The Role of Dynamic Magnetic Resonance Imaging in Cervical Spondylotic Myelopathy

Surgical management of congenital cervical spondylolytic spondylolisthesis: illustrative case

BACKGROUND

Congenital cervical spondylolytic spondylolisthesis is a rare and complex disorder of the cervical spine. Surgical treatment is reserved for those symptomatic patients who do not improve with conservative management.

OBSERVATIONS

A 34-year-old man presented with bilateral C7 radiculopathy for the past 6 months. Magnetic resonance imaging of the cervical spine revealed grade II C6-7 spondylolisthesis. Computed tomography showed the presence of spondyloarthritis, bilateral pedicle dysplasia, bilateral isthmic defect, and spinous process schisis. Dynamic radiographs showed no signs of vertebral instability. Dynamic magnetic resonance imaging showed kinking of the spinal cord over the fulcrum of C6-7 kyphosis during flexion, with no signs of myelopathy. The patient underwent C6-7 anterior fusion surgery. His symptoms improved postoperatively, with a 2-month computed tomography scan showing initial bony bridging.

LESSONS

The absence of evident instability on radiography does not always correspond to the absence of actual functional compression of neurological structures. Spinal misalignment, muscle dysfunction, and kyphotic deformity with kinking of the spinal cord and stretching of the nerve roots may also contribute to the development of symptoms. In this setting, dynamic magnetic resonance imaging can be extremely useful. Single-level anterior fusion surgery without posterior fixation can achieve solid fusion and improve the clinical conditions of patients. https://thejns.org/doi/10.3171/CASE24174.

C1 Facetectomy and Ventral Fixation of Occipitoatlantoaxial Complex for Concurrent Congenital Atlanto-Occipital Dislocation and Atlantoaxial Instability in a Toy Poodle

An 8-month-old, 3.4 kg, castrated male Toy Poodle was referred for progressive tetraparesis and respiratory disorder without a history of trauma. Repeated computed tomography (CT) and magnetic resonance imaging (MRI) with different positions of the neck revealed concurrent atlanto-occipital dislocation (AOD) and atlantoaxial instability (AAI) with spinal cord compression. This case was unique due to its congenital nature and the absence of trauma. The surgical treatment involved precise removal of the C1 vertebra's ventral articular facet, which was compressing on the spinal cord, attributed to its fixed and malaligned position within the atlantooccipital joint. Following facetectomy, the stabilization of the occipital bone to the C2 vertebra was achieved by screws, wire, and polymethyl methacrylate. Two days after surgery, the dog recovered ambulation and showed gradual improvement in gait, despite mild residual ataxia. Postoperative CT and radiographs showed successful decompression of the spinal cord. The screw loosening was confirmed at 114 days, which was managed successfully by extracting the affected screws. Through the 21-month monitoring period, the dog showed a normal gait with a wide-based stance of the pelvic limbs when standing and experienced no pain. This case represents the first report of concurrent congenital AOD and AAI treated with a ventral surgical approach, contributing new insights to the understanding and management of such complex cranio-cervical junction disorders in veterinary neurosurgery.

Dynamic Flexion-Extension Magnetic Resonance Imaging of the Cervical Spine: An Evolutionary Tool for Diagnosis and Management of Cervical Spondylotic Myelopathy

Dynamic problems need dynamic solutions. High motility of the cervical spine causes a common age-related degenerative condition called cervical spondylotic myelopathy (CSM), manifested by neurological impairments. An accurate and reliable diagnosis of CSM is crucial for determining appropriate management strategies. Traditional static magnetic resonance imaging (MRI) has been the gold standard for imaging CSM; however, it may not fully capture dynamic changes during neck movement. Dynamic flexion-extension (DFE) MRI is an innovative imaging technique that allows for real-time visualization of cervical spine motion. This review article aims to scrutinize the role of DFE MRI in assessing CSM, its added value to clinical implementations, and its limitations. Finally, by addressing the knowledge gaps, this survey sheds light on the road ahead to incorporate DFE MRI into a standard version of the practice.

Finite Element Analysis for Degenerative Cervical Myelopathy: Scoping Review of the Current Findings and Design Approaches, Including Recommendations on the Choice of Material Properties

BACKGROUND

Degenerative cervical myelopathy (DCM) is a slow-motion spinal cord injury caused via chronic mechanical loading by spinal degenerative changes. A range of different degenerative changes can occur. Finite element analysis (FEA) can predict the distribution of mechanical stress and strain on the spinal cord to help understand the implications of any mechanical loading. One of the critical assumptions for FEA is the behavior of each anatomical element under loading (ie, its material properties).

OBJECTIVE

This scoping review aims to undertake a structured process to select the most appropriate material properties for use in DCM FEA. In doing so, it also provides an overview of existing modeling approaches in spinal cord disease and clinical insights into DCM.

METHODS

We conducted a scoping review using qualitative synthesis. Observational studies that discussed the use of FEA models involving the spinal cord in either health or disease (including DCM) were eligible for inclusion in the review. We followed the PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews) guidelines. The MEDLINE and Embase databases were searched to September 1, 2021. This was supplemented with citation searching to retrieve the literature used to define material properties. Duplicate title and abstract screening and data extraction were performed. The quality of evidence was appraised using the quality assessment tool we developed, adapted from the Newcastle-Ottawa Scale, and shortlisted with respect to DCM material properties, with a final recommendation provided. A qualitative synthesis of the literature is presented according to the Synthesis Without Meta-Analysis reporting guidelines.

RESULTS

A total of 60 papers were included: 41 (68%) "FEA articles" and 19 (32%) "source articles." Most FEA articles (33/41, 80%) modeled the gray matter and white matter separately, with models typically based on tabulated data or, less frequently, a hyperelastic Ogden variant or linear elastic function. Of the 19 source articles, 14 (74%) were identified as describing the material properties of the spinal cord, of which 3 (21%) were considered most relevant to DCM. Of the 41 FEA articles, 15 (37%) focused on DCM, of which 9 (60%) focused on ossification of the posterior longitudinal ligament. Our aggregated results of DCM FEA indicate that spinal cord loading is influenced by the pattern of degenerative changes, with decompression alone (eg, laminectomy) sufficient to address this as opposed to decompression combined with other procedures (eg, laminectomy and fusion).

CONCLUSIONS

FEA is a promising technique for exploring the pathobiology of DCM and informing clinical care. This review describes a structured approach to help future investigators deploy FEA for DCM. However, there are limitations to these recommendations and wider uncertainties. It is likely that these will need to be overcome to support the clinical translation of FEA to DCM.

Efficacy of Dynamic Magnetic Resonance Imaging in the Diagnosis of Degenerative Cervical Myelopathy: Systematic Review Protocol

Cervical degenerative myelopathy (CDM) is a cervical spine condition resulting in clinical manifestations of spinal cord compression related to the chronic, non-traumatic, and progressive narrowing of the cervical spinal canal. Conventional magnetic resonance imaging (MRI) is the gold standard test to diagnose and assess the severity of CDM. However, the patient is in a neutral and static position during the MRI scan, which may devalue the dynamic factors of CDM, underestimating the risk of spinal cord injury related to cervical spine flexion and extension movements. Dynamic MRI is a promising technique to change this scenario. Therefore, the present review aims to answer the following question: "Is dynamic MRI of the cervical spine more accurate in diagnosing CDM than conventional MRI?". We will search for studies in the MEDLINE (via PubMed), Embase, Scopus, Web of Science, LILACS, and SciELO databases. The search strategy will contain a combination of terms related to cervical myelopathy and magnetic resonance imaging . Two independent reviewers will select studies, extract data, and assess the risk of bias. The synthesis of results will be descriptive, considering the main findings of the studies about the outcomes of interest.

Cervical Foraminal Changes in Patients with Intermittent Arm Radiculopathy Studied with a New MRI-Compatible Compression Device

Diagnosing cervical foraminal stenosis with intermittent arm radiculopathy is challenging due to discrepancies between MRI findings and symptoms. This can be attributed to the fact that MRI images are often obtained in a relaxed supine position. This study aims to evaluate the feasibility of the Dynamic MRI Compression System (DMRICS) and to assess possible changes in cervical foramina, with both quantitative measurements and qualitative grading systems, with MRI during a simulated Spurling test. Ten patients (five women and five men, ages 29-45) with previously confirmed cervical foraminal stenosis underwent MRI scans using DMRICS. MRI images were acquired in both relaxed and provoked states. A radiologist assessed 30 foramina (C4-C7) on the symptomatic side in both patient positions. Quantitative and qualitative measures were performed, including the numeric rating scale (NRS) and the Park and Kim grading systems. The provoked state induced concordant neck and arm pain in 9 of 10 patients. Significant shifts in Park and Kim foraminal gradings were noted: 13 of 27 Park gradings and 9 of 27 Kim gradings escalated post provocation. No quantitative changes were observed. This pilot study indicates that the DMRICS device has the potential to improve diagnostic accuracy for cervical radiculopathy, demonstrating induced cervical foraminal changes during a simulated Spurling test while performing MRI.

Novel Grading Scales for Static and Flexion-Extension Magnetic Resonance Imaging in Patients with Cervical Spondylotic Myelopathy

BACKGROUND

Flexion-extension magnetic resonance imaging (MRI) has potential to identify cervical pathology not detectable on conventional static MRI. Our study evaluated standard quantitative and novel subjective grading scales for assessing the severity of cervical spondylotic myelopathy in dynamic sagittal MRI as well as in static axial and sagittal images.

METHODS

Forty-five patients underwent both conventional and flexion-extension MRI prior to anterior cervical discectomy and fusion from C4 through C7. In addition to measuring Cobb angles and cervical canal diameter, grading scales were developed for assessment of vertebral body translation, loss of disc height, change in disc contour, deformation of cord contour, and cord edema. Data were collected at all levels from C2-C3 through C7-T1. Variations in measurements between cervical levels and from flexion through neutral to extension were assessed using Mann-Whitney, Kruskal-Wallis, and two-way ANOVA tests.

RESULTS

Cervical canal diameter, vertebral translation, and posterior disc opening changed significantly from flexion to neutral to extension positions (P < 0.01). When comparing operative versus nonoperative cervical levels, significant differences were found when measuring sagittal cervical canal dimensions, vertebral translation, and posterior disc opening (P < 0.01). Degenerative loss of disc height, disc dehydration, deformation of ventral cord contour, and cord edema were all significantly increased at operative levels versus nonoperative levels (P < 0.01).

CONCLUSIONS

Flexion-extension MRI demonstrated significant changes not available from conventional MRI. Subjective scales for assessing degenerative changes were significantly more severe at levels with operative cervical spondylotic myelopathy. The utility of these scales for planning surgical intervention at specific and adjacent levels is currently under investigation.

Contribution of dynamic cervical MRI to surgical planning for degenerative cervical myelopathy: Revision rate and clinical outcomes at 5 years' postoperative

INTRODUCTION

Cervical MRI is the gold standard for surgical planning of degenerative cervical myelopathy; however, the symptomatic postoperative recurrence rate is high in the medium and long terms (9.1% to 10.7%) and may bring into question the quality of the preoperative surgical plan. The objective of this study was to evaluate cervical spinal stenosis and intramedullary hyperintensity with dynamic cervical MRI to determine the recurrence rate and clinical improvement in a cohort of patients who had dynamic cervical MRI incorporated into their surgical plan.

METHODS

This was a prospective, single-center study. Upon enrolment and at each follow-up visit, patients completed the mJOA score, NDI, cervical pain on visual analog scale (VAS) and radicular pain on VAS. Every enrolled patient underwent dynamic cervical MRI (in neutral, flexion and extension positions). Five levels were measured in the three positions, resulting in 915 levels for analysis.

RESULTS

Sixty-one patients were included. Eighty-four levels had an intramedullary hyperintensity in neutral position, 93 in extension and 112 in flexion. The mean sagittal diameter varied the most at C4-C5, going from 7.13mm (SD 2.32) on average in neutral to 6.30mm (SD 2.22) in extension and 8.29mm (SD 2.10) in flexion, a variation of -12% and +16%, respectively. A Mühle grade≥2 was found in 134 levels in neutral position versus 189 in extension and 110 in flexion. None of the patients had worse neurological symptoms following the dynamic cervical MRI. The mean postoperative follow-up was 4.4 years (SD 0.88). Two patients (3.1%) required surgical revision because the implants had shifted. One patient developed symptomatic adjacent segment disease.

CONCLUSION

Preoperative surgical planning that incorporates dynamic cervical MRI before the surgical treatment of degenerative cervical myelopathy appears to be a safe and reliable method and one that helps reduce symptoms in the long term.

LEVEL OF EVIDENCE

IV.

The value of dynamic MRI in cervical spondylotic myelopathy: About 24 cases

Dynamic magnetic resonance imaging (MRI) of the cervical spine is extremely useful in assessing pathological changes at the spinal cord, vertebrae, discs, ligaments and facet joints. We attempted to document the radiological changes that the cervical spine undergoes during dynamic maneuvers and the effects of Dynamic MRI in management of cervical myelopathy, emphasizing on the changes in treatment protocol effected by the new findings discovered. Our work is based on 24 consecutive patients with cervical spondylotic myelopathy had cervical MR imaging in neutral position, in flexion and extension of the cervical spine between January 2021 and December 2021. The result found the mean age was 57.9 years (range 26–85 years). Among these 24 patients, there were 11 males and 13 females. Total number of levels of compression were 47 and the additional levels of involvement were 17. Additional levels of compression were noted in 12 patients, among these 17 new levels, 7 were in the posterior and 10 in the anterior. The most affected level was C5C6 with 16 cases. All additional levels of compression were noted in extension; Reduction of the cervical canal was observed in 20 patients only in extension. In the bending sequences we have noticed an increase of the canal diameter in 3 patients. The location of the compression is in 15 cases anterior, 2 cases posterior and 5 cases are mixed anterior and posterior Surgery was considered in 17 patients. Anterior procedures were 11 (ACDF/corpectomy and fusion) and Posterior surgeries were 6 (laminoplasty/laminectomy), and. The rest of the patients did not require surgery and was conservatively treated. A change of the signal was found in 3 patients during the acquisition in extension position a. Most studies have shown a reduction of the root canal with an increase of the compression level, which was the case in our study. MRI is a useful tool for diagnosis of CM, it does not give an exact idea as to which is the offending level in a multilevel compression that requires surgery. Even the approach and procedure cannot be decided on a static examination and hence are subject to significant interpractitioner the role of extension MRI in determining cervical compression levels. Thus, dynamic cervical spine MRI should be an important investigation before we decide to write off surgical treatment in patients with cervical myelopathy and cord signal changes without definitive compression on static MRI. Flexion and extension MRI is an important tool for decision making and planning appropriate management in cervical compressive myelopathy.

•

Dynamic magnetic resonance imaging (MRI) of the cervical spine is extremely useful in assessing pathological changes at the spinal cord. We attempted to document the radiological changes during dynamic maneuvers and the effects of Dynamic MRI in management of cervical myelopathy.

•

Most studies have shown a reduction of the root canal with an increase of the compression level, which was the case in our study. MRI is a useful tool for diagnosis of CM, it does not give an exact idea as to which is the offending level in a multilevel compression that requires surgery. Even the approach and procedure cannot be decided on a static examination and hence are subject to significant interpractitioner the role of extension MRI in determining cervical compression levels. Thus, dynamic cervical spine MRI should be an important investigation before we decide to write off surgical treatment.

•

Flexion and extension MRI is an important tool for decision making and planning appropriate management in cervical compressive myelopathy.

Degenerative Cervical Myelopathy: Development and Natural History [AO Spine RECODE-DCM Research Priority Number 2]

STUDY DESIGN

Narrative review.

OBJECTIVES

To discuss the current understanding of the natural history of degenerative cervical myelopathy (DCM).

METHODS

Literature review summarizing current evidence pertaining to the natural history and risk factors of DCM.

RESULTS

DCM is a common condition in which progressive arthritic disease of the cervical spine leads to spinal cord compression resulting in a constellation of neurological symptoms, in particular upper extremity dysfunction and gait impairment. Anatomical factors including cord-canal mismatch, congenitally fused vertebrae and genetic factors may increase individuals' risk for DCM development. Non-myelopathic spinal cord compression (NMSCC) is a common phenomenon with a prevalence of 24.2% in the healthy population, and 35.3% among individuals >60 years of age. Clinical radiculopathy and/or electrophysiological signs of cervical cord dysfunction appear to be risk factors for myelopathy development. Radiological progression of incidental Ossification of the Posterior Longitudinal Ligament (OPLL) is estimated at 18.3% over 81-months and development of myelopathy ranges between 0-61.5% (follow-up ranging from 40 to 124 months between studies) among studies. In patients with symptomatic DCM undergoing non-operative treatment, 20-62% will experience neurological deterioration within 3-6 years.

CONCLUSION

Current estimates surrounding the natural history of DCM, particularly those individuals with mild or minimal impairment, lack precision. Clear predictors of clinical deterioration for those treated with non-operative care are yet to be identified. Future studies are needed on this topic to help improve treatment counseling and clinical prognostication.

Does Spondylolisthesis Affect Severity and Outcome of Degenerative Cervical Myelopathy? A Systematic Review and Meta-analysis

STUDY DESIGN

This was a systematic review and meta-analysis.

OBJECTIVES

Degenerative cervical myelopathy (DCM) with spondylolisthesis remains not well defined, poorly studied, and underreported and plays a minor role in the therapeutic decision-making. Spondylolisthesis, however, is not uncommon and may result in dynamic injury to the spinal cord. We aim to describe the impact of spondylolisthesis in DCM severity and postoperative outcomes.

METHODS

Two independent reviewers conducted a Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA 2015)-based review between 1970 and May 2020 for articles reporting outcome of DCM in patients with degenerative cervical spondylolisthesis. Patient clinical and radiological data was recorded at baseline and during postoperative follow-up (FU). A meta-analysis comparing surgical outcome between DCM patients with and without spondylolisthesis assessed by the regular/modified Japanese Orthopaedic Association Assessment Scale (mJOA) recovery ratio was completed.

RESULTS

A total of 3 studies were included (1 ambispective and 2 retrospective cohorts); 607 patients with DCM were identified, 102 (16.8%) of whom also had spondylolisthesis. DCM patients with spondylolisthesis were significantly older (P < .05), presented with worse baseline mJOA and Nurick grades (P < .05 in 2 studies), and were more commonly operated via posterior approaches (P < .05). All groups experienced a (m)JOA and/or Neck Disability Index score improvement during FU. In the pooled meta-analysis, spondylolisthesis patients showed a significantly lower functional recovery ratio at 2 years compared with other DCM patients (P = .05).

CONCLUSIONS

Spondylolisthesis is frequent in older DCM patients and may be a predictor of a more advanced degeneration and subsequent worse baseline conditions and postoperative outcome.

Influence of dynamic neck motion on the clinical usefulness of multi-positional MRI in cervical degenerative spondylosis

PURPOSE

The purpose of this study was to find out additional indications for multi-positional MRI in cervical degenerative spondylosis (CDS) patients.

MATERIAL AND METHODS

A total of 63 patients with cervical spondylotic myelopathy that underwent multi-positional MRI and X-ray were included. Muhle's grade, C2-7 angle, and C7 slope were measured. Patients were assigned to the stenosis group (Group S) when Muhle's grades were increased by more than two or maximum grade was reached. Other patients were assigned to the maintenance group (Group M). Receiver operating characteristic (ROC) analysis was performed. Statistical significance was accepted for p values of < 0.05.

RESULTS

A total of 24 patients were assigned to the S group and 39 patients to the M group. Mean C2-7 angle difference in extension (eC27A) between S and M groups was 10.97° (p = 0.002). The mean inter-group difference between C2-7 angle in extension and neutral positions (e-nC27A) was 14.39° (p = 0.000). Mean C7 slope difference in neutral position was  - 6.53° (p = 0.002). Based on areas under ROC curves (AUCs), e-nC27A, eC27A, and negative C7 slope had AUCs of 0.934 (95% CI 0.876-0.992), 0.752 (95% CI 0.624-0.880), and 0.720 (95% CI 0.588-0.851), respectively. The optimal cutoff value of e-nC27A was 15.4 degrees, which had a diagnostic accuracy of 88.9%.

CONCLUSION

Multi-positional MRI helps to find dynamic cord compressive lesion in CDS patients. The higher eC27A, e-nC27A values and smaller C7 slope were found to increase the likelihood of cervical dynamic stenosis. Among other factors, we recommend multi-positional MRI before surgery especially when a patient's e-nC27A is > 15.4 degrees.

LEVEL OF EVIDENCE I

Diagnostic: individual cross-sectional studies with the consistently applied reference standard and blinding.

The value of dynamic MRI in the treatment of cervical spondylotic myelopathy: a protocol for a prospective randomized clinical trial

Background

Cervical spondylotic myelopathy (CSM) is the most severe type of cervical spondylosis and the most common cause of spinal cord dysfunction among adults over 55 years old. MRI plays an important role in the diagnosis and evaluation of CSM, which can directly demonstrate the correlation between disc, spinal cord, posterior structures and abnormal signal in spinal cord. Static MRI can only show the static and neutral position of spinal cord, which is not enough to understand the pathogenesis of CSM. Dynamic MRI demonstrating the extension and flexion position of spinal cord can be a better tool for the treatment of CSM, especially the surgical decision making.

Method

A total of 180 CSM patients who have indications for surgery will be recruited in outpatient of Peking University Third Hospital and assigned to three groups (Group A, B and C) based on their static MRI after consent. Group A (incomplete dura compression) means the signal of cerebral spinal fluid (CSF) is still visible. Group B (complete dura compression) means no CSF signal and no shape change of spinal cord. Group C (spinal cord compression) means shape change of spinal cord. Two surgical plans will be made for each participant by one professional surgeon according to the static MRI and dynamic MRI respectively and we will randomly choose one to perform via a random number system. Follow-up will be maintained at 3, 6, and 12 months after surgery through outpatient or telephone interview, including mJOA score, 10-s G&R (grip and release) and 10-s step test, SF-36 score, radiographic examination and complications. Finally, data collection and statistical analysis will be finished by researchers who are blinded to recruitment and treatment.

Discussion

This study will help us to explore the indication of dynamic MRI and the value of dynamic MRI in the treatment of CSM, especially the surgical decision making. Dynamic MRI can be a useful tool in the treatment of CSM patients.

Trial registration

ChiCTR1900023014. Registered on May 7th, 2019.

Degenerative cervical myelopathy: Recent updates and future directions

Advances in patient selection, surgical techniques, and postoperative care have facilitated spine surgeons to manage complex spine cases with shorter operative times, reduced hospital stay and improved outcomes. We focus this article on a few areas which have shown maximum developments in management of degenerative cervical myelopathy and also throw a glimpse into the future ahead. Imaging modalities, surgical decision making, robotics and neuro-navigation, minimally invasive spinal surgery, motion preservation, use of biologics are few of them. Through this review article, we hope to provide the readers with an insight into the present state of art in cervical myelopathy and what the future has in store for us.

Cervical Spondylotic Myelopathy: Natural Course and the Value of Diagnostic Techniques -WFNS Spine Committee Recommendations

Objective

This study presents the results of a systematic literature review conducted to determine most up-to-date information on the natural outcome of cervical spondylotic myelopathy (CSM) and the most reliable diagnostic techniques.

Methods

A literature search was performed for articles published during the last 10 years.

Results

The natural course of patients with cervical stenosis and signs of myelopathy is quite variable. In patients with no symptoms, but significant stenosis, the risk of developing myelopathy with cervical stenosis is approximately 3% per year. Myelopathic signs are useful for the clinical diagnosis of CSM. However, they are not highly sensitive and may be absent in approximately one-fifth of patients with myelopathy. The electrophysiological tests to be used in CSM patients are motor evoked potential (MEP), spinal cord evoked potential, somatosensory evoked potential, and electromyography (EMG). The differential diagnosis of CSM from other neurological conditions can be accomplished by those tests. MEP and EMG monitoring are useful to reduce C5 root palsy during CSM surgery. Notable spinal cord T2 hyperintensity on cervical magnetic resonance imaging (MRI) is correlated with a worse outcome, whereas lighter signal changes may predict better outcomes. T1 hypointensity should be considered a sign of more advanced disease.

Conclusion

The natural course of CSM is quite variable. Signal changes on MRI and some electrophysiological tests are valuable adjuncts to diagnosis.

A New Diagnostic Medium for Cervical Spondylotic Myelopathy: Dynamic Somatosensory Evoked Potentials

OBJECTIVE

To identify and reveal the sensitivity and efficiency of dynamic somatosensory evoked potentials (DSSEPs) in the diagnosis of cervical spondylotic myelopathy (CSM).

METHODS

This retrospective study included 31 CSM and 15 control patients. All patients received SSEP examination with stimulation of median and ulnar nerves at neutral, flexed, and extended cervical positions; latency and amplitude were recorded at the C₂ and C₅ spinous processes and in the scalp over the primary sensory area (C_3'/4'). The percentage changes in latency and amplitude with dynamic motion were examined for each lead and compared between groups; the diagnostic cutoff values were determined using receiver operating characteristic curve analysis.

RESULTS

All the patients with CSM received surgeries and were followed up for 1 year. Amplitude parameters varied with a dynamic position in both groups; all recorded dynamic SSEP indices except right median stimulus recorded at C5 spinous process, right ulnar stimulus recorded at scalp point C3, and right ulnar stimulus recorded at C2 spinous process were significantly different between groups (P < 0.05), but latency was not (P > 0.05). At the neutral position, the amplitude of left media stimulus recorded at C2 spinous process (LMC₂) was associated with CSM, but with low diagnostic accuracy (area under the curve = 0.199). At a dynamic position, the percentage change in amplitude of LMC₂ and of left ulnar stimulus recorded at C2 spinous process (LUC₂) were determined to be diagnostic of CSM (P < 0.05), with areas under the curve of 0.891 and 0.912, respectively. Both records had high sensitivity and specificity in the diagnosis of CSM; the diagnostic cutoff values of LMC₂ and LUC₂ were calculated as 10.2% and 19.25%, respectively.

CONCLUSIONS

The percentage change in amplitude was obvious during cervical dynamic motion, with records from LMC₂ and LUC₂ being predictive of CSM diagnosis; dynamic SSEPs provided a simple, accurate, and noninvasive supplementary test for the diagnosis of complicated CSM.

Recent advances in the management of cervical spondylotic myelopathy: bibliometric analysis and surgical perspectives

OBJECTIVE

Cervical spondylotic myelopathy (CSM) has become a prevalent cause of spinal cord dysfunction among the aging population worldwide. Although great strides have been made in spine surgery in past decades, the optimal timing and surgical strategy to treat CSM have remained controversial. In this article the authors aimed to analyze the current trends in studies of CSM and to summarize the recent advances of surgical techniques in its treatment.

METHODS

The PubMed database was searched using the keywords pertaining to CSM in human studies that were published between 1975 and 2018. Analyses of both the bibliometrics and contents, including the types of papers, authors, affiliations and countries, number of patients, and the surgical approaches were conducted. A systematic review of the literature was also performed with emphasis on the diagnosis and treatment of mild CSM.

RESULTS

A total of 1008 papers published during the span of 44 years were analyzed. These CSM studies mainly focused on the natural history, diagnosis, and treatment, and only a few prospective randomized trials were reported. For the authors and affiliations, there was a shift of clustering of papers toward Asian countries in the past decades. Regarding the treatment for CSM, there was an exponential growth of surgical series published, and there was a trend toward slightly more anterior than posterior approaches through the past decade. Patients with CSM had increased risks of neurological deterioration or spinal cord injury with nonoperative management. Because surgery might reduce the risks, and early surgery was likely to be correlated with better outcomes, there was a trend toward attention to mildly symptomatic CSM.

CONCLUSIONS

There is emerging enthusiasm for research on CSM worldwide, with more publications originating in Asian countries over the past few decades. The surgical management of CSM is evolving continuously toward early and anterior approaches. More prospective investigations on the optimal timing and choices of surgery are therefore needed.

Dynamic Cord Compression Causing Cervical Myelopathy

Due to the highly mobile nature of the cervical spine, and the fact that most magnetic resonance imagings (MRIs) and computed tomography scans are obtained only in one single position, dynamic cord compression can be an elusive diagnosis that is often missed and not well-understood. In this context, dynamic MRI (dMRI) has been utilized to improve the diagnostic accuracy of cervical stenosis. We performed a literature review on dynamic cord compression in the context of cervical spondylotic myelopathy (CSM), with particular emphasis on the role of dMRI. Cadaveric studies report that the spinal cord lengthens in flexion and the spinal canal dimension increases, whereas the spinal cord relaxes and shortens in extension and the spinal canal decreases. These changes may lead to biomechanical stress in the spinal cord with movement, especially in patients with critical cervical stenosis. The majority of the studies using dMRI in CSM reported that this imaging modality is more sensitive at detecting cervical cord compression compared to routine MRIs done in a neutral position, especially with the neck in extension. Dynamic MRI was also useful to diagnose dynamic cervical cord compression after laminectomies in patients with clinical deterioration without evident cord compression on neutral static MRI. Finally, dMRI is more sensitive in detecting stenosis in patients with CSM than in those with ossification of the posterior longitudinal ligament (OPLL), likely because OPLL patients often have a more limited range of motion than CSM patients. Thus, dMRI is a promising new tool that can help spine surgeons in diagnosing and treating CSM.

Difference of Dynamic Morphometric Changes Between in Patients with Ossification of Posterior Longitudinal Ligament and Patients with Cervical Spondylosis: Assessment by Cervical Dynamic Magnetic Resonance Imaging

PURPOSE

To evaluate differences between thicknesses of the ligamentum flavum (LF) and diameter of the spinal canal in different neck positions in patients with ossification of the posterior longitudinal ligament (OPLL) and patients with cervical degenerative spondylosis (CDS) using cervical dynamic magnetic resonance imaging (MRI).

METHODS

Eighty-eight patients (66 CDS and 22 OPLL) who underwent neutral and dynamic MRI at our institute from February 2014 to July 2017 were the subjects of this retrospective study. Canal diameters and LF thicknesses were measured and Muhle's grades were determined in neutral and dynamic MRI from C2-C3 to C7-T1. Patients with CDS and OPLL were compared with respect to changes in morphometric parameters. Statistical analysis was performed using SPSS software and statistical significance was accepted for P values < 0.05.

RESULTS

Mean ages in the CDS and OPLL groups were 68.2 ± 12.27 and 63.1 ± 9.36 years, respectively. Mean canal diameters were smaller in extension than in neutral at all measured levels, especially between C3-C4 and C6-C7 in patients with CDS. LF thickness in extension was significantly greater than in neutral and flexion positions in the CDS group, but not in the OPLL group. In addition, positional changes in Muhle's grades in the CDS group were significantly greater than in the OPLL group (P = 0.042).

CONCLUSIONS

Dynamic morphometric changes were found to be significantly greater in the CDS group than in the OPLL group. The study shows dynamic MRI may provide additional information in CDS patients.

Cervical Spine and Cord Angle Mismatch in the Pathogenesis of Myelopathy

BACKGROUND

Cervical myelopathy is a complex pathology and dynamic compression of the tethered cervical cord, which may be responsible for clinical symptoms.

METHODS

Patients with cervical canal stenosis who had magnetic resonance imaging in flexion and extension positions were retrospectively reviewed. All cases were evaluated in Nurick grade. The cervical parameters-cervical cord (CC) angle, cervical lordosis, and spine/cord (S/C) angle ratio-were measured on the magnetic resonance imaging. Mean values of these parameters were compared between nonmyelopathic (Nurick grade 0) and myelopathic groups (Nurick grades 1-5). A multinomial ordinal logistic regression was used to predict outcome for Nurick grade using the CC angle, the cervical lordosis angle, and the S/C angle ratio as independent variables.

RESULTS

A total of 65 patients (35 men) with the mean age of 58.6 ± 11.4 years were analyzed. A comparison of means between Nurick grade 0 against each of myelopathic grades 1-5 revealed significant differences only for the S/C angle ratio. A cumulative comparison between nonmyelopathic and myelopathic grades for the S/C angle ratio showed significant difference of 0.29 (1.16 ± 0.5 vs. 1.45 ± 0.6, respectively; P < 0.05). Cumulative comparison for the CC angle difference in flexion and extension lordosis did not show substantial differences. The S/C angle ratio was the only significant parameter in the prediction of the Nurick grade with an odds ratio of 2.63 (95% confidence interval 2.11-2.79).

CONCLUSIONS

A positive correlation between Nurick grade and cervical spine and cord angle mismatch was found.