Spinal Cord Evoked Potentials Research Articles

Prediction of Post-operative Long-Term Outcome of the Motor Function by Multimodal Intraoperative Neuromonitoring With Transcranial Motor-Evoked Potential and Spinal Cord-Evoked Potential After Microsurgical Resection for Spinal Cord Tumors.

ObjectiveTo examine the effect of multimodal intraoperative neuromonitoring on the long-term outcome of motor function after microsurgical resection for spinal cord tumors.Materials and MethodsConsecutive fourteen patients with spinal tumors who were surgically treated at the University of Fukui Hospital between 2009 and 2020 [M:F = 10:4, ages ranging from 22 to 83 years (mean ± SD = 58 ± 21 years)] were included in this study. There were eight intra-axial tumors and six extra-axial tumors. There were four patients with hypertension, two patients with diabetes mellitus, and four patients with hyperlipidemia. Three patients were under antithrombotic medication, two were under steroid medication, four were current smokers, and four were current drinkers. Manual muscle test (MMT) of the upper and lower extremities of the patients was examined before surgery, 2 weeks after surgery, and at the final follow-up. The mean follow-up period was 38 ± 37 months. McCormick scores were examined before surgery and at the final follow-up. Microsurgical resection of the tumor was underwent through the posterior approach under transcranial motor-evoked potential (TcMEP) monitoring. The MEP of 46 extremities was recorded during the surgery. Gross total resection was achieved in 13 of 14 surgeries. Spinal cord-evoked potential (Sp-SCEP) monitoring was performed in eight of 14 patients.ResultsThe length of peritumoral edema was significantly longer in patients with deterioration of McCormick scores than in patients with preservation of McCormick scores (p = 0.0274). Sp-SCEP could not predict the deterioration. The ratio of MEP at the beginning of the surgery to that at the end of the surgery was the only significant negative factor that predicts deterioration of motor function of the extremity at the final follow-up (p = 0.0374, odds ratio [OR] 1.02E-05, 95% CI 9.13E+01–7.15E+18). A receiver operating characteristic (ROC) analysis revealed that the cutoff value of the ratio of MEP to predict the deterioration at the final follow-up was 0.23 (specificity 100%, specificity 88%, positive predictive value 100%, and negative predictive value 88%) to predict deterioration at the final follow-up.ConclusionsRatio MEP was the most significant negative factor to predict the deterioration of motor weakness at spinal tumor surgery. The setting of the cutoff value should be more strict as compared to the brain surgery and might be different depending on the institutions.

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.

Retrospective multicenter cohort study. 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. 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. 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). TES-MEPs with D-wave in high-risk spine surgeries did not affect rescue case rates. However, it helped reduce the false-positivity rate.

Targeted inhibition of STAT3 in neural stem cells promotes neuronal differentiation and functional recovery in rats with spinal cord injury.

STAT3 is expressed in neural stem cells (NSCs), where a number of studies have previously shown that STAT3 is involved in regulating NSC differentiation. However, the possible molecular mechanism and role of STAT3 in spinal cord injury (SCI) remain unclear. In the present study, the potential effect of STAT3 in NSCs was first investigated by using short hairpin RNA (shRNA)-mediated STAT3 knockdown in rat NSCs in vitro. Immunofluorescence of β3-tubulin and glial fibrillary acidic protein staining and western blotting showed that knocking down STAT3 expression promoted NSC neuronal differentiation, where the activity of mTOR was upregulated. Subsequently, rats underwent laminectomy and complete spinal cord transection followed by transplantation of NSCs transfected with control-shRNA or STAT3-shRNA at the injured site in vivo. Spinal cord-evoked potentials and the Basso-Beattie-Bresnahan scores were used to examine functional recovery. In addition, axonal regeneration and tissue repair were assessed using retrograde tracing with FluoroGold, hematoxylin and eosin, Nissl and immunofluorescence staining of β3-tubulin, glial fibrillary acidic protein and microtubule-associated protein 2 following SCI. The results showed that transplantation with NSCs transfected with STAT3-RNA enhanced functional recovery following SCI and promoted tissue repair in rats, in addition to improving neuronal differentiation of the transplanted NSCs in the injury site. Taken together, in vitro and in vivo evidence that inhibiting STAT3 could promote NSC neuronal differentiation was demonstrated in the present study. Therefore, transplantation with NSCs with STAT3 expression knocked down appears to hold promising potential for enhancing the benefit of NSC-mediated regenerative cell therapy for SCI.

The Impact of Anterior Spondylolisthesis and Kyphotic Alignment on Dynamic Changes in Spinal Cord Compression and Neurological Status in Cervical Spondylotic Myelopathy: A Radiological Analysis Involving Kinematic CT Myelography and Multimodal Spinal Cord Evoked Potentials.

A retrospective study of prospectively collected data. This study aimed to examine how radiological parameters affect dynamic changes in the cross-sectional area of the spinal cord (CSA) in cervical spondylotic myelopathy (CSM) patients and how they correlate with the severity of myelopathy, by evaluating multi-modal spinal cord evoked potentials (SCEPs). Appropriate assessments of dynamic factors should reveal hidden spinal cord compression and provide useful information for choosing surgical procedures. Seventy-nine CSM patients were enrolled. They were examined with kinematic CT myelography (CTM), and the spinal levels responsible for their CSM were determined via SCEP examinations. The C2-7 angle, C2-7 range of motion, and percentage of slip were measured on the midsagittal view during flexion and extension, and the CSA was measured on the axial view in each neck position using kinematic CTM. The patients who exhibited the smallest CSA values during extension and flexion were classified into Groups E and F, respectively. Fifty-two (65.8%) and 27 (34.2%) cases were included in Groups E and F, respectively. The preoperative JOA score did not differ significantly between the groups; however, the preoperative lower-limb JOA score of Group F was significantly lower than that of Group E (2.24 ± 0.82 vs. 2.83 ± 1.09, P = 0.016). In the multiple logistic regression analysis, a small C2-7 angle during extension (β = 5°, odds ratio: 0.69, 95% confidence interval [CI]: 0.54-0.90) and the slip percentage during flexion (β = 5%, odds ratio: 1.42, 95% CI: 1.09-1.85) were identified as significant predictors of belonging to Group F. Exhibiting more severe spinal cord compression during neck flexion was associated with a small C2-7 angle and anterior spondylolisthesis. The neurological status of the patients in Group F was characterized by severe lower limb dysfunction because of a disturbed blood supply to the anterior column.Level of Evidence: 4.

The radiological characteristics associated with the development of myelopathy due to ossification of the posterior longitudinal ligaments at each responsible level based on spinal cord evoked potentials

Study designThis was a retrospective study of prospectively collected data. ObjectiveThis study aimed to characterize the factors associated with the development of myelopathy at each cervical level based on spinal cord evoked potentials (SCEPs) and radiological parameters in patients with cervical ossification of the posterior longitudinal ligament (OPLL). Summary of background dataStatic factors, dynamic factors, and combinations of these factors are associated with the development of OPLL-related myelopathy. Patients and MethodsFifty patients with OPLL were enrolled in this study. They underwent kinematic computed tomography myelography (CTM), MRI, and X-ray examinations, and the levels responsible for their myelopathy were determined by intraoperatively assessing SCEPs. C2–7 lordosis, C2–7 range of motion (ROM), and segmental ROM were assessed on the midsagittal view during flexion and extension and in the neutral position using the Cobb method, and the cross-sectional area of the spinal cord (CSA) was measured on the axial view in each neck position using kinematic CTM. The cervical levels were classified into responsible (Group R) and non-responsible (Group N) levels. ResultsThe responsible level was C3–4, C4–5, C5–6, and C6–7 in 18, 23, 18, and 4 patients, respectively. In the multivariate analysis, the CSA was significantly smaller in Group R than in Group N at all responsible levels, but the dynamic change in the CSA was only associated with myelopathy at the C3–4 and C4–5 levels. ConclusionMyelopathy at the C3–4 level was more strongly associated with dynamic factors and a shorter disease duration, than myelopathy at the C5–6 level. This study provides useful information for assessing the pathophysiology of OPLL-related cervical myelopathy and managing the condition.

Cerebrolysin enhances spinal cord conduction and reduces blood-spinal cord barrier breakdown, edema formation, immediate early gene expression and cord pathology after injury.

Spinal cord evoked potentials (SCEP) are good indicators of spinal cord function in health and disease. Disturbances in SCEP amplitudes and latencies during spinal cord monitoring predict spinal cord pathology following trauma. Treatment with neuroprotective agents preserves SCEP and reduces cord pathology after injury. The possibility that cerebrolysin, a balanced composition of neurotrophic factors improves spinal cord conduction, attenuates blood-spinal cord barrier (BSCB) disruption, edema formation, and cord pathology was examined in spinal cord injury (SCI). SCEP is recorded from epidural space over rat spinal cord T9 and T12 segments after peripheral nerves stimulation. SCEP consists of a small positive peak (MPP), followed by a prominent negative peak (MNP) that is stable before SCI. A longitudinal incision (2mm deep and 5mm long) into the right dorsal horn (T10 and T11 segments) resulted in an immediate long-lasting depression of the rostral MNP with an increase in the latencies. Pretreatment with either cerebrolysin (CBL 5mL/kg, i.v. 30min before) alone or TiO2 nanowired delivery of cerebrolysin (NWCBL 2.5mL/kg, i.v.) prevented the loss of MNP amplitude and even enhanced further from the pre-injury level after SCI without affecting latencies. At 5h, SCI induced edema, BSCB breakdown, and cell injuries were significantly reduced by CBL and NWCBL pretreatment. Interestingly this effect on SCEP and cord pathology was still prominent when the NWCBL was delivered 2min after SCI. Moreover, expressions of c-fos and c-jun genes that are prominent at 5h in untreated SCI are also considerably reduced by CBL and NWCBL treatment. These results are the first to show that CBL and NWCBL enhanced SCEP activity and thwarted the development of cord pathology after SCI. Furthermore, NWCBL in low doses has superior neuroprotective effects on SCEP and cord pathology, not reported earlier. The functional significance and future clinical potential of CBL and NWCBL in SCI are discussed.

Assessment of spinal cord relative vulnerability in C4–C5 compressive cervical myelopathy using multi-modal spinal cord evoked potentials and neurological findings

Objective: The correlation between the progression of spinal cord lesions using spinal cord evoked potentials (SCEPs) and neurological findings are unclear. The purpose is to electrophysiologically evaluate relative vulnerability of spinal cord in patients with compressive cervical myelopathy (CCM) at C4–C5 intervertebral level using SCEPs and correlate the progression of spinal cord lesions with neurological findings. Design: Retrospective study. Setting: Yamaguchi University Hospital. Participants: 36 patients. Methods: SCEPs following median nerve stimulation (MN-SCEPs), ulnar nerve stimulation (UN-SCEPs), transcranial electric stimulation (TCE-SCEPs), and spinal cord stimulation (SC-SCEPs) were intraoperatively recorded. MN-SCEPs are mediated by posterior horns (4, 5 layers), UN-SCEPs by the Burdach tract, TCE-SCEPs by the lateral corticospinal tract, and SC-SCEPs by the Goll tract. We evaluated the neurological findings (numbness, tactile sense and pain sense in the C6 area, tactile sense in the lower extremities, and triceps tendon reflex [TTR]). Results: The incidence of electrophysiological and clinical abnormalities decreased in the order of UN-SCEPs (100%), TCE-SCEPs (94.4%), MN-SCEPs (77.8%), and SC-SCEPs (69.4%), and in the order of numbness (100%), pain sense (97.2%), TTR (91.7%), tactile sense in the C6 area (83.3%), and tactile sense in the lower extremities (70.0%), respectively. Conclusions: The relative vulnerability of spinal cord occurred in the order of the Burdach tract, the lateral corticospinal tract, posterior horns (4, 5 layers), and the Goll tract in most patients with CCM at the C4–C5 intervertebral level.

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

Exploratory clinical study. 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). Kochi Medical School Hospital, Japan. 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. 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. 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.

Use of Central Motor Conduction Time and Spinal Cord Evoked Potentials in the Electrophysiological Assessment of Compressive Cervical Myelopathy.

A retrospective study. This study investigated the pathophysiology of compressive cervical myelopathy (CCM) with prolonged central motor conduction time (CMCT) in the upper limbs (ULs) rather than lower limbs (LLs) and prolonged CMCT at the thoracic level (TL). Earlier reports indicated the usefulness of CMCT to assess preoperative CCM severity. However, little information exists on patients with prolonged CMCT-UL rather than CMCT-LL and prolonged CMCT-TL. Ninety-four patients (61 men, 33 women; age 28-87 years) with CCM who underwent cervical laminoplasty participated. Fifty-three volunteers provided normal data on CMCT-UL and LL. CMCT-TL was calculated as CMCT-LL - CMCT-UL. We defined three groups: group U, prolonged CMCT-UL rather than CMCT-LL (n = 14); group E, prolonged CMCT-UL and CMCT-LL equality (n = 43); and group L, prolonged CMCT-TL (n = 37). We evaluated intraoperative recording of spinal cord evoked potentials (SCEPs), neurological findings, and surgical outcomes. Control mean CMCT-UL was 5.2 ± 0.7 ms, CMCT-LL was 11.8 ± 1.1 ms, and CMCT-TL was 6.6 ± 1.2 ms. SCEPs results were significantly different between CCM patients in group U and L (P < 0.01). Almost all patients in three groups showed hyperreflexia of the patellar tendon reflex, but great toe position sense was abnormal in most patients in group L only. Japanese Orthopedics Association (JOA) scores improved postoperatively in all patients. There was a significant difference in recovery rate of the JOA score between group L and other groups (both P < 0.05). Multimodal SCEPs, clinical findings, and surgical outcomes showed that patients with CCM and prolonged CMCT-TL had substantial disorders of the gray matter, lateral corticospinal tract, and posterior funiculus. Spine surgeons should be aware that prognosis may be poor even after surgery in patients with severe myelopathy such as prolonged CMCT-TL. 4.

Correlation Between Spinal Cord Function Assessed by Intraoperative SCEPs and Morphology of the Compressed Spinal Cord on MRI.

Retrospective study. The objective of this study was to examine whether the morphology of the compressed spinal cord reflects spinal cord dysfunction in cervical spondylotic myelopathy (CSM). Segmental levels responsible for clinical symptoms in CSM are usually diagnosed by neurological examination and imaging studies such as magnetic resonance imaging (MRI). Electrophysiological examination makes it possible to assess the spinal cord function quantitatively. There are few detailed studies about correlation between intraoperative spinal cord-evoked potentials (following SCEPs) and preoperative MRI. A total of 25 CSM cases diagnosed with single intervertebral dysfunction based on preoperative neurological findings and intraoperative SCEPs were included. We recorded 3 different SCEPs and divided the cases into 2 groups: the transverse type (T-type) (n=18) that had abnormalities in all SCEPs; and the upper limbs sensory (abnormal only for MN-SCEPs) and posterolateral (abnormalities in the MN-SCEPs and Tc-SCEPs) type (US-PL-type) (n=7) that had abnormalities other than SCEPs following thoracic spinal cord stimulation. Morphometry was performed on MRI T1-weighed axial images. Clinical preoperative impairment was evaluated using the Japanese Orthopedic Association score. The average Japanese Orthopedic Association score of T-type cases was 8.1 points and that of US-PL-type cases was 10.5. There were no severe cases with <7 points in the US-PL-type group, but there were 9 cases in the T-type group. By morphometric comparison, both the central and the 1/4-lateral compression ratio were significantly lower in the T-type cases. Spinal cord morphology, as observed on MRI in patients with CSM reflected spinal cord dysfunction to some extent and could become the index for functional diagnosis, but it is necessary to consider a dynamic factor.

Targeted Inhibition of Leucine-Rich Repeat and Immunoglobulin Domain-Containing Protein 1 in Transplanted Neural Stem Cells Promotes Neuronal Differentiation and Functional Recovery in Rats Subjected to Spinal Cord Injury.

Leucine-rich repeat and immunoglobulin domain-containing protein (LINGO)-1 is expressed in neural stem cells, and its neutralization results in sustained neuronal immaturity. Thus, targeted inhibition of LINGO-1 via RNA interference may enhance transplanted neural stem cell survival and neuronal differentiation in vivo. Furthermore, LINGO-1 RNA interference in neural stem cells represents a potential therapeutic strategy for spinal cord injury. Department of Spine Surgery, First Affiliated Hospital of Sun Yat-sen University. Translational Medicine Center Research Laboratory, First Affiliated Hospital of Sun Yat-sen University. Female Sprague-Dawley rats. The animals were divided into three groups that underwent laminectomy and complete spinal cord transection accompanied by transplantation of control-RNA interference-treated or LINGO-1-RNA interference-treated neural stem cells at the injured site in vivo. In vitro, neural stem cells were divided into four groups for the following treatments: control, control RNA interference lentivirus, LINGO-1 RNA interference lentivirus and LINGO-1 complementary DNA lentivirusand the Key Projects of the Natural Science Foundation of Guangdong Province (No. S2013020012818). Neural stem cells in each treatment group were examined for cell survival and neuronal differentiation in vitro and in vivo via immunofluorescence and Western blot analysis. Axonal regeneration and tissue repair were assessed via retrograde tracing using Fluorogold, electron microscopy, hematoxylin-eosin staining and MRI. Rats were also examined for functional recovery based on the measurement of spinal cord-evoked potentials and the Basso-Beattie-Bresnahan score. LINGO-1-RNA interference-treated neural stem cell transplantation increased tissue repair and functional recovery of the injured spinal cord in rats. Similarly, LINGO-1 RNA interference increased neural stem cell survival and neuronal differentiation in vitro. The mechanism underlying the effect of LINGO-1 RNA interference on the injured rat spinal cord may be that the significant inhibition of LINGO-1 expression in neural stem cells inactivated the RhoA and Notch signaling pathways, which act downstream of LINGO-1. Our findings indicate that transplantation of LINGO-1-RNA interference-treated neural stem cells facilitates functional recovery after spinal cord injury and represents a promising potential strategy for the repair of spinal cord injury.

Characteristics of C6-7 myelopathy: assessment of clinical symptoms and electrophysiological findings.

This is a single-center retrospective study. The objective of this study was to study the clinical symptoms and electrophysiological features of C6-7 myelopathy. This study was conducted at the Department of Orthopedic surgery, Yamaguchi University Graduate school of medicine, Japan. A total of 20 patients with cervical compressive myelopathy were determined by spinal cord-evoked potentials or a single level of obvious magnetic resonance imaging (MRI)-documented cervical spinal cord compression. Neurological examinations included manual muscle testing and investigation of deep tendon reflex, including Hoffmann sign, and of sensory disturbance areas. Motor-evoked potentials (MEPs), compound muscle action potentials (CMAPs) and F-wave were recorded from bilateral abductor digit minim and abductor halluces muscles. Central motor conduction time was calculated as follows: MEPs latency-(CMAPs latency+F latency-1)/2 (ms). Eighteen patients (90%) had negative Hoffmann sign. Eight patients (40%) had no sensory disturbance in the upper limbs and 8 patients (40%) had no muscle weakness in the upper limbs. We determined that patients had cervical myelopathy when their central motor conduction time measured in abductor digit minim was longer than 6.76 ms (+2 s.d.). Using this definition, the sensitivity for myelopathy was 42.8%. Patients with C6-7 myelopathy may lack clinical symptoms in their hands and central motor conduction time measured in abductor digit minim tended to be less prolonged, and it only showed symptoms in their lower limbs as gait disturbance. Surgeons should bear in mind the possibility of disorders of caudal C6-7 when they encounter patients with no or few symptoms in their hands and with leg weakness or numbness.

Cortical activity after stimulation of the corticospinal tract in the spinal cord

ObjectiveIntraoperative electrical stimulation of the spinal cord evokes not only high amplitude cortical somatosensory evoked potentials (ScEPs: spinal cord-evoked potentials) recorded from the scalp but also early potentials. It has been postulated that the early potential recorded from the scalp could be generated by antidromic stimulation of the cortico-spinal tract (ACSP: Antidromic Corticospinal tract Potential or “anti D-wave”). In this study, we aimed to investigate the anti D-wave evoked by epidural stimulation in a population of neurologically uncompromised/compromised patients during spine and spinal cord surgery. To better define its origin, we examined its spatial distribution, response to stimulation modification and recording parameters, and finally, we correlated anti D-waves and corresponding epidural recorded D-waves after a transcranial electric stimulation at the same level of spinal cord stimulation. MethodsTibial nerve somatosensory evoked potentials (SEPs), transcranially elicited muscle motor evoked potentials (m-MEPs), epidural motor evoked potentials (D-wave), and cortical spinal cord-evoked potentials (ScEPs) as well as Antidromic Cortico Spinal tract Potential (anti D-wave) were intraoperatively recorded in 30 subjects with different degrees of neurological involvement. ScEPs and anti D-wave were evoked by epidural stimulation of the spinal cord, both cranially and caudally to the surgery site and were recorded over the scalp at the midline. The effects of the stimulus rate and high pass filter were also tested. ResultsThe anti D-wave was recordable in all neurologically intact patients and was clearly isolated from the ScEPs by its very short latency; recordings of the anti D-wave were limited to the anterior midline, and its amplitude was only slightly reduced by increasing the stimulus rate or by changing the high pass filter, and its latency was slightly longer than that of the D-wave latency.In neurologically compromised patients, the anti D-wave and D-wave exhibit a similar behaviour, both of which were present in neurologically intact or moderately compromised patients and absent in patients with quadri/paraplegia. In a patient with paraplegia due to T8 meningioma and in neurologically intact patients in whom the cauda/conus stimulated the anti D-wave, cortical ScEPs were absent when the stimulation was performed caudally to the surgical site. ConclusionsWe provide evidence that the anti D-wave behaviour and its parameters have a close correlation with the behaviour of the D-wave; specifically, its distribution, response to filtering, stimulus rate, and absence in paraplegic patients. SignificanceThe presented data demonstrate that the anti D-wave is generated by the antidromic stimulation of fast neurons of the corticospinal tract, and consistent findings have been previously published in animals.

Application of diffusion tensor imaging for the diagnosis of segmental level of dysfunction in cervical spondylotic myelopathy

A retrospective study. Diffusion tensor imaging (DTI) reflects pathological change in the spinal cord more sensitively than conventional magnetic resonance imaging (MRI). Electrophysiological examination enables quantitative assessment of spinal cord function. Few studies have addressed the correlation between intraoperative spinal cord-evoked potentials (SCEPs) and DTI. The purpose of this study was to examine whether DTI is an objective index for the diagnosis of the segmental level of dysfunction in cervical spondylotic myelopathy (CSM). Yamaguchi University Graduate School of Medicine, Japan. Using 3.0-Tesla MRI, DTI values for the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were measured at the disc level C2/C3 through C6/C7 in 11 normal subjects and 10 subjects with CSM. Subjects with CSM were divided into two groups based on the extent of compression according to conventional MRI: single level (n=3) and multilevel (n=7). Intraoperative SCEPs were measured in subjects with CSM. For each group, the ADC and FA values were compared with SCEPs with respect to the segmental levels of dysfunction. For all three subjects with single-level compression and six of seven with multilevel compression, the maximal ADC value was observed at the segmental level of dysfunction as per the SCEP. Minimum FA values were observed at those sites in two of three patients with single-level compression and in only two of seven with multi-level compression. Our results suggest that ADC might serve as a supplementary diagnostic indicator of the segmental levels of dysfunction in CSM.

Novel aspects of spinal cord evoked potentials (SCEPs) in the evaluation of dorso-ventral and lateral mechanical impacts on the spinal cord

Objectives. The aim of the current study was to mimic mechanical impacts on the spinal cord by manifesting the effects of dorsoventral (DVMP) and lateral (LMP) mechanical pressure on neural activity to address points to be considered during surgery for different purposes, including spinal cord decompression. Approaches. Spinal cords of anesthetized rats were compressed at T13. Different characteristics of axons, including vulnerability, excitability, and conduction velocity (CV), in response to promptness, severity, and duration of pressure were assessed by spinal cord evoked potentials (SCEPs). Real-time SCEPs recorded at L4-5 revealed N1, N2, and N3 peaks that were used to represent the activity of injured sensory afferents, interneurons, and MN fibers. The averaged SCEP recordings were fitted by trust-region algorithm to find the equivalent Gaussian and polynomial equations. Main results. The pyramidal and extrapyramidal pathways possessed CVs of 3–11 and 16–80 m s−1, respectively. DVMP decreased the excitability of myelinated neural fibers in antidromic and orthodromic pathways. The excitability of fibers in extrapyramidal and pyramidal pathways of lateral corticospinal (LCS) and anterior corticospinal (ACS) tracts decreased following LMP. A significant drop in the amplitude of N3 and its conduction velocity (CV) revealed higher susceptibility of less-myelinated fibers to both DVMP and LMP. The best parametric fitting model for triplet healthy spinal cord CAP was a six-term Gaussian equation (G6) that fell into a five-term equation (G5) at the complete compression stage. Significance. The spinal cord is more susceptible to dorsoventral than lateral mechanical pressures, and this should be considered in spinal cord operations. SCEPs have shown promising capabilities for evaluating the severity of SCI and thus can be applied for diagnostic or prognostic intraoperative monitoring (IOM).

Transintercostal-Evoked Spinal Cord Potential in Thoracic Aortic Surgery

We have developed a novel method of measuring spinal cord-evoked potentials with stimulation and recording at the intercostal nerves (transintercostal-evoked spinal cord potential: Tic-ESCP). The purpose of this study was to examine the feasibility and accuracy of Tic-ESCP during thoracic aortic surgery. In addition to the conventional electrodes (cranial and intrathecal), stimulating and recording electrodes were placed on the intercostal nerves that were located at a cephalad and caudal level relative to the aneurysm after the pleura on the intercostal nerves was opened. Specially designed hook-type electrodes were anchored to the nerves and surroundings atraumatically and fixed on the pleura. The conventional transcranial motor-evoked potential (Tc-MEP) and Tic-ESCP were recorded simultaneously. Eight patients were examined in this study. In all patients, Tic-ESCP could be clearly recorded with biphasic waveforms consisting of first a positive wave and a subsequent negative wave. In all 8 patients, the waveform of Tc-MEP and Tic-ESCP changed during aortic reconstruction. In 2 cases, the waveform of Tc-MEP and Tic-ESCP decreased below 50% of baseline during aortic clamping and the intercostal arteries were reconstructed with no resultant spinal cord injury. In 1 case with a shaggy aorta, Tc-MEP and Tic-ESCP had different values and each evoked potential could have reflected that regional spinal cord infarction and paraplegia had occurred. Tic-ESCP was clinically feasible and changes were compatible with the conventional Tc-MEP. The Tic-ESCP waveforms were simple and appeared to be specific to the spinal cord within the target range, in contrast to the other evoked potentials which are multimorphic and reflect the amplitudes at the brain and multiple levels of the spinal cord.

Management of Subaxial Cervical Facet Dislocation Through Anterior Approach Monitored by Spinal Cord Evoked Potential

Retrospective case series. To discuss the clinical efficacy of anterior cervical surgery of decompression, reduction, stabilization, and fusion in treating subaxial cervical facet dislocation without spinal cord injury or with mild spinal cord injury monitored by spinal cord evoked potential. The optimal treatment of lower cervical facet dislocation has been controversial. Because of the risk of iatrogenic damage of neurological function, it is challenging for surgeons to manage the lower cervical facet dislocation without or with mild spinal cord injury. To avoid the risks, more secure strategy need to be designed. A retrospective study was performed on 17 cases of subaxial cervical facet dislocation without spinal cord injury or with mild spinal cord injury treated by anterior cervical surgery under spinal cord evoked potential monitor from January 2008 to June 2012. There were 12 males, 5 females, with a mean age of 40.1 years (from 21 to 73 yr). Dislocation sites: 1 in C3-C4, 2 in C4-C5, 6 in C5-C6, 8 in C6-C7; 10 cases with unilateral cervical facet dislocation, 7 cases with bilateral dislocation. Thirteen patients were preoperatively classified as grade D and 4 as E according to Frankel standard. All patients were followed up for average of 16 months. All operations were completed successfully. Postoperative radiographs showed that the sequence and curvature of the cervical spine were well recovered. And, evidence of intervertebral fusion was observed at 3 months in all cases. No redislocation or symptoms of spinal cord injury occurred. Thirteen cases with mild spinal cord injury recovered at 1 month after operation. Anterior cervical surgery of decompression, reduction, stabilization, and fusion monitored by spinal cord evoked potential is an effective and safe method for treatment of subaxial cervical facet dislocation without or with mild spinal cord injury. 4.

Protective effect of low molecular weight polyethylene glycol on the repair of experimentally damaged neural membranes in rat’s spinal cord

Objectives: Membrane disruption is one of the main factors that cause axonal damage and functional deficits manifested in spinal cord injury (SCI). In this study, we used polyethylene glycol (PEG) to induce immediate membrane sealing and to promote functional recovery after SCI.Methods: The effects of PEG (200–2000 Da) on the damaged membrane were monitored by means of spinal cord evoked potentials (SCEPs) in an SCI model in rats. In a parallel study, membranes of neural cells were mechanically damaged in culture by ultrasound waves (20 kHz) and the repairing effects of PEGs were examined afterwards at the single cell level.Results: Analysis of SCEPs showed that the smaller the PEG, the higher was the ultimate recovery of SCEP (i.e. 200 Da caused 49·5% and 2000 Da up to 16·3%). The rate of recovery was maximum with a polynomial trend, when the damaged spinal cord was treated with PEG200 for 25 minutes.The analysis of survival rate of mechanically damaged cells in culture, measured by MTT assay, showed that again smaller PEGs, caused higher membrane sealing rate; 77·8±3·5 for PEG400 (20% w/w) vs 32·1±6·9 for PEG2000 (20% w/w). The large ones (PEG1000 and 2000) that presented minor repair at low concentration, showed no significant sealing effects at high concentrations (>50%).Conclusion: Our studies showed that the application of low molecular weight PEGs, (<50% w/w) can be considered as one of the effective early treatments for SCI.

Biophysical Effects of a Novel Biodegradable Copolymer on the Repair of Damaged Neural Membranes

The pathophysiology of Spinal cord injury (SCI) is involved primary mechanical injury followed by secondary delayed injury. Neural membrane is the most susceptible part of the cell and most of the time mechanical injury results in axolemma disruption and failure to function as an electrical and ionic barrier. This leads to blockage of nerve impulse conduction, deregulation of ionic gradients; free radical associated lipid peroxidation of membrane and increased influx of calcium ions that activates calpain and caspase-dependent cell death cascades. Thus immediate membrane repair can prevent various destructive processes, restoring of the physicochemical balance of the cytoplasm and ultimate functional recovery in neurons. Several degradable polymers and surfactants including PEG, Poloxamer 188, and poloxamine 1107 have shown to be effective in sealing and halting progressive permeabilization. Here, we applied ultrasound wave as mechanical insult to make transient breaches in membrane to simulate membrane damage in SCI and used a novel triblock copolymer of PEG-(fumaric-sebacic acids)-PEG to seal membrane breaches. Cell survival and membrane integrity were checked by MTT assay and Trypan blue exclusion test respectively. The results showed that this copolymer can be a promising candidate for membrane sealing. Now we are assessing the effects of this polymer on in vivo spinal cord evoked potential (SCEP).

Efficacy and limitations of intraoperative spinal cord monitoring using nasopharyngeal tube electrodes

Motor evoked potentials are widely used for intraoperative spinal cord monitoring. However, there are problems with anesthetic constraints and high trial-by-trial variability of compound muscle action potential amplitude in muscle motor evoked potential monitoring. It is difficult to determine when to warn the surgeon of an occurrence of spinal cord risk. A method of estimation for motor function in the spinal cord has not been established. To monitor spinal cord function with reliable evoked potentials, including the upper cervical spinal cord and the ventral spinal cord, the authors developed a nasopharyngeal tube electrode that can be placed in front of the upper and ventral cervical spinal cord. The purpose of this study was to investigate the origins and pathways of descending or ascending spinal cord evoked potentials (SCEPs) elicited with this electrode, and the usefulness and limitations of this method. A nasopharyngeal tube electrode was inserted into the nostril. A catheter electrode was placed in the epidural or subarachnoid space at the thoracic spine. Ventral SCEP was recorded from the thoracic spinal cord after transpharyngeal stimulation, and dorsal SCEP was recorded with the nasopharyngeal electrode after thoracic spinal cord stimulation. There was no restriction of anesthetic technique in recording. When the amplitude of either of the SCEPs declined to 80% of the baseline, a warning was provided to the surgeon during the observed operative procedure. At the end of surgery, less than 50% or more than 30% of the baseline amplitude was considered a significant change in both SCEPs. The sensitivity and specificity for both SCEPs to detect neurological deterioration were calculated. The electrode provided noninvasive access to the ventral cervicomedullary junction. The SCEPs showed stable responses. A response change was only observed in situations involving a risky procedure for the spinal cord. Ventral SCEPs showed high sensitivity (73.1%) for identifying patients with new neurological deficits or an exacerbation of preexisting neurological deficits after surgery, but dorsal SCEPs showed lower sensitivity (46.1%) in the total number of cases. Both SCEPs showed high specificities. The sensitivities of ventral SCEP, dorsal SCEP, and either SCEP were 100.0%, 50.0%, and 100.0% for the upper cervical spinal cord, 33.3%, 0%, and 55.6% for the lower cervical spinal cord, and 77.8%, 64.7%, and 88.2% for the thoracic spinal cord. Combined recording of both SCEPs estimated the ventral and dorsal white matter function in the spinal cord. Measuring the SCEPs with the nasopharyngeal electrode can be another useful approach for upper cervical and thoracic spinal cord monitoring. Ventral SCEP was more reliable for monitoring postoperative spinal cord function than dorsal SCEP. Ventral SCEP does not estimate the gray matter and spinal root functions in the lower cervical spinal cord.