胎儿小脑蚓部发育的MRI研究

摘要

Objective: to measure the main dimensions of fetal cerebellar vermis and assess its development. To explore the MRI features of Dandy-Walker syndrome(DWS). Methods: 52 of the 63 fetal specimens(gestational age 15-40 weeks) scanned on a 3. 0T MR system met the inclusion criteria. The anterior posterior diameter(APD)of cerebellar vermis, the height of anterior vermis and posterior vermis were measured and analysed. The MRI findings of DWS(n = 6) confirmed by MRI scan were analyzed retrospectively. Results: APD and the height of anterior vermis and posterior vermis increased linearly with gestational age,the height of anterior vermis was greater than posterior vermis( P <0. 05) ,primary and infero-posterior fissure could be visualized on midsagittal T1 and T2weighted images. The main MRI findings of DWS were observed as follows: absence of the cerehellar vermis or partial agenesis of the separative cerebellar hemispheres,cystic dialation of the fourth ventricle communicating with enlargement of posterior fossa cyst. Conclusion; The development of fetal cerebellar vermis could be assessed by MRI after a gestational age of 17 weeks. There are characteristic MRI findings in the DWS and MRI scan is a valuable method for an early diagnosis of DWS.%目的:描述正常胎儿标本小脑蚓部在不同孕周的正常发育生长曲线,并探讨胎儿丹迪-沃克综合征(DWS)的MRI表现.方法:对63例胎龄15～40周的胎儿标本行3.0 T MRI扫描,从中选出52例符合要求的进行测量,扫描序列为T1WI、T2WI;扫描方位:矢状位扫描为主,辅以冠状位及横轴位；观察及测量内容:测量小脑蚓部的前后径(正中矢状面第四脑室顶点至水平裂处蚓部后缘最大距离)、上蚓高度及下蚓高度(上蚓的最高点及下蚓的最低点分别到前后径线的垂直距离).对上述测量结果与孕龄间作回归分析.然后对6例经MRI诊断为DWS的病例进行回顾性分析.结果:小脑蚓部前后径、上蚓高度及下蚓高度分别与孕龄呈线性正相关,而上蚓高度总是略大于下蚓高度(P＜0.05),多数标本正中矢状面T1WI、T2WI可清晰显示原裂及下后裂.DWS主要表现为小脑蚓部缺如或发育不良,测量数据小于正常胎儿,第四脑室与后颅窝囊肿相通或小脑延髓池增宽.结论:MRI可明确显示正常胎儿小脑蚓部在17孕周以后的正常发育表现及变化规律,而DWS的MRI表现具有特征性,MRI是诊断DWS最理想的影像学方法.