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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。
OBJECTIVE: To analyze the relationship between the degree of cerebellar tonsillar herniation and the morphology of the posterior fossa and the posterior fossa linear volume in Chiari malformation type Ⅰ (CM Ⅰ) patient and to explore the posterior fossa anatomy factors affecting the degree of cerebellar tonsil herniation. Methods: From June 2003 to June 2011, 59 patients with CM Ⅰ were enrolled in our department and met the inclusion criteria. There were 34 males and 25 females, aged 16-20 years (mean 17.9 years), grade 5 Risser, There are complete MRI data (including head and whole spinal cord sagittal scan images); no intracranial space-occupying lesions, skull destruction, posterior fossa surgery history or acquired Chiari deformity. All cases were associated with different forms of syringomyelia, 55 cases (93.2%) with varying degrees of scoliosis. The degree of cerebellar tonsillar herniation and the type of syringomyelia were evaluated on MRI T1-weighted median sagittal scan level. The posterior fossa slope length, anteroposterior diameter of foramen magnum, occipital scale length, sagittal diameter of posterior fossa, Posterior fossa height and slope angle. CM Ⅰ patients according to the severity of cerebellar tonsillar hernia was divided into three degrees: Ⅰ degree, the lower edge of the cerebellar tonsil beyond the foramen magnum 5mm but did not reach the upper edge of C1 after the arch; Ⅱ degree, cerebellar tonsils lower tail shift more than C1 The upper edge of the posterior arch does not exceed the lower edge of the posterior arch of C1; the third degree, the caudal displacement of the inferior edge of the cerebellar tonsillar beyond the lower edge of the posterior arch of C1. Divided according to the type of syringomyelia intumescent, rosary type, slender type and limited type four groups. The difference of posterior fossa linear volume between different groups was compared, and correlation analysis was carried out. Results: The length of posterior fossa slope of CM Ⅰ patients with grade Ⅰ tonsil hernia was significantly greater than that of CM Ⅱ patients with grade Ⅱ or Ⅲ tonsil hernia (P <0.05). The inclination angle of patients with grade Ⅲ tonsil hernia was significantly lower than that of patients with grade Ⅰ and Ⅱ (P <0.05). There was no significant difference among the other three groups. There was a significant negative correlation between the slope angle and the degree of cerebellar tonsillar hernia in CM Ⅰ patients (r = -0.626, P = 0.005). The incline slope of intumescent patients with syringomyelia was significantly less than that of other types of patients with syringomyelia (P <0.05). There was no significant difference between the other types of systole. Conclusion: Short posterior fossa slope may be one of the important factors to promote the aggravating of cerebellar tonsillar herniation in patients with CM Ⅰ. Meanwhile, the formation and development of syringomyelia in CM Ⅰ patients are also affected.