3.0T MRA对椎基底动脉开窗畸形的诊断价值

文永霞，王　静，李建红，马艳茹，刘彩云



3.0T MRA对椎基底动脉开窗畸形的诊断价值

文永霞，王静，李建红，马艳茹，刘彩云

目的探讨3.0T MRI三维时间飞跃法(3D TOF)或增强磁共振血管造影(CEMRA)对头颈部动脉开窗畸形的诊断价值。方法搜集2012年10月-2014年8月行头颈部3.0T MRI(3D TOF)或CEMRA检查的患者资料371例，原始和减影图像经工作站后处理，得到容积重组(VR)、最大密度投影(MIP)、薄层最大密度投影多平面或曲面重组( thin sliceMIP,TSMIP)，比较各组图像对血管异常的显示情况。结果371例中，头颈部动脉开窗畸形18例(检出率4.9%,18/371),位于基底动脉11例(检出率3.0%,11/371),其中10例位于基底动脉起始处,1例位于基底动脉干;位于椎动脉入颅底段3例(检出率0.8%,3/371);位于右侧大脑前动脉A1段1例;位于前交通动脉1例;位于大脑中动脉2例。18例中,3例(16.7%,3/18)椎基底动脉开窗畸形合并动脉瘤。结论CEMRA或3D TOFMRA能清楚显示和诊断头颈部动脉开窗畸形这一少见血管异常。

磁共振血管造影术；开窗；头颈部动脉；椎动脉；基底动脉

头颈部动脉开窗畸形(或称为有孔型头颈部动脉)是动脉发育异常中的一种少见的先天性疾病，发生在椎基底动脉最为多见[1],但椎基底动脉开窗畸形发生率很低，据相关文献报道为1.3%～5.3%[2];血管造影检出率为0.4%～0.6%[3]。但报道有关头颈部开窗畸形磁共振血管造影(MRA)研究文献极为少见[4]。我们回顾分析近2 y来我院利用3.0T超导型磁共振扫描仪行头颈部增强磁共振血管造影(contrast-enhanced MRA,CEMRA)和三维时间飞跃(three-dimensional time-of-flight,3D TOF)技术的患者资料，以探讨3.0T MRI(3D TOF)或CEMRA对头颈部动脉开窗畸形的诊断价值。

1　材料与方法

1.1一般资料搜集从2012年10月-2014年8月371例患者，并行头颈部CE MRA或3D TOFMRA检查，发现头颈部动脉开窗畸形患者18例,其中男11例,女7例,年龄40岁～89岁,平均58.6岁。16例有伴随头痛、眩晕、等临床症状,5例同时伴有单侧肢体活动受限或肢体麻木；另4例伴有言语含混不清、意识障碍。14例行头颈部CEMRA,7例行3D TOFMRA,其中3例同时行颅颈部CE MRA和3D TOFMRA。

1.2检查方法MRA检查所用设备为3.0T超导型磁共振扫描仪(Philips Achieva 3.0T),相控颈、脊柱线圈联合采集与正交头颅线圈,图像在最后经工作站Viewform R 5.1处理。磁共振高压注射器(Me-drao,Spectris)用于增强扫描。3D CEMRA:每例均行头颈部CEMRA二维相位对比(2D PC)矢状面的定位。测定延迟时间使用注射0.5～1.0 ml钆喷替酸葡甲胺( Gd-DTPA)团注(testbolus)。三维扰相快速小角度梯度回波(3D FLASH)倾斜冠状面成像用于头、颈扫描,按照扫描范围和部位不同,扫描时间约9～23 s设定层厚为0.80～1.25 mm,。扫描方法:先进行第一次动态扫描作为减影的蒙片,然后注射Gd-DTPA,并从肘前静脉以2.5～3.0 ml/s的流率注射20～30 ml Gd-DTPA,延迟时间测算完成后，开始第2次动态扫描,在工作站进行后处理送到的图像。

3D TOFMRA:采用3D FLASH序列,单纯水激励成像(water excite,WE),应用磁化传递(magnetic transfer contras,tMTC),TR 30 ms,TE 3.4 ms,翻转角20°,矩阵256 mm×384 mm～360 mm×768 mm,视野192 mm×230 mm,层厚0.8 mm,扫描层数96～128。图像三维后处理技术采用:(1)容积重组(VR)；(2)最大密度投影(MIP)；(3)薄层最大密度投影(thin slice MIP,TSMIP)多平面或曲面重组。

2　结　果

在本组371例患者中,一共检测出了基底动脉开窗畸形11例(检出率3.0%,11/371),其中1例位于基底动脉中部，还有10例位于基底动脉起始部，还有头颈部动脉开窗畸形18例(检出率4.9%,18/371)。位于基底动脉起始处的10例患者轮廓开窗动脉的呈梭形,血管异常2支间形成圆孔状充盈缺损样改变，位于基底动脉中部的1例,形成了裂缝样开窗动脉。4例椎基底动脉开窗畸形位于颈动脉系统,2例位于大脑中动脉，3例椎动脉开窗畸形(检出率为0.8%,3/371),位于前交通动脉1例。其中开窗椎基底动脉合并颈动脉系统动脉瘤3例,颈动脉系统开窗畸形未伴有动脉瘤4例。

3　讨　论

有文献报道头颈部动脉开窗畸形[5,6]发生部位最常见为基底动脉,第2位为椎动脉、大脑中动脉和大脑前动脉较少。发生机制有两种胚胎发育机制学说，其中De Cara等[7]提出另一种胚胎学机制,基底动脉开窗畸形不是因为原始成对动脉不完全融合导致的。还有Padget等[8]认为在胚胎发育第5周,胎儿的基底动脉由纵行且成对的神经动脉融合而成，纵行且成对的胚胎神经动脉如果在某一点停止融合,基底动脉发育成开窗畸形就发生了。而是由于脑内残存了原始侧动脉染色体部分,这两种不同的机制都有道理。更多的观点认为椎动脉开窗畸形的形成由这两个观点共同作用的。而椎动脉开窗畸形机制更为复杂[9],考虑与发育时丛状血管吻合不全或部分原始椎动脉残留或再通有关。有两种头颈部动脉开窗畸形,一种是凸透镜状开窗畸形[10]；另一种是裂缝状开窗畸形。基脑内动脉开窗畸形最好发部位是基底动脉,根据好发部位不同分3类:起始部、中间部、远侧部。其中最为多见[11～14]为基底动脉起始部。

随着影像技术发展和软件系统升级,诊断头颈部动脉疾病CE-MRA或3D-TOFMRA的优越性日渐明显,1.5T MRI 3.0T MRI与相比，3.0T MRI判断头颈部动脉开窗畸形更佳，本组搜集的371例头颈部MRA,均行3.0T 3D TOF或CEMRA检查。本组18例头颈部开窗畸形动脉都经CE MRA或3D TOFMRA处理并获得满意图像。开窗畸形血管在MIP中清楚显示，并可旋转角度来鉴别分支血管。椎基底动脉开窗畸形在头颈部CEMRA中清楚的显示,头颈部血管异常不用对比剂3D TOFMRA就能清楚显示。

在本组病例中,371例行3.0T MRA检查,11例基底动脉开窗畸形,检出率为3.0%,18例头颈部动脉开窗畸形,检出率为4.9%,比Uchino等[15]报道的1.7%的检出率高。最好发的部位是基底动脉，尤其是基底动脉起始部,18例头颈部动脉开窗畸形当中有10例位于基底动脉起始部,基底动脉中间部只有1例,位于远端的没有发现，头颈部动脉开窗畸形好发部位也多见于椎动脉,在18例中,在椎动脉入颅底段有3例。在本组18例中,位于颈动脉系统有4例,分别位于大脑前动脉、大脑中动脉和前交通动脉。

371例患者行3.0T 3D CE MRA或3D TOFMRA检查中,基底动脉开窗畸形检出率3.0%,头颈部动脉开窗畸形检出率达4.9%,检出比值高于多数经DSA诊断的文献报道[3],几乎于尸检有近似的发现率[2]。由此可见，影像学检查和尸检发现椎基底动脉开窗畸形差异很大，其中原因可能有：(1)影像学检查方法血管显示尚不充分；(2)国内文献报道少，头颈部血管开窗畸形的诊断中存在认识不足；(3)颈部2D TOFMRA对椎基底动脉显示不佳，而头部3D TOFMRA扫描范围以Willis环为中心，易出现漏诊。

椎基底动脉合并单发或多发动脉瘤在基底动脉开窗畸形中比较多见[16,17],基底动脉开窗畸形伴发动脉瘤类似于分叉血管的末端好发动脉瘤，所以认为是由于基底动脉的组织学和血流动力学的双重作用所致，18例头颈部动脉开窗畸形中,伴发动脉瘤的3例椎基底动脉开窗畸形,但均位于颈动脉系统,而有待于进一步研究的是椎基底动脉开窗畸形与颈动脉系统动脉瘤的关系,与Uchino等[18,19]报道吻合的是4例颈动脉系统开窗畸形血管均未伴发动脉瘤。

头颈部动脉开窗畸形在临床中症状不明显，大多在影像学或尸检时偶然发现,临床意义主要在神经介入和头颈外科治疗时的提示作用。头颈部动脉开窗畸形可能增加血管内介入栓塞治疗难度,容易导致手术中血管损伤。也由于一些高位颈髓被头颈部动脉开窗畸形压迫[20],并可因为手术损伤或者压迫开窗畸形的分支血管，从而可能导致严重的脑卒中[21]。所以充分利用3.0T CEMRA或TOFMRA检查技术来判断头颈部动脉开窗畸形在临床中是非常重要的。

[1]Sanders WP,Sorek PA,Mehta BA.Fenestration of intracranial arter-ieswith special attention to associated aneurysms and other anoma-lies[J].AJNR,1993,14:677.

[2]Wollschlaeger G,Wollschlaeger PB,Lucas FV,et al.Experience andresultwith postmortem cerebral angiography performed as routine procedure of the autopsy[J].AJR,1967,101:83.

[3]Takahashi M,Tamakawa Y,Kishikama T,et al.Fenestration of the basilar artery[J].Radiology,1973,109:81.

[4]Wentz KU,Roether J,Schwartz A,et al.Intracranial vertebrobasilar system:MR angiography[J].Radiology,1994,190:108.

[5]San-Galli F,Leman C,Kien P,et al.Cerebral arterial fenestrations associated with intracranial saccular aneurysms[J].Neurosurgery,1992,30:281.

[6]Islak C,Kocer N,Kantarci F,et al.Endovascular management of bas-ilar artery aneurysms associated with fenestrations[J].AJNR,2002,23:961.

[7]DeCaro R,Serafini MT,Galli S.Anatomy of segmental duplication in the human basilar artery:possible site of aneurysm formation[J].Clin Neuropathol,1995,14:307.

[8]Padget DH.The development of the cranialarteries in the human em-bryo[J].Contrib Embryo,1948,32:234.

[9]Giuffre R,Sherkat S.The vertebral artery:development pathology[J].J Neurosurg Sci,1999,43:183.

[10]Uchino A,Kato A,Takase Y,et al.Basilar artery fenestrations detec-ted by MR angiography[J].Radiat Med,2001,19:73.

[11]Black SPW,Ansbacher LE.Saccular aneurysm associated with seg-mentalduplication of the basilarartery:amorphological study[J].J Neurosurg,1984,61:1007.

[12]Hemmati M,Kim KS.A ruptured aneurysm at the basilar artery fen-estration[J].Radiology,1979,130:174.

[13]Campos J,Fox AJ,Vinuela F.Saccular aneurysms in basilar artery fenestration[J].AJNR,1987,8:235.

[14]蒋飙,何伟良,许晓英,等.有孔型椎基底动脉的MR血管成像诊断[J].中华放射学杂志,2004,38:527.

[15]Uchino A,Kato A,Takase Y,et al.Basilar artery fenestrations detected by MR angiography[J].Radiation Medicine,2001,19:271.

[16]王效恩,刘怀军,王藏海,等.磁共振血管成像诊断颅内动脉瘤MRA与DSA的比较研究[J].临床放射学杂志,2000,19:474.

[17]Saatci I,Cekirge HS,Karcaaltincaba M,et al.Endovascular treatment of kissing aneurysms at the fenestrated basilarartery:case report with literature review[J].Surg Neurol,2002,58:56.

[18]Ferguson GG.Physical factors in the initiation,growth,and rupture of human intracranial saccular aneurysms[J].J Neurosurg,1972,37:667.

[19]Uchino A,Takase Y,Nomiyama K,et al.Fenestration of the middle cerebral artery detected by MR angiography[J].Magn Reson Med Sci,2006,5:53.

[20]Furumoto T,Sagase J,Takahashi K,et al.Cervicalmyelophthy caused by the anomalus vertebral artery[J].Spine,1996,21:2282.

[21]Schievink WI,Hunter SF,Marsh WR,et al.Traumatic occlusion of one limb of an intracranial arterial fenestration:an uncommon cause of stroke[J].Neurology,1996,47:278.

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

(宁夏第三人民医院神经内科,宁夏 银川 750011 )

文永霞,E-mail：wyongxia@163.com

R743.4

A