小腦橋腦角區(qū)罕見(jiàn)腫瘤診斷李飛平引言

小腦橋腦角區(qū)（CPA）是腫瘤的好發(fā)區(qū)域，占所有顱內(nèi)腫瘤的6%-10%，最常見(jiàn)的是聽(tīng)神經(jīng)瘤（前庭神經(jīng)鞘瘤）和腦膜瘤，兩者約占85%-90%，其他各種罕見(jiàn)腫瘤共占10%-15%。由于MRI技術(shù)敏感性和準(zhǔn)確性的不斷提高，影像診斷工作者將會(huì)越來(lái)越頻繁的碰到一些罕見(jiàn)CPA區(qū)腫瘤，因此熟悉和掌握其影像學(xué)特征，對(duì)診斷及術(shù)前評(píng)估都有著十分重要的意義。起源于CPA的腫瘤CPA是由小腦橋腦角池腦膜圍繞形成，內(nèi)除含腦脊液之外還包括神經(jīng)、動(dòng)脈血管及可能存在的胚胎殘余物，上述成分均有可能成為CPA少見(jiàn)腫瘤起源的結(jié)構(gòu)。Arachnoidcystina27-year-oldwomanwithheadaches.(a)AxialT1-weightedMRimageshowsanarachnoidcystwithsignalintensity

similartothatofCSFstretchingtheleftseventhandeighthcranialnervecomplex(arrow).

(b)AxialT2-weightedMR

imageshowsthe

lobulatedmarginsofthecystimpingingonthepons(arrowhead).

(c)AxialheavilyT2-weighted(constructiveinterferenceinthesteadystate)MRimageshowstheextentofthetumor.蛛網(wǎng)膜囊腫蛛網(wǎng)膜囊腫是囊樣蛛網(wǎng)膜內(nèi)腫塊，內(nèi)充滿腦脊液，起源不確定。影像上其密度、信號(hào)強(qiáng)度與腦脊液相似，呈圓形，邊緣光滑，周圍神經(jīng)脈管結(jié)構(gòu)受推移，臨近骨質(zhì)受累及，無(wú)鈣化及強(qiáng)化。

(b)AxialT2-weightedMRimageshowsthecystdisplacingthevascularstructuresoftheCPA(arrowheads).

Lipomaina7-year-oldboywith

apolymalformationsyndrome.(a)AxialCTscanshowsawell-definedhypoattenuatinglipomaoftheleftCPA.神經(jīng)鞘瘤盡管前庭神經(jīng)鞘瘤占了顱內(nèi)神經(jīng)鞘瘤的95%，CPA其他所有神經(jīng)也可發(fā)生神經(jīng)鞘瘤，特別是三叉神經(jīng)、面神經(jīng)以及IX-XII顱神經(jīng)。其影像學(xué)表現(xiàn)同前庭神經(jīng)鞘瘤相似，包括可能的囊變與出血，診斷的關(guān)鍵是神經(jīng)解剖學(xué)定位。Schwannomaina34-year-oldmanwithrighttrigeminalneuralgia.Contrastmaterial-enhancedaxialT1-weightedMRimageshowsahomogeneous,enhanced,dumbbell-shapedrighttrigeminalschwannomainvolvingthecisternalpartofthenerveandMeckelcave.Schwannomaina52-year-oldwomanwithleftearpain.(a)Gadolinium-enhancedcoronalT1-weightedMRimageshowsanenhancingschwannomaoftheninth,10th,and11thcranialnervesinthelowestpartoftheCPA.(b)CoronalT2-weightedMRimageshowstheextentoftheschwannomaalongthecourseofthenerves(arrows)andbeneaththenormalleftinternalauditorycanal

(arrowheads).(c)AxialCTscanshowssmootherosionoftheskullbaseandespeciallythejugularforamenbytheschwannoma.AxialT2-weightedMRimageshowsananeurysmoftheleftposteriorinferiorcerebellararterywithtypicallackofsignal(arrow).Aneurysmina75-year-oldmanwithhypoglossalnervepalsy.(a)AxialT2-weightedMRimageshowsathrombosedaneurysmoftherightposteriorinferiorcerebellararterywithfocalcalcification(arrowhead).Notethenormalrighthypoglossalcanal(arrow),afindinginconsistentwithaschwannoma.黑素細(xì)胞瘤黑素細(xì)胞瘤一般發(fā)生在后顱窩柔腦膜，有良性和惡性兩種，良性黑素細(xì)胞瘤即腦膜黑素細(xì)胞瘤，而轉(zhuǎn)移性惡性黑素細(xì)胞瘤一般遠(yuǎn)多于原發(fā)性黑素細(xì)胞瘤。原發(fā)性黑素細(xì)胞瘤一般較局限，CT上成等低密度，強(qiáng)化均勻；MRI上由于腫瘤內(nèi)黑色素的含量不同，在T1、T2上信號(hào)強(qiáng)度也各異；一般在T1上為等高信號(hào)，T2上為等低信號(hào)，增強(qiáng)有強(qiáng)化。Melanomaina58-year-oldwomanwithaleftcerebellarsyndrome.(a)AxialCTscanshowsahyperattenuatingmelanomaoftheleftCPA.(c)Gadolinium-enhancedaxialT1-weightedMRimageshowsanormalleftinternalauditorycanal(arrow)andlackofduraltailenhancement.轉(zhuǎn)移瘤Metastasesina67-year-oldmanwithlungcancerandright-sidedhypoacusia,vertigo,andearpain

(a)AxialT2-weightedMRimageshowsametastasisoftherightCPAthatmimicsavestibularschwannomabutwithunusualassociatedmiddleearretention(b)Contrast-enhancedaxialT1-weightedMRimageshowsintenseenhancementofthelesion,whichextendsintothecochlea(arrow).Notethepresenceofanotherenhancinglesionatthetipoftherightpetrousbone(arrowhead).膽固醇肉芽腫膽固醇肉芽腫可發(fā)生于任何受阻的氣房?jī)?nèi)，通常發(fā)生于巖谷尖部，長(zhǎng)到足夠大時(shí)可伸入后顱窩內(nèi)壓迫神經(jīng)從而產(chǎn)生相應(yīng)的神經(jīng)癥狀。CT：顳骨內(nèi)邊緣光滑、銳利的膨脹性腫塊，相對(duì)腦組織呈等密度，無(wú)強(qiáng)化；MRI：T1、T2都表現(xiàn)為中心高信號(hào)，周邊可見(jiàn)低信號(hào)帶，T1特發(fā)性中心均勻高信號(hào)是其特征性表現(xiàn)。(a)AxialT1-weightedMRimageshowsacholesterolgranulomaattheapexoftherightpetrousbonewithtypicalhighsignalintensity.Anadditionalsuggestivefeatureisthethinhypointenserim(arrowheads),whichrepresentsexpandedcorticalboneofthepetrousapex.(b)AxialT2-weightedMRimageshowsthatthegranulomahasheterogeneoussignalintensitysurroundedbyahypointenserim(arrowheads).(c)Contrast-enhancedcoronalT1-weightedMRimageshowsthenormalrighttrigeminalnerve(arrow)atthetopofthemass神經(jīng)節(jié)細(xì)胞瘤侵犯CPA的神經(jīng)節(jié)細(xì)胞瘤，起源于位于頸靜脈孔內(nèi)沿著迷走神經(jīng)或鼓室神經(jīng)走行的微小體，可破壞顳骨巖部，腫瘤增大可累及CPA。CT：邊界清楚，有強(qiáng)化的軟組織腫塊，周圍骨質(zhì)呈蟲(chóng)蝕樣破壞；MRI：富含血管的軟組織腫塊，內(nèi)部表現(xiàn)為斑點(diǎn)狀、蛇紋樣無(wú)信號(hào)區(qū)。瘤內(nèi)局部出血在T1上可見(jiàn)表現(xiàn)為局部高信號(hào)，出現(xiàn)特征性的“鹽胡椒征”。(a)ahugeparagangliomadestroyingthepetrousboneandinvadingtherightCPA.Massiveflowvoids(arrowheads)reflectthehypervascularityofthelesion.NotethethinlayeroftrappedCSF(arrow)betweenthemassandthebrainstem,whichindicatesanextraaxialorigin.(b)AxialT1-weightedMRimageshowsthesuggestivesalt-and-pepperappearanceoftheparaganglioma.(c)Contrast-enhancedaxialT1-weightedMRimageshowsintenseenhancementofthelesionalongwithunusualduraltailenhancementofthemeninges(arrows).軟骨瘤和軟骨肉瘤軟骨腫瘤發(fā)生來(lái)自封閉于顱底骨骼內(nèi)胚胎時(shí)期軟骨的殘余物，一般發(fā)生在巖枕或蝶枕結(jié)合出，破壞臨近骨質(zhì)。Chondrosarcomaina25-year-oldwomanwithintracranialhypertension.(a)AxialT2-weightedMRimageshowsawell-definedchondrosarcomawithmarkedmasseffectontheponsandfourthventricle.(b)AxialT1-weightedMRimageshowsaskullbasepedicle.(c)Contrast-enhancedcoronalT1-weightedMRimageshowspunctateenhancement,whichcouldsuggestachondromatouslesion.(d)AxialCTscansh