Electrophysiological evidence of functional improvement in the corticospinal tract after laminoplasty in patients with cervical compressive myelopathy

Magnetic Resonance Imaging-CCCFLS Scoring System: Toward Predicting Clinical Symptoms and C5 Paralysis

STUDY DESIGN

A retrospective study.

OBJECTIVE

To develop a new MRI scoring system to assess patients' clinical characteristics, outcomes and complications.

METHODS

A retrospective 1-year follow-up study of 366 patients with cervical spondylosis from 2017 to 2021. The CCCFLS scores (cervical curvature and balance (CC), spinal cord curvature (SC), spinal cord compression ratio (CR), cerebrospinal fluid space (CFS). Spinal cord and lesion location (SL). Increased Signal Intensity (ISI) were divided into Mild group (0-6), Moderate group (6-12), and Severe group (12-18) for comparison, and the Japanese Orthopaedic Association (JOA) scores, visual analog scale (VAS), numerical rating scale (NRS), Neck Disability Index (NDI) and Nurick scores were evaluated. Correlation and regression analyses were performed between each variable and the total model in relation to clinical symptoms and C5 palsy.

RESULTS

The CCCFLS scoring system was linearly correlated with JOA, NRS, Nurick and NDI scores, with significant differences in JOA scores among patients with different CC, CR, CFS, ISI scores, with a predictive model (R2 = 69.3%), and significant differences in preoperative and final follow-up clinical scores among the 3 groups, with a higher rate of improvement in JOA in the severe group (P < .05), while patients with and without C5 paralysis had significant differences in preoperative SC and SL (P < .05).

CONCLUSION

CCCFLS scoring system can be divided into mild (0-6). moderate (6-12), severe (12-18) groups. It can effectively reflect the severity of clinical symptoms, and the improvement rate of JOA is better in the severe group, while the preoperative SC and SL scores are closely related to C5 palsy.

LEVEL OF EVIDENCE

III.

Differentiation Between Compressive Cervical and Thoracic Myelopathy Using the Central Motor Conduction Time Ratio

PURPOSE

Thoracic myelopathy is a rare condition whose diagnosis is often missed or delayed. This study aimed to differentiate between cervical and thoracic myelopathy using motor-evoked potential testing.

METHODS

The authors included 835 patients with compressive cervical myelopathy and 94 patients with compressive thoracic myelopathy. Myelopathy using motor-evoked potentials were recorded from the bilateral abductor digiti minimi and abductor hallucis muscles through transcranial magnetic stimulation. The peripheral conduction time was measured through electrical stimulation of the ulnar and tibial nerves; moreover, the central motor conduction time (CMCT) was calculated by subtracting the peripheral conduction time from the myelopathy using motor-evoked potential latency.

RESULTS

The most accurate differentiation between compressive cervical myelopathy and compressive thoracic myelopathy was achieved by the CMCT ratios (CMCT-ADM:CMCT-AH; cutoff value of 0.490, sensitivity of 83.0%, and specificity of 80.5%). After excluding patients with compressive cervical myelopathy who had spinal cord compression at C6-7, the cutoff value was 0.490, with a sensitivity of 83.0% and specificity of 87.3%.

CONCLUSIONS

Determining the CMCT ratio (cutoff value of 0.490) through motor-evoked potential testing could facilitate differentiation between compressive cervical myelopathy and compressive thoracic myelopathy.

Diagnostic and prognostic significance of preoperative evoked potential tests in degenerative cervical myelopathy

BACKGROUND CONTEXT

Decompression surgery is a treatment option for patients with degenerative cervical myelopathy (DCM). Surgical decisions primarily depend on clinical symptoms and radiological examinations. The diagnostic and prognostic significance of evoked potential tests for surgical outcomes in patients with DCM has not been thoroughly examined.

PURPOSE

To identify the diagnostic and prognostic significance of preoperative evoked potential tests in patients with DCM who underwent decompression surgery.

STUDY DESIGN

This was a retrospective observational study.

PATIENT SAMPLE

One hundred two consecutive patients who underwent evoked potential tests and surgical treatment between January 2016 and December 2020 in a single spine center and had a minimum follow-up of 6 months.

OUTCOME MEASURES

Japanese Orthopedic Association (JOA) scores obtained preoperatively and 6 months after surgery.

METHODS

This study evaluated the preoperative central motor conduction time (CMCT), somatosensory evoked potentials, and Japanese Orthopedic Association (JOA) scores obtained preoperatively and 6 months after surgery.

RESULTS

Abnormal CMCT findings were observed in 94 patients (92.2%). Abnormal somatosensory evoked potentials were observed in 77 patients (75.5%). There was a statistically significant correlation between preoperative JOA score and abductor pollicis brevis (APB)-CMCT (r=-0.546, p=.001), tibialis anterior (TA)-CMCT (r=-0.517, p<.001), median nerve (MN)-SSEP (r=-0.353, p=.001), and tibial nerve (TN)-SSEP (r=-0.349, p=.003). There were significant differences in recovery rates associated with diabetes mellitus (DM), preoperative severity of myelopathy, TA-CMCT, MN-SSEP, and TN-SSEP. Stepwise multiple regression analysis showed that the major factors affecting the clinical outcomes were TN-SSEP (β=0.327, p=.004), preoperative JOA score (β=0.278, p=.012), and DM (β=0.241, p=.025).

CONCLUSIONS

Evoked potential testing is a functional diagnostic tool that can indicate the severity of myelopathic symptoms in patients with DCM. Additionally, preoperative TN-SSEP may have significant prognostic value in predicting postoperative clinical outcomes. Thus, preoperative evoked potential tests could be helpful for determining suitable surgical treatment candidates and forecasting postoperative prognosis.

Clinical diagnostic utility of transcranial magnetic stimulation in neurological disorders. Updated report of an IFCN committee

The review provides a comprehensive update (previous report: Chen R, Cros D, Curra A, Di Lazzaro V, Lefaucheur JP, Magistris MR, et al. The clinical diagnostic utility of transcranial magnetic stimulation: report of an IFCN committee. Clin Neurophysiol 2008;119(3):504-32) on clinical diagnostic utility of transcranial magnetic stimulation (TMS) in neurological diseases. Most TMS measures rely on stimulation of motor cortex and recording of motor evoked potentials. Paired-pulse TMS techniques, incorporating conventional amplitude-based and threshold tracking, have established clinical utility in neurodegenerative, movement, episodic (epilepsy, migraines), chronic pain and functional diseases. Cortical hyperexcitability has emerged as a diagnostic aid in amyotrophic lateral sclerosis. Single-pulse TMS measures are of utility in stroke, and myelopathy even in the absence of radiological changes. Short-latency afferent inhibition, related to central cholinergic transmission, is reduced in Alzheimer's disease. The triple stimulation technique (TST) may enhance diagnostic utility of conventional TMS measures to detect upper motor neuron involvement. The recording of motor evoked potentials can be used to perform functional mapping of the motor cortex or in preoperative assessment of eloquent brain regions before surgical resection of brain tumors. TMS exhibits utility in assessing lumbosacral/cervical nerve root function, especially in demyelinating neuropathies, and may be of utility in localizing the site of facial nerve palsies. TMS measures also have high sensitivity in detecting subclinical corticospinal lesions in multiple sclerosis. Abnormalities in central motor conduction time or TST correlate with motor impairment and disability in MS. Cerebellar stimulation may detect lesions in the cerebellum or cerebello-dentato-thalamo-motor cortical pathways. Combining TMS with electroencephalography, provides a novel method to measure parameters altered in neurological disorders, including cortical excitability, effective connectivity, and response complexity.

Electrophysiological evidence of diabetes' impacts on central conduction recoveries in degenerative cervical myelopathy after surgery

OBJECTIVES

To assess the impact of diabetes mellitus (DM) on the postoperative motor and somatosensory functional recoveries of degenerative cervical myelopathy (DCM) patients.

METHODS

Motor and somatosensory evoked potentials (MEP and SSEPs) and modified Japanese Orthopedic Association (mJOA) scores were recorded in 27 diabetic (DCM-DM group) and 38 non-diabetic DCM patients (DCM group) before and 1 year after surgery. The central motor (CMCT) and somatosensory (CSCT) conduction time were recorded to evaluate the conductive functions of the spinal cord.

RESULTS

The mJOA scores, CMCT and CSCT improved (t test, p < 0.05) in both of the DCM-DM and DCM groups 1 year after surgery. The mJOA recovery rate (RR) and CSCT recovery ratio were significantly worse (t test, p < 0.05) in the DCM-DM group compared to the DCM group. DM proved to be a significant independent risk factor for poor CSCT recovery (OR = 4.52, 95% CI 2.32-7.12) after adjusting for possible confounding factors. In DCM-DM group, CSCT recovery ratio was also correlated with preoperative HbA1 level (R =  - 0.55, p = 0.003). Furthermore, DM duration longer than 10 years and insulin dependence were risk factors for lower mJOA, CMCT and CSCT recoveries among all DCM-DM patients (t test, p < 0.05).

CONCLUSIONS

DM may directly hinders spinal cord conduction recovery in DCM patients after surgery. Corticospinal tract impairments are similar between DCM and DCM-DM patients, but significantly worsened in chronic or insulin-dependent DM patients. The dorsal column is more sensitively affected in all DCM-DM patients. Deeper investigation into the mechanisms and neural regeneration strategies is needed.

The Role of Magnetic Transcranial Stimulation in the Diagnosis and Post-Surgical Follow-Up of Cervical Spondylotic Myelopathy

Degenerative cervical myelopathy (DCM) consists of spinal cord damage due to its compression through the cervical spine. The leading cause is degenerative. The diagnosis is clinical, and the therapeutic approach is usually surgical. Confirmation of the diagnostic suspicion is done by magnetic resonance imaging (MRI); however, this test lacks functional information of the spinal cord, the abnormality of which may precede involvement in neuroimaging. Neurophysiological examination using somatosensory evoked potentials (SSEPs) and transcranial magnetic stimulation (TMS) allows for an evaluation of spinal cord function, and provides information in the diagnostic process. Its role in the post-surgical follow-up of patients undergoing decompressive surgery is being studied. We present a retrospective study of 24 patients with DCM and surgical decompression who underwent neurophysiological tests (TMS and SSEP) before, 6, and 12 months after surgery. The result of the TMS and the SSEP in the post-operative follow-up did not correlate with the clinical outcome, either subjective or measured by clinical scales at six months. We only found post-surgical improvement of central conduction times (CMCTs) in patients with severe pre-surgical motor impairment on TMS. In patients with normal pre-surgical CMCT, we found a transient worsening with return to baseline at the one-year follow-up. Most patients presented pre-surgical increased P40 latency at diagnosis. CMCT and SSEP were more related to clinical outcomes one year after the surgical procedure and were very useful in diagnosing.

Application of electrophysiological measures in degenerative cervical myelopathy

Degenerative cervical myelopathy (DCM) is one of the leading causes of progressive spinal cord dysfunction in the elderly. Early diagnosis and treatment of DCM are essential to avoid permanent disability. The pathophysiology of DCM includes chronic ischemia, destruction of the blood–spinal cord barrier, demyelination, and neuronal apoptosis. Electrophysiological studies including electromyography (EMG), nerve conduction study (NCS), motor evoked potentials (MEPs) and somatosensory evoked potentials (SEPs) are useful in detecting the presymptomatic pathological changes of the spinal cord, and thus supplementing the early clinical and radiographic examinations in the management of DCM. Preoperatively, they are helpful in detecting DCM and ruling out other diseases, assessing the spinal cord compression level and severity, predicting short- and long-term prognosis, and thus deciding the treatment methods. Intra- and postoperatively, they are also useful in monitoring neurological function change during surgeries and disease progression during follow-up rehabilitation. Here, we reviewed articles from 1979 to 2021, and tried to provide a comprehensive, evidence-based review of electrophysiological examinations in DCM. With this review, we aim to equip spinal surgeons with the basic knowledge to diagnosis and treat DCM using ancillary electrophysiological tests.

Transcranial Magnetic Stimulation and Transcranial Electrical Stimulation in Horses

Depending on the localization of the lesion, spinal cord ataxia is the most common type of ataxia in horses. Most prevalent diagnoses include cervical vertebral stenotic myelopathy (CVSM), equine protozoal myeloencephalitis (EPM), trauma and equine degenerative myeloencephalopathy (EDM). Other causes of ataxia and weakness are associated with infectious causes, trauma and neoplasia. A neurologic examination is indispensable to identify the type of ataxia. In addition, clinical neurophysiology offers tools to locate functional abnormalities in the central and peripheral nervous system. Clinical EMG assessment looks at the lower motoneuron function (LMN) and is used to differentiate between neuropathy in peripheral nerves, which belong to LMNs and myopathy. As LMNs reside in the spinal cord, it is possible to grossly localize lesions in the myelum by muscle examination. Transcranial (tc) stimulation techniques are gaining importance in all areas of medicine to assess the motor function of the spinal cord along the motor tracts to the LMNs. Applications in diagnostics, intraoperative neurophysiological monitoring (IONM), and evaluation of effects of treatment are still evolving in human medicine and offer new challenges in equine medicine. Tc stimulation techniques comprise transcranial magnetic stimulation (TMS) and transcranial electrical stimulation (TES). TMS was first applied in horses in 1996 by Mayhew and colleagues and followed by TES. The methods are exchangeable for clinical diagnostic assessment but show a few differences. An outline is given on the principles, current clinical diagnostic applications and challenging possibilities of muscle evoked potentials (MEP) from transcranial stimulation in horses.

Quantitative evaluation of abnormal finger movements in myelopathy hand during the grip and release test using gyro sensors

Previous studies have reported qualitative characteristics of myelopathy hand, but few studies have reported quantitative kinematic parameters of this condition. Our purpose of this study was to quantitatively evaluate the abnormal finger movements in patients with cervical compressive myelopathy (CCM) (termed myelopathy hand) and to understand the characteristics of myelopathy hand during the grip and release test (GRT) using gyro sensors. Sixty patients with CCM (severe: n = 30; mild-to-moderate: n = 30) and sixty healthy adults (age-matched control: n = 30; young control: n = 30) were included in this study. All participants performed the GRT. The index and little fingers’ and the wrist’s movements during the GRT were recorded using three gyro sensors. The number of cycles, switching time-delay, time per cycle, and peak angular velocity were calculated and compared between groups. Patients with severe CCM had the lowest number of cycles and longest switching time-delays, followed by patients with mild-to-moderate CCM, the age-matched control group, and the young control group. The time per cycle and the peak angular velocities of fingers in participants with severe CCM were significantly lower than those in participants with mild-to-moderate CCM; however, there were no significant differences between the control groups. The peak angular velocities of fingers were significantly lower during extension motions than during flexion motions in participants with CCM. Participants with CCM have lower peak angular velocities during finger movement. Finger extension also is impaired in participants with CCM. Abnormal finger movements and the severity of myelopathy in participants with CCM can be assessed using gyro sensors.

Therapeutic repetitive Transcranial Magnetic stimulation (rTMS) for neurological dysfunction in Degenerative cervical Myelopathy: An unexplored opportunity? Findings from a systematic review

Degenerative Cervical Myelopathy (DCM) is one of the commonest causes of non-traumatic Spinal Cord Injury (SCI) leading to significant neurological impairments and reduced health-related quality of life. Guidelines recommend surgical intervention to halt disease progression in moderate-to-severe cases, and whilst many do experience neurological recovery, this is incomplete leading to lifelong disability. A James Lind Alliance (JLA) research priority setting partnership for DCM highlighted novel therapies and rehabilitation as top 10 research priority in DCM. Neurological recovery following decompressive surgery in DCM has been attributed neuroplasticity, and therapies influencing neuroplasticity are of interest. Electrical neuromodulation interventions such as repetitive Transcranial Magnetic Stimulation (rTMS), are being increasingly explored in related fields such as spinal cord injury to improve recovery and symptoms. The aim of this systematic review was to determine the role and efficacy of rTMS as a therapeutic tool in managing neurological dysfunction in DCM. We searched the databases of Medline, EMBASE, CINAHIL and Cochrane Central Register of Controlled Trials (CENTRAL). No studies were identified that had investigated the therapeutic use of rTMS in DCM. A significant number of studies had explored TMS based neurophysiological assessments indicating its role as a screening and prognostication tool in DCM. Post-operative rehabilitation interventions including TMS and non-operative management of DCM is a field which requires further investigation, as required in the AO Spine JLA DCM research priorities. rTMS is a safe neuromodulatory intervention and may have a role in enhancing recovery in DCM. Further research in these fields are required.

Multidimensional assessment of cervical spondylotic myelopathy patients. Usefulness of a comprehensive score system

OBJECTIVE

Cervical spondylotic myelopathy (CSM) is caused by cervical spine degeneration and surgery may be beneficial, but selection for surgery might be challenging. We performed a multimodal analysis to assess predicting factors that may be useful to help surgeons in this choice.

PATIENTS AND METHODS

We retrospectively evaluated clinical, motor evoked potentials (MEP), and MRI data of patients who undergone surgery for CSM. Seventy-six consecutive patients (46 males) were enrolled. The median age was 65.5 [IQR: 57-71] years, and the duration of symptoms was 11 [8-13] months. A multivariate analysis in order to assess predictors of outcome and ROC curve analysis were performed.

RESULTS

Thirty patients (M:18, 39.5%) gained 6 or more points on mJOA and they were collected in good recovery group, whereas 46 patients (60.5%, M:28) showed a fair recovery. We developed a comprehensive score system (CSS) taking into account clinical, neurophysiological, and neuroradiological data. ROC curve analysis was performed to determine the discriminative power of four models derived from the multivariate logistic regression analysis for predictors of good outcome considering only clinical variables, MRI variables, and MEP variables or considering the comprehensive model, demonstrating a good accuracy of CSS model to predict outcome.

CONCLUSION

This study demonstrates that CSS model taking into consideration functional assessment by mJOA score, neurologic evaluation, cervical MRI, and MEP may be a feasible method to predict outcome in patients candidate to surgery, supporting surgeon's decisions both for those patients candidate to surgery and for patients in whom a "wait and see" approach could be proposed.

The prediction of intraoperative cervical cord function changes by different motor evoked potentials phenotypes in cervical myelopathy patients

Background

Surgery is usually the treatment of choice for patients with cervical compressive myelopathy (CCM). Motor evoked potential (MEP) has proved to be helpful tool in evaluating intraoperative cervical spinal cord function change of those patients. This study aims to describe and evaluate different MEP baseline phenotypes for predicting MEP changes during CCM surgery.

Methods

A total of 105 consecutive CCM patients underwent posterior cervical spine decompression were prospectively collected between December 2012 and November 2016. All intraoperative MEP baselines recorded before spinal cord decompression were classified into 5 types (I to V) that were carefully designed according to the different MEP parameters. The postoperative neurologic status of each patient was assessed immediately after surgery.

Results

The mean intraoperative MEP changes range were 10.2% ± 5.8, 14.7% ± 9.2, 54.8% ± 31.9, 74.1% ± 24.3, and 110% ± 40 in Type I, II, III, IV, and V, respectively. There was a significant correlation of the intraoperative MEP change rate with different MEP baseline phenotypes (r = 0.84, P < 0.01). Postoperative transient new spinal deficits were found 0/31 case in Type I, 0/21 in Type II, 1/14 in Type III, 2/24 in Type IV, and 4/15 in Type V. No permanent neurological injury was found in our cases series.

Conclusions

The MEP baselines categories for predicting intraoperative cervical cord function change is proposed through this work. The more serious the MEP baseline abnormality, the higher the probability of intraoperative MEP changes, which is beneficial to early warning for the cervical cord injury.

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

STUDY DESIGN

A retrospective study.

OBJECTIVE

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).

SUMMARY OF BACKGROUND DATA

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.

METHODS

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.

RESULTS

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).

CONCLUSION

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.

LEVEL OF EVIDENCE

4.

Electrophysiological assessments of the motor pathway in diabetic patients with compressive cervical myelopathy

OBJECT

The occurrence of compressive cervical myelopathy (CCM) increases in adults over 50 years of age. In addition, diabetes mellitus (DM) is a frequent comorbidity for people of this age and may impact the severity of CCM. The authors assessed motor pathway function in diabetic patients with CCM to investigate the correlation between electrophysiological parameters and clinical symptoms.

METHODS

Motor evoked potentials (MEPs) were measured from the abductor digiti minimi muscle (ADM) and the abductor hallucis muscle (AH) following transcranial magnetic stimulation, as were M- and F-waves following electrical stimulation of the ulnar and tibial nerves, in 22 patients with CCM and diabetes mellitus (DM) who had not experienced symptomatic diabetic neuropathy (CCM-DM group), in 92 patients with CCM alone (CCM group), and in 24 healthy adults (control group). The peripheral conduction time (PCT; measured from the ADM and AH) was calculated as follows: (M-wave latency + F-wave latency −1)/2. The central motor conduction time (CMCT; measured from the ADM and AH) was calculated by subtracting the PCT from the onset latency of the MEPs. The Japanese Orthopaedic Association (JOA) score for cervical myelopathy was obtained before and 1 year after surgery as a clinical outcome measure.

RESULTS

MEP, PCT, and CMCT parameters in the CCM-DM and CCM groups were significantly longer than those in the control group (p = 0.000−0.007). The PCTs in the CCM-DM group were significantly longer than those in the CCM group (p = 0.001−0.003). No significant differences were detected in the MEP and CMCT parameters between the CCM-DM and CCM groups (p = 0.080–1.000). The JOA score before surgery in the CCM-DM group was 10.7 ± 2.0 points and was significantly lower than that in the CCM group (12.2 ± 2.5 points, p = 0.015). In the CCM-DM group, JOA scores before surgery correlated with MEP-AH (r = −0.610, p = 0.012) and PCT-AH (r = −0.676, p = 0.004) values, but not with CMCT values, while the JOA scores were related to both MEP and CMCT parameters in the CCM group. The JOA scores improved to 13.8 ± 2.2 points after surgery (p = 0.001) and correlated with MEP-AH (r = −0.667, p = 0.005) and PCT-AH (r = −0.611, p = 0.012) in the CCM-DM group.

CONCLUSIONS

The results suggest that MEP, PCT, and CMCT parameters each reveal abnormalities in the upper and lower motor neurons even in patients with DM. The results also show a prolonged PCT in CCM-DM patients, despite having no history of diabetic neuropathy. Corticospinal tract impairments are similar between CCM and CCM-DM patients, while the JOA score of the CCM-DM patients is lower than that in the CCM patients. The JOA score in CCM-DM patients may be influenced by additional impairments in peripheral nerves or other diabetic complications. These electrophysiological studies may be useful for screening motor pathway function for CCM in patients with DM.