目的

探讨胎儿蛛网膜囊肿（AC）影像学表现、遗传学特征及病理特点。

方法

选择2023年7月在东莞市人民医院诊治的1例胎龄为32周时产前胎儿超声结果提示巨大AC胎儿（胎儿1）为研究对象。采用回顾性分析法，对引产前胎儿超声及胎儿头颅MRI检查结果与引产后胎儿遗传学检测及解剖结果进行分析。以 “蛛网膜” “胎儿”“arachnoid cyst” “fetus ” “fetal” “intracranial”为中、英文关键词，在中国知网、万方数据知识服务平台及Pub Med、Web of Science数据库中，检索与胎儿AC相关研究文献。本次文献检索时间设定为上述数据库建库至2024年1月。本研究遵循的程序符合2013年修订的《世界医学协会赫尔辛基宣言》，并经南方医科大学第十附属医院（东莞市人民医院）伦理委员会批准（审批文号：IRB2023-WZ-156）。孕妇对诊断及治疗均知情同意。

结果

①对孕妇孕龄为32孕周时，产前胎儿超声检查结果提示，胎儿1发育相当于胎龄为32周，右侧蛛网膜可见一囊性占位（9.7 cm×3.3 cm），边界清、透声好，囊性包括内未见明显血流信号，双侧大脑半球不对称，左侧大、右侧小，脑中线向左侧偏移，左侧脑室最大测量值为1.4 cm，拟诊为右侧AC，左侧脑室增宽。②孕妇孕龄为32孕周时，胎儿头颅MRI检查结果显示：胎儿1右侧大脑半球蛛网膜间隙整体增宽呈新月状，轴位测量最大面积为10.6 mm×2.3 mm，大脑右侧占位大脑镰整体左移，脑实质未见异常信号，双侧大脑半球不对称，右侧半球较对侧体积小，脑沟双侧不对称，右侧部分脑沟变浅，左侧脑室最大径为1.6 cm，提示右侧AC、右侧大脑发育较对侧延迟、左侧脑室增宽。③胎儿1尸体解剖显示：女性胎儿，大脑镰左移，右外侧蛛网膜与周围组织间少量积液。双侧大脑稍不对称，右侧大脑体积较左侧稍小；脑膜组织切片经HE染色，高倍镜下显示硬脑膜和蛛网膜分离，形成腔隙。胎儿其他器官未见异常。④胎儿1家系遗传病全外显子组测序（WES），未检出与该家系临床表型相关的致病/疑似致病基因变异。对胎儿1基因组DNA 拷贝数变异分析，未发现长度＞100 kb的具有临床意义的微缺失或微重复拷贝数变异。⑤文献复习结果显示，共检索到10篇关于胎儿AC 相关研究文献，共计纳入465例产前被诊断的AC 胎儿，最常见AC 位于幕上区大脑半球间隙，其次为鞍上区。50%～70%AC体积大小于孕期无明显变化，约20%AC 体积于孕期或生后持续增大，3%～28%AC新生儿需手术治疗，孤立性AC胎儿预后较好，70%～91%患儿术后随访正常。

结论

胎儿1产前胎儿超声和胎儿MRI与大脑解剖相符，影像学检查可提供胎儿AC有效诊断依据。

Objective

To explore the imaging manifestations，genetic characteristics，and pathological features of fetal arachnoid cysts（AC）.

Methods

A case of a 32-week-gestational-age fetus with a prenatal ultrasound showing a large AC treated at Dongguan People's Hospital in July 2023 was selected in the study.A retrospective analysis was conducted on the fetal ultrasound examination and fetal head MRI examination results before termination of pregnancy，as well as the genetic testing and pathological autopsy results after termination of pregnancy.The literature on fetal AC was retrieved from the China National Knowledge Infrastructure，Wanfang Data Knowledge Service Platform，and Pub Med，Web of Science databases using the Chinese and English keywords"arachnoid cyst""fetus""fetal""intracranial".The literature search time was set from the establishment of the above databases to January 2024.This study followed the procedures in accordance with the 2013 revision of the Declaration of Helsinki by the World Medical Association and adhered to the ethical standards set by the Ethics Committee of the Tenth Affiliated Hospital of Southern Medical University ^（Dongguan People's Hospital） （Approval No.IRB2023-WZ-156）.The pregnant woman gave informed consent for the diagnosis and treatment.

Results

①The fetus's ultrasound examination at 32 weeks of gestation indicated that the fetal development was equivalent to 32 weeks，with a 9.7 cm×3.3 cm cystic occupancy in the right arachnoid，clear boundaries，good transmission，no obvious blood flow signals，asymmetrical bilateral cerebral hemispheres，the left side larger than that of the right，the midline of the brain shifted to the left，and the maximum measurement of the left ventricle was 1.4 cm，tentatively diagnosed as right AC，and dilatation of the left ventricle.②The fetus's head MRI at 32 weeks of gestation showed：the arachnoid space of the right cerebral hemisphere of the fetus was overall widened in a crescent shape，with the maximum diameter measured in the axial position as 10.6 mm×2.3 mm，the cerebrum and the falx cerebri were shifted to the left as a whole，no abnormal signal was seen in the cerebral substance，the bilateral cerebral hemispheres were asymmetrical，the right hemisphere was smaller than that of the opposite side，the cerebral sulci were asymmetrical bilaterally，some of the right cerebral sulci were shallower，and the maximum diameter of the left ventricle was 1.6 cm，indicating right AC，delayed development of the right cerebrum compared to the opposite side，and dilatation of the left ventricle.③The pathological autopsy of the fetus showed：the falx cerebri was shifted to the left，and there was a small amount of fluid between the right outer arachnoid and the surrounding tissue.The bilateral cerebral hemispheres were slightly asymmetrical，with the right cerebral volume slightly smaller than that of the left；the meningeal tissue section was stained with HE，and under high magnification，it was shown that the dura mater and arachnoid were separated，forming a cavity.④Whole-exome sequencing（WES）results of the family of this case showed no pathogenic/likely pathogenic variations related to the clinical phenotype of this family.⑤The literature review showed that a total of 10 related documents were retrieved，including 465 fetuses diagnosed with AC prenatally.The most common location of AC was the interhemispheric space of the supratentorial region，followed by the suprasellar region.And 50%to 70%of the cysts showed no significant change in volume during pregnancy，about 20%of the cysts continued to enlarge during pregnancy or after birth，and 3%to 28%of the children needed surgical treatment after birth，and the prognosis of isolated cysts was good，with 70%to 91%of the fetuses followed up normally after birth.

Conclusions

The results of prenatal ultrasound and fetal MRI were consistent with the pathological autopsy results，and imaging examination can provide an effective basis for the diagnosis of fetal AC.