ChiariⅠ型畸形的发病机制探讨及测量方法比较

Investigation of the Pathogenesis and Craniometry of Chiari Type Ⅰ Malformation

目的 探讨ChiariⅠ型畸形的发病机制并对测量方法进行比较。资料与方法 利用医用计算机图像处理软件OSIRIS对年龄在 18岁以上、MRI资料完整、不伴颅内高压、环枕融合和颅底凹陷的 2 7例ChiariⅠ型畸形病例及年龄在 18岁以上、不伴中枢神经系统疾病的 40例 (对照组 )的头颅MR图像分别进行颅腔和脑实质的径线、角度与面积的测量 ,并对测量结果作统计学分析。结果 ChiariⅠ型畸形组的枕底长与斜坡长的比值明显小于对照组 ,后脑面积与后颅窝面积的比值明显大于对照组 ,而后颅面积与全颅面积的比值明显小于对照组 (P <0 .0 5 )。结论 ChiariⅠ型畸形的最可能的发病机制为胚胎枕节发育不良导致后颅窝狭小 ,难以完全容纳正常发育的后脑 ,使小脑扁桃体向下疝入椎管。采用长径和宽径的乘积代表不规则颅腔面积的研究方法具有可参照性。

Objective To investigate the pathogenesis and measuring methods of Chiari type Ⅰ malformation.Materials and Methods Several radial lines, angles and areas of the posterior cranial cavity and the brain on MRI were ascertained by OSIRIS, a medical image processing software, in 27 cases (study group) with Chiari type Ⅰ malformation (having no hydrocephalus, atloido-occipital fusion or basilar invagination) and in 40 healthy individuals (control group). The results were statistically analyzed.Results In study group, the basioocciput-clivus ratio was significantly smaller, while the posterior brain-fossa area ratio was significantly higher, than that in control group. The posterior fossa to the total cranial area ratio in the study group was significantly smaller than that in control group (P<0.05). Conclusion The most possible pathogenesis of Chiari type Ⅰ malformation is the embryonic underdevelopment of occipital bone, resulting in a narrowed and small posterior cranial fossa, which causes the cerebellar tonsil to be herniated into the vertebral canal. Measuring the area of the irregular cranial cavity by multiplying the length with the width is helpful for its diagnosis.