ChiariⅠ型畸形并发脊髓空洞症的MRI颅脑测量及临床意义

MR morphometric study and its clinical significance in syringomyelia Chiari I malformation

目的 运用MRI对ChiariI型畸形患者进行颅脑形态学测量 ,探讨ChiariI型畸形患者脊髓空洞症的发病机制。方法 在颅脑正中矢状面上分别对 5 0例正常国人和 2 4例合并脊髓空洞症及 2 6例不合并脊髓空洞症的ChiariI型畸形患者的后颅窝骨性和神经结构进行测量 ,测量结果用t检验进行统计分析。结果 畸形组与正常组枕大孔平面延前池前后径分别为 (4 2± 1 8)mm和 (6 6±1 4)mm ,前者明显小于后者 (t=7 30 ,P <0 0 1) ,畸形组脑颅比明显大于正常组 (t =7 33,P <0 0 1) ,后脑大小两组间无显著性差异 (t=0 2 8,P >0 0 5 )。ChiariI型畸形脊髓空洞组和无空洞组枕大孔平面的延前池前后径分别为 (2 9± 1 4)mm和 (5 5± 1 1)mm ,前者明显小于后者 (t=7 2 6 ,P <0 0 1) ,脊髓空洞组枕大孔平面延髓前后径大于无空洞组 (t=2 16 ,P <0 0 5 ) ,小脑扁桃体前后径大于无空洞组(t=3 97,P <0 0 1) ,小脑扁桃体后脑脊液间隙的前后径小于无空洞组 (t=5 77,P <0 0 1) ;脊髓空洞组的脑颅比大于无空洞组 (t=2 6 8,P <0 0 5 ) ,延髓下移程度大于无空洞组 (t=3 2 5 ,P <0 0 1) ;后颅窝颅腔形态两组间无显著性差异。结论 ChiariI型畸形患者的后颅窝及枕大孔区过度拥挤导致第4脑室出口受阻 。

Objective To investigate the pathogenesis of the syringomyelia in Chiari I malformation by measuring the posterior cranial fossa structures. Methods The posterior cranial fossa structures on mid sagittal MR image were measured in 50 normal subjects,and 24 Chiari I malformation patients associated with syringomyelia and 26 Chiari I malformation patients without syringomyelia. The t test was used for statistical analysis. Results In Chiari I malformation patients and normal subjects, the width of the CSF space anterior to the medulla oblongata was (4 2±1 8) mm and (6 6±1 4) mm respectively( t =7 30, P <0 01). The brain skull ratio of Chiari I malformation group was larger than normal subjects( t =7 33, P <0 01), there was no significant difference in the size of posterior brain between the two groups( t =0 28, P >0 05). In Chiari I malformation with syringomyelia group and without syringomyelia group, the width of the CSF space anterior to the medulla oblongata was (2 9±1 4) mm and (5 5±1 1) mm respectively( t =7 30, P <0 01). In Chiari I malformation with syringomyelia group, the width of the medulla oblongata and the tonsil of cerebellum was wider than in the control group,the width of the CSF space posterior to the tonsil of cerebellum was narrower than control group. The location of the medulla oblongata was significantly lower than in the control group. There was no significant difference in the morphology of posterior cranial fossa between the two groups. Conclusion The overcrowding in the posterior fossa and the froamen magnum region, and the compression on the junction of medulla oblongata with the spinal cord could influence the circulation of cerebrospinal fluid and may lead to the development of syringomyelia. The MRI measurement of the posterior cranial fossa structures is very useful in the treatment and prognosis of the Chiari I malformation.