Kinetic magnetic resonance imaging of the cervical spine: a review of the literature

Congenital Cervical Stenosis: a Review of the Current Literature

PURPOSE OF REVIEW

Congenital cervical stenosis (CCS) is a phenomenon in which an individual has a narrow canal due to abnormal anatomy which can present with earlier degenerative symptoms due to a reduced sagittal diameter. The diagnosis of CCS is important to individual treatment and preventative measures. Often, athletes are warned against sport participation that may cause damage to the cervical spine. There may be a predisposition in certain populations, but lack of data limits conclusions. The current review investigates recent literature on the definition, pathoanatomy, clinical presentation, and management of CCS. It specifically interrogates potential populations predisposed to this condition.

RECENT FINDINGS

The current literature reveals a potential predisposition for CCS in the black population when compared to the white population; however, many studies do not report race when discussing CCS patients. The lack of data limits a consensus on specific populations with a congenitally narrow canal. CCS may be more prevalent in specific populations. With knowledge of populations more at risk for this condition, physicians and teams can be alert when evaluating players and young adults. Furthermore, this may provide insight into risk for symptoms with degenerative disease. These findings introduce an avenue for further research into CCS.

Pontomedullary junction as a reference for spinal cord cross-sectional area: validation across neck positions

Spinal cord cross-sectional area (CSA) is an important MRI biomarker to assess spinal cord atrophy in various neurodegenerative and traumatic spinal cord diseases. However, the conventional method of computing CSA based on vertebral levels is inherently flawed, as the prediction of spinal levels from vertebral levels lacks reliability, leading to considerable variability in CSA measurements. Computing CSA from an intrinsic neuroanatomical reference, the pontomedullary junction (PMJ), has been proposed in previous work to overcome limitations associated with using a vertebral reference. However, the validation of this alternative approach, along with its variability across and within participants under variable neck extensions, remains unexplored. The goal of this study was to determine if the variability of CSA across neck flexions/extensions is reduced when using the PMJ, compared to vertebral levels. Ten participants underwent a 3T MRI T2w isotropic scan at 0.6 mm3 for 3 neck positions: extension, neutral and flexion. Spinal cord segmentation, vertebral labeling, PMJ labeling, and CSA were computed automatically while spinal segments were labeled manually. Mean coefficient of variation for CSA across neck positions was 3.99 ± 2.96% for the PMJ method vs. 4.02 ± 3.01% for manual spinal segment method vs. 4.46 ± 3.10% for the disc method. These differences were not statistically significant. The PMJ method was slightly more reliable than the disc-based method to compute CSA at specific spinal segments, although the difference was not statistically significant. This suggests that the PMJ can serve as a valuable alternative and reliable method for estimating CSA when a disc-based approach is challenging or not feasible, such as in cases involving fused discs in individuals with spinal cord injuries.

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.

Craniocervical instability in patients with Ehlers-Danlos syndrome: controversies in diagnosis and management

Ehlers-Danlos syndrome (EDS) is a rare hereditary condition that can result in ligamentous laxity and hypermobility of the cervical spine. A subset of patients can develop clinical instability of the craniocervical junction associated with pain and neurological dysfunction, potentially warranting treatment with occipitocervical fixation (OCF). Surgical decision-making in patients with EDS can be complicated by difficulty distinguishing from hypermobility inherent in the disease and true pathological instability necessitating intervention. Here we comprehensively review the available medical literature to critically appraise the evidence behind various proposed definitions of instability in the EDS population, and summarize the available outcomes data after OCF. Several radiographic parameters have been used, including the clivo-axial angle, basion-axial interval, and pB-C2 measurement. Despite increasing recognition of EDS by spine surgeons, there remains a paucity of data supporting proposed radiographic parameters for spinal instability among EDS patients. Furthermore, there is a lack of high-quality evidence concerning the efficacy of surgical treatments for chronic debilitating pain prevalent in this population. More standardized clinical measures and rigorous study methodologies are needed to elucidate the role of surgical intervention in this complex patient population.

Upright Magnetic Resonance Imaging Study of Cervical Flexor/Extensor Musculature and Cervical Lordosis in Females After Helmet Wear

INTRODUCTION

Addition of head-supported mass imparts greater demand on the human neck to maintain functionality. The same head-supported mass induces greater demand on the female spine than the male spine because female necks are comparatively slender. Prevalence of neck pain is greater in military than civilian population because of the head-borne mass (among other factors). The goal of this study is to determine quantifiable parameters related to muscle geometry using female human volunteers and upright magnetic resonance imaging.

MATERIALS AND METHODS

Young healthy subjects were consented. Demographics and head-neck anthropometry were recorded. For all the 7 subjects, the T1- and T2-weighted magnetic resonance imaging in the neutral sitting position was obtained immediately following donning and after 4 hours of continuous wear of standard issued military helmet, while seated in the same posture for 4 hours. Cross-sectional areas of sternocleidomastoid and multifidus muscles from C2-C7, overall and segmental Cobb angles (C2-T1), and centroid and radius of each muscle were calculated. Data were compared with determine differences with the continuous helmet wear.

RESULTS

There were level specific changes in morphological parameters for each of the muscles. Significant difference (P < 0.05) in cross-sectional areas was noted at C2-3 level for sternocleidomastoid and at C3-4 and C5-6 levels for multifidus. For centroid angles, significant difference (P < 0.05) was observed at C2-3 and C5-6 levels for sternocleidomastoid and at C3-4 level for multifidus. There was no significant difference (P > 0.05) in muscle centroid radii between the pre- and posttest conditions.

CONCLUSIONS

Alterations in muscle geometries were muscle specific and level specific: sternocleidomastoid was significant at the upper level, whereas multifidus was significant at the mid-lower cervical spine segments. The insignificant difference in the Cobb angles was attributed to length of time of continuous helmet wear attributed and sample size. Helmet wear can lead to morphometric alterations in cervical flexor/extensor musculature in females.

Occipitocervical measurements: correlation and consistency between multi-positional magnetic resonance imaging and dynamic radiographs

PURPOSE

To evaluate the reliability and validity of the multi-positional magnetic resonance imaging in measuring occipitocervical parameters using the standard cervical dynamic radiographs as a reference.

METHODS

Patients were included if they underwent both dynamic radiograph and cervical multi-positional MRI within a 2-week interval from January 2013 to December 2016. Twelve occipitocervical parameters were measured on both image modalities in all positions (neutral, flexion and extension): Posterior Atlanto-Dental Interval, Anterior Atlanto-Dental Interval (AADI), Dens-to-McRae distance, Dens-to-McGregor distance, Occipito-atlantal Cobb angle (C01 angle), Occipito-axis Cobb angle (C02 Cobb angle), Atlas-axis Cobb angle (C12 angle), Redlund-Johnell, Modified Ranawat, Clivus canal angle, Occiput inclination, and Occiput cervical distance. Pearson correlation and linear regression analysis were used to evaluate the correlation of both modalities for each parameter. A p value of < 0.05 was considered statistically significant.

RESULTS

Cervical images of 70 patients were measured and analyzed. There was a significant positive correlation between dynamic X-ray and multi-positional MRI for all parameters (p < 0.05) except AADI. Dens-to-McGregor distance and Redlund-Johnell parameter demonstrated a very strong correlation in the neutral position (r = 0.72, r = 0.79 respectively) and moderate to very strong correlation(r > 0.4) for Modified Ranawat, Clivus canal angle, C02 Cobb angle and C02 distance in all neck position. The intra-class correlation (ICC) of intra- and inter-observer showed good to excellent reliability, and ICCs were 0.67-0.98.

CONCLUSIONS

Multi-positional MRI can be a reliable imaging option for diagnosis of occipitocervical instability or basilar invagination compared to standard dynamic radiographs.

Thoracic spine disc degeneration, translation, and angular motion: An analysis using thoracic spine kinematic MRI (kMRI)

The aim of this study was to evaluate disc degeneration and kinematic changes in translation and angular motion of the thoracic spine using kinematic MRI (kMRI). 105 thoracic spine kMRI were analyzed from T4-5 to T11-12 using MRAnalyzer3. Translational and angular motion were evaluated in neutral, flexion, and extension positions. Thoracic disc height and disc degeneration grading were measured in the neutral position. Intraclass Correlation Coefficients were used to analyze agreement among three observers. The Friedman's test was used to analyze the difference in disc height, disc degeneration, translational motion, and angular motion. The Wilcoxon-signed rank test was used for post-hoc analysis with a Bonferroni correction. A p-value of 0.00625 was used to establish a statistically significant difference. Analysis using the Friedman's test revealed that translational motion, disc height, and disc degeneration were significantly different from T4-5 to T11-12 (p < 0.001). The T4-5 level showed the least translational motion, while the T10-11 showed the most translational motion. The lower thoracic level (T8-12) showed significantly more translational motion, more advanced disc degeneration, and greater disc height than the upper thoracic level (T4-8, p < 0.001). T11-12 showed the most advanced disc degeneration. There was a significant negative correlation between disc degeneration and translational motion at the upper thoracic level (p = 0.013). The lower thoracic region (below T8) had significantly more translational motion, more advanced disc degeneration, and greater disc height. This information is crucial in further understanding thoracic spinal kinematics and may contribute to determining the stopping level in fusion surgeries involving the thoracic spine.

Small C7-T1 lordotic angle and muscle degeneration at C7 level were independent radiological characteristics of patients with cervical imbalance: a propensity score-matched analysis

BACKGROUND CONTEXT

Cervical sagittal vertical axis (cSVA) of ≥40 mm is recognized as the key factor of poor health-related quality of life, poor surgical outcomes, and correction loss after surgery for cervical deformity. However, little is known about the radiological characteristics of patients with cSVA≥40 mm.

PURPOSE

The purpose of this study was to identify the radiological characteristics of patients with cervical imbalance.

DESIGN

Retrospective analysis of weight-bearing cervical magnetic resonance (MR) images.

PATIENT SAMPLE

Consecutive 1,500 MR images of symptomatic patients in weight-bearing position.

OUTCOME MEASURES

Cervical sagittal vertical axis, cervical alignment, cervical balance parameters (T1 slope, Co-C2 angle, C2-C7 angle, C7-T1 angle, neck tilt, and thoracic inlet angle), disc degeneration (Pfirmann and Suzuki classification), end plate degeneration (Modic change), spondylolisthesis (antero- and retrolisthesis), anteroposterior (AP) diameter of dural sac, cross-sectional area (CSA), and fat infiltration ratio of the transversospinalis muscles at C4 and C7 levels.

METHODS

Patients were divided into two groups: cSVA≥40 mm and cSVA<40 mm. Gender, age, and cervical alignment were analyzed. Subsequently, matched imbalance (cSVA≥40 mm) and control (<40 mm) groups were created using the propensity score to adjust for age, gender, and cervical alignment. Cervicothoracic angular parameters, disc degeneration, Modic change, spondylolisthesis, and degeneration of the transversospinalis muscles at C4 and C7 were compared. Variables with p<.05 were included in the multinomial logistic regression model to identify factors that relate to the cervical balance grouping.

RESULTS

The incidence of patients with cervical imbalance was 2.5% (37 patients). Those patients had a higher incidence of kyphosis, were older, and there were more male patients. In the matched imbalance group, the T1 slope was greater (p=.028), C7-T1 lordotic angle was smaller (p<.001), the number of anterolisthesis was greater (p=.012), and the fat infiltration ratio at C4 and C7 was higher (p=.023, 0.030) compared with the control. Logistic regression analysis showed that the C7-T1 angle (adjusted odds ratio [aOR]=0.592, p=.001) and fat infiltration ratio at C7 level (aOR=1.178, p=.030) were significant independent variables.

CONCLUSIONS

Smaller C7-T1 lordotic angle and severe muscle degeneration at C7 level were independent characteristics of patients with cervical imbalance.

Dynamic MRI in the evaluation of the spine: state of the art

INTRODUCTION

Degenerative disease of the spine is a generic term encompassing a wide range of different disease processes, which leads to spinal instability; traumatic/neoplastic events can accelerate this aging process. Therefore, the dynamic nature of the spine and its mobility across multiple segments is difficult to depict with any single imaging modality.

METHODS

A review of PubMed databases for articles published about kMRI in patients with cervical and lumbar spinal desease was performed. We focused on the physiopathological changes in the transition from supine to upright position in spine instability.

DISCUSSION

Until a few years ago, X-ray was the only imaging modality for the spine in the upright position. Of the imaging techniques currently available, MRI provides the greatest range of information and the most accurate delineation of soft-tissue and osseous structures. Conventional MRI examinations of the spine usually are performed in supine position, in functional rest, but the lumbar spine instability is often shown only by upright standing. This can result in negative findings, even in the presence of symptoms. Regardless, the final result is distorted. To overcome this limitation, Kinetic MRI (kMRI) can image patients in a weight-bearing position and in flexed and extended positions, thus revealing abnormalities that are missed by traditional MRI studies.

CONCLUSION

Despite some limitations, the upright MRI can be a complementary investigation to the traditional methods when there are negative results in conventional MRI in symptomatic patients or when surgical therapy is scheduled.

Can multi-positional magnetic resonance imaging be used to evaluate angular parameters in cervical spine? A comparison of multi-positional MRI to dynamic plain radiograph

PURPOSE

To test the reliability and validity of the multi-positional magnetic resonance imaging (MRI) in measuring cervical angular parameter using the standard dynamic cervical X-ray as a reference.

METHODS

All patients who underwent both cervical dynamic plain radiograph and multi-positional MRI on the same day between 2010 and 2016 were included in this study. The C2-7 angle and the segmental angles of the C2-3 to C6-7 segments were measured in all three positions (neutral, flexion, and extension) using multi-positional MRI and dynamic radiograph. The Pearson's correlation coefficients and linear regression analysis were used for statistical analysis.

RESULTS

46 patients were enrolled in this study. All angular parameters showed significant positive correlation between multi-positional MRI and dynamic X-ray (p < 0.05). The angle of C2-7 showed significantly positive correlation between multi-positional MRI and X-ray (r = 0.552-0.756). All segmental angles from C2-3 to C6-7 showed moderate correlation (r = 0.401-0.636). The linear regression analysis showed that C2-7 angles and all angular parameters had significant correlation between multi-positional MRI and dynamic X-ray (p < 0.05, R ² = 0.107-0.571).

CONCLUSIONS

The C2-7 angle and segmental cervical angles measured by multi-positional MRI were valid, and reliability substituted the dynamic X-ray measurement within the acceptable range of error. Multi-positional MRI can be used as a reliable tool for angular parameter measurement and detection of angular instability in the cervical spine.

Current concept in upright spinal MRI

Magnetic resonance imaging (MRI) is the established technique for evaluating the spine. Unfortunately, the supine position of the patient during conventional MRI scanning does not truly reflect the physiological forces experienced by the discoligamentous structures during normal upright posture and ambulation. Upright MRI is a relatively new technique that allows the patient to be scanned in several different weight-bearing positions, which may potentially demonstrate occult pathology not visualised in the supine position. The imaging technique and current clinical indications of upright spinal MRI would be discussed.

Diagnosis and treatment of hidden lesions in "mild" cervical spondylotic myelopathy patients with apparent symptoms

Patients with apparent symptoms of cervical spondylotic myelopathy (CSM) may only show a mild compressive lesion in ordinary magnetic resonance imaging (MRI). The aim of this study was to investigate the characteristics of CSM patients with "hidden" lesions on kinetic MRI and to determine an effective treatment.Thirty-one patients with obvious spinal cord compression only on kinetic MRI were included in our study. A variety of parameters were calculated from MRI of the cervical spine at different postures. The anterior cervical decompression and fusion (ACDF) procedure were used for treatment of CSM. To evaluate the effect of surgery, a further 31 age- and gender-matched ordinary CSM patients that received ACDF procedures were enrolled as the control group.The diameter of the cervical cord at the narrowest level in extension was significantly lower than that in the neutral posture (P < .01). The percentage of spinal cord compression was 34.6%. The diameter of the cervical canal at the narrowest level in the extension posture was significantly lower than that in the neutral posture (P < .01). The percentage of cervical canal stenosis was 43.6%. The anteroposterior diameter of the cervical canal in the case group was significantly lower than that in the control group (P < .01). However, the recovery rate of the Japanese Orthopaedic Association score at final follow-up was comparable between the case group and the control group (P = .53).Kinetic MRI is useful for the diagnosis of CSM with hidden lesions. ACDF is an effective procedure for treatment of CSM.

Kinematic Magnetic Resonance Imaging Assessment of the Degenerative Cervical Spine: Changes after Anterior Decompression and Cage Fusion

Study Design A prospective cohort study. Objective Decompression and fusion of cervical vertebrae is a combined procedure that has a high success rate in relieving radicular symptoms and stabilizing or improving cervical myelopathy. However, fusion may lead to increased motion of the adjacent vertebrae and cervical deformity. Both have been postulated to lead to adjacent segment pathology (ASP). Kinematic magnetic resonance imaging (MRI) has been increasingly used to evaluate range of motion (ROM) of the cervical spine and ASP. Our objective was to measure ASP, cervical curvature, and ROM of individual segments of the cervical spine using kinematic MRI before and 24 months after monosegmental cage fusion. Methods Eighteen patients who had single-level interbody fusion were included. ROM (using kinematic MRI) and degeneration, spinal stenosis, and cervical curvature were measured preoperatively and 24 months postoperatively. Results Using kinematic MRI, segmental motion of the cervical segments was measured with a precision of less than 3 degrees. The cervical fusion did not affect the ROM of adjacent levels. However, pre- and postoperative ROM was higher at the levels immediately adjacent to the fusion level compared with those further away. In addition, at 24 months postoperatively, the number of cases with ASP was higher at the levels immediately adjacent to fusion level. Conclusions Using kinematic MRI, ROM after spinal fusion can be measured with high precision. Kinematic MRI can be used not only in clinical practice, but also to study intervention and its effect on postoperative biomechanics and ASP of cervical vertebrae.

DynaCT angiography for the diagnosis of bilateral bow hunter's syndrome

We herein present a rare case of bilateral positional vertebrobasilar insufficiency secondary to mechanical obstruction of the V2 segment of the vertebral artery in a 71-year-old patient presenting with vertigo, occipital headache, tremors and respiratory irregularities. Two-dimensional digital subtraction angiography is the traditional diagnostic imaging standard but does not capture any peri-vascular bony or soft tissue abnormalities that are important to understand the three-dimensional pathophysiology. Intra-procedural cone-beam computed tomography (CT) is an increasingly used diagnostic adjunct, available in most modern angiographic suites that allows for the three-dimensional visualization of the vasculature as well as CT-like soft tissue visualization of its surrounding anatomy. In this case, we report the additional value of three-dimensional reconstructed cone-beam CT angiographic imaging that led to the successful diagnosis of bilateral positional vertebrobasilar disease. The patient subsequently received C4-C6 cervical decompression and fusion and remains symptom free at 1 year follow-up.

Kinetic magnetic resonance imaging analysis of spinal degeneration: a systematic review

OBJECTIVE

To evaluate the clinical use of kinetic magnetic resonance imaging (kMRI) in spinal degenerative diseases.

METHODS

A systematic search of PubMed, EMBASE and ISI databases for articles that had been published between January 1978 and February 2013 concerning patients who had undergone kMRI for spinal problems was performed. All selected patients had undergone kMRI in neutral, flexion, and extension weight-bearing positions. Evaluation of cervical and lumbar degeneration by kMRI was analyzed. kMRI showed significant reduction of mobility in cervical segments of patients with severe disc degeneration; in addition, it was more severely reduced in patients with severe cord compression than in those without it. In the cervical spine, it was found that although disc height, translational motion, and angular variation were significantly affected at the level of disc herniation, no significant changes were apparent in adjacent segments. kMRI also showed that lumbar degeneration is closely associated with disc degeneration, facet joint osteoarthritis and the pathological characteristics of the interspinous ligaments, ligamentum flavum and paraspinal muscles.

RESULTS

Eleven articles (4162 patients) fulfilled the inclusion criteria and were reviewed. It was found that kMRI is more specific and sensitive than conventional MRI regarding relating patients' symptoms to objective findings on imaging that demonstrate pathology and biomechanics. In the kinetic position, kMRI improves detection of disc herniation by 5.78%-19.46% and thus provides a new means of studying the biomechanical mechanism(s) in degenerative spines.

CONCLUSION

Kinetic MRI is effective for diagnosing, evaluating, and managing degenerative disease within the spine; however, it still has some limitations.

Positional Magnetic Resonance Imaging for People With Ehlers-Danlos Syndrome or Suspected Craniovertebral or Cervical Spine Abnormalities: An Evidence-Based Analysis

BACKGROUND

Ehlers-Danlos syndrome (EDS) is an inherited disorder affecting the connective tissue. EDS can manifest with symptoms attributable to the spine or craniovertebral junction (CVJ). In addition to EDS, numerous congenital, developmental, or acquired disorders can increase ligamentous laxity in the CVJ and cervical spine. Resulting abnormalities can lead to morbidity and serious neurologic complications. Appropriate imaging and diagnosis is needed to determine patient management and need for complex surgery. Some spinal abnormalities cause symptoms or are more pronounced while patients sit, stand, or perform specific movements. Positional magnetic resonance imaging (pMRI) allows imaging of the spine or CVJ with patients in upright, weight-bearing positions and can be combined with dynamic maneuvers, such as flexion, extension, or rotation. Imaging in these positions could allow diagnosticians to better detect spinal or CVJ abnormalities than recumbent MRI or even a combination of other available imaging modalities might allow.

OBJECTIVES

To determine the diagnostic impact and clinical utility of pMRI for the assessment of (a) craniovertebral or spinal abnormalities among people with EDS and (b) major craniovertebral or cervical spine abnormalities among symptomatic people.

DATA SOURCES

A literature search was performed using Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid Embase, and EBM Reviews, for studies published from January 1, 1998, to September 28, 2014.

REVIEW METHODS

Studies comparing pMRI to recumbent MRI or other available imaging modalities for diagnosis and management of spinal or CVJ abnormalities were reviewed. All studies of spinal or CVJ imaging in people with EDS were included as well as studies among people with suspected major CVJ or cervical spine abnormalities (cervical or craniovertebral spine instability, basilar invagination, cranial settling, cervical stenosis, spinal cord compression, Chiari malformation).

RESULTS

No studies were identified that met the inclusion criteria.

CONCLUSIONS

We did not identify any evidence that assessed the diagnostic impact or clinical utility of pMRI for (a) craniovertebral or spinal abnormalities among people with EDS or (b) major craniovertebral or cervical spine abnormalities among symptomatic people relative to currently available diagnostic modalities.