Missed cervical disc bulges diagnosed with kinematic magnetic resonance imaging

Utility of cervical dynamic magnetic resonance imaging for evaluating patients with cervical myelopathy: a retrospective study

STUDY DESIGN

Retrospective observational study.

PURPOSE

This study aimed to evaluate the utility of cervical dynamic magnetic resonance imaging (dMRI) in the assessment of cervical canal stenosis.

OVERVIEW OF LITERATURE

Cervical spondylotic myelopathy has been intricately linked to both static and dynamic narrowing of the cervical spinal canal. Traditional MRI with the neck in a neutral position fails to identify the dynamic changes and may lead to misdiagnosis. Cervical dMRI is a promising tool for evaluating cervical myelopathy, enabling clinicians to assess spinal cord compression, segmental instability, and alterations in range of motion, often missed on conventional imaging.

METHODS

A retrospective analysis was conducted on 369 patients with symptoms of cervical myelopathy assessed using cervical dMRI. After assessing the subaxial cervical spine at each disc level (C3-T1), significant changes in the degree of central canal stenosis were determined. The appearance and extent of hyperintense lesions on T2-weighted sequences were also noted.

RESULTS

Overall, 653/1,845 (35.39%) disc levels showed an increase in stenosis grade on extension MRI, with 168/653 (25.72%) and 180/653 (27.56%) disc levels changing from grades 0/1 to grades 2 and 3, respectively. Moreover, 120/369 (32.52%) patients showed a mean increase of 1.55±0.75 levels of compression on extension MRI when compared to neutral MRI. A fresh-appearing hyperintense lesion was observed in 79 (4.28%) disc levels on flexion MRI, which was not visualized on neutral MRI.

CONCLUSIONS

Cervical dMRI may help surgeons plan for surgery, discuss the prognosis with the patient, and safeguard themselves from medico-legal issues arising from improper or missed diagnosis and treatment.

Utility of a 2D kinematic HASTE sequence in magnetic resonance imaging assessment of adjacent segment degeneration following anterior cervical discectomy and fusion

OBJECTIVES

To evaluate a dynamic half-Fourier acquired single turbo spin echo (HASTE) sequence following anterior cervical discectomy and fusion (ACDF) at the junctional level for adjacent segment degeneration comparing dynamic listhesis to radiographs and assessing dynamic cord contact and deformity during flexion-extension METHODS: Patients with ACDF referred for cervical spine MRI underwent a kinematic flexion-extension sagittal 2D HASTE sequence in addition to routine sequences. Images were independently reviewed by three radiologists for static/dynamic listhesis, and compared to flexion-extension radiographs. Blinded assessment of the HASTE sequence was performed for cord contact/deformity between neutral, flexion, and extension, to evaluate concordance between readers and inter-modality agreement. Inter-reader agreement for dynamic listhesis and impingement grade and inter-modality agreement for dynamic listhesis on MRI and radiographs was assessed using the kappa coefficient and percentage concordance.

RESULTS

A total of 28 patients, mean age 60.2 years, were included. Mean HASTE acquisition time was 42 s. 14.3% demonstrated high grade dynamic stenosis (> grade 4) at the adjacent segment. There was substantial agreement for dynamic cord impingement with 70.2% concordance (kappa = 0.62). Concordance across readers for dynamic listhesis using HASTE was 81.0% (68/84) (kappa = 0.16) compared with 71.4% (60/84) (kappa = 0.40) for radiographs. Inter-modality agreement between flexion-extension radiographs and MRI assessment for dynamic listhesis across the readers was moderate (kappa = 0.41; 95% confidence interval: 0.16 to 0.67).

CONCLUSIONS

A sagittal flexion-extension HASTE cine sequence provides substantial agreement between readers for dynamic cord deformity and moderate agreement between radiographs and MRI for dynamic listhesis.

CLINICAL RELEVANCE STATEMENT

Degeneration of the adjacent segment with instability and myelopathy is one of the most common causes of pain and neurological deterioration requiring re-operation following cervical fusion surgery.

KEY POINTS

• A real-time kinematic 2D sagittal HASTE flexion-extension sequence can be used to assess for dynamic listhesis, cervical cord, contact and deformity. • The additional kinematic cine sequence was well tolerated and the mean acquisition time for the 2D HASTE sequence was 42 s (range 31-44 s). • A sagittal flexion-extension HASTE cine sequence provides substantial agreement between readers for dynamic cord deformity and moderate agreement between radiographs and MRI for dynamic listhesis.

Dynamic evaluation of the cervical spine by kinematic MRI in patients with cervical spinal cord injury without fracture and dislocation

BACKGROUND

The pattern of changes in the cervical spine and the spinal cord and their dynamic characteristics in patients with cervical spinal cord injury without fracture and dislocation remain unclear. This study aimed to evaluate the dynamic changes in the cervical spine and spinal cord from C2/3 to C7/T1 in different positions by using kinematic magnetic resonance imaging in patients with cervical spinal cord injury without fracture and dislocation. This study was approved by the ethics committee of Yuebei People's Hospital.

METHODS

Using median sagittal T2-weighted images for 16 patients with cervical spinal cord injury without fracture and dislocation who underwent cervical kinematic MRI, the anterior space available for the cord, spinal cord diameter, posterior space available for the cord from C2/3 to C7/T1, and Muhle's grade were determined. The spinal canal diameter was calculated by adding the anterior space available for the cord, spinal cord diameter, and posterior space available for the cord.

RESULTS

The anterior space available for the cord, posterior space available for the cord, and spinal canal diameters at C2/3 and C7/T1 were significantly higher than those from C3/4 to C6/7. Muhle's grades at C2/3 and C7/T1 were significantly lower than those at the other levels. Spinal canal diameter was lower in extension than in the neutral and flexion positions. In the operated segments, significantly lesser space was available for the cord (anterior space available for the cord + posterior space available for the cord), and the spinal cord diameter/spinal canal diameter ratio was higher than those in the C2/3, C7/T1, and non-operated segments.

CONCLUSION

Kinematic MRI demonstrated dynamic pathoanatomical changes, such as canal stenosis in different positions, in patients with cervical spinal cord injury without fracture and dislocation. The injured segment had a small canal diameter, high Muhle's grade, low space available for the cord, and high spinal cord diameter/spinal canal diameter ratio.

High reliability and accuracy of dynamic magnetic resonance imaging in the diagnosis of cervical Spondylotic myelopathy: a multicenter study

BACKGROUND

Cervical spondylotic myelopathy (CSM) is a critical condition that results in significant neurologic deterioration. An accurate diagnosis is essential for determining its outcome and prognosis. The pathology is strongly associated with dynamic factors; therefore, dynamic magnetic resonance (MR) image could be crucial to accurately detect CSM. However, very few studies have evaluated the reliability and accuracy of dynamic MR in CSM. In this study, we aimed to compare intra- and interobserver reliabilities and accuracy of dynamic MR in detecting CSM using sagittal MR scans of the neck in the flexed, neutral, and extended position.

METHODS

Out of 131 patients who underwent surgical treatments for CSM, 107 were enrolled in this study. The patient underwent three-types of sagittal MR scans that were obtained separately in different neck positions (neutral, flexion, and extension postures). The MR scans of the cervical spine were evaluated independently by three spine professionals, on the basis of tabled questionnaires. For accuracy, we performed a receiver operator characteristic analysis, and the overall discriminating ability of each method was measured by calculating the area under the ROC curve. The Cohen's kappa coefficient and the Fleiss-generalized kappa coefficient was used to the inter- and intra-observer reliabilities.

RESULTS

The intraobserver reliability (using the Cohen's kappa coefficient) and interobserver reliability (using the Fless kappa coefficient) were respectively 0.64 and 0.52 for the neutral sagittal MR. The accuracy of neutral sagittal MR in detecting CSM was 0.735 (95% CI, 0.720 to 0.741) while that of extension sagittal MRI was 0.932 (96% CI, 0.921 to 0.948).

CONCLUSIONS

Dynamic MR significantly showed better diagnostic reliability and accuracy in detecting CSM compared to conventional MR. In particular, extension MR scans could provide a more accurate diagnosis than other images.

The Radial Bulging and Axial Strains of Intervertebral Discs during Creep Obtained with the 3D-DIC System

Creep-associated changes in disc bulging and axial strains are essential for the research and development of mechano-bionic biomaterials and have been assessed in various ways in ex vivo creep studies. Nonetheless, the reported methods for measurement were limited by location inaccuracy, a lack of synchronousness, and destructiveness. To this end, this study focuses on the accurate, synchronous, and noninvasive assessment of bugling and strains using the 3D digital image correlation (3D-DIC) system and the impact of creep on them. After a preload of 30 min, the porcine cervical discs were loaded with different loads for 4 h of creep. Axial strains and lateral bulging of three locations on the discs were synchronously measured. The three-parameter solid model and the newly proposed horizontal asymptote models were used to fit the acquired data. The results showed that the load application reduced disc strains by 6.39% under 300 N, 11.28% under 400 N, and 12.59% under 500 N. Meanwhile, the largest protrusion occurred in the middle of discs with a bugling of 1.50 mm, 1.67 mm, and 1.87 mm. Comparison of the peer results showed that the 3D-DIC system could be used in ex vivo biomechanical studies with reliability and had potential in the assessment of the mechanical behavior of novel biomaterials. The phenomenon of the largest middle protrusion enlightened further the strength of spinal implants in this area. The mathematical characterizations of bulging and strains under different loads yielded various model parameters, which are prerequisites for developing implanted biomaterials.

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.

Clinical feasibility of 2D dynamic sagittal HASTE flexion-extension imaging of the cervical spine for the assessment of spondylolisthesis and cervical cord impingement

PURPOSE

To assess the utility of a 2D dynamic HASTE sequence in assessment of cervical spine flexion-extension, specifically (1) comparing dynamic spondylolisthesis to radiographs and (2) assessing dynamic contact upon or deformity of the cord.

METHODS

Patients with a dynamic flexion-extension sagittal 2D HASTE sequence in addition to routine cervical spine sequences were identified. Static and dynamic listhesis was first determined on flexion-extension radiographs reviewed in consensus. Blinded assessment of the dynamic HASTE sequence was independently performed by 2 radiologists for (1) listhesis and translation during flexion-extension and (2) dynamic spinal cord impingement (cord contact or deformity between neutral, flexion and extension).

RESULTS

32 scans in 32 patients (9 males, 23 females) met inclusion criteria acquired on 1.5 T (n = 15) and 3 T (n = 17) scanners. The mean acquisition time was 51.8 s (range 20-95 seconds). Dynamic translation was seen in 14 patients on flexion-extension radiographs compared to 12 (reader 1) and 13 (reader 2) patients on HASTE, with 90.6 % agreement (K = 0.83; p = 0.789). In all cases dynamic listhesis was ≤3 mm translation with one patient showing dynamic listhesis in the range 4-6 mm. Four cases (13 %) demonstrated deformity of the cord between flexion-extension, not present in the neutral position. For cord impingement there was strong inter-reader agreement (K = 0.93) and the paired sample Wilcoxon signed rank test found no significant difference between the impingement scores of the two readers (p = 0.787).

CONCLUSIONS

A sagittal dynamic flexion-extension HASTE sequence provides a rapid addition to standard MRI cervical spine protocols, which may useful for assessment of dynamic spondylolisthesis and cord deformity.

Feasibility and Safety of Cervical Kinematic Magnetic Resonance Imaging in Patients with Cervical Spinal Cord Injury without Fracture and Dislocation

Objective

To evaluate the feasibility and safety of cervical kinematic MRI (KMRI) in patients with cervical spinal cord injury without fracture and dislocation (CSCIWFD).

Methods

This was a single‐institution case‐only study. Patients with CSCIWFD were enrolled in our institution from February 2015 to July 2019. Cervical radiography and CT were performed first to exclude cervical tumors, and major fracture or dislocation. Then neutral static and kinematic (flexion and extension) MRI was performed for patients who met the inclusion criteria under the supervision of a spinal surgeon. Any adverse events during the KMRI examination were recorded. Patients received surgical or conservative treatment based on the imaging results and patients’ own wishes. The American Spinal Injury Association impairment scale (AIS) grade and the Japanese Orthopedic Association (JOA) score were evaluated on admission, before KMRI examination, and after KMRI examination. For the surgical patients, AIS grade and JOA score were evaluated again 1 week after the operation. The JOA scores were compared among different time points using the paired t‐test.

Results

A total of 16 patients (12 men and 4 women, mean age: 51.1 [30–73] years) with CSCIWFD were included in the present study. Clinical symptoms included facial trauma, neck pain, paraplegia, paresthesia, hyperalgesia, sensory loss or weakness below the injury level, and dyskinesia. On admission, AIS grades were B for 2 cases, C for 5, and D for 9. A total of 14 patients underwent neutral, flexion, and extension cervical MRI examination; 2 patients underwent neutral and flexion examination because they could not maintain the position for a prolonged duration. No patient experienced deterioration of neurological function after the examinations. The AIS grades and JOA scores evaluated post‐examination were similar to those evaluated pre‐examination (P > 0.05) and significantly higher than those on admission (P < 0.05). A total of 12 patients received surgical treatment, 11 of whom underwent anterior cervical discectomy and interbody fusion and 1 underwent posterior C3/4 fusion with lateral mass screws. The remaining 4 patients were offered conservative therapy. None of the patients experienced any complications during the perioperative period. The AIS grade did not change in most surgical patients, except that 1 patient changed from grade C to D 1 week after the operation. The JOA score 1 week after surgery was significantly higher than those on admission and around examination for the surgical patients (P < 0.05).

Conclusion

Cervical KMRI is a safe and useful technique for diagnosis of CSCIWFD, which is superior to static cervical MRI for therapeutic decision‐making in patients with CSCIWFD.

Measurement of in vivo spinal cord displacement and strain fields of healthy and myelopathic cervical spinal cord

OBJECTIVE

Cervical myelopathy (CM) is a common and debilitating form of spinal cord injury caused by chronic compression; however, little is known about the in vivo mechanics of the healthy spinal cord during motion and how these mechanics are altered in CM. The authors sought to measure 3D in vivo spinal cord displacement and strain fields from MR images obtained during physiological motion of healthy individuals and cervical myelopathic patients.

METHODS

Nineteen study participants, 9 healthy controls and 10 CM patients, were enrolled in the study. All study participants had 3T MR images acquired of the cervical spine in neutral, flexed, and extended positions. Displacement and strain fields and corresponding principal strain were obtained from the MR images using image registration.

RESULTS

The healthy spinal cord displaces superiorly in flexion and inferiorly in extension. Principal strain is evenly distributed along the spinal cord. The CM spinal cord displaces less than the healthy cord and the magnitude of principal strain is higher, at the midcervical levels.

CONCLUSIONS

Increased spinal cord compression during cervical myelopathy limits motion of the spinal cord and increases spinal cord strain during physiological motion. Future studies are needed to investigate how treatment, such as surgical intervention, affects spinal cord mechanics.

Dynamic Cervical Cord Compression Post-laminectomy Visualized by Flexion-extension Magnetic Resonance Imaging: Case Report

Flexion-extension magnetic resonance imaging (MRI) in the cervical spine is not universally used in cervical spine surgery. However, flexion-extension MRIs can identify previously undetected spinal stenosis, improve surgical decision-making, and maybe a better tool to evaluate postoperative outcomes. One uncommon complication after laminectomy, to treat cervical spinal stenosis, is muscle weakness due to subsequent dynamic cord compression by posterior paraspinal musculature. We present a case of a 41-year-old male who underwent posterior cervical decompression and developed subsequent neurological deficits and muscle weakness. MRI with neutral cervical positioning did not show spinal stenosis necessitating surgical intervention. However, given the patient’s increasing tetraparesis, flexion-extension MRI was performed and it revealed significant spinal stenosis in both flexion and extension positions due to spondylosis and compression from paraspinal muscles. This case demonstrates the utility of flexion-extension MRI in identifying pathologies such as cord compression by paraspinal muscles. Exclusive use of a neutral-position MRI scan may not be sufficient to provide proper diagnoses for cervical spine pathologies. Flexion-extension MRI should be considered when the degree of neurological symptoms outweighs minimal or absent pathology seen on neutral-position sagittal MRI.

Dynamic changes in the reflex exam of patients with sub-axial cervical stenosis

Though dynamic changes in the physical exam of patients being evaluated for cervical spine pathology have been reported, there is limited information on the prevalence and clinical features associated with reflex changes in a population undergoing surgical evaluation for cervical spine pathology. Fifty-one patients with at least grade 1 cervical stenosis on MRI underwent initial surgical evaluation for cervical spine pathology. All patients received complete neurologic examinations including dynamic reflex testing in three positions (neck neutral, extended, and flexed) by 2 spine surgeons. The average age was 58.7 years (range, 34-80), with 28 (55%) patients being male. Stenosis at the symptomatic levels was grade 1 in 18 patients (35%), grade 2 in 11 (21%), and grade 3 in 22 (43%). Twenty-one patients (41%) had a dynamic change in reflex exam. The most common change in reflex exam was seen in the Hoffman's reflex with 14 patients (28%). Patients with grade 3 stenosis were more likely to have a static Hoffman's reflex (64%) compared with grade 1 (17%) and grade 2 (18%) (p < 0.05). Patients with grade 3 stenosis had a higher rate of either a static or dynamic Hoffman's reflex (82%) compared with grade 1 (44%) (p < 0.05), but there was no difference between grade 3 and grade 2 (64%) (Table 2). Dynamic changes in reflex exam are commonly seen in patients being evaluated for symptomatic cervical stenosis. The routine neurologic exam can be supplemented with dynamic reflex testing, especially in cases where clinical history or imaging is concerning for cervical myelopathy.

A Dynamic Magnetic Resonance Imaging Study of Changes in Severity of Cervical Spinal Stenosis in Flexion and Extension

Objective

To evaluate changes in the severity of cervical spinal stenosis (CSS) in flexion and extension and determine whether the rate of change with motion varied with severity.

Methods

The study included 92 symptomatic patients with a mean age of 57.80±10.41, who underwent cervical spine dynamic magnetic resonance imaging. The severity of stenosis was evaluated using a semi-quantitative CSS score, ranging from 0 (no spinal stenosis) to 18 (severe stenosis). Radiological evaluation included flexion, neutral, and extension measurements, as determined by the C2–C7 Cobb angle. The severity of stenosis was represented by the total CSS score. The total CSS score in flexion, neutral, and extension positions was compared using repeated measures one-way analysis of variance. The change rate of stenosis per angle motion (CRSPAM) was defined as change in total CSS score divided by change in Cobb angle. The correlation of CRSPAM with severity of stenosis, represented by total CSS score in neutral position, was evaluated using Pearson correlation analysis.

Results

The total CSS score was significantly higher in extension (6.04±2.68) than in neutral position (5.25±2.47) (p<0.001), and significantly higher in neutral than in flexion position (4.40±2.45) (p<0.001). The CRSPAM was significantly and positively correlated with total CSS score in neutral position in the flexion-extension range (r=0.22, p=0.04) and flexion-neutral range (r=0.27, p=0.01).

Conclusion

In symptomatic CSS patients, the radiological severity of stenosis increases with extension and decreases with flexion. In patients with CSS, the rate of variation in spinal stenosis increases with increased severity.

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.

Dynamic MRI to quantify musculoskeletal motion: A systematic review of concurrent validity and reliability, and perspectives for evaluation of musculoskeletal disorders

Purpose

To report evidence for the concurrent validity and reliability of dynamic MRI techniques to evaluate in vivo joint and muscle mechanics, and to propose recommendations for their use in the assessment of normal and impaired musculoskeletal function.

Materials and methods

The search was conducted on articles published in Web of science, PubMed, Scopus, Academic search Premier, and Cochrane Library between 1990 and August 2017. Studies that reported the concurrent validity and/or reliability of dynamic MRI techniques for in vivo evaluation of joint or muscle mechanics were included after assessment by two independent reviewers. Selected articles were assessed using an adapted quality assessment tool and a data extraction process. Results for concurrent validity and reliability were categorized as poor, moderate, or excellent.

Results

Twenty articles fulfilled the inclusion criteria with a mean quality assessment score of 66% (±10.4%). Concurrent validity and/or reliability of eight dynamic MRI techniques were reported, with the knee being the most evaluated joint (seven studies). Moderate to excellent concurrent validity and reliability were reported for seven out of eight dynamic MRI techniques. Cine phase contrast and real-time MRI appeared to be the most valid and reliable techniques to evaluate joint motion, and spin tag for muscle motion.

Conclusion

Dynamic MRI techniques are promising for the in vivo evaluation of musculoskeletal mechanics; however results should be evaluated with caution since validity and reliability have not been determined for all joints and muscles, nor for many pathological conditions.

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.

Myelopathy

Myelopathy is an inclusive term, referring to pathology leading to a neurologic deficit related to the spinal cord. The clinical diagnosis of myelopathy requires a detailed history and physical examination to define the clinical syndrome. Neuroimaging is indicated in most instances of new-onset myelopathy. It is indicated also when the worsening of a myelopathy is unexplained. Advances in neuroimaging have proved to play a vital role in diagnosis. Appropriate diagnosis and treatment are dependent upon an adequate imaging evaluation to establish the presence of mechanical stability, extrinsic spinal cord compression, or an intramedullary lesion. The most frequent etiology of myelopathy is related to degenerative disease of the spine from osteophyte or extruded disc material causing compression of the spinal cord in the cervical or thoracic spine. The next common etiologies are spinal cord compression due to extradural masses caused by metastatic disease to bone or blunt trauma. In these cases, emergency imaging should be performed to assess the nature of the lesion causing the myelopathy and plan the most appropriate treatment. Also urgent imaging should be performed when an abscess in the spinal canal is suspected. Less urgent is imaging of primary neoplasms of the meninges, roots, or spinal cord, as well as noninfectious inflammatory processes, such as multiple sclerosis, and neurodegenerative, vascular, nutritional, or idiopathic disorders leading to myelopathy. Although a survey of the entire spinal cord can be performed with imaging, it is more appropriate to define from the clinical findings what levels of the spine and spinal cord should be imaged. This approach helps limit the likelihood of false-positive imaging findings that may encourage needless attempts to fix what is not broken. Similarly, the most appropriate imaging study and protocol should be selected in order to provide a timely and accurate diagnosis. To do so requires detailed knowledge regarding the strengths and limitations of the multiple imaging modalities available. This chapter outlines an approach to proper study selection based on the likely etiology of myelopathy from the clinical findings. Chapters 33-39 cover these disorders in detail.

Kinematic Magnetic Resonance Imaging for Evaluation of Disc-Associated Cervical Spondylomyelopathy in Doberman Pinschers

BACKGROUND

The dynamic component of disc-associated cervical spondylomyelopathy (DA-CSM) currently is evaluated using traction magnetic resonance imaging (MRI), which does not assess changes in flexion and extension of the cervical vertebral column. In humans with cervical spondylotic myelopathy, kinematic MRI is used to identify dynamic compressions.

HYPOTHESIS/OBJECTIVES

To evaluate the feasibility and utility of kMRI in Doberman Pinschers with DA-CSM using a novel positioning device. We hypothesized that kMRI would identify compressive lesions not observed with neutral positioning and change the dimensions of the spinal cord and cervical vertebral canal.

ANIMALS

Nine client-owned Doberman Pinschers with DA-CSM.

METHODS

Prospective study. After standard MR imaging of the cervical spine confirmed DA-CSM, dogs were placed on a positioning device to allow imaging in flexion and extension. Morphologic and morphometric assessments were compared between neutral, flexion, and extension images.

RESULTS

Flexion was associated with improvement or resolution of spinal cord compression in 4/9 patients, whereas extension caused worsening of compressions in 6/9 patients. Extension identified 6 new compressive lesions and was significantly associated with dorsal and ventral compression at C5-C6 (P = .021) and C6-C7 (P = .031). A significant decrease in spinal cord height occurred at C6-C7 from neutral to extension (P = .003) and in vertebral canal height at C5-C6 and C6-C7 from neutral to extension (P = .011 and .017, respectively).

CONCLUSIONS AND CLINICAL IMPORTANCE

Our results suggest that kMRI is feasible and provides additional information beyond what is observed with neutral imaging, primarily when using extension views, in dogs with DA-CSM.

Influence of T1 Slope on the Cervical Sagittal Balance in Degenerative Cervical Spine: An Analysis Using Kinematic MRI

STUDY DESIGN

A retrospective kinematic magnetic resonance imaging (kMRI) study.

OBJECTIVE

To evaluate the utility of kMRI in determining the relationship between cervical sagittal balance and TI alignment.

SUMMARY OF BACKGROUND DATA

Thoracic inlet parameters play an important role in cervical spine sagittal balance. However, most of the literature is based on lower resolution cervical X-rays or CT scans in the supine position.

METHODS

Cervical spine kMRI of 83 patients with degenerative cervical spine conditions (20-68 yr of age) was analyzed for: (1) cervical spine parameters: C2-C7 angle, C2-C7 sagittal vertical axis (SVA), cranial tilt, and cervical tilt; and (2) T1 parameters: thoracic inlet angle (TIA), T1 slope, and neck tilt (NT). Multiple logistic regression analysis and Pearson correlation coefficients were performed.

RESULTS

The mean TIA, T1 slope, and NT were 78.0, 33.2, and 44.8°, respectively. The mean C2-7 angle, SVA of C2-C7, cervical tilt, and cranial tilt were -15.4°, 22.0 mm, 18.1°, and 15.1°, respectively. The ratio of cervical:cranial tilt was maintained as 55:45%. A significant correlation was found between the C2-C7 angle and T1 slope (r = 0.731), TIA and C2-C7 angle (r = 0.406), cervical tilt with C2-C7 angle (r = 0.671), T1 slope with TIA (r = 0.429), TIA with neck tilt (r = 0.733), TIA with cervical tilt (r = 0.377), SVA C2-C7 with cervical tilt (r = -0.480), SVA C2-C7 with cranial tilt (r = 0.912), and C2-7 SVA with the ratio of cranial tilt to cervical tilt (r = 0.694).

CONCLUSION

An individual with a large T1 slope required large cervical lordosis to preserve physiologic sagittal balance of the cervical spine. Cranial tilt was the cervical parameter most strongly correlated with SVA C2-C7, and thus may be a good parameter to assess decompensation of cervical sagittal balance.

LEVEL OF EVIDENCE

3.

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.

Effect of disc degeneration on lumbar segmental mobility analyzed by kinetic magnetic resonance imaging

STUDY DESIGN

Retrospective radiographical study.

OBJECTIVE

To define the relationship between the grade of disc degeneration and the motion of the lumbar spine by using kinetic magnetic resonance imaging.

SUMMARY OF BACKGROUND DATA

Disc degeneration is common after middle age. Lumbar instability has generally been recognized as a potential risk factor of low back pain. However, correlations between the grade of disc degeneration and the motion of the lumbar spine need more investigation.

METHODS

Kinetic magnetic resonance imaging was performed in 162 patients with symptomatic low back pain without prior history of surgery. The lumbar intervertebral discs were graded by spine surgeons according to the degenerative grading system (grades I-V). Translational motion and angular variation were measured at each segment from L1-L2 through L5-S1. The relationship between the degree of lumbar disc degeneration and extent of lumbar spine mobility was analyzed.

RESULTS

The translational motion in discs with grade I through IV increased gradually, but decreased with grade V. Compared with other less degenerative grades, grade V discs had significantly decreased total intervertebral translational motion (P < 0.05). The angular variation in discs with grade I through IV was fairly constant, but decreased with grade V. Compared with other degenerative grades (I-IV), grade V discs had significantly decreased total intervertebral translational motion (P < 0.05). For less degenerative grades I and II discs, the L2-L3 and L3-L4 segmental units contributed the majority of total angular mobility of the spine. However, for the severely degenerated segments, grade V discs, the contributions of the L2-L3 and L3-L4 significantly decreased (P < 0.01).

CONCLUSION

As disc degeneration developed from the normal to an increasingly severe stage, the motion of lumbar spine progressed from the normal stage to an unstable phase with higher mobility and finally to an ankylosed stage where stability was increased.

LEVEL OF EVIDENCE

3.