Additional benefit of ultrasonography to evaluate nerve root condition of degenerative cervical spine disease.

STUDY DESIGN: A cross-sectional explanatory study. OBJECTIVES: To clarify the nerve root condition and the association between nerve root cross-sectional area (CA) on ultrasonography (US) and other examinations such as MRI or compound muscle action potentials (CMAPs) in degenerative cervical spine diseases. SETTING: A university hospital in Japan. METHODS: Fifty-one patients diagnosed with proximal cervical spondylotic amyotrophy (CSA) (13 patients), cervical radiculopathy of C5 or C6 nerve root (CR) (26 patients), or cervical spondylotic myelopathy (CSM) (12 patients), and twenty-nine healthy volunteers were included in this study. Neurological findings, US findings and CMAPs of deltoid and biceps muscles of all participants were evaluated. In addition, CSA, CR, and CSM patients underwent MRI. RESULTS: A significant correlation was not observed between CA and CMAP amplitude or foraminal diameter on MRI (P > 0.05). In the US examination, the C6 CA of the affected side of the CR group was significantly larger than that of both the normal side and the other groups (P < 0.001). The C5 CA of the affected side of the CSA group clearly showed a bimodal distribution: enlarged and small CA groups. In the CMAP findings, CSA cases respectively showed the lower amplitude of deltoid and bicep CMAPs on both the normal and the affected side (P ≦ 0.01). CSM and healthy volunteers were nearly identical in CA and CMAPs. CONCLUSION: Utilizing US in addition to NCS and MRI can contribute towards an evaluation of the nerve root condition of degenerative cervical spine disease. SPONSORSHIP: no sponsorship.

Nerve root morphological and functional changes after degenerative cervical myelopathy surgery: preliminary study using ultrasound and electrophysiology.

STUDY DESIGN: A prospective observational study. OBJECTIVES: To depict morphological and functional changes in the cervical nerve roots before and after spinal cord decompression surgery for degenerative cervical myelopathy (DCM). SETTING: A general hospital in Japan. METHODS: Thirteen DCM patients who underwent posterior spinal cord decompression surgery, laminoplasty or laminectomy, were included in this study. The neural foramen shown on MRI and the cross-sectional area (CSA) of the nerve roots on ultrasound were used to evaluate the C5 and C6 nerve roots. The compound muscle action potentials (CMAPs) of deltoid and biceps muscle were also recorded. RESULTS: All patients showed sensorimotor functional improvement without the postoperative C5 palsy after surgery. Foraminal stenosis and preoperative CSA of the nerve root: C4/5 foramen and C5 nerve root, C5/6 foramen and C6 nerve root, had no significant correlation (P = 0.53 and 0.08). CSA of the C5 nerve root displayed no significant change before and after surgery (P = 0.2), however, that of the C6 nerve root reduced significantly after surgery (P = 0.038). The amplitude of the deltoid and biceps CMAPs displayed no significant change before and after surgery (P = 0.05 and 0.05). CONCLUSION: The C6 nerve root CSA change was observed after spinal cord decompression surgery with functional recovery. However, deltoid and biceps CMAPs amplitude showed no significant change. Independent CSA changes on ultrasound might be useful when conducting a functional evaluation of the postoperative nerve root. SPONSORSHIP: The Grant of Japan Orthopaedics and Traumatology Research Foundation No. 395.

Understanding the effect of non-surgical factors in a transcranial motor-evoked potential alert: A retrospective cohort study.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Discrepancy between functional recovery and cutaneous silent period change in surgically treated degenerative cervical myelopathy: a prospective pilot study.

STUDY DESIGN: Exploratory research OBJECTIVES: Cutaneous silent periods (CSPs) that reflect the inhibitory spinal cord reflex, can sensitively detect spinal cord dysfunction, and contribute to the diagnosis of degenerative cervical myelopathy (DCM). However, CSP changes after DCM surgery related to functional improvement have not been reported. SETTING: University hospital in Nankoku, Japan METHODS: CSP recorded at four time points-before surgery, 3, 6, 12 months after surgery-were investigated in 31 hands of 16 DCM patients. CSPs were categorized as follows: normal, delayed onset latency, shortened duration, onset delay with shortened duration, and absent CSP. Myelopathic symptoms were evaluated by the Japanese Orthopaedic Association score (JOA score). RESULTS: Normal CSPs were observed in five hands (16%) before surgery and six hands (19%) twelve months after surgery (P > 0.05). Either onset delay or shortened duration or both were observed in 18 hands (58%) before surgery and 16 hands (52%) twelve months after surgery (P > 0.05). Absent CSPs were observed in eight hands (26%) before surgery and nine hands (29%) twelve months after surgery (P > 0.05). Measured values of onset latency and duration also did not change throughout the study period (P > 0.05). On the other hand, JOA scores improved after surgery. (P = 0.003). CONCLUSIONS: CSP abnormalities persisted after surgery in most cases, indicating irreversible damage of the intramedullary reflex circuit. JOA score recovery without CSP recovery provides insight into postoperative neural recovery in DCM.

Localization of the primary sites of involvement in the spinal sensory and motor pathways for multilevel MRI abnormalities in degenerative cervical myelopathy.

STUDY DESIGN: Exploratory clinical study. OBJECTIVES: To localize the sites of conduction block in the spinal sensory and motor pathways for minimizing the level of surgical intervention despite MRI evidence of compression at several levels in degenerative cervical myelopathy (DCM). SETTING: Kochi Medical School Hospital, Japan. METHODS: We analyzed 83 DCM patients (69 ± 12 years) who underwent serial intervertebral recording of both ascending (A-SCEPs) and descending spinal cord-evoked potentials (D-SCEPs) after epidural and transcranial stimulation, respectively, during surgery before decompression procedures. The site of conduction block was identified by an abrupt reduction of the negative peak accompanied by an enlargement of the initial-positive peak. T1-weighted MRI allowed quantitative assessments of cord compression in relation to the level of conduction block. RESULTS: The A-SCEP and D-SCEP studies revealed conduction blocks at the same single level in 78 patients (94%) and at two separate levels in five patients (6%) for MRI abnormalities extending to 3.1 ± 1.1 levels. The site of conduction block had intense cord compression on MRI with either the smallest (81%) or the second smallest (19%) anteroposterior diameter and cross-sectional area of the cord. Based on the SCEP findings, 44 patients were treated by a single-level (35) or a two-level (9) anterior operation for MRI abnormalities of 2.7 ± 1.1 levels. CONCLUSIONS: Combined A-SCEP and D-SCEP studies served as useful additions to MRI in localizing the primary sites responsible for myelopathy, which helped exclude clinically silent compressions to minimize surgical intervention in 34 patients with anterior operation.

Unilateral repetitive tibial nerve stimulation improves neurogenic claudication and bilateral F-wave conduction in central lumbar spinal stenosis.

BACKGROUND: Repetitive electrical nerve stimulation of the lower limb may improve neurogenic claudication in patients with lumbar spinal stenosis (LSS) as originally described by Tamaki et al. We tested if this neuromodulation technique affects the F-wave conduction on both sides to explore the underlying physiologic mechanisms. METHODS: We studied a total of 26 LSS patients, assigning 16 to a study group receiving repetitive tibial nerve stimulation at the ankle (RTNS) on one leg, and 10 to a group without RTNS. RTNS conditioning consisted of a 0.3-ms duration square-wave pulse with an intensity 20% above the motor threshold, delivered at a rate of 5 Hz for 5 min. All patients underwent the walking test and the F-wave and M-wave studies for the tibial nerve on both sides twice; once as the baseline, and once after either the 5-min RTNS or 5-min rest. RESULTS: Compared to the baselines, a 5-min RTNS increased claudication distance (176 ± 96 m vs 329 ± 133 m; p = 0.0004) and slightly but significantly shortened F-wave minimal onset latency (i.e., increased F-wave conduction velocity) not only on the side receiving RTNS (50.7 ± 4.0 ms vs 49.2 ± 4.2 ms; p = 0.00081) but also on the contralateral side (50.1 ± 4.6 ms vs 47.9 ± 4.2 ms; p = 0.011). A 5-min rest in the group not receiving RTNS neither had a significant change on claudication distance nor on any F-wave measurements. The M response remained unchanged in both groups. CONCLUSIONS: The present study verified a beneficial effect of unilaterally applied RTNS of a mild intensity on neurogenic claudication and bilateral F-wave conduction. Our F-wave data suggest that this type of neuromodulation could be best explained by an RTNS-induced widespread sympathetic tone reduction with vasodilation, which partially counters a walking-induced further decline in nerve blood flow in LSS patients who already have ischemic cauda equina.

Can cantilever transforaminal lumbar interbody fusion (C-TLIF) maintain segmental lordosis for degenerative spondylolisthesis on a long-term basis?

PURPOSE: To determine if cantilever transforaminal lumbar interbody fusion (C-TLIF) using the crescent-shaped titanium interbody spacer (IBS) favors acquisition of segmental and lumbar lordosis even for degenerative spondylolisthesis (DS) on a long-term basis. METHODS: We analyzed 23 consecutive patients who underwent C-TLIF with pedicle screw instrumentations fixed with compression for a single-level DS. Measurements on the lateral radiographs taken preoperatively, 2 weeks postoperatively and at final follow-up included disc angle (DA), segmental angle (SA), lumbar lordosis (LL), disc height (%DH) and slip rate (%slip). RESULTS: There was a good functional recovery with 100 % fusion rate at the mean follow-up of 62 months. Segmental lordosis (DA and SA) and %DH initially increased, but subsequently decreased with the subsidence of the interbody spacer, resulting in a significant increase (p = 0.046) only in SA from 13.2° ± 5.5° preoperatively to 14.7° ± 6.4° at the final follow-up. Changes of LL and %slip were more consistent without correction loss finally showing an increase of LL by 3.6° (p = 0.005) and a slip reduction by 6.7 % (p < 0.001). CONCLUSIONS: Despite the inherent limitation of placing the IBS against the anterior endplate of the upper vertebra in the presence of DS, the C-TLIF helped significantly restore segmental as well as lumbar lordosis on a long-term basis, which would be of benefit in preventing hypolordosis-induced back pain and the adjacent level disc disease.

A genome-wide sib-pair linkage analysis of ossification of the posterior longitudinal ligament of the spine.

Ossification of the posterior longitudinal ligament of the spine (OPLL) is a common musculoskeletal disease among people after middle age. The OPLL presents with serious neurological abnormalities due to compression of the spinal cord and nerve roots. The OPLL is caused by genetic and environment factors; however, its etiology and pathogenesis still remain to be elucidated. To determine the susceptibility loci for OPLL, we performed a genome-wide linkage study using 214 affected sib-pairs of Japanese. In stratification analyses for definite cervical OPLL, we found loci with suggestive linkage on 1p21, 2p22-2p24, 7q22, 16q24 and 20p12. Fine mapping using additional markers detected the highest non-parametric linkage score (3.43, P = 0.00027) at D20S894 on chromosome 20p12 in a subgroup that had no complication of diabetes mellitus. Our result would shed a new light on genetic aspects of OPLL.

T-reflex studies in human upper limb muscles during voluntary contraction: normative data and diagnostic value for cervical radiculopathy.

OBJECTIVE: To evaluate the diagnostic utility of the T reflexes elicited from the upper limb muscles during standardized volitional contraction monitored by a real-time integrating electromyographic analyzer. DESIGN: Prospective descriptive study. SETTING: Department of orthopedic surgery at a university hospital. PARTICIPANTS: Healthy subjects (n=80) evenly distributed across decades of age from 21 to 79 years, and 12 consecutive patients with a single cervical root lesion based on clinical and magnetic resonance imaging studies and diagnostic block. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Using a special hammer, which externally triggers the sweep on skin contact, we evoked T reflexes in the biceps (C5), brachioradialis (C6), triceps (C7), and the first dorsal interosseous muscles (C8). RESULTS: Simultaneous regression analyses yielded clinically useful upper limits of normative values for latencies, side-to-side differences, and amplitude ratios adjusted to age and arm span. Comparison of the T reflexes between the 2 sides localized the solitary root lesions with a high sensitivity (92%), specificity (81%), and accuracy (83%). T-reflex studies proved helpful to localize the lesion even in patients who solely complained of upper limb pain. CONCLUSIONS: The T reflexes with a standardized facilitation of the upper limb muscles provide a clinically useful, noninvasive measure to localize the C5 to C8 radiculopathies. This study contributes in reassessing the currently underused T reflex as an electrodiagnostic technique.

A comparison of reoperation rates after single-level anterior cervical discectomy and fusion (ACDF) between the procedures with and without anterior plate fixation.

INTRODUCTION: The plate fixation for anterior cervical discectomy and fusion (ACDF) has become increasingly widespread for facilitating early mobilization and improving fusion rate. However, apart from multilevel operations, there is still some controversy over its use for single-level ACDF. This retrospective study has compared the reoperation rates after single-level ACDFs performed at our institution between the procedures with and without plate fixation. METHODS: This retrospective study included a total of 131 patients with???1-year of follow-up after a single-level ACDF, consisting of 100 patients without plating (conventional ACDF) and 31 patients with plate fixation (plated ACDF). RESULTS: Eleven patients (8.4% of all patients):four conventional ACDFs (4% of the conventional ACDFs) and seven plated ACDFs (22.6% of the plated ACDFs), had reoperation surgeries. The incidence of reoperation was significantly higher in the plated ACDFs than in the conventional ACDFs (P=0.0037). The log-rank test revealed a significant difference (P=0.00003) in 5-year reoperation-free survival rates between the conventional (96.9%) and the plated groups (68.3%). CONCLUSION: Anterior cervical plating may have a negative impact on the adjacent segment integrity, resulting in an increased reoperation rate after a single-level ACDF at relatively shorter postoperative time points. J. Med. Invest. 70 : 334-342, August, 2023.

Current Trends in Intraoperative Spinal Cord Monitoring: A Survey Analysis among Japanese Expert Spine Surgeons.

Introduction: Although intraoperative spinal neuromonitoring (IONM) is recommended for spine surgeries, there are no guidelines regarding its use in Japan, and its usage is mainly based on the surgeon's preferences. Therefore, this study aimed to provide an overview of the current trends in IONM usage in Japan. Methods: In this web-based survey, expert spine surgeons belonging to the Japanese Society for Spine Surgery and Related Research were asked to respond to a questionnaire regarding IONM management. The questionnaire covered various aspects of IONM usage, including the preferred modality, operation of IONM, details regarding muscle-evoked potential after electrical stimulation of the brain (Br(E)-MsEP), and need for consistent use of IONM in major spine surgeries. Results: Responses were received from 134 of 186 expert spine surgeons (response rate, 72%). Of these, 124 respondents used IONM routinely. Medical staff rarely performed IONM without a medical doctor. Br(E)-MsEP was predominantly used for IONM. One-third of the respondents reported complications, such as bite injuries caused by Br(E)-MsEP. Interestingly, two-thirds of the respondents did not plan responses to alarm points. Intramedullary spinal cord tumor, scoliosis (idiopathic, congenital, or neuromuscular in pediatric), and thoracic ossification of the posterior longitudinal ligament were representative diseases that require IONM. Conclusions: IONM has become an essential tool in Japan, and Br(E)-MsEP is a predominant modality for IONM at present. Although we investigated spine surgeries for which consistent use of IONM is supported, a cost-benefit analysis may be required.

Efficacy of Transcranial Motor Evoked Potential Monitoring During Intra- and Extramedullary Spinal Cord Tumor Surgery: A Prospective Multicenter Study of the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research.

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.

Role of Transcranial Motor Evoked Potential Monitoring During Traumatic Spinal Injury Surgery: A Prospective Multicenter Study of the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research.

STUDY DESIGN: A prospective multicenter observational cohort study. OBJECTIVE: This study aimed to investigate the role of transcranial motor evoked potential (TcMEP) monitoring during traumatic spinal injury surgery, the timing of TcMEP alerts, and intervention strategies to avoid intraoperative neurological complications. SUMMARY OF BACKGROUND DATA: Intraoperative neuromonitoring, including TcMEP monitoring, is commonly used in high-risk spinal surgery to predict intraoperative spinal cord injury; however, little information is available on its use in traumatic spinal injury surgery. METHODS: The TcMEP monitoring data of 350 consecutive patients who underwent traumatic spinal injury surgery (mean age, 69.3 y) between 2017 and 2021 were prospectively reviewed. In this study, a TcMEP amplitude reduction ≥70% was established as a TcMEP alert. A rescue case was defined as a case with the recovery of TcMEP amplitudes after certain procedures and without postoperative neurological complications. RESULTS: Among the 350 patients who underwent traumatic spinal injury surgery (TcMEP derivation rate 94%), TcMEP monitoring revealed seven true-positive (TP) (2.0%), three rescues (0.9%; rescue rate 30%), 31 false-positive, one false-negative, and 287 true-negative cases, resulting in 88% sensitivity, 90% specificity, 18% positive predictive value, and 99% negative predictive value. The TP rate in patients with preoperative motor deficits was 2.9%, which was higher than that in patients without preoperative motor deficits (1.1%). The most common timing of TcMEP alerts was during decompression (40%). During decompression, suspension of surgery with intravenous steroid injection was ineffective (rescue rate, 0%), and additional decompression was effective. CONCLUSION: Given the low prevalence of neurological complications (2.3%) and the low positive predictive value (18.4%), single usage of TcMEP monitoring during traumatic spinal injury surgery is not recommended. Further efforts should be made to reduce FP alert rates through better interpretation of multimodal Intraoperative neuromonitorings and the incorporation of anesthesiology to improve the positive predictive value. LEVEL OF EVIDENCE: 3.

Impact of Preoperative Motor Status for the Positive Predictive Value of Transcranial Motor-Evoked Potentials Alerts in Thoracic Spine Surgery: A Prospective Multicenter Study by the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research.

STUDY DESIGN: Prospective multicenter study. OBJECTIVE: To investigate the validity of transcranial motor-evoked potentials (Tc-MEP) in thoracic spine surgery and evaluate the impact of specific factors associated with positive predictive value (PPV). METHODS: One thousand hundred and fifty-six cases of thoracic spine surgeries were examined by comparing patient backgrounds, disease type, preoperative motor status, and Tc-MEP alert timing. Tc-MEP alerts were defined as an amplitude decrease of more than 70% from the baseline waveform. Factors were compared according to preoperative motor status and the result of Tc-MEP alerts. Factors that showed significant differences were identified by univariate and multivariate analysis. RESULTS: Overall sensitivity was 91.9% and specificity was 88.4%. The PPV was significantly higher in the preoperative motor deficits group than in the preoperative no-motor deficits group for both high-risk (60.3% vs 38.3%) and non-high-risk surgery groups (35.1% vs 12.8%). In multivariate logistic analysis, the significant factors associated with true positive were surgical maneuvers related to ossification of the posterior longitudinal ligament (odds ratio = 11.88; 95% CI: 3.17-44.55), resection of intradural intramedullary spinal cord tumor (odds ratio = 8.83; 95% CI: 2.89-27), preoperative motor deficit (odds ratio = 3.46; 95% CI: 1.64-7.3) and resection of intradural extramedullary spinal cord tumor (odds ratio = 3.0; 95% CI: 1.16-7.8). The significant factor associated with false positive was non-attributable alerts (odds ratio = .28; 95% CI: .09-.85). CONCLUSION: Surgeons are strongly encouraged to use Tc-MEP in patients with preoperative motor deficits, regardless of whether they are undergoing high-risk spine surgery or not. Knowledge of PPV characteristics will greatly assist in effective Tc-MEP enforcement and minimize neurological complications with appropriate interventions.

Efficacy of D-Wave Monitoring Combined With the Transcranial Motor-Evoked Potentials in High-Risk Spinal Surgery: A Retrospective Multicenter Study of the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research.

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.

Finger trembling improvement after surgery in Hirayama disease: a case report.

INTRODUCTION: Finger trembling is a characteristic physical finding in Hirayama disease. Although conservative treatment is recommended to stop disease progression, surgery is optional in some cases. However, the postoperative recovery of finger trembling is scarcely reported. CASE PRESENTATION: A 26-year-old Japanese female patient whose chief complaint was left finger trembling with active finger extension presented at our hospital. Hand weakness without muscle atrophy of the left arm was observed. MRI showed left-side oriented intramedullary signal change with concomitant cord atrophy at C4-5 and C5-6. The CT myelogram (CTM) on flexion showed anterior cord compression and anterior shift of posterior dura matter from C4 to C6. And CTM on extension showed the resolution of both findings. Electrophysiological studies showed active and chronic neuronal damage and preserved motor neuron pool of hand muscle. Since she had exhibited a gradual aggravation of symptoms over a period of 5 years, she underwent anterior cervical discectomy and fusion after careful assessment of both conservative and surgical treatment. Finger trembling recovered soon after surgery. DISCUSSION: Finger trembling is an unfamiliar physical finding in terms of postoperative recovery prediction. Anterior horn cell impairment is postulated as a cause of finger trembling. Postural restoration of spinal cord shape and cerebrospinal fluid around the cord with preserved neural function could facilitate functional recovery.

Transcranial Motor-evoked Potentials for Intraoperative Nerve Root Monitoring During Adult Spinal Deformity Surgery: A Prospective Multicenter Study.

STUDY DESIGN: A prospective, multicenter study. OBJECTIVE: This study clarified the uses and limitations of transcranial motor-evoked potentials (Tc-MEPs) for nerve root monitoring during adult spinal deformity (ASD) surgeries. SUMMARY OF BACKGROUND DATA: Whether Tc-MEPs can detect nerve root injuries (NRIs) in ASD surgeries remains controversial. MATERIALS AND METHODS: 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. RESULTS: 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 ( P <0.001, odds ratio=10.41) and three-column osteotomies ( P =0.008, odds ratio=7.397). CONCLUSIONS: 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.

The Utility of Transcranial Stimulated Motor-Evoked Potential Alerts in Cervical Spine Surgery Varies Based on Preoperative Motor Status.

STUDY DESIGN: A prospective multicenter observational study. OBJECTIVE: 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. SUMMARY OF BACKGROUND DATA: The sensitivity and specificity of Tc-MEP for detecting motor paralysis are high; however, false-positives sometimes occur. MATERIALS AND METHODS: 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. RESULTS: 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 ( P <0.001, 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. CONCLUSION: 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.

Comparison of intraoperative neuromonitoring accuracies and procedures associated with alarms in anterior versus posterior fusion for cervical spinal disorders: A prospective multi-institutional cohort study.

A prospective multicenter cohort study. To clarify the differences in the accuracy of transcranial motor-evoked potentials (TcE-MEPs) and procedures associated with the alarms between cervical anterior spinal fusion (ASF) and posterior spinal fusion (PSF). Neurological complications after TcE-MEP alarms have been prevented by appropriate interventions for cervical degenerative disorders. The differences in the accuracy of TcE-MEPs and the timing of alarms between cervical ASF and PSF noted in the existing literature remain unclear. Patients (n = 415) who underwent cervical ASF (n = 171) or PSF (n = 244) at multiple institutions for cervical spondylotic myelopathy, ossification of the posterior longitudinal ligament, spinal injury, and others were analyzed. Neurological complications, TcE-MEP alarms defined as a decreased amplitude of ≤70% compared to the control waveform, interventions after alarms, and TcE-MEP results were compared between the 2 surgeries. The incidence of neurological complications was 1.2% in the ASF group and 2.0% in the PSF group, with no significant intergroup differences (P-value was .493). Sensitivity, specificity, negative predictive value, and rate of rescue were 50.0%, 95.2%, 99.4%, and 1.8%, respectively, in the ASF group, and 80.0%, 90.9%, 99.5%, and 2.9%, respectively, in the PSF group. The accuracy of TcE-MEPs was not significantly different between the 2 groups (P-value was .427 in sensitivity, .109 in specificity, and .674 in negative predictive value). The procedures associated with the alarms were decompression in 3 cases and distraction in 1 patient in the ASF group. The PSF group showed Tc-MEPs decreased during decompression, mounting rods, turning positions, and others. Most alarms went off during decompression in ASF, whereas various stages of the surgical procedures were associated with the alarms in PSF. There were no significant differences in the accuracy of TcE-MEPs between the 2 surgeries.

Characteristics of Tc-MEP Waveforms for Different Locations of Intradural Extramedullary Tumors: A Prospective Multicenter Study of the Monitoring Committee of the Japanese Society for Spine Surgery and Related Research.

STUDY DESIGN: Prospective multicenter study. OBJECTIVE: To examine transcranial motor-evoked potential (Tc-MEP) waveforms in intraoperative neurophysiological monitoring 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. Intraoperative neurophysiological monitoring 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 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 ±â€Š18.1 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 < 0.05) and significantly more frequent intraoperative alarms (20%, 31%, 15%, P < 0.05). Use of Tc-MEPs for predicting neurological deficits after IDEM surgery had sensitivity of 87% and specificity of 89%; however, the positive predictive value was low. CONCLUSION: Poor derivation of waveforms, appearance of alarms, and worse final waveforms were all significantly more frequent for thoracic lesions. Thus, amplification of the waveform amplitude, using multimodal monitoring, and more appropriate interventions after an alarm may be particularly important in surgery for thoracic IDEM tumors.Level of Evidence: 3.