Cerebralhydatiddisease-Cerebralhydatiddisease-EchinococcusgranulosusEchinococcusgranulosusinfectionMRIdiagnoseinfectionMRIdiagnose脑包虫病脑包虫病--细粒棘球绦虫感染细粒棘球绦虫感染MRIMRI诊断诊断2012.2.272012.2.27概述概述HydatiddiseaseisaworldwidezoonosisproducedbythelarvalstageoftheEchinococcustapeworm.包虫病是一种流行于全世界范围的动物源性寄生虫病，主要是由棘球绦虫幼虫所引发。ThetwomaintypesofhydatiddiseasearecausedbyEgranulosusandEmultilocularis.Egranulosusisthemorecommontype.引发包虫病的两种主要的寄生虫类型分别是细粒棘球绦虫和多房棘球绦虫，细粒棘球绦虫更常见。whereasEmultilocularisislesscommonbutmoreinvasive,mimickingamalignancy.多房棘球绦虫少见但侵袭性更强，其表现类似于恶性病变。ItiscommonlyseeninthegreatgrazingregionsoftheWorld,particularlytheMediterraneanregion,Africa,SouthAmerica,theMiddleEast,Australia,andNewZealand.它常见于世界上的的牧区，特别是地中海区域、非洲、南美、东亚、澳大利亚和新西兰。Dogsorothercarnivoresaredefinitivehosts,whereassheeporotherruminantsareintermediatehosts.狗或其他的肉食动物是终宿主，而羊或其他的反刍性动物是中间宿主。Humansaresecondarilyinfectedbytheingestionoffoodorwaterthathasbeencontaminatedbydogfecescontainingtheeggsoftheparasite.被包含有寄生虫卵的狗粪所污染的食物或水被人类摄入从而引起继发性感染。Intracranialgranulosusechinococcosisoccursinonlyapproximately2%ofcasesofhydatiddisease.颅内的细粒棘球绦虫感染仅见于约2％的包虫病病例。typicallyinvolvingthecerebralparenchyma,especiallytheparietallobes,correspondingtothemiddlecerebralarterywatershedterritory.IntracranialsubarachnoidspacesarethesecondmostcommonlocationofthediseaseintheCNS,althoughtheiroccurrenceisfarlessfrequent.通常累及大脑实质，特别是顶叶，符合大脑中动脉分水岭区，颅内的蛛网膜下腔是第二好发部位。Casesofcerebralaqueductcyst,giganticcystarisingfromthediploeofcranialboneswithintracranialextension,andintraduralspinalhydatidcystshavebeenreported.发生于大脑导水管的囊肿、起源于颅骨板障并延伸至颅内的巨大囊肿、以及椎管内硬膜下囊肿都有报道。Cystsareusuallysingleandmaybeunilocularormultilocular.囊肿常常是单发的，可以是单房或多房。Cerebralhydatidcystismorecommoninchildrenthaninadults.儿童大脑包虫囊肿比成人更常见。AtMRI,cerebralhydatiddiseasegenerallyappearsunilocularandisisointenserelativetocerebrospinalfluid.大脑包虫病通常表现为单房病变，信号与脑脊液相仿。Thelackofsurroundingedemaandthemarkedmasseffectmakeiteasytodistinguishcerebralhydatiddiseasefromabscessandcystictumor.无周边水肿，明显的占位效应可以与脓肿和其他囊性肿瘤相鉴别。Thepresenceofahypointenserim,especiallyonT2-weightedMRimages,ischaracteristicofhydatidcystofthebrain.病变可以出现一个低信号环，尤其是在T2序列上，这是脑包虫囊肿特征性病变。Cerebralhydatidcystisgenerallysolitarybutmaybemultiplewhenitrupturesspontaneouslyorduetotraumaorsurgery.脑包虫囊肿通常是单囊的,当它自发破裂或由于外伤或手术而成为多囊。Multivesicularcystsarerareinthebrain.Calcificationoccursinlessthan1%ofcases.颅内的多囊状病变是相当少的，不超过1％的病例可以出现钙化。T1andT2weightedMRimagesdemonstratetwohomogeneouscystswithsignalintensitysimilartocerebrospinalfluidandverythin-walls(yellowarrows).Thereissignificantmasseffectonthelateralventricularsystem.T1和T2序列显示两个信号均匀的囊状影，其内信号类似于脑脊液，伴有非常薄的囊壁，囊肿对邻近的侧脑室有明显的推移挤压。MRI表现ContrastenhancedMRIshowslackofenhancementofthecystwalls.增强MRI囊...
