Biomechanical analysis of cervical spondylotic myelopathy: the influence of dynamic factors and morphometry of the spinal cord

Objective

Patients with cervical spondylotic myelopathy (CSM) have the same clinical symptoms that vary according to the degree of spinal cord compression and the cross-sectional cord shape. We used a three-dimensional finite element method (3D-FEM) to analyze the stress distributions of the spinal cord with neck extension under three cross-sectional cord shapes.

Methods

Experimental condition for the 3D-FEM spinal cord, ligamentum flavum, and anterior compression shape (central, lateral, and diffuse types) was established. To simulate neck extension, the spinal cord was extended by 20° and the ligamentum flavum was shifted distally according to movement of the cephalad lamina.

Results

The stress distribution in the spinal cord increased due to invagination of the ligamentum flavum into the neck extension. The range of stress distribution observed for the diffuse type was wider than for the central and lateral types. In addition, the stress distribution in the spinal cord was increased by the pincer movement of the ligamentum flavum and by the anterior compression of the spinal cord. The range of stress distribution observed for the diffuse type under antero-posterior compression was also wider than for the central and lateral types.

Conclusion

This simulation model showed that the clinical symptoms of CSM due to compression of the diffuse type may be stronger than for the central and lateral types. Therefore, careful follow-up is recommended for anterior compression of the spinal cord of diffuse type.     

颈椎黄韧带叠压症

目的：研究颈椎黄韧带叠压对脊髓压迫和影响。方法：对1994年以来,经后路颈椎管扩大成形术后随访的67例黄韧带叠压症,进行影像学、病理学和临床观察。结果：切除黄韧带、椎管扩大成形术后67例临床症状显著改善,优良率91％。结论：长期屈颈位工作和颈椎间盘等退变,使黄韧带过长、变韧、骨化,尤于颈椎过伸时,引起黄韧带叠压颈脊髓,是本症出现临床症状体征的原因。     

Thoracic spinal cord compression caused by hypopbosphataemic rickets: a case report and review of the world literature

Vitamin D resistant hypophosphataemic rickets is a rare cause of spinal cord compression. The compression is caused by a combination of thickening of the laminae and calcification of the ligamentum flavum. Modern imaging techniques including CT and MRI provide excellent detail of both the level and degree of compression. MRI is particularly useful for examining the rest of the spinal cord for areas of impending compression and for postoperative follow-up. With careful surgical decompression a full neurological recovery can be achieved.     

胸椎黄韧带骨化症的手术方法选择

目的 探讨不同类型胸椎黄韧带骨化症的手术方法.方法 1994年1月至2008年6月,手术治疗56例胸椎黄韧带骨化症患者,男40例,女16例;年龄43～76岁,平均58.1岁;病程3个月至5年,平均13.4个月.通过CT及MR检查观察骨化累及节段、分布特点、骨化巢形态、椎管狭窄程度以及脊髓压迫程度等.患者均采用全椎板整块或分解切除加后外侧融合术进行治疗.术后手术疗效采用日本骨科协会(Japanese Orthopaedic Association,JOA)评分进行评价.结果 术后患者均获得随访,随访时间18～70个月,平均25个月.JOA评分由术前平均(6.25±2.47)分(0～10分)改善至末次随访时(7.53±3.20)分(0～11分).术后恢复率为-116.7%～100%;56例中优25例,良20例,可6例,差5例,优良率80.4%.CT扫描显示根据骨化巢形态胸椎黄韧带骨化分为外侧型6例,弥漫型17例,厚结节型33例.6例外侧型患者采用整块全椎板切除法,手术优良率为83.3%(5/6);弥漫型患者中,采用整块全椎板切除法11例、椎板分解切除法6例,手术优良率分别为81.8%(9/11)、83.3%(5/6);厚结节型患者中,采用整块全椎板切除法4例、椎板分解切除法29例,手术优良率分别为50%(2/4)、82.8%(24/29),并各有2例术后疗效差.结论 全椎板整块切除加后外侧融合适用于治疗外侧型、弥漫型胸椎黄韧带骨化,而全椎板分解切除法加后外侧融合适用于厚结节型胸椎黄韧带骨化.     

Flexion Model Simulating Spinal Cord Injury Without Radiographic Abnormality in Patients With Ossification of the Longitudinal Ligament: The Influence of Flexion Speed on the Cervical Spine

Abstract

Background/Objective: It is suspected that the speed of the motion of the spinal cord under static compression may be the cause of spinal cord injury (SCI). However, little is known about the relationship between the speed of the motion of the spinal cord and its stress distributions. The objective was to carry out a biomechanical study of SCI in patients with ossification of the longitudinal ligament without radiologic evidence of injury.

Methods: A 3-dimensional finite element spinal cord model was established. After the application of static compression, the model underwent anterior flexion to simulate SCI in ossification of the longitudinal ligament patients without radiologic abnormality. Flexion of the spine was assumed to occur at 1 motor segment. Flexion angle was 5°, and flexion speeds were 0.5°/s, 5°/s, and 50°/s. Stress distributions inside of the spinal cord were evaluated.

Results: Stresses on the spinal cord increased slightly after the application of 5° of flexion at a speed of 0.5°/s. Stresses became much higher at a speed of 5°/s and increased further at 50°s.

Conclusions: The stress distribution of the spinal cord under static compression increased with faster flexion speed of the spinal cord. High-speed motion of the spinal cord under static compression may be one of the causes of SCI in the absence of radiologic abnormality.     

Cervical ossification of the posterior longitudinal ligament: Biomechanical analysis of the influence of static and dynamic factors

Objective

Cervical myelopathy due to ossification of the posterior longitudinal ligament (OPLL) is induced by static factors, dynamic factors, or a combination of both. We used a three-dimensional finite element method (3D-FEM) to analyze the stress distributions in the cervical spinal cord under static compression, dynamic compression, or a combination of both in the context of OPLL.

Methods

Experimental conditions were established for the 3D-FEM spinal cord, lamina, and hill-shaped OPLL. To simulate static compression of the spinal cord, anterior compression at 10, 20, and 30% of the anterior–posterior diameter of the spinal cord was applied by the OPLL. To simulate dynamic compression, the OPLL was rotated 5°, 10°, and 15° in the flexion direction. To simulate combined static and dynamic compression under 10 and 20% anterior static compression, the OPLL was rotated 5°, 10°, and 15° in the flexion direction.

Results

The stress distribution in the spinal cord increased following static and dynamic compression by cervical OPLL. However, the stress distribution did not increase throughout the entire spinal cord. For combined static and dynamic compression, the stress distribution increased as the static compression increased, even for a mild range of motion (ROM).

Conclusion

Symptoms may appear under static or dynamic compression only. However, under static compression, the stress distribution increases with the ROM of the responsible level and this makes it very likely that symptoms will worsen. We conclude that cervical OPLL myelopathy is induced by static factors, dynamic factors, and a combination of both.     

Stress analysis of the cervical spinal cord: Impact of the morphology of spinal cord segments on stress

Objective: Although there are several classifications for cervical myelopathy, these do not take differences between spinal cord segments into account. Moreover, there has been no report of stress analyses for individual segments to date.

Methods: By using the finite element method, we constructed 3-dimensional spinal cord models comprised of gray matter, white matter, and pia mater of the second to eighth cervical vertebrae (C2–C8). We placed compression components (disc and yellow ligament) at the front and back of these models, and applied compression to the posterior section covering 10%, 20%, 30%, or 40% of the anteroposterior diameter of each cervical spinal cord segment.

Results: Our results revealed that, under compression applied to an area covering 10%, 20%, or 30% of the anteroposterior diameter of the cervical spinal cord segment, sites of increased stress varied depending on the morphology of each cervical spinal cord segment. Under 40% compression, stress was increased in the gray matter, lateral funiculus, and posterior funiculus of all spinal cord segments, and stress differences between the segments were smaller.

Conclusion: These results indicate that, under moderate compression, sites of increased stress vary depending on the morphology of each spinal cord segment or the shape of compression components, and also that the variability of symptoms may depend on the direction of compression. However, under severe compression, the differences among the cervical spinal segments are smaller, which may facilitate diagnosis.     

颈脊髓后方致压三维运动下生物力学分析

目的研究颈黄韧带病变对颈脊髓后方致压,颈脊髓所受压力与致压深度、颈脊柱三维运动的关系,为探讨黄韧带病变所致颈脊髓病的发病机制提供运动学、生物力学依据。方法采用5具新鲜成人尸体颈脊柱标本(C2～C7)通过后方C4～5间骨窗伸入直径9．58 mm的半球形致压物模拟颈椎黄韧带病变时对颈脊髓后方所形成的压迫。实验对颈脊髓由后向前致压,致压深度分别为椎管中矢径的10％～60％、依次增加10％。分别测量各运动位置,不同致压深度下,颈脊膜脊髓后方所受压力。结果 (1)随致压深度的增加颈脊髓脊膜后方所受压力明显加大,两者呈非线性关系。(2)颈脊髓后方致压时,测得颈脊髓脊膜后方所受压力,在前屈后伸运动中,20％～60％各相邻致压深度两两比较,差异有统计学意义(P<0．05);在中立位、左右侧弯、左右旋转运动中运动中 30％～60％各相邻致压深度两两比较,差异有统计学意义(P<0．05);(3)左右侧弯、左右旋转时, 相同致压深度,两侧侧弯、旋转各自比较差异无统计学意义(P>0．05)。予以合并取均数分别命名为侧弯30°位、旋转15°位。(4)在各运动位置,不同致压深度颈脊髓脊膜后方所受压力变化比较, 30％～60％致压深度时,前屈30°位>侧弯30°位>后伸30°位>中立位>旋转15°位。10％～20％致压深度时,侧弯30°位>后伸30°位>前屈30°中立位>旋转15°位。结论颈脊髓后方所受压力与致压深度和颈脊柱运动有着密切联系。所受压力随致压深度增加而增大,深度超出30％临界值后有统计学意义。相同致压深度颈脊髓后方所受压力大小随运动方向不同而改变,前屈后伸运动对颈脊髓的压力影响最大。     

Ossification of the ligamentum flavum induced by bone morphogenetic protein. An experimental study in mice.

Ossification of the ligamentum flavum and secondary spinal-cord compression were produced experimentally in mice by implanting bone morphogenetic protein (BMP) in the lumbar extradural space. The ligamentum flavum became hypertrophied and ossified, and protruded into the spinal canal. The thickness of the ossified ligament increased gradually with time, leading to compression and deformation of the spinal cord which showed various degrees of degeneration. Demyelination occurred in the posterior and lateral white columns and neuronal loss or chromatolysis in the grey matter. The pathological findings in the experimental animals closely resemble those found in the human disease and suggest that BMP may be a causative factor of ossification of the ligamentum flavum in man. This experimental model may be useful for the study of myelopathy caused by gradual spinal-cord compression.     

下颈椎损伤改良Moore分类的临床应用研究

目的：探讨改良Moore分类法在下颈椎损伤中的临床应用。方法：2006年8月至2010年3月收治下颈椎损伤患者200例,男165例,女35例;年龄19-88岁,平均52岁。应用下颈椎损伤改良Moore分类全面地描述下颈椎损伤的状态,颈椎损伤严重程度（稳定性）量化评分与有否神经症状表现相结合,根据骨折类型和稳定性、脊髓或神经根受压损伤情况、韧带损伤后的稳定程度及其他参考因素进行分类诊治,选择治疗方法。其中伴有脊髓神经损伤者130例（ASIA评分：A级6例,B级13例,C级43例,D级68例）,不伴有脊髓神经损伤者70例。对伴有脊髓神经损伤的下颈椎损伤患者,根据ASIA评分进行疗效评定;对不伴有脊髓神经损伤的患者,根据影像学检查对颈椎的序列和高度进行观察。结果：前、左、右侧和后柱均损伤35例;前柱损伤33例;前、后柱均损伤90例;前、左侧和后柱均损伤5例;前、右侧和后柱均损伤3例;前、左侧和右侧柱均损伤3例;前、右侧柱损伤2例;前、左侧柱损伤5例;后柱损伤12例;左侧柱损伤7例;右侧柱损伤5例。200例患者中手术治疗98例,非手术治疗102例（其中可以手术而患者家属要求非手术治疗39例）。完全性脊髓损伤患者中3例行手术后脊髓功能无恢复迹象,ASIA分级无变化,但其肢体麻木、疼痛等症状有不同程度的缓解,另3例未手术患者脊髓功能及肢体症状均无变化。不完全性脊髓损伤患者手术后脊髓功能均有一定程度恢复,ASIA评分平均提高1．2级。未手术的不完全性脊髓损伤患者非手术治疗后ASIA评分平均提高0.3级。不伴有脊髓神经损伤者手术后经影像学检查显示均恢复了颈椎的正常序列和高度。结论：根据改良Moore分类法,稳定性量化评分值大于等于4分有下颈椎不稳可能,需要手术治疗,分值越大,手术指征越明显,若伴有脊髓或神经根受压损伤表现者则有绝对手术指征。稳定性量化评分为3分且伴有脊髓或神经根受压损伤表现者一般也有手术指征。稳定性量化评分为3分不伴有脊髓或神经根受压损伤表现者或3分以下者均不需要手术治疗。应用改良Moore分类法有利于下颈椎损伤患者的临床规范化、标准化诊治,以获得较满意的疗效。     

Apoptosis of neurons and oligodendrocytes in the spinal cord of spinal hyperostotic mouse (<Emphasis Type="Italic">twy/twy</Emphasis>): possible pathomechanism of human cervical compressive myelopathy

Introduction  

Cervical compressive myelopathy is the most serious complication of cervical spondylosis or ossification of the posterior longitudinal ligament (OPLL) and the most frequent cause of spinal cord dysfunction. There is little information on the exact pathophysiological mechanism responsible for the progressive loss of neural tissue in the spinal cord of such patients. In this study, we used the spinal hyperostotic mouse (twy/twy) as a suitable model of human spondylosis, and OPLL to investigate the cellular and molecular changes in the spinal cord. Mutant twy/twy mouse developed ossification of the ligamentum flavum at C2–C3 and exhibited progressive paralysis.     

Calcification des ligaments jaunes du rachis cervical chez l’antillais

Objective. Calcification of the ligamentum flavum at the cervical spine is an uncommon condition reported mainly in Japanese patients. We describe the clinical manifestations, imaging study findings, and outcomes in six cases seen in the French West Indies. Patients and methods. We retrospectively reviewed the medical charts of six patients admitted to an orthopedics department for spinal cord compression shown upon computed tomography to be caused by calcification of the ligamentum flavum. There were five women and one man, mean age at admission was 71.7 years (range, 64-79 years), and all six patients were black. Results. Five patients had cervical myelopathy and one was asymptomatic. All five symptomatic patients had cervical spinal stenosis, explaining the rapid symptom onset (within six and a half months) and severe motor loss. Computed tomography reconstruction in the sagittal plane ruled out ossification of the ligamentum flavum. Magnetic resonance imaging of the neck failed to demonstrate the calcifications but was useful in evaluating the severity of the spinal cord compression. One patient had articular chondrocalcinosis in both knees and another had calcifications in the basal ganglia. Surgical decompression by the posterior route was performed in two patients and was effective in both, whereas two of the three symptomatic patients who did not have surgery experienced worsening neurological loss. Analysis of the operative specimens from the two surgically treated patients showed a mixture of calcium pyrophosphate dihydrate crystals and apatite microcrystals. Conclusion. Calcification of the ligamentum flavum is probably underrecognized in blacks. This condition causes severe neurological loss. Imaging studies provide the diagnosis. The pathogenesis remains unclear.     

Infolding of the ligamentum flavum: a cause of spinal cord compression after reduction of cervical facet injuries

Controversy exists regarding management of cervical facet injuries. Previous literature has focused on associated disc herniations reported to cause neurologic injury upon reduction. Although rupture of the ligamentum flavum has been noted with these injuries, its clinical significance has not been examined. In this case report, we present two patients in whom neurologic deterioration occurred due to infolding of the torn ligamentum flavum with spinal cord compression after reduction of cervical facet subluxations. Both had large flaps of ligamentum flavum arising from the caudal lamina which infolded upon reduction and became trapped between the spinal cord and cephalad lamina. Both patients regained normal motor function after removal of the pathologically infolded ligamentum. Neither patient had a disc herniation, hypotensive/anemic/hypoxic event, or epidural hematoma that could have otherwise been causative of the neurologic deficit. Pathologic infolding of ligamentum flavum, in addition to extruded disc herniations, should be recognized as another potential cause for spinal cord compression with reduction of cervical facet injuries. In particular, if there is a long flap of flavum arising from the caudal lamina poised to become entrapped in the spinal canal with reduction and the patient has a congenitally narrow canal, the surgeon should consider removal of the ligamentum flavum prior to reduction.     

Unusual appearance of an en plaque meningioma of the cervical spinal canal. A case report and literature review

STUDY DESIGN: A case report of a patient with cervical spinal cord and nerve root compression caused by a meningioma en plaque together with calcification of the posterior longitudinal ligament is presented,with a review of the literature. OBJECTIVE: To present the diagnosis of a calcified dural meningioma en plaque, with extradural extension into the ligamentum flavum, in a woman with cervical myelopathy and neuropathy. SUMMARY OF BACKGROUND DATA: This case demonstrates that the cervical spine can be involved in dural meningioma en plaque with calcifications, in a manner mimicking ossification of the ligamentum flavum, which has never been previously reported. METHODS: A patient presenting with cervical cord and nerve root compression caused by ossification of the posterior longitudinal ligament and a concurrent calcified dural meningioma en plaque was treated surgically and has made a gradual recovery. Imaging studies,surgical findings, and histopathologic evaluation were analyzed to support the diagnosis. RESULTS: At surgery, ossification of the posterior longitudinal ligament was noted, along with a calcified lesion involving the posterior cervical dura and the adjacent ligamentum flavum. A calcified meningioma was diagnosed by histopathologic examination of the dural-based lesion. CONCLUSION: Although previously not described, the diagnosis of calcified dural meningioma en plaque should be considered in all patients presenting with spinal cord and/or nerve root compression,even at cervical levels. Although ossification of the posterior longitudinal ligament and ossification of the ligamentum flavum are more common etiologies of partially circumferential spinal calcification, dural-based meningiomas with extension into the surrounding ligaments demand early recognition because they can be associated with a poorer prognosis.     

Diffusion tensor imaging of somatosensory tract in cervical spondylotic myelopathy and its link with electrophysiological evaluation

Background and contextAbnormal somatosensory evoked potential (SEP) (ie, prolonged latency) has been associated with poor surgical prognosis of cervical spondylotic myelopathy (CSM).PurposeTo further characterize the extent of microstructural damage to the somatosensory tract in CSM patients using diffusion tensor imaging (DTI).Study design/settingRetrospective study.Patient sampleA total of 40 volunteers (25 healthy subjects and 15 CSM patients).Outcome measuresClinical, electrophysiological, and radiological evaluations were performed using the modified Japanese Orthopedic Association (mJOA) scoring system, SEP, and cord compression ratio in anatomic magnetic resonance (MR) images, respectively. Axial diffusion MR images were taken using a pulsed gradient, spin-echo-echo-planar imaging sequence with a 3-T MR system. The diffusion indices in different regions of the spinal cord were measured.MethodsComparison of diffusion indices among healthy and myelopathic spinal cord with intact and impaired SEP responses were performed using one-way analysis of variance.ResultsIn healthy subjects, fractional anisotropy (FA) values were higher in the dorsal (0.73±0.11) and lateral columns (0.72±0.13) than in the ventral column of white matter (0.58±0.10) (eg, at C4/5) (p<.05). FA was dramatically dropped in the dorsal (0.54±0.16) and lateral columns (0.51±0.13) with little change in the ventral column (0.48±0.15) at the compressive lesions in CSM patients. There were no significant differences in the mJOA scores or cord compression ratios between CSM patients with or without abnormal SEP. However, patients with abnormal SEP showed an FA decrease in the dorsal column cephalic to the lesion (0.56±0.06) (ie, at C1/2, compared with healthy subjects [0.66±0.02]), but the same decrease was not observed for those without a SEP abnormality (0.67±0.02).ConclusionSpinal tracts were not uniformly affected in the myelopathic cervical cord. Changes in diffusion indices could delineate focal or extensive myelopathic lesions in CSM, which could account for abnormal SEP. DTI analysis of spinal tracts might provide additional information not available from conventional diagnostic tools for prognosis of CSM.     

脊髓型颈椎病脊髓前动脉CT血管造影观察

目的通过颈脊髓前动脉CT血管造影观察脊髓型颈椎病患者的颈脊髓前动脉。方法 2009年2月~2012年8月,采用64排螺旋CT机对17例脊髓型颈椎病患者行脊髓前动脉造影,观察脊髓前动脉阻塞和梗阻,以及MRI T2高信号与脊髓前动脉的关系。结果 2例脊髓型颈椎病并发脊髓前动脉综合征患者脊髓前动脉造影显示颈脊髓前动脉于病变部位中断;其余15例脊髓型颈椎病患者CT脊髓前动脉造影均显影,未见明显中断。结论 64排CT脊髓前动脉造影术可以显像脊髓型颈椎病的颈脊髓前动脉。脊髓型颈椎病脊髓前动脉不易被压迫中断。脊髓型颈椎病MRI图像T2高信号与颈脊髓前动脉无直接关系。     

腰椎管狭窄症的影像学诊断

目的：探讨腰椎管狭窄症的X线、CT及MRI诊断价值。方法：分析130例临床诊断和影像学检查征象典型的腰椎管狭窄症的病例资料。男83例,女47例;年龄27～75岁,平均43.5岁。所有病例均行CT检查,其中23例行X线检查,57例行MRI扫描。结果：腰椎管狭窄位于L3,4水平25例,L4,5水平48例,L5S1水平57例。CT显示椎体后缘、椎板、下关节突骨质增生46例,椎板上下关节突肥大7例,黄韧带钙化、骨化13例,椎体向前滑脱5例,侧隐窝狭窄24例,椎间孔狭窄35例。MRI显示椎间盘突出伴黄韧带肥厚23例,黄韧带对称性肥厚18例,广泛多节段增生肥厚9例,局限性黄韧带肥厚7例。结论：继发性腰椎管狭窄症的最常见原因是退变。传统X线检查有很大的局限性,CT和MRI具有多方位成像和分辨率高的优点,但在韧带骨化上MRI难于显示,而CT能很好的显示韧带钙化与骨化及骨质改变,腰椎管狭窄症检查应该首选CT。     

The narrowing of the lumbar spinal canal during loaded MRI: the effects of the disc and ligamentum flavum

Load and activity changes of the spine typically cause symptoms of nerve root compression in subjects with spinal stenosis. Protrusion of the intervertebral disc has been regarded as the main cause of the compression. The objective was to determine the changes in the size of the lumbar spinal canal and especially those caused by the ligamentum flavum and the disc during loaded MRI. For this purpose an interventional clinical study on consecutive patients was made. The lumbar spines in 24 supine patients were examined with MRI: first without any external load and then with an axial load corresponding to half the body weight. The effect of the load was determined through the cross-sectional areas of the spinal canal and the ligamentum flavum, the thickness of ligamentum flavum, the posterior bulge of the disc and the intervertebral angle. External load decreased the size of the spinal canal. Bulging of the ligamentum flavum contributed to between 50 and 85% of the spinal canal narrowing. It was concluded that the ligamentum flavum, not the disc had a dominating role for the load induced narrowing of the lumbar spinal canal, a finding that can improve the understanding of the patho-physiology in spinal stenosis.     

脊髓型颈椎病患者颈椎动态MRI检查价值与安全性分析

目的 探究脊髓型颈椎病（CSM）患者颈椎动态MRI（DMRI）检查的价值与安全性。方法 2019年1月—2021年9月，87例CSM患者于苏州大学附属第二医院行颈椎DMRI检查。在矢状面前屈、后伸和中立位MRI T2加权像上观察是否存在脊髓隐匿性压迫。记录患者在DMRI检查前后的症状及体征、疼痛视觉模拟量表（VAS）评分。以DMRI检查后原有症状或体征加重或出现新的症状与体征考虑为短期内脊髓损伤加重。结果 87例患者中17例（19.5%）存在脊髓隐匿性压迫，其中2例在前屈位MRI检查中发现，15例在后伸位MRI检查中发现。DMRI检查后73例患者无明显不适，出现颈肩部不适5例，轻度头晕4例，呼吸不畅、轻度胸闷3例，恶心2例，DMRI检查后VAS评分无下降。85例患者无脊髓神经损伤加重，2例脊髓钳夹伴MRI T2加权像高信号改变患者检查后症状、体征加重。结论 颈椎DMRI是一种相对安全的补充检查，19.5%（17/87）的CSM患者在屈、伸位MRI检查中可发现脊髓隐匿压迫，脊髓钳夹损伤伴MRI T2加权像高信号改变的CSM患者应慎行DMRI检查。     

Increased spinal cord movements in cervical spondylotic myelopathy

Background context

Magnetic resonance imaging (MRI) is a very useful diagnostic test for cervical spondylotic myelopathy (CSM) because it can identify degenerative changes within the spinal cord (SC), disclose the extent, localization, and the kind of SC compression, and help rule out other SC disorders. However, the relationships between changes in cerebrospinal fluid (CSF) flow, cord motion, the extent and severity of spinal canal stenosis, and the development of CSM symptoms are not well understood.

Purpose

To evaluate if changes in the velocity of CSF and SC movements provide additional insight into the pathophysiological mechanisms underlying CSM beyond MRI observations of cord compression.

Study design

Prospective radiologic study of recruited patients.

Patient sample

Thirteen CSM subjects and 15 age and gender matched controls.

Outcome measures

Magnetic resonance imaging measures included CSF and SC movement. Cervical cord condition was assessed by the Japanese Orthopaedic Association (JOA) score, compression ratio (CR), and somatosensory evoked potentials (SSEPs) of the tibial and ulnar nerves.

Methods

Phase-contrast imaging at the level of stenosis for patients and at C5 for controls and T₂-weighted images were compared with clinical findings.

Results

Cerebrospinal fluid velocity was significantly reduced in CSM subjects as compared with controls and was related to cord CR. Changes in CSF velocity and cord compression were not correlated with clinical measures (JOA scores, SSEP) or the presence of T₂ hyperintensities. Spinal cord movements, that is, cord displacement and velocity in the craniocaudal axis, were increased in CSM patients. Increased SC movements (ie, total cord displacement) both in the controls and CSM subjects were associated with altered spinal conduction as assessed by SSEP.

Conclusions

This study revealed rather unexpected increased cord movements in the craniocaudal axis in CSM patients that may contribute to myelopathic deteriorations in combination with spinal canal compression. Understanding the relevance of cord movements with respect to supporting the clinical CSM diagnosis or disease monitoring requires further long-term follow-up studies.