青少年特发性脊柱侧凸患者颅颈交界处的脑脊液动力学特征的MR比较研究

目的 本研究旨在明确青少年特发性脊柱侧凸(AIS)患者颅颈交界处是否亦存在脑脊液阻塞及其与小脑扁桃体位置、枕骨大孑L大小及体表皮层诱发电位异常的相关性.方法 对30例AIS和30例年龄、性别匹配的正常对照组进行常规和相位对比法核磁共振检查.在枕骨大孑L处蛛网膜下腹侧和背侧分别选择4个兴趣Ⅸ测量两组的脑脊液流动峰值速度.在正中矢状面上测量小脑扁桃体相对枕骨大孔连线的位置,枕骨大孔前后径、横径以及面积.将测量参数与体表皮层诱发电位进行相关性分析.结果 AIS患者枕骨大孔处脑脊液流动速度峰值与正常对照组差异无统计学意义.尽管AIS患者中有50％的小脑扁桃体低于枕骨大孔连线1 mm且位置明显低于正常对照组,其枕骨大孔的前后径及面积明显大于正常对照组,小脑扁桃体位置和枕骨大孔面积呈明显负相关.体表皮层诱发电位止常和异常的AIS患者脑脊液流速以及枕骨大孔形态均无明显差异.结论 尽管A1S患者存在低位小脑扁桃体,但其枕骨大孔处脑脊液流动并无明显阻塞,这可能是山于小脑扁桃体位置越低者其枕骨大孔越大而产生的中和代偿结果.AIS患者的体表皮层诱发电位异常亦与其枕骨大孔处的脑脊液流动无相关性.     

Cobb角大于40°的青少年特发性脊柱侧凸患者的小脑扁桃体位置分析

目的探讨小脑扁桃体位置在临床诊治大弯度青少年特发性脊柱侧凸(adolescent idio-pathic scoliosis,AIS)中的意义。方法AIS患者203例,男27例,女176例;年龄平均(14.6±1.6)岁;Cobb角平均55.3°±16.6°。对照组86例,男、女各43例,年龄平均(15.7±1.8)岁,均未患有大脑、中脑、小脑、脊髓病变及脊柱侧凸、后凸和脊柱发育异常等。在MRI图像上测量AIS患者和对照组青少年的小脑扁桃体位置,分析二组之间的差异,以及年龄和性别对小脑扁桃体位置的影响。在AIS组内分析不同侧凸角度和侧凸类型患者的小脑扁桃体位置的差异。结果AIS患者的小脑扁桃体平均位置明显低于对照组(分别为枕骨大孔上0.9mm和2.9mm)。AIS患者中小脑扁桃体异位的发生率(34.5%)明显高于正常对照组(5.8%)。年龄、性别和Cobb角对小脑扁桃体位置均无显著的影响。在不同的侧凸类型中,双胸弯AIS患者小脑扁桃体异位的发生率(62.5%)最高。腰部侧凸的患者中小脑扁桃体异位发生率显著低于胸和胸腰部侧凸的患者。结论大弯度AIS患者的小脑扁桃体位置明显低于正常对照组,小脑扁桃体异位的发生率明显高于正常对照组。小脑扁桃体异位低于枕骨大孔2mm为异常,而在中国大陆此比例极低。AIS患者小脑扁桃体异位的发生可能与侧凸类型存在一定的关联。     

青少年特发性脊柱侧凸患者小脑扁桃体位置与异常体感诱发电位的相关性分析

目的 探讨青少年特发性脊柱侧凸(AIS)患者小脑扁桃体位置与异常体感诱发电位(SEP)的相关性,分析其在AIS临床诊治中的意义.方法 对171例AIS患者行MRI扫描和胫后神经SEP检查;并以45名年龄匹配的健康青少年的胫后神经SEP作为正常值参考对照.在MRI图像上测量AIS患者的小脑扁桃体位置.小脑扁桃体位置低于枕骨大孔前后缘骨皮质的最低点之间的连线定义为小脑扁桃体异位.SEP波形消失、峰潜伏期延长及峰潜伏期不对称定义为SEP异常的标准.分别计算AIS患者小脑扁桃体异位发生率及SEP异常率,并分析小脑扁桃体异位与SEP异常的相关性.分析小脑扁桃体异位与SEP异常对侧凸严重程度的影响.结果 171例AIS患者中小脑扁桃体异位者总共有63例(36.8%),SEP异常者共有62例(36.3%).根据不同侧凸严重程度分组分析,结果提示小脑扁桃体异位和SEP异常均与侧凸严重程度无关,小脑扁桃体异位与SEP异常无明显相关,P值均>0.05.结论 部分AIS患者存在小脑扁桃体异位或躯体感觉传导通路异常,两者之间并无相关性,可能与AIS的不同发病机制有关.     

特发性脊柱侧凸患者小脑扁桃体位置与后颅窝容积关系的影像学观察

目的:比较特发性脊柱侧凸(idiopathic scoliosis,IS)患者与年龄匹配的非脊柱畸形患者后颅窝容积的差异,探讨IS患者后颅窝发育异常与小脑扁桃体生理性下疝的关系。方法:从2009年1月至2011年6月我科收治的500例IS患者中选取70例年龄16～20岁、Risser征5级、术前行站立位全脊柱正侧位X线片及颈枕部MRI检查的患者为研究对象(A组),男48例,女22例,侧凸平均Cobb角51.2°±14.1°。选取年龄匹配的58例非脊柱畸形患者作为对照组(B组),男27例,女31例。测量两组研究对象头颈正中矢状位MRI中小脑扁桃体下缘超出枕骨大孔连线(AB线)的距离(d值)、枕骨大孔前后径(AB)、斜坡长度(AD)、枕上长度(BC)以及后颅窝矢状径(CD),比较两组小脑扁桃体位置及后颅窝容积差异。根据MRI表现,将IS组患者分为伴生理性小脑扁桃体下疝组(A1组)和不伴生理性小脑扁桃体下疝组(A2组),分析后颅窝容积与小脑扁桃体生理性下疝间关系及主弯Cobb角与小脑扁桃体生理性下疝程度的相关性。结果:A组d值和枕骨大孔前后径明显大于B组(P<0.05),而AD、BC以及CD均明显小于B组(P<0.05)。A组患者d值与主弯Cobb角无显著相关性(P>0.05),其生理性小脑扁桃体下疝发生率为22.9%,A1组患者BC显著小于A2组患者(P<0.05),AB、AD、CD两组间均无显著性差异(P>0.05)。结论:IS患者小脑扁桃体位置低可能与其后颅窝枕骨大孔增大而斜坡、枕骨发育受限有关,IS患者成骨异常可能也影响到了其后颅窝发育。     

青少年特发性脊柱侧凸的全脊柱三维MRI特点及与侧凸严重度相关性研究

目的 研究青少年特发性脊柱侧凸(adolescent idiopathic seoliosis,AIS)的MRI特征性变化,探讨AIS的MRI特征性变化与侧凸严重度的相关性.方法 应用三维莺建MRI技术对90例青少年(49例AIS,41名健康青少年)进行全脊髓脊柱和后脑MR检查.测量颈椎和胸椎各节段的脊髓最大前后径(AP)、最大横向直径(TS)和凸凹侧脊髓旁间隙(LCS)、小脑扁桃体与枕骨大孔基线的距离、齿突与枕骨大孔基线的距离、颈髓中轴线与延髓中轴线夹角(α)、枕骨大孔基线与延髓中轴线夹角(β)、脊髓面积、椎管面积、脊髓椎管面积比,测量脊髓全长、脊柱全长、脊髓脊柱全长比.结果 与健康对照组相比,AIS患者的AP、TS、AP/TS 和LCS比值明显增加,小脑扁桃体位置相对枕骨大孔明显下移,脊髓圆锥位置相对上移,β角减小,脊髓椎管面积比增大(P＜0.01);AIS组与对照组相比,全脊髓或全脊柱长度差异无统计学意义,但脊髓脊柱全长比明显减小(P＜0.01),与Cobb角无明显相关性.AP、AP/TS和LCS比值与Cobb角明显正相关(P＜0.05).结论 AIS患者在脊髓和脊柱的横断面上存在显著性形态学异常,部分与Cobb角有明显正相关;脊髓和脊柱纵轴上存在明显的脊髓牵拉受限,提示可能存在神经系统和骨骼系统的生长不平衡,这些可能与AIS的发病机制有关.     

Ⅰ型Chiari畸形和(或)脊髓空洞相关脊柱侧凸术前评估和治疗选择

Ⅰ型Chiari畸形是小脑扁桃体下疝畸形,为后脑的先天性畸形,其病理特征是小脑扁桃体疝入椎管内,小脑低于枕骨大孔5mm以上。虽然非特发性脊柱侧凸中较少见的为伴发Chiari畸形和(或)脊髓空洞者,但随着诊断技术的提高,该类患者已变得不那么少见。检索Chiari畸形合并脊柱侧凸,得到相关中英文文献100篇,作者对相关文献进行综述,以了解Ⅰ型Chiari畸形合并脊柱侧凸研究进展。     

彩色多普勒超声评价Chiari Ⅰ畸形寰枕减压硬膜成形术后疗效的可行性探讨

目的探讨采用彩色多普勒超声评价ChiariⅠ畸形（CMI）寰枕减压硬膜成形术后疗效与枕大孔区脑脊液（CSF）流动恢复的关系。方法2008年12月~2009年4月ChiariⅠ畸形18例,其中合并脊髓空洞14例,男8例,女10例。年龄10~57岁,（42.3±13.1）岁。采用后正中入路枕大孔区减压硬膜成形术,用人工硬膜（Neuropatch）修补硬膜。于术后10~12天采用PHILLIP IU22彩色多普勒超声经枕部骨性减压窗测量小脑扁桃体下缘水平脊髓腹背侧蛛网膜下腔脑脊液的头向及尾向流动的流速。根据Tator评分评价术后效果对比分析术后改善组与术后稳定组CSF流速差异。术后MR复查脊髓空洞消减情况。结果患者均痊愈出院。出院前13例为优（改善组）,余5例为良（稳定组）。术后MRI示14例合并脊髓空洞者中10例有明显缩小（改善组7例,稳定组3例）,余4例无明显改变。彩色多普勒超声检查18例小脑扁桃体下缘水平脊髓背侧蛛网膜下腔均可见脑脊液的头向及尾向流动,与心动周期相关,尾向流速（8.52±5.28）cm/s[改善组（6.35±2.81）cm/s,稳定组（14.18±6.29）cm/s,t=-3.734,P=0.002],头向流速（6.42±2.17）cm/s[改善组（5.88±1.97）cm/s,稳定组（7.81±2.22）cm/s,t=-1.804,P=0.090）。结论寰枕减压硬膜成形术治疗CMI可有效恢复术后枕大孔区脑脊液流动,疗效肯定。彩色多普勒超声术后测量枕大孔区脑脊液流速恢复情况与疗效有一定关系。     

Chiari畸形和(或)脊髓空洞合并脊柱侧凸的临床特征

Chiari畸形由胚胎期后脑先天性发育异常所致，在解剖上表现为小脑扁桃体等结构的位置降低超出枕大孔，并疝人上颈椎管内。Chiari畸形可以伴发与脑脊液循环障碍有关的脊髓空洞，而临床上脊髓空洞也可单独存在。Chiari畸形和（或）脊髓空洞患者可伴发脊柱侧凸，其中部分患者以脊柱侧凸为首诊原因。由于这类脊柱侧凸一般不合并其他先天性的脊椎异常，临床易误诊为特发性脊柱侧凸。颅脑和全脊髓的MRI由于价格昂贵，不宜作为常规检查。因此临床上需先筛查出可疑的患者，再有选择地进行MRI检查以明确诊断。     

Chiari畸形后路减压手术术后近期并发症分析

Arnold Chiari畸形（Arnold Chiari malformation，ACM），也称小脑扁桃体下疝畸形,是一种以小脑扁桃体下疝人枕骨大孔为特征的先天性畸形。Chiari畸形的手术目的是解除颈枕部组织对脊髓的压迫，恢复正常的脑脊液动力学，缓解脊髓空洞。我院1998年1月～2006年6月共手术治疗Chiari畸形154例，对术后1个月内出现的各种并发症进行总结，报告如下。     

Chiari畸形Ⅰ型患者小脑扁桃体下疝程度及脊髓空洞形态与后颅窝容积的相关性

目的:分析Chiari畸形Ⅰ型(Chiari malformation typeⅠ,CMⅠ)患者小脑扁桃体下疝程度及脊髓空洞形态与后颅窝线性容积的关系,探讨影响小脑扁桃体下疝程度的后颅窝解剖学因素。方法:2003年6月~2011年6月在我科接受治疗并符合入选标准的CMⅠ患者共59例,男34例,女25例,年龄16~20岁,平均17.9岁,Risser征5级,均有完整MRI资料(包括头枕部及全脊髓矢状面扫描图像);均无颅内占位性病变、颅骨破坏、后颅窝手术史或获得性Chiari畸形。均伴有不同形态的脊髓空洞,55例(93.2%)伴有不同程度的脊柱侧凸畸形。在MRI T1加权像正中矢状位扫描层面上评估患者的小脑扁桃体下疝程度和脊髓空洞类型;测量后颅窝斜坡长度、枕骨大孔前后径、枕骨鳞部长度、后颅窝矢状径、后颅窝高径和斜坡倾斜角。将CMⅠ患者按照小脑扁桃体下疝严重程度分为三度:Ⅰ度,小脑扁桃体下缘超过枕骨大孔水平5mm但没有到达C1后弓上缘;Ⅱ度,小脑扁桃体下缘尾向移位超过C1后弓上缘但未超过C1后弓下缘;Ⅲ度,小脑扁桃体下缘尾向移位超过C1后弓下缘。依据脊髓空洞类型分为膨胀型、念珠型、细长型和局限型四组。比较不同组间后颅窝线性容积的差异,并对相关指标进行相关性分析。结果:Ⅰ度扁桃体下疝CMⅠ患者的后颅窝斜坡长度明显大于Ⅱ、Ⅲ度扁桃体下疝CMⅠ患者(P<0.05),Ⅲ度扁桃体下疝患者的斜坡倾斜角较Ⅰ、Ⅱ度患者明显减小(P<0.05),其余指标三组间无显著性差异;CMⅠ患者的斜坡倾斜角与小脑扁桃体下疝程度之间存在显著性负相关关系(r=-0.626,P=0.005)。膨胀型脊髓空洞患者的斜坡倾斜角显著小于其他类型的脊髓空洞患者(P<0.05),其余指标各类型之间无显著性差异。结论:后颅窝斜坡短平可能是促使CMⅠ患者小脑扁桃体下疝加重的重要因素之一,同时对CMⅠ患者的脊髓空洞的形成和发展也存在影响。     

Elucidating the pathophysiology of syringomyelia.

OBJECT: Syringomyelia causes progressive myelopathy. Most patients with syringomyelia have a Chiari I malformation of the cerebellar tonsils. Determination of the pathophysiological mechanisms underlying the progression of syringomyelia associated with the Chiari I malformation should improve strategies to halt progression of myelopathy. METHODS: The authors prospectively studied 20 adult patients with both Chiari I malformation and symptomatic syringomyelia. Testing before surgery included the following: clinical examination; evaluation of anatomy by using T1-weighted magnetic resonance (MR) imaging; evaluation of the syrinx and cerebrospinal fluid (CSF) velocity and flow by using phase-contrast cine MR imaging; and evaluation of lumbar and cervical subarachnoid pressure at rest, during the Valsalva maneuver, during jugular compression, and following removal of CSF (CSF compliance measurement). During surgery, cardiac-gated ultrasonography and pressure measurements were obtained from the intracranial, cervical subarachnoid, and lumbar intrathecal spaces and syrinx. Six months after surgery, clinical examinations, MR imaging studies, and CSF pressure recordings were repeated. Clinical examinations and MR imaging studies were repeated annually. For comparison, 18 healthy volunteers underwent T1-weighted MR imaging, cine MR imaging, and cervical and lumbar subarachnoid pressure testing. Compared with healthy volunteers, before surgery, the patients had decreased anteroposterior diameters of the ventral and dorsal CSF spaces at the foramen magnum. In patients, CSF velocity at the foramen magnum was increased, but CSF flow was reduced. Transmission of intracranial pressure across the foramen magnum to the spinal subarachnoid space in response to jugular compression was partially obstructed. Spinal CSF compliance was reduced, whereas cervical subarachnoid pressure and pulse pressure were increased. Syrinx fluid flowed inferiorly during systole and superiorly during diastole on cine MR imaging. At surgery, the cerebellar tonsils abruptly descended during systole and ascended during diastole, and the upper pole of the syrinx contracted in a manner synchronous with tonsillar descent and with the peak systolic cervical subarachnoid pressure wave. Following surgery, the diameter of the CSF passages at the foramen magnum increased compared with preoperative values, and the maximum flow rate of CSF across the foramen magnum during systole increased. Transmission of pressure across the foramen magnum to the spinal subarachnoid space in response to jugular compression was normal and cervical subarachnoid mean pressure and pulse pressure decreased to normal. The maximum syrinx diameter decreased on MR imaging in all patients. Cine MR imaging documented reduced velocity and flow of the syrinx fluid. Clinical symptoms and signs improved or remained stable in all patients, and the tonsils resumed a normal shape. CONCLUSIONS: The progression of syringomyelia associated with Chiari I malformation is produced by the action of the cerebellar tonsils, which partially occlude the subarachnoid space at the foramen magnum and act as a piston on the partially enclosed spinal subarachnoid space. This creates enlarged cervical subarachnoid pressure waves that compress the spinal cord from without, not from within, and propagate syrinx fluid caudally with each heartbeat, which leads to syrinx progression. The disappearance of the abnormal shape and position of the tonsils after simple decompressive extraarachnoidal surgery suggests that the Chiari I malformation of the cerebellar tonsils is acquired, not congenital. Surgery limited to suboccipital craniectomy, C-I laminectomy, and duraplasty eliminates this mechanism and eliminates syringomyelia and its progression without the risk of more invasive procedures.     

Advanced Chiari malformation type I with marked spinal cord atrophy. Case report

The authors discuss the results obtained in patients who underwent foramen magnum decompression for longstanding advanced Chiari I malformation in which marked spinal cord atrophy was present. This 50-year-old woman presented with progressive quadriparesis and sensory disorders. Magnetic resonance imaging revealed the descent of cerebellar tonsils and medulla associated with remarkable C1-L2 spinal cord atrophy. After a C-1 laminectomy-based foramen magnum decompression, arachnoid dissection and duraplasty were undertaken. These procedures resulted in remarkable neurological improvement, even after 40 years of clinical progression. Spinal cord atrophy may be caused by chronic pressure of entrapped cerebrospinal fluid in the spinal canal.     

Acute foramen magnum syndrome from acquired Chiari I malformation relieved by ventriculoperitoneal shunt revision

An adult case of shunt malfunction presenting with acute quadriparesis as a manifestation of foramen magnum syndrome with acquired Chiari type I malformation is described in this study. The corticospinal function was restored after shunt revision. MRI showing considerable ascent of cerebellar tonsils after surgery is shown. Theories regarding the formation of acquired Chiari I malformations, alongside the possible synergistic roles of intracranial pathologies and cerebrospinal fluid drainage in the development of this entity are discussed.     

Tailored operative technique for Chiari type I malformation using intraoperative color Doppler ultrasonography

OBJECTIVE: We describe an operative technique for Chiari Type I malformation that uses color Doppler ultrasonography as a guide for performing patient-specific posterior fossa decompressions. The technique has been used since 1999 in more than 300 operations. METHODS: On the basis of real-time anatomic and physiological measurements, the following goals of surgery were monitored: 1) adequate decompression of the cervicomedullary junction; 2) creation of a retrocerebellar space of 8 to 10 cm(3) volume; and 3) establishment of optimal cerebrospinal fluid flow between the cranial and spinal compartments. RESULTS: The size of the craniectomy was tailored to conform to the area of cerebellar impaction as demarcated by compressed subarachnoid spaces. A laminectomy was not performed unless the cerebellar tonsils were herniated below C1. Before opening the dura, color Doppler ultrasonography imaging was invaluable in planning operative strategies. A simple duraplasty without additional steps was found to be appropriate treatment in occasional patients with minimal tonsillar herniation (5-8 mm). In all other cases, it was necessary to perform an internal decompression that included lysis of the arachnoid and shrinkage of the cerebellar tonsils to achieve the goals of surgery. Optimal cerebrospinal fluid flow through the foramen magnum in anesthetized, prone patients was found to have the following characteristics: a peak velocity of 3 to 5 cm/s, bidirectional movement, and a waveform exhibiting vascular and respiratory variations. The attainment of surgical goals was confirmed in most patients by postoperative neuroimaging. CONCLUSION: Color Doppler ultrasonography imaging is an important technological advance that permits the neurosurgeon to tailor the steps of Chiari surgery according to patient-specific variables. The success of this technique depends on the mastery of a new and sophisticated monitoring modality.     

Chiari type I malformations in adults: a morphometric analysis of the posterior cranial fossa

OBJECTIVE: Chiari type I malformation (CMI) is a congenital disorder characterized by caudal displacement of the cerebellar tonsils through the foramen magnum into the spinal canal. Recent studies suggest that overcrowding in the posterior cranial fossa (PCF) because of underdeveloped bony structures in the intrauterine life is the main cause of this malformation. For this reason, the authors want to contribute to the current literature, which focuses on bone abnormalities in the PCF in patients with CMIs. METHODS: We examined a retrospective cohort of 60 adult patients with CMIs, and multiple measurements were made on magnetic resonance imaging. The results were compared to 30 healthy adult control subjects. Mann-Whitney U test was used as a statistical method. RESULTS: All measurements except mean anteroposterior diameter of the foramen magnum were reduced in patients compared to control. An increase in the anteroposterior mid-sagittal distance of the foramen magnum in patients reached statistically significant difference compared to control. All patients had tonsillar herniation at least 5 mm below the plane of the foramen magnum. Chiari type I malformation in this study was associated with syringomyelia in 46 patients. CONCLUSION: This study with a limited number of patients suggests that the bony components of the PCF are not developed fully, supporting the current concept that CMI is a disorder of the para-axial mesoderm.     

Chiari type I presenting as left glossopharyngeal neuralgia with cardiac syncope

Glossopharyngeal neuralgia is an uncommon craniofacial pain syndrome that is occasionally associated with cardiac syncope. However, we relate Chiari I syndrome as a cause of this clinical picture for the first time in the literature. The authors analyze the relevant literature and discuss the pathogenesis and treatment of associated syndromes. We describe the case of a 45-year-old female patient who presented with a 3-year history of left glossopharyngeal neuralgia with occasional dysphagia and episodes of syncope when eating or swallowing. The pain was not disseminated to the right side and was fairly well controlled by carbamazepine. The syncopal attacks had a duration of about 10 sec. Neurological examination elicited a faint dysphonia associated with paradoxical dysphagia. The cranial magnetic resonance imaging scan showed a bilateral herniation of the cerebellar tonsils through the foramen magnum, more evidently on the left side. The patient received a suboccipital craniectomy and resection of the posterior arch of C1. The dura mater was opened, and we found both tonsils displaced into the foramen magnum extending caudally toward the C1 level. Both tonsils were compressing the brainstem and especially the low cranial nerves bilaterally. The lower cranial nerves were compressed between the posterior inferior cerebellar artery (PICA) and the herniated cerebellar tonsil on both sides. Both PICAs were dissected by microsurgical technique and all the arachnoid adherences were cut. The left tonsil was resected by means of ultrasonic aspirator. Duraplasty was performed with the occipital pericranium. The paroxysmal pain attacks and the syncopal picture disappeared immediately after the operation. The patient was discharged on the 7th postoperative day. One year later, she was free of symptoms. This case provides clinical evidence of close connections between the glossopharyngeal and vagus nerves, which control visceral sensation; and compression of the IX and X nerves between the herniated tonsil and PICA or vertebral artery may cause an irritative sensory phenomenon, which is the origin of the algic sensation and the cardiac syncope by means of cross talk between the fibers of the same nerve. Electronic Publication     

Computed tomography in developmental anomalies of craniocervical junction

We reviewed 27 patients with developmental anomalies in craniovertebral junction, and special attention was paid to computed tomography (CT) findings in congenital atlantoaxial dislocation (AAD), basilar invagination and Chiari malformations. In ADD, CT clearly demonstrated the relationships of the atlas to the axis in axial plane. Four major types were distinguished; anteroposterior (6 cases), transverse (0 case), anteroposterior-transverse (4 cases) and rotatory (5 cases) dislocations. It was feasible by CT to analyse the pathomechanics in each individual with AAD. Soft tissue wad was shown on the posterior aspect of the odontoid in 7 out of 15 patients with AAD. Those two features, pathomechanics of AAD and intraspinal soft tissue wad, were felt to be important for patient's symptomatology. Basilar invagination presented in no patient as a single deformity and was always associated with other bony and neural abnormalities in 14 patients. Basilar invagination might be suggested of its existence in such a case as CT showing; (1) the odontoid at or above the level of the foramen magnum, (2) distinctive margin of the foramen magnum above the bottom of the posterior fossa, and (3) the posterior arch of the atlas at the same level as foramen magnum. Nevertheless, it is essential to confirm occipital hypoplasia by using either reformatting CT images in coronal and sagittal plane or conventional tomography; whereas high resolutional CT machine provides new dimension for demonstration of bony details. In Chiari malformations, plain CT scanned by high resolutional machine often makes it possible to delineate caudal migration of the cerebellar tonsils, so that it may be a choice of examination as a screening of the anomaly. In addition, metrizamide CT clearly demonstrated caudal migration both of cerebellar tonsils and medulla oblongata. Therefore, CT apparently exceeds other diagnostic modalities in evaluating this anomaly.     

Spinal cord and brain stem anomalies in scoliosis. MR screening of 26 cases

The spinal cord and brain were examined with magnetic resonance (MR) in 26 patients with idiopathic scoliosis to study the prevalence of spinal cord and brainstem anomalies. Two patients had small centrally located spinal cord syrinxes, one at C6-C8 and the other at T6-T8, without association with any brainstem or cerebellar deformity. The lowest position of the cerebellar tonsils was 0.5 cm below the foramen magnum, which was also seen in 2 other patients. Scoliosis associated with syringomyelia may be more common than previously thought, and may be wrongly classified as idiopathic. A neurogenic cause of scoliosis should always be considered, and at least in atypical cases be excluded by MR imaging of the spinal cord. MR should be mandatory before bracing or operative correction of scoliosis.     

Spinal cord and brain stem anomalies in scoliosis: MR screening of 26 cases

The spinal cord and brain were examined with magnetic resonance (MR) in 26 patients with idiopathic scoliosis to study the prevalence of spinal cord and brainstem anomalies. Two patients had small centrally located spinal cord syrinxes, one at C6-C8 and the other at T6-T8, without association with any brainstem or cerebellar deformity. the lowest position of the cerebellar tonsils was 0.5 cm below the foramen magnum, which was also seen in 2 other patients. Scoliosis associated with syringomyelia may be more common than previously thought, and may be wrongly classified as idiopathic. A neurogenic cause of scoliosis should always be considered, and at least in atypical cases be excluded by MR imaging of the spinal cord. MR should be mandatory before bracing or operative correction of scoliosis.