文永霞，王　靜，李建紅，馬艷茹，劉彩云

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3.0T MRA對(duì)椎基底動(dòng)脈開窗畸形的診斷價(jià)值

文永霞，王靜，李建紅，馬艷茹，劉彩云

目的探討3.0T MRI三維時(shí)間飛躍法(3D TOF)或增強(qiáng)磁共振血管造影(CEMRA)對(duì)頭頸部動(dòng)脈開窗畸形的診斷價(jià)值。方法搜集2012年10月-2014年8月行頭頸部3.0T MRI(3D TOF)或CEMRA檢查的患者資料371例，原始和減影圖像經(jīng)工作站后處理，得到容積重組(VR)、最大密度投影(MIP)、薄層最大密度投影多平面或曲面重組( thin sliceMIP,TSMIP)，比較各組圖像對(duì)血管異常的顯示情況。結(jié)果371例中，頭頸部動(dòng)脈開窗畸形18例(檢出率4.9%,18/371),位于基底動(dòng)脈11例(檢出率3.0%,11/371),其中10例位于基底動(dòng)脈起始處,1例位于基底動(dòng)脈干;位于椎動(dòng)脈入顱底段3例(檢出率0.8%,3/371);位于右側(cè)大腦前動(dòng)脈A1段1例;位于前交通動(dòng)脈1例;位于大腦中動(dòng)脈2例。18例中,3例(16.7%,3/18)椎基底動(dòng)脈開窗畸形合并動(dòng)脈瘤。結(jié)論CEMRA或3D TOFMRA能清楚顯示和診斷頭頸部動(dòng)脈開窗畸形這一少見血管異常。

磁共振血管造影術(shù)；開窗；頭頸部動(dòng)脈；椎動(dòng)脈；基底動(dòng)脈

頭頸部動(dòng)脈開窗畸形(或稱為有孔型頭頸部動(dòng)脈)是動(dòng)脈發(fā)育異常中的一種少見的先天性疾病，發(fā)生在椎基底動(dòng)脈最為多見[1],但椎基底動(dòng)脈開窗畸形發(fā)生率很低，據(jù)相關(guān)文獻(xiàn)報(bào)道為1.3%～5.3%[2];血管造影檢出率為0.4%～0.6%[3]。但報(bào)道有關(guān)頭頸部開窗畸形磁共振血管造影(MRA)研究文獻(xiàn)極為少見[4]。我們回顧分析近2 y來我院利用3.0T超導(dǎo)型磁共振掃描儀行頭頸部增強(qiáng)磁共振血管造影(contrast-enhanced MRA,CEMRA)和三維時(shí)間飛躍(three-dimensional time-of-flight,3D TOF)技術(shù)的患者資料，以探討3.0T MRI(3D TOF)或CEMRA對(duì)頭頸部動(dòng)脈開窗畸形的診斷價(jià)值。

1　材料與方法

1.1一般資料搜集從2012年10月-2014年8月371例患者，并行頭頸部CE MRA或3D TOFMRA檢查，發(fā)現(xiàn)頭頸部動(dòng)脈開窗畸形患者18例,其中男11例,女7例,年齡40歲～89歲,平均58.6歲。16例有伴隨頭痛、眩暈、等臨床癥狀,5例同時(shí)伴有單側(cè)肢體活動(dòng)受限或肢體麻木；另4例伴有言語含混不清、意識(shí)障礙。14例行頭頸部CEMRA,7例行3D TOFMRA,其中3例同時(shí)行顱頸部CE MRA和3D TOFMRA。

1.2檢查方法MRA檢查所用設(shè)備為3.0T超導(dǎo)型磁共振掃描儀(Philips Achieva 3.0T),相控頸、脊柱線圈聯(lián)合采集與正交頭顱線圈,圖像在最后經(jīng)工作站Viewform R 5.1處理。磁共振高壓注射器(Me-drao,Spectris)用于增強(qiáng)掃描。3D CEMRA:每例均行頭頸部CEMRA二維相位對(duì)比(2D PC)矢狀面的定位。測(cè)定延遲時(shí)間使用注射0.5～1.0 ml釓噴替酸葡甲胺( Gd-DTPA)團(tuán)注(testbolus)。三維擾相快速小角度梯度回波(3D FLASH)傾斜冠狀面成像用于頭、頸掃描,按照掃描范圍和部位不同,掃描時(shí)間約9～23 s設(shè)定層厚為0.80～1.25 mm,。掃描方法:先進(jìn)行第一次動(dòng)態(tài)掃描作為減影的蒙片,然后注射Gd-DTPA,并從肘前靜脈以2.5～3.0 ml/s的流率注射20～30 ml Gd-DTPA,延遲時(shí)間測(cè)算完成后，開始第2次動(dòng)態(tài)掃描,在工作站進(jìn)行后處理送到的圖像。

3D TOFMRA:采用3D FLASH序列,單純水激勵(lì)成像(water excite,WE),應(yīng)用磁化傳遞(magnetic transfer contras,tMTC),TR 30 ms,TE 3.4 ms,翻轉(zhuǎn)角20°,矩陣256 mm×384 mm～360 mm×768 mm,視野192 mm×230 mm,層厚0.8 mm,掃描層數(shù)96～128。圖像三維后處理技術(shù)采用:(1)容積重組(VR)；(2)最大密度投影(MIP)；(3)薄層最大密度投影(thin slice MIP,TSMIP)多平面或曲面重組。

2　結(jié)　果

在本組371例患者中,一共檢測(cè)出了基底動(dòng)脈開窗畸形11例(檢出率3.0%,11/371),其中1例位于基底動(dòng)脈中部，還有10例位于基底動(dòng)脈起始部，還有頭頸部動(dòng)脈開窗畸形18例(檢出率4.9%,18/371)。位于基底動(dòng)脈起始處的10例患者輪廓開窗動(dòng)脈的呈梭形,血管異常2支間形成圓孔狀充盈缺損樣改變，位于基底動(dòng)脈中部的1例,形成了裂縫樣開窗動(dòng)脈。4例椎基底動(dòng)脈開窗畸形位于頸動(dòng)脈系統(tǒng),2例位于大腦中動(dòng)脈，3例椎動(dòng)脈開窗畸形(檢出率為0.8%,3/371),位于前交通動(dòng)脈1例。其中開窗椎基底動(dòng)脈合并頸動(dòng)脈系統(tǒng)動(dòng)脈瘤3例,頸動(dòng)脈系統(tǒng)開窗畸形未伴有動(dòng)脈瘤4例。

3　討　論

有文獻(xiàn)報(bào)道頭頸部動(dòng)脈開窗畸形[5,6]發(fā)生部位最常見為基底動(dòng)脈,第2位為椎動(dòng)脈、大腦中動(dòng)脈和大腦前動(dòng)脈較少。發(fā)生機(jī)制有兩種胚胎發(fā)育機(jī)制學(xué)說，其中De Cara等[7]提出另一種胚胎學(xué)機(jī)制,基底動(dòng)脈開窗畸形不是因?yàn)樵汲蓪?duì)動(dòng)脈不完全融合導(dǎo)致的。還有Padget等[8]認(rèn)為在胚胎發(fā)育第5周,胎兒的基底動(dòng)脈由縱行且成對(duì)的神經(jīng)動(dòng)脈融合而成，縱行且成對(duì)的胚胎神經(jīng)動(dòng)脈如果在某一點(diǎn)停止融合,基底動(dòng)脈發(fā)育成開窗畸形就發(fā)生了。而是由于腦內(nèi)殘存了原始側(cè)動(dòng)脈染色體部分,這兩種不同的機(jī)制都有道理。更多的觀點(diǎn)認(rèn)為椎動(dòng)脈開窗畸形的形成由這兩個(gè)觀點(diǎn)共同作用的。而椎動(dòng)脈開窗畸形機(jī)制更為復(fù)雜[9],考慮與發(fā)育時(shí)叢狀血管吻合不全或部分原始椎動(dòng)脈殘留或再通有關(guān)。有兩種頭頸部動(dòng)脈開窗畸形,一種是凸透鏡狀開窗畸形[10]；另一種是裂縫狀開窗畸形。基腦內(nèi)動(dòng)脈開窗畸形最好發(fā)部位是基底動(dòng)脈,根據(jù)好發(fā)部位不同分3類:起始部、中間部、遠(yuǎn)側(cè)部。其中最為多見[11～14]為基底動(dòng)脈起始部。

隨著影像技術(shù)發(fā)展和軟件系統(tǒng)升級(jí),診斷頭頸部動(dòng)脈疾病CE-MRA或3D-TOFMRA的優(yōu)越性日漸明顯,1.5T MRI 3.0T MRI與相比，3.0T MRI判斷頭頸部動(dòng)脈開窗畸形更佳，本組搜集的371例頭頸部MRA,均行3.0T 3D TOF或CEMRA檢查。本組18例頭頸部開窗畸形動(dòng)脈都經(jīng)CE MRA或3D TOFMRA處理并獲得滿意圖像。開窗畸形血管在MIP中清楚顯示，并可旋轉(zhuǎn)角度來鑒別分支血管。椎基底動(dòng)脈開窗畸形在頭頸部CEMRA中清楚的顯示,頭頸部血管異常不用對(duì)比劑3D TOFMRA就能清楚顯示。

在本組病例中,371例行3.0T MRA檢查,11例基底動(dòng)脈開窗畸形,檢出率為3.0%,18例頭頸部動(dòng)脈開窗畸形,檢出率為4.9%,比Uchino等[15]報(bào)道的1.7%的檢出率高。最好發(fā)的部位是基底動(dòng)脈，尤其是基底動(dòng)脈起始部,18例頭頸部動(dòng)脈開窗畸形當(dāng)中有10例位于基底動(dòng)脈起始部,基底動(dòng)脈中間部只有1例,位于遠(yuǎn)端的沒有發(fā)現(xiàn)，頭頸部動(dòng)脈開窗畸形好發(fā)部位也多見于椎動(dòng)脈,在18例中,在椎動(dòng)脈入顱底段有3例。在本組18例中,位于頸動(dòng)脈系統(tǒng)有4例,分別位于大腦前動(dòng)脈、大腦中動(dòng)脈和前交通動(dòng)脈。

371例患者行3.0T 3D CE MRA或3D TOFMRA檢查中,基底動(dòng)脈開窗畸形檢出率3.0%,頭頸部動(dòng)脈開窗畸形檢出率達(dá)4.9%,檢出比值高于多數(shù)經(jīng)DSA診斷的文獻(xiàn)報(bào)道[3],幾乎于尸檢有近似的發(fā)現(xiàn)率[2]。由此可見，影像學(xué)檢查和尸檢發(fā)現(xiàn)椎基底動(dòng)脈開窗畸形差異很大，其中原因可能有：(1)影像學(xué)檢查方法血管顯示尚不充分；(2)國(guó)內(nèi)文獻(xiàn)報(bào)道少，頭頸部血管開窗畸形的診斷中存在認(rèn)識(shí)不足；(3)頸部2D TOFMRA對(duì)椎基底動(dòng)脈顯示不佳，而頭部3D TOFMRA掃描范圍以Willis環(huán)為中心，易出現(xiàn)漏診。

椎基底動(dòng)脈合并單發(fā)或多發(fā)動(dòng)脈瘤在基底動(dòng)脈開窗畸形中比較多見[16,17],基底動(dòng)脈開窗畸形伴發(fā)動(dòng)脈瘤類似于分叉血管的末端好發(fā)動(dòng)脈瘤，所以認(rèn)為是由于基底動(dòng)脈的組織學(xué)和血流動(dòng)力學(xué)的雙重作用所致，18例頭頸部動(dòng)脈開窗畸形中,伴發(fā)動(dòng)脈瘤的3例椎基底動(dòng)脈開窗畸形,但均位于頸動(dòng)脈系統(tǒng),而有待于進(jìn)一步研究的是椎基底動(dòng)脈開窗畸形與頸動(dòng)脈系統(tǒng)動(dòng)脈瘤的關(guān)系,與Uchino等[18,19]報(bào)道吻合的是4例頸動(dòng)脈系統(tǒng)開窗畸形血管均未伴發(fā)動(dòng)脈瘤。

頭頸部動(dòng)脈開窗畸形在臨床中癥狀不明顯，大多在影像學(xué)或尸檢時(shí)偶然發(fā)現(xiàn),臨床意義主要在神經(jīng)介入和頭頸外科治療時(shí)的提示作用。頭頸部動(dòng)脈開窗畸形可能增加血管內(nèi)介入栓塞治療難度,容易導(dǎo)致手術(shù)中血管損傷。也由于一些高位頸髓被頭頸部動(dòng)脈開窗畸形壓迫[20],并可因?yàn)槭中g(shù)損傷或者壓迫開窗畸形的分支血管，從而可能導(dǎo)致嚴(yán)重的腦卒中[21]。所以充分利用3.0T CEMRA或TOFMRA檢查技術(shù)來判斷頭頸部動(dòng)脈開窗畸形在臨床中是非常重要的。

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3.0T MRA evaluation in fenestration of the intra and extracranial artery

WENYongxia,WANGJing,LIJianhong,etal.

(DepartmentofNeurology,theNo.3ProvincialPeople’sHospitaloftheNingxiaHuiAutonomousRegion,Yinchuan750011,China)

ObjectiveTo discuss the value of 3.0T magnetic resonance angiography(MRA) in diagnosis of fenestration in intra and extracranial artery.MethodsBetween October 2010 and August 2012,three dimensional contrast enhanced (CEMRA) or three dimensional time of flight (3D TOF) MR angiographies of 371 head and carotid arteries were collected.The reconstructed images were then processed into volume rending (VR),maximal intensity projection(MIP) and thin slicemultiplane reconstruction(TSMIP).And the different images were compared.Results18(4.9%,18/371) fenestrations of intra and extracranial artery were detected.In 18 fenestrations,11(3.0%,11/371) fenestrations were located in basilar atrety:10 fenestrations were located in proximal portion of basilar artery trunk,1 fenestration was present at basilar artery trunk；3 fenestrations were present at vertebrobasilar junction；1 fenestration was located in anterior cerebral artery；1 fenestrationwas located in anterior communicating artery；2 fenestrations were located in middle cerebral artery.3(16.7%,3/18) of these fenestrations were associated with cerebral intracranial aneurysms.ConclusionCEMRA and 3D TOFMRA can clearly detect intra and extracranial artery fenestrations.

Magnetic resonance angiography；Fenestration；Intra and extracranial artery；Vertebral artery；Basilar artery

1003-2754(2016)02-0120-03

2015-12-28；

2016-02-02

(寧夏第三人民醫(yī)院神經(jīng)內(nèi)科,寧夏 銀川 750011 )

文永霞,E-mail：wyongxia@163.com

R743.4

A