MRI对双胎异常的诊断价值

MRI manifestations of abnormalities in twin fetuses

目的 分析MRI在胎儿异常诊断中的作用.方法 回顾性分析2005年9月至2012年12月间产前超声检查提示异常的22例双胎患者的MRI.所有患者均进行MRI检查,扫描序列主要采用快速稳态进动采集（FIESTA）和快速反转恢复运动抑制（FIRM）序列.将MRI检查结果与产前超声检查结果进行比较分析,并以引产或生后随访治疗的结果证实诊断.结果 22例双胎中,20例孕妇23个异常胎儿,2例双胎正常.中枢神经系统异常3例3个异常胎儿,无脑儿、脑膜脑膨出、侧脑室扩大各1个.脑膜脑膨出MRI示后枕部脑组织自缺损的颅板处突出,该例超声诊断为淋巴管囊肿.无脑儿与侧脑室扩大MRI诊断与超声一致.胸部异常5例5个异常胎儿,均为双胎之一左侧膈疝.超声诊断膈疝可能,MRI确定超声的诊断.腹部异常7例8个异常胎儿,1例2个胎儿肠腔均扩张,结肠直肠扩张1个,脐膨出5个.7例均与超声诊断一致.肢体异常1例异常胎儿2个,双胎均为四肢短小畸形.其他异常为4例5个异常胎儿,包括1例胸腹联体双胎,MRI见双胎各有1个心脏,共用肝脏,泌尿系统、胃、直肠相互独立;死胎1个,形态较正常胎儿小,皮肤水肿;无心无脑严重畸形2个.MRI表现正常2例,1例超声诊断羊水多,消化道异常可能,而MRI显示羊水偏多,胎儿各系统MRI表现正常;1例超声怀疑隐性脊柱裂,MRI未见异常,出生后随访证实MRI表现.结论 MRI作为胎儿产前超声检查的一种重要补充方法,可对病变多方位显示,可给临床诊断及治疗予以很大帮助.

Objective To investigate the supplementary roles of MRI in the diagnosis of fetal abnormalities in twin fetuses.Methods MRI manifestations of 22 twins were retrospectively analyzed after abnormalities were found by prenatal ultrasonography （US） from Sep 2005 to Dec 2012.Two rapid scanning sequences were used in the study,fast-imaging employing steady-state acquisition （FIESTA） and fast inversion recovery motion insensitive （FIRM）.MRI findings were compared with those of prenatal US,induced labour or postpartum diagnosis.Results A total of 22 twins were reported with 23 abnormal fetuses in 20 twins and 2 normal twins.MRI confirmed central nervous system abnormalities in 3 abnormal fetuses which were anencephalus,meningoencephalocele and enlargement of lateral ventricles respectively.The case of meningoencephalocele was showed brain tissue protruding from the occipital defect on MRI,which was misdiagnosed as a cystic lymphagioma by US.The MRI diagnosis of anencephalus and enlarged lateral ventricles were accordant with US.MRI made the definite diagnosis in 5 chest abnormalities,which were left congenital diaphragmatic hernia （CDH） in 5 abnormal fetuses.They were diagnosed as possible CDH by US.Abdominal abnormalities （n=7,8 abnormal fetuses） included two fetuses in one twin with expanded digestive tract,one fetus with expanded colon and rectus and five fetuses with omphalocele.MRI diagnosis was compatible with US diagnosis in the 7 cases.Twins micromelia were found in one case with 2 abnormal fetuses.Conjoined twins in chest and abdomen were found in another case,which manifested as two hearts,one shared liver and independent urinary tracts and gastrointestinal tracts on MRI.One fetus in twin was dead （n=1,1 abnormal fetus）.MRI showed small size and skin edema of the dead fetus.One acephalus acardius of twins （n=2,2 abnormal fetuses） was proved.Normal MRI manifestations were indicated in 2 cases which were suspected by US for abnormal digestive tract and cryptorachischisis respectively.Conclusions MRI,an important supplementary method of prenatal US diagnosis,shows valuable advantages including multi-plane manifestations,more extensive visual field and good soft tissue contrast.It is especially helpful in the diagnosis and treatment of multiple pregnancy.