neck pain after surgery at the final visit. Radiographic parameters were evaluated at 1, 3, and 5 years after surgery. Postoperative segmental fusion was defined as the level at which the segmental flexion-extension range of motion was1°.There was no significant difference in JOA score or recovery rate between the groups. NRS score was significantly lower in the BG group, indicating less neck pain (P .01). The lordotic angle and range of motion at C2-C7 were significantly decreased in the BG group (P .05). The segmental fusion was evident from 1 year postoperatively in both groups, but the fusion rate was significantly higher in the BG group (P .05).Neurologic outcomes were similar between the two groups, whereas axial symptom was lower in the BG group than in the non-BG group.Ⅳ.

Objective To establish a method for magnetospinography (MSG) measurement after ulnar nerve stimulation and to clarify its characteristics. Methods Using a 132-channel magnetoneurography system with a superconducting quantum interference device, cervical MSG measurements were obtained for 10 healthy volunteers after stimulation of the ulnar nerve at the elbow and the wrist, and neural current distribution was calculated and superimposed on the cervical X-ray images. Results Neuromagnetic signals were obtained in all participants after applying the stimulus artifact removal algorithm. The measured magnetic field intensity after elbow stimulation was about twice that after wrist stimulation. Calculated neural currents flowed into the intervertebral foramina at C6/7 to T1/2 and propagated cranially along the spinal canal. The conduction velocity from the peak latency of inward currents at C5-C7 was 73.4 ± 19.6 m/s. Conclusions We successfully obtained MSG measurements after ulnar nerve stimulation. The neural currents flowed into the spinal canal from more caudal segments after ulnar nerve stimulation compared with median nerve stimulation, and these MSG measurements were effective in examining the spinal tracts at C5/6/7. Significance This is the first report on the use of MSG to visualize electrical activity in the cervical spinal cord and nerve root after ulnar nerve stimulation.

Study design Retrospective observational study. Objective We investigated whether bone turnover markers could be a useful indicator for prediction of nonunion. Summary of background data Nonunion is a major complication of lumbar spinal fusion surgery. The involvement of bone turnover in the process of bony union in spinal fusion surgery is, however, poorly understood. Methods Of the 74 patients analyzed, 13 were diagnosed with nonunion. We evaluated the significance of the following risk factors: age, sex, number of fused segments, serum levels of total alkaline phosphatase, procollagen type 1 amino-terminal propeptide (P1NP), tartrate-resistant acid phosphatase 5b (TRACP-5b), and albumin, and history of diabetes mellitus, cigarette smoking, or alcohol use. We also defined the bone turnover ratio (BTR) as a value that equals serum TRACP-5b concentration divided by serum P1NP concentration to evaluate patients' individual bone turnover balance and investigated the significance of BTR as a risk factor. Results Univariate analysis showed that older age, malnutrition, and lower P1NP are risk factors for nonunion. Stepwise logistic regression analysis revealed that in the presence of lower P1NP, higher TRACP-5b becomes a risk factor. Furthermore, we identified BTR as the most significant risk factor for nonunion. The optimum cut-off value of BTR by receiver-operating characteristic curve was 11.74. Conclusion These findings show a relation between bone turnover and nonunion after spinal fusion surgery. The measurement of bone turnover markers could potentially be used to predict nonunion after spinal fusion surgery. Level of evidence 4.

Background Neurovascular injury is a critical complication in total hip arthroplasty (THA). However, neurovascular geographic variations around the hip joint in different body positions have not been examined. This study investigated the differences in hip neurovascular geography in the supine and lateral positions using magnetic resonance imaging (MRI). Hypothesis The neurovascular geography of the hip is influenced by differences in surgical body position. Patients and methods This was a single-center prospective study of 15 healthy volunteers enrolled between January 2018 and March 2019. Each subject's bilateral hips were scanned with a 3-T MRI scanner in both the supine and lateral positions. In T1-weighted axial images at the level of the hip center, the anterior and posterior acetabular edges were defined as reference points at which retractors are commonly placed during surgery. We measured the distance between the anterior acetabular edge and the femoral nerve (dFN), femoral artery (dFA), and femoral vein (dFV), as well as that between the posterior acetabular edge and the sciatic nerve (dSN). The primary outcome measures were the distances in both the supine and lateral positions. Results dFN, dFA, and dFV in the supine and lateral positions (mm, mean ± standard deviation) were 25.8 ± 5.6 and 32.4 ± 6.4 (p Discussion THA in the supine position may be accompanied by a higher risk of femoral neurovascular injury than that in the lateral position. The application of our findings could reduce the risk of femoral neurovascular injury during THA. Level of Evidence : III; Prospective Diagnostic case control study.

Neurovascular injury is a critical complication in total hip arthroplasty (THA). However, neurovascular geographic variations around the hip joint in different body positions have not been examined. This study investigated the differences in hip neurovascular geography in the supine and lateral positions using magnetic resonance imaging (MRI).The neurovascular geography of the hip is influenced by differences in surgical body position.This was a single-center prospective study of 15 healthy volunteers enrolled between January 2018 and March 2019. Each subject's bilateral hips were scanned with a 3-T MRI scanner in both the supine and lateral positions. In T1-weighted axial images at the level of the hip center, the anterior and posterior acetabular edges were defined as reference points at which retractors are commonly placed during surgery. We measured the distance between the anterior acetabular edge and the femoral nerve (dFN), femoral artery (dFA), and femoral vein (dFV), as well as that between the posterior acetabular edge and the sciatic nerve (dSN). The primary outcome measures were the distances in both the supine and lateral positions.dFN, dFA, and dFV in the supine and lateral positions (mm, mean±standard deviation) were 25.8±5.6 and 32.4±6.4 (p0.0001), 25.7±4.5 and 32.2±5.0 (p0.0001), and 26.5±4.8 and 32.3±5.1 (p0.0001), respectively. Most of these elements moved anteromedially in the lateral position compared to the supine position. There was no significant difference in dSN between the supine and lateral positions (23.7±4.9 and 24.5±6.5 (p=0.46).THA in the supine position may be accompanied by a higher risk of femoral neurovascular injury than that in the lateral position. The application of our findings could reduce the risk of femoral neurovascular injury during THA.III; prospective diagnostic case control study.

This study sought to evaluate the facilitation effect of repetitive multi-train transcranial electrical stimulation (mt-TES) at 2 repetition rates on transcranial electrical motor evoked potential (Tc-MEP) monitoring during spinal surgery, and to assess the induction rate in patients with impaired motor function from a compromised spinal cord or spinal nerve. We studied 32 consecutive patients with impaired motor function undergoing cervical or thoracic spinal surgery (470 muscles). A series of 10 TESs with 5 pulse trains were preoperatively delivered at 2 repetition rates (1 and 5 Hz). All peak-topeak amplitudes of the MEPs of the upper and lower extremity muscles elicited by the 10 TESs were measured. The induction rates of the lower extremity muscles were also assessed with muscle and preoperative lower extremity motor function scores. In each of the muscles, MEP amplitudes were augmented by about 2-3 times at 1 Hz and 5-6 times at 5 Hz. Under the 5-Hz condition, all limb muscles showed significant amplification. Also, in all preoperative motor function score groups, the amplitudes and induction rates of the lower extremity muscles were significantly increased. Moreover, the facilitation effects tended to peak in the last half of the series of 10 TESs. In all score groups of patients with preoperative neurological deficits, repetitive mt-TES delivered at a frequency of 5 Hz markedly facilitated the MEPs of all limb muscles and increased the induction rate. We recommend this method to improve the reliability of intraoperative monitoring during spinal surgery.

We developed a magnetospinogram (MSG) system equipped with a closed-cycle helium recondensing unit. The MSG system detects weak magnetic fields evoked by neural activity of spinal cords using superconducting quantum interference devices (SQUIDs) and provides functional images effective for the diagnosis of spinal cord diseases. Thus far, the cost of liquid helium (LHe) required to maintain the superconductivity of the SQUID magnetometers has prevented the MSG from being used widely. Here, we combine an LHe recycling system using a pulse tube cryocooler and a low-loss transfer tube for transporting LHe to the system. This allows the superconducting state of SQUIDs to be maintained for half a year without refilling the LHe. The frequency band of noise from the recondensing system was different from that of the MSG signals. Therefore, the MSG signals were obtained at a sufficient signal-to-noise ratio even when the recondensing system, which is located just beside the magnetically shielded room, was in operation. In this paper, the details of the developed MSG system and the results from preliminary measurements using the system are reported.

Diagnosis of nervous system disease is greatly aided by functional assessments and imaging techniques that localize neural activity abnormalities. Electrophysiological methods are helpful but often insufficient to locate neural lesions precisely. One proposed noninvasive alternative is magnetoneurography (MNG); we have developed MNG of the spinal cord (magnetospinography, MSG). Using a 120-channel superconducting quantum interference device biomagnetometer system in a magnetically shielded room, cervical spinal cord evoked magnetic fields (SCEFs) were recorded after stimulation of the lower thoracic cord in healthy subjects and a patient with cervical spondylotic myelopathy and after median nerve stimulation in healthy subjects. Electrophysiological activities in the spinal cord were reconstructed from SCEFs and visualized by a spatial filter, a recursive null-steering beamformer. Here, we show for the first time that MSG with high spatial and temporal resolution can be used to map electrophysiological activities in the cervical spinal cord and spinal nerve.