婴幼儿脑外积液的MRI研究:脑外间隙发育性与病理性的扩大

目的 分析婴幼儿脑外积液的MRI特征，明确脑外积液的病因及与脑发育的关系。方法 选择经MRI确诊的46例年龄〈2岁的脑外积液患儿，分析其MRI特征。并按月龄分7组，在T2WI上测量脑外间隙宽度并与正常值对照。结果 引起婴幼儿脑外积液的主要原发病有感染性疾病、硬膜下或蛛网膜下出血、缺氧缺血性脑病（HIE）占67．4％（31／46例），原因不明占26．1％（12／46例）。脑外积液主要发生在大脑凸面的前部，以蛛网膜下腔积液多见，占80．4％（37／46例），硬膜下积液8．7％（4／46例），硬膜下和蛛网膜下积液并存10．9％（5／46例）。其中，化脓性脑膜炎可致硬脑膜或软脑膜的信号在T1WI或T2WI上增高，常引起硬膜下积液或与蛛网膜下腔积液并存。硬膜下和（或）蛛网膜下腔出血常为硬膜下和蛛网膜下腔积液并存，并常见大脑表面静脉（皮质静脉）增粗、淤滞和出血，在T1WI上信号增高。HIE所致脑外积液为蛛网膜下腔积液，可见HIE所致的特征性改变，常有髓鞘化落后占63．6％（7／11例）。原因不明者多为双侧对称性的蛛网膜下腔积液。脑室扩大主要见于HIE和硬膜下或蛛网膜下出血。结论 婴幼儿脑外积液多有明确病因，以出血、感染和HIE为多见，积液的部位与脑发育的特性有关，MRI对明确脑外积液的性质，判断病因有帮助。

MR imaging study on external hydrocephalus in infants: extracerebral space developmental and pathological enlargement

Objective To analyze the characteristics of external hydrocephalus in infancy with MR imaging,and to explore the cause of accumulation of extracerebral fluid and the relation with brain development.Methods Conventional magnetic resonance T_1 weighted imaging(T_1WI) and T_2 weighted imaging(T_2WI) were performed in 46 infants aged 2 years or younger with external hydrocephalus(EH),and the results were analyzed.They were divided into 7 age groups.The width of extracerabral space was measured on T_2WI and compared with normal standard.Results EH mainly resulted from infection,subdural hematoma or subarachnoid hemorrhage,HIE,which were 67.4%(31/46 cases) of the cases;EH with unknown cause were 26.1%(12/46 cases).EH was mainly located at the foreside of cerebral convexity,of which 80.4%(37/46 cases)was predominantly in the subarachnoid space,8.7%(4/46 cases) in subdural space,10.9% was subdural coexisted with subarachnoid collection.Duramater and piamater were high signal on T_1WI or T_2WI in purulent meningitis,and subdural or coexisted with subarachnoid collection often occurred.In subdural and(or) subarachnoid hematoma,subdural collection commonly coexisted with subarachnoid collection,and the cerebral cortical veins were often seen thickened diameter,stasis and hemorrhage with high signals on T_1WI.HIE caused subarachnoid collection,63.6%(7/11 cases) of which were concurred with delayed myelination.EH with unknown cause often appeared bilateral symmetrical subarachnoid collection.Enlargement of ventricular size were predominantly seen in HIE,subdural hematoma or subarachnoid hemorrhage.Conclusion EH often had definite etiological factor,which were mainly hemorrhage,infection and HIE.The location was associated with brain development.MR imaging was useful for judging reason and ascertaining character of EH.