Forward shifting of posterior dural sac during flexion cervical magnetic resonance imaging in Hirayama disease: An initial study on normal subjects compared to patients with Hirayama disease

Objective

Forward shifting of the posterior cervical dural sac is the most important sign in diagnosing Hirayama disease but can also be seen in normal subjects, causing potential diagnostic dilemma. We aim to explore the degree of forward displacement of posterior dural sac in normal subjects compared to that with Hirayama disease.

Materials and methods

50 healthy male teenagers and 3 patients with Hirayama disease were recruited into the control group and patient group, respectively. MR imaging of the cervical spine was performed in both neutral and flexion positions for all subjects, with the following parameters measured: maximal distance of forward shifting of posterior dural sac, dimension of dural sac and spinal cord.

Results

Forward shifting of the posterior cervical dural sac was depicted in 46% of normal subjects upon flexion position but without associated cord compression due to intrinsic expansion of the spinal canal volume. This intrinsic compensatory mechanism was inadequate in diseased patients leading to cord compression with significant increment in ratio of anteroposterior diameter of forward displacement of posterior dural wall/anteroposterior diameter of spinal canal (“x/y”), and decrement in ratio of anteroposterior diameter of spinal cord/perpendicular transverse diameter of spinal cord (“a/b”).

Conclusion

Depicting of forward shifting of posterior dural sac alone on flexion position cannot reliably diagnose Hirayama disease, which should be established only if there is forward shifting of posterior dural sac, plus increased ratio of x/y and decreased ratio of a/b on flexion position from associated mass effect on the spinal cord.     

Classification system based on kinematic MR imaging in cervical spondylitic myelopathy.

BACKGROUND AND PURPOSEFunctional myelographic studies are often used to evaluate the dynamic changes of the cervical spinal canal during flexion and extension. The purposes of this study were to use kinematic MR imaging to assess the dynamic changes of the cervical spine in patients at different stages of degenerative disease and to describe a classification system based on static and dynamic factors in the pathogenesis of cervical spondylitic myelopathy.METHODSEighty-one patients with different stages (I-IV) of degenerative disease of the cervical spine were examined with MR imaging. In the neutral position (0 degrees) and at maximum flexion and extension, spinal stenosis was classified for each segment according to the following grading system: 0 = normal, 1 = partial obliteration of the anterior or posterior subarachnoid space, 2 = complete obliteration of the anterior or posterior subarachnoid space, and 3 = cervical cord compression or displacement.RESULTSAt flexion and extension, the prevalence of spinal stenosis and cervical cord impingement increased as the stage of degenerative disease progressed. With regard to a pincer effect (anterior and posterior cord impingement) and cord encroachment at multiple segments, statistically significant differences were observed at stages III and IV as compared with stages I and II. Significant increase in cord impingement was seen in 22 (27%) of 81 patients at extension, as compared with four (5%) of 81 patients at flexion.CONCLUSIONRegardless of the stage of degenerative disease and grade of spinal stenosis at the neutral position (0 degrees), cervical spinal motion may contribute to the development of cervical spondylitic myelopathy.     

Are magnetic resonance flexion views useful in evaluating the cervical spine of patients with rheumatoid arthritis?

Objective. To determine whether MR imaging in flexion adds value relative to imaging in the neutral position with respect to displaying involvement of the subarachnoid space, brainstem and spinal cord. Design and patients. T1-weighted MR images of the cervical spine in 42 rheumatoid arthritis patients with cervical spine involvement were obtained and analyzed prospectively. We assessed changes between images obtained in the neutral position and following active flexion, especially horizontal atlantoaxial and subaxial motion, presence or absence of brainstem compression, subarachnoid space involvement at the atlantoaxial and subaxial level and the cervicomedullary angle. Vertical atlantoaxial subluxation and the amount of pannus were correlated with motion and change in subarachnoid space. Results. The flexion images showed horizontal atlantoaxial motion in 21 patients and subaxial motion in one patient. The flexion view displayed brainstem compression in only one patient. Involvement of the subarachnoid space increased at the atlantoaxial level in eight (19%) patients (P=0.004) and at the level below C2 in five (12%) patients (P=0.03). There were no patients with a normal subarachnoid space in neutral position and compression in the flexed position. The cervicomedullary angle changed significantly with flexion. Vertical atlantoaxial subluxation and the amount of pannus did not show a significant correlation with motion or subarachnoid space involvement. Conclusion. MR imaging in the flexed position shows a statistically significant narrowing of the subarachnoid space at the atlantoaxial level and below C2. Cord compression is only observed on flexion views if the subarachnoid space in neutral position is already decreased. MR imaging in the flexed position might be useful, since subarachnoid space involvement may be an indicator for the development of neurologic dysfunction. Received: 15 June 1999 Revision requested: 29 July 1999, 20 September 1999 Revision received: 2 October 1999 Accepted: 26 October 1999     

Dynamics of the spinal cord: an analysis of functional myelography by CT scan

Summary The antero-posterior movement of the spinal cord with flexion and extension of the neck was analyzed in order to clarify the mechanism of spinal cord compression in cases with postoperative spinal deformity, and to contribute to the improvement of the surgical methods of conventional laminectomy. The control subjects were 47 cases without cervico-thoracic neurological symptoms, who underwent CT myelography in flexion and extension of the neck; the cervical spinal cord was examined in 27 of these cases and the thoracic cord in the other 20. CT myelography was also carried out in 16 patients with cervical myelopathy and in 5 patients after posterior decompression surgery (suspension laminotomy). CT sections in flexion and extension of the neck were analyzed for 1) change of configuration of the dura mater and the spinal cord, and 2) antero-posterior shift of the spinal cord in the subarachnoid space. In the control subjects, the configuration of the dura mater was slightly flattened at C5/6, C6 and C6/7 in extension of the neck. The cervical spinal cord shifted anteriorly in flexion and posteriorly in extension of the neck, and was flattened at the midcervical level in flexion in the control subjects. There was a statistically significant correlation between the location of the spinal cord and the adjacent intervertebral angles at the levels of C4, C5 and C6. These results were compared with the results from the 16 patients with cervical myelopathy and 5 patients after suspension laminotomy. The thoracic spinal cord shifted anteriorly in neck flexion and posteriorly in extension, especially at upper thoracic level. In order to avoid spinal cord compression due to anterior shift of the spinal cord caused by postoperative kyphosis, it is necessary to employ the surgical method which can prevent postoperative kyphotic deformity.Presented at the 17th World Congress of the Société Internationale de Chirurgie Orthopédique et de Traumatologie (SICOT 87), Munich, FRG, 16–21 August 1987     

Pre- and postoperative MR imaging of the craniocervical junction in rheumatoid arthritis

Ten patients with severe chronic rheumatoid arthritis with atlantoaxial subluxation were examined with conventional radiography and MR imaging of the cervical spine before and at an average of 6 months after posterior occipitocervical fusion. Periodontoid pannus formation was revealed by MR preoperatively in nine patients, all with mobile horizontal atlantoaxial subluxation. Compression of the medulla and/or upper cervical cord, due to subluxation and periodontoid pannus bulging into the spinal canal, was seen in seven patients. After the stabilizing surgery the periodontoid pannus had decreased in size in all patients with preoperative pannus. This reduction in the pannus seems to be the result of the atlantoaxial immobility achieved by the posterior fusion. Postoperatively, three patients had some remaining compression of the medulla and/or cord secondary to immobile subluxation, while the pannus posterior to the odontoid process had disappeared. Artifacts from the surgical stainless steel fixation material were confined to the posterior part of the neck on short TR/short TE MR images and did not interfere with the evaluation of the periodontoid region and the anterior part of the medulla/cervical cord. We found that flexion and extension lateral radiographs, combined with sagittal short TR/short TE MR images in the neutral position, enable preoperative evaluation of patients with rheumatoid arthritis in the cervical spine. Postoperative MR should be performed only if there are residual or new symptoms.     

Cervical spine fractures in ankylosing spondylitis: MR findings

Purpose: The purpose of this study is to evaluate the MR findings in patients with long-term ankylosing spondylitis (AS) and acute cervical spine fractures. Materials and methods: The magnetic resonance imaging (MRI) studies of five patients with AS and acute cervical spine fractures were retrospectively reviewed for the presence of cervical spine instability, spinal cord compression, and epidural hematoma. Results: Spinal fractures were unstable in all five patients. Three patients had neurological symptoms and abnormal signal within the spinal cord. All patients with neurological deficits had epidural hematomas posterior to the dural sac. Conclusion: MRI is useful for assessment of the integrity of intervertebral disks and spinal ligaments and, therefore, of the instability of the spinal fracture. MRI is mandatory in patients with neurological symptoms, especially in those with a symptom-free interval and those with neurological deterioration after established spinal cord injury, when suspicion for epidural hematoma is high. Electronic Publication     

Hirayama disease: MR diagnosis.

We report the MR findings in two cases of Hirayama disease, a kind of cervical myelopathy related to flexion movements of the neck. In flexion MR studies, we can see the striking and pathognomonic picture of anterior shifting of posterior dura at the lower cervical spinal canal. In nonflexion studies, we find that asymmetric cord atrophy, especially at the lower cervical cord, though subtle, is highly suggestive of Hirayama disease. When it is seen, a flexion MR study is warranted to prove this diagnosis.     

Hirayama disease in unilateral and bilateral forms-3 case reports

Hirayama disease is a benign, nonprogressive motor neuron disease affecting the upper limbs. It is secondary to an abnormal anterior displacement of the posterior dura with secondary compression of the lower cervical spinal cord. It should be suspected in young male patients with a chronic history of weakness and atrophy involving the upper extremities followed by clinical stability in few years. The involvement is usually unilateral but may be bilateral. MR imaging is the best way to make the diagnosis but it necessitates the use of both extension/flexion and post contrast studies.     

Delayed neurologic deterioration in the patient with spinal trauma: role of MR imaging.

PURPOSE: To 1) correlate spinal MR features and modes of clinical presentation associated with symptomatic neurologic deterioration following longstanding spinal trauma; 2) correlate degree of neurologic deficit with spinal MR appearance in these patients; and 3) determine the relationship between new symptoms and ongoing cord compression. METHODS: Retrospective examination of MR images, and correlation with clinical data, in 94 consecutive patients. RESULTS: Sixty-seven patients presented with either an increase in degree of myelopathy or ascending neurologic level. Spinal cord atrophy (43%), syrinx (41%), and cord compression (24%) were found most frequently. Whereas in patients with complete motor and sensory deficit cord atrophy was the most frequent finding (52%), 75% of patients with useful motor function had normal spinal cords. There was a significant association (P less than .05) between cord compression and the MR findings of cord atrophy and myelomalacia, whereas a normal cord was over twice as frequent in patients without spinal cord compression. MR imaging led to an active change in management in 15% of patients, with improvement following surgery in all operated cases. CONCLUSION: Although syrinx is a frequent, and treatable cause of delayed neurologic deterioration, MR will frequently show other abnormalities such as ongoing cord compression. MR imaging should be performed urgently in all patients with new symptoms to enable early treatment to prevent irreversible loss of function.     

MRI运动扫描分析脊髓型颈椎病的脊髓致压因素

目的 探讨动态运动MR扫描揭示椎管内退变结构对脊髓的动力性致压作用，提高脊髓型颈椎病的早期诊断作用。方法 在开放式MR机上，通过颈椎的多角度分次扫描、关节运动扫描和MR透视扫描3种方法检查60例颈椎病患者，分别观察退变结构在常规自然位、前屈位和后伸位时对脊髓的致压作用。结果 (1)椎管内退变结构在颈椎伸屈活动时常形成较自然位更加严重的脊髓压迫征象，而且它们间还有“动态叠加作用”。(2)椎间盘突出(29例)、椎体骨赘增生、椎体错位滑脱(7例)、后纵韧带增厚(36例)等在前屈位时常较自然位形成更明显的混合性致压物。(3)34例患者的退变黄韧带在后伸位时皱折凸入椎管，凸入黄韧带又可与脊髓前方致压物形成“钳夹效应”而严重压迫脊髓(9例)。(4)14例患者在伸屈活动时加重椎体的错位滑脱。(5)硬膜囊前间隙在前屈位(41例)和后伸位(16例)时较自然位变小；囊后间隙后伸位变小见于43例，前屈位对其影响较小(4例)。结论 颈椎病患者动态MR扫描不仅从形态上而且能从致病作用上显示出早期的、潜在性的、动态性的脊髓致压因素，从而起到较静态扫描更早期地对脊髓型颈椎病的诊断作用。     

Prediction of neurologic outcome in acute spinal cord injury: the role of CT and MR.

PURPOSE: 1) To determine whether MR appearances of the spinal cord in acute trauma correlate with clinical prognosis, and 2) to identify other MR and CT prognostic factors in acute spinal trauma. METHODS: Retrospective evaluation of MR, CT, and clinical examinations in 32 acute spinal trauma patients examined between 1987 and 1990. RESULTS: All 21 patients with abnormal spinal cords on MR had complete motor paralysis at presentation, compared to only three of 11 patients with normal cords. Whereas cord transection and hemorrhagic contusion had poor prognoses, 73% of patients with cord edema and 100% of patients with normal cord had useful motor function at outcome. At follow-up MR, areas of cord contusion developed into cysts, while edema resolved, leaving residual areas of myelomalacia. Associated spinal fractures, ligament injury, and cord compression were associated (P < .05) with a worse prognosis. Spondylotic changes were a significant risk factor for spinal cord injury, mediated by cord compression. CONCLUSIONS: MR and CT are valuable techniques for quantifying injury and predicting prognosis in acute spinal trauma.     

平山病的MRI诊断价值

目的:探讨平山病的MR表现和价值,认识平山病的临床特征和可能的发病机制.方法:5例经临床确诊的平山病患者均隐匿起病,病变局限于上肢远端肌肉,4例单侧上肢前臂受累,1例双侧不对称性受累.5例患者均行颈椎X线平片检查,及颈髓常规自然体位MR平扫及屈颈位平扫 增强扫描.所有患者均进行常规生化检查,脑脊液检查,肌电图检查和肌肉活检.结果:5例患者普通X线检查4例可见颈椎生理曲度变直,自然体位MR平扫3例有低位脊髓萎缩变扁(萎缩水平在颈5-胸1,最明显在颈6水平),2例萎缩的脊髓内信号异常.曲颈MR检查时,除了可见自然体位MR的表现外,5例患者均可见特征性的颈髓前移、变平,硬脊膜向前移位,硬脊膜外腔增宽,4例患者在增宽的硬膜外腔均可见流空血管信号,增强扫描5例患者在增宽的硬脊膜外腔均可见强化的静脉丛.结论:平山病的MR表现存在一定的特征性,MR屈曲位平扫 增强扫描对平山病的诊断及其发病机制的理解有重要的价值.     

MR imaging of recent spinal trauma

Proper therapeutic management of acute spinal trauma depends considerably on the assessment of the condition of the underlying spinal cord and the relative stability of the surrounding bony architecture. A series of 14 patients who were examined by magnetic resonance (MR) imaging following spinal trauma is presented. Comparison of information gained by MR with that obtained by conventional CT indicates that MR is useful in assessing spinal cord compression, traumatic disk pathology, and post-traumatic intramedullary abnormalities. Computed tomography is more accurate in detecting posterior neural arch fractures and in assessing the number of displaced fragments.     

Cervical degenerative disease at flexion-extension MR imaging: prediction criteria

PURPOSE: To determine if there are any neutral-position imaging criteria that can help predict functional cord impingement at flexion-extension cervical magnetic resonance (MR) imaging. MATERIALS AND METHODS: Sixty-two patients with cervical degenerative disease were evaluated with regard to the dynamic changes of canal stenosis at flexion-extension MR imaging. Functional cord impingement was considered if the cord was impinged or more impinged after neck flexion or extension. Selection criteria for neutral-position MR imaging, such as cervical curvature, canal space, degenerative stage, intramedullary high signal intensity on T2-weighted images, and resting instability, were evaluated for their ability to predict functional cord impingement at flexion-extension MR imaging (Fisher exact test, logistic regression analysis). RESULTS: MR images in 19 (31%) of 62 patients showed functional cord impingement at extension MR imaging compared with images in two (3%) patients at flexion MR imaging. Statistically significant differences were found for the criteria cervical degeneration stage (P <.001) and spinal canal space (P =.037) for predicting functional cord impingement at extension MR imaging. In contrast, no significant differences were found among selection criteria for flexion MR imaging. Probabilities of functional cord impingement at extension MR imaging were calculated with different combinations of degenerative stages and canal spaces. Probability could increase to 79% if the patient had both stabilization degeneration (disk protrusion or osteophytic formation with hypertrophy of the ligamentum flavum) and C7 canal space of 10 mm or less. CONCLUSION: None of the selection criteria evaluated in this study has the ability to predict functional cord impingement at flexion MR imaging; however, prediction of impingement at extension MR imaging can increase from 31% to 79% if proper criteria are selected.     

平山病的MRI诊断

目的：探讨平山病（hirayama disease）的MR影像学表现,提高对该病的认识。方法通过查阅相关文献,回顾性分析2例临床已确诊的平山病MR自然位和过屈位影像表现,观察其低位颈髓的动态变化,并与健康自愿者的同条件扫描影像相比较,总结平山病的MR影像学表现。结果①自然位：曲线多有异常,下段颈髓萎缩,髓内可有异常信号,有失连接现象;②过屈位：所有患者均出现颈髓前移、变扁,硬脊膜后有月牙形、集簇状异常信号影;③2例患者强化检查示过屈位脊膜后异常信号影有强化;④志愿者自然位扫描显示颈椎曲度自然,颈髓粗细均匀,不存在失连接现象,过屈位脊膜后无异常信号影。结论MR颈椎检查特别是过屈位扫描能够显示出平山病的特征性影像学改变,对于平山病的早期诊断具有重大价值。     

上颈椎疾病手术方法选择

 目的 分析上颈椎疾病的病因、寰枢椎复位和脊髓受压情况,探讨上颈椎疾病的手术方法选择.方法 2003-01至2007-06收治169例上颈椎疾病,根据病因分为:上颈椎骨折74例,先天性上颈椎疾病65例,肿瘤21例,其他病因导致寰枢椎不稳9例.根据病因、寰枢椎复位情况和脊髓受压情况分别采用前路手术、后路手术或者前后路手术.结果 28例可复位齿状突骨折患者采用前路空心螺钉内固定.97例上颈椎可复位,脊髓前方无明显受压患者采用单纯后路复位内固定,取自体松质骨植骨融合.44例难复位或脊髓前方明显受压患者采用前路减压、复位,后路内固定、取自体松质骨植骨融合.结论 根据上颈椎疾病病因、复位和脊髓受压情况,应分别选择前路、后路或者前后路联合手术治疗.     

Spinal cord compression due to metastatic disease: diagnosis with MR imaging versus myelography

To determine the efficacy of magnetic resonance (MR) imaging and myelography for the diagnosis of spinal cord compression due to metastatic disease, the authors prospectively examined 70 patients who had known or suspected spinal involvement by malignancy. Most MR examinations consisted of T1-weighted sagittal imaging of the entire spine, with additional sequences as needed for clarification. Extradural masses were found in 46 patients, 25 of whom had cord compression. For extradural masses causing cord compression, the sensitivity and specificity of MR imaging was .92 and .90, respectively, compared with .95 and .88 for myelography. For extradural masses without cord compression the sensitivity and specificity of MR imaging was .73 and .90, versus .49 and .88 for myelography. MR imaging was much more sensitive for metastases to bone (.90 vs .49), as expected. MR imaging is an acceptable alternative to myelography for diagnosing spinal cord compression and is preferable as a first study because it is noninvasive and better tolerated.     

Acute cervical spine trauma: correlation of MR imaging findings with degree of neurologic deficit

A retrospective analysis of magnetic resonance (MR) imaging studies of 78 patients with acute cervical spinal cord injuries was undertaken to determine which observations related directly to the neurologic injury. All MR imaging studies were performed on a 1.5-T unit and assessed with respect to 14 parameters related to the bony spine, ligaments, prevertebral soft tissues, intervertebral disks, and spinal cord. Forty-eight patients also underwent non-contrast material-enhanced thin-section computed tomography (CT) of the cervical spine. MR imaging was the definitive modality in the assessment of soft-tissue injury, especially in the evaluation of the spinal cord and intervertebral disks. All patients with a neurologic deficit had abnormal spinal cords at MR imaging. Intramedullary hemorrhage was predictive of a complete lesion. The degree of associated bone and soft-tissue injury had no bearing on the extent of spinal cord injury or neurologic deficit. Patients with residual cord compression following reduction demonstrated greater neurologic compromise than those without compression.     

平山病MRI诊断价值的初步研究

目的：探讨平山病的MRI表现及其诊断价值,加深对平山病的MRI表现及其可能的发病机制的认识。方法：回顾性分析5例经临床证实为平山病的MRI资料。所有患者均行颈椎常规仰卧位和屈颈位平扫及增强MRI检查。结果：常规仰卧位MPA显示5例患者中3例低位颈髓（C5-C7）萎缩,变扁平,髓内出现信号异常（主要位于灰质前角内）;屈颈位砌平扫5例均可见下段颈髓前移、变扁平加剧;4例硬脊膜外间隙增宽。增强MRI 3例患者可见增宽的硬膜外间隙内异常增粗并明显强化的静脉丛。结论：平山病的MRI表现有一定的特征性,屈颈位平扫及增强MRI对平山病的诊断有重要的价值。     

MR imaging of syringomyelia and hydromyelia

The relative effectiveness of plain computed tomography (CT), metrizamide CT, conventional myelography, and magnetic resonance (MR) imaging was compared for the examination of cystic spinal cord lesions. Intramedullary cavities in 18 patients were demonstrated by MR imaging: cavities were uncomplicated in 13 patients, associated with spinal tumors in two, and studied after occipital craniectomy for treatment of Chiari malformation and syringomyelia in two. Cavities were shown by MR imaging in all enlarged spinal cords, but a cavity was shown in only one of four small cords. The rostral limits of the cavities were demonstrated better than were the caudal extensions. Ventricular communication was not demonstrated. Chiari malformation was shown only in cavities that did not involve the medulla. Syringes associated with tumor were indistinguishable from uncomplicated cavities, but the tumor had abnormal signal on long spin-echo sequences in two cases. Cystic cord tumor (one case) had an inhomogeneous appearance. Caudal displacement of the cerebellar hemisphere through the surgical defect associated with compression of the fourth ventricle was shown in two cases after posterior fossa craniectomy. Thirteen patients were studied with metrizamide CT also. MR imaging proved to be as accurate as metrizamide CT in the diagnosis of intramedullary cavities that result in spinal cord enlargement, but it was less sensitive in detecting cavities within normal-sized or diminished spinal cords. It had the advantage that tumor tissue could be distinguished from associated syrinx cavities by differences in signal characteristics; and cerebellar ectopia was evaluated easily on sagittal MR views.