大腦中動(dòng)脈分叉角大小與動(dòng)脈瘤形成的關(guān)系*

劉元早,王　霖

(1.銅仁市人民醫(yī)院放射科，貴州銅仁 554302；2.銅仁市人口和計(jì)劃生育宣傳技術(shù)指導(dǎo)所，貴州銅仁 554300)

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·技術(shù)與方法·

大腦中動(dòng)脈分叉角大小與動(dòng)脈瘤形成的關(guān)系*

劉元早1,王霖2△

(1.銅仁市人民醫(yī)院放射科，貴州銅仁 554302；2.銅仁市人口和計(jì)劃生育宣傳技術(shù)指導(dǎo)所，貴州銅仁 554300)

目的探討大腦中動(dòng)脈水平段(M1段)分叉動(dòng)脈瘤的發(fā)生與分叉角的關(guān)系。方法回顧性研究銅仁市人民醫(yī)院2012年1月至2013年6月經(jīng)三維CT血管成像(3D-CTA)診斷并經(jīng)手術(shù)或三維數(shù)學(xué)血管造影證實(shí)的單側(cè)大腦中動(dòng)脈(雙干型)分叉動(dòng)脈瘤患者24例，在圖像后處理工作站上使用三維角度測(cè)量工具在容積再現(xiàn)(圖像上分別測(cè)量患側(cè)與健側(cè)M1段分叉角，分別記為γ1和γ2，使用SPSS20.0進(jìn)行配對(duì)t檢驗(yàn)分析。結(jié)果γ1平均值為(129.48±22.38)°，γ2平均值為(111.33±20.90)°；γ1-γ2=(18.15±3.10)°，經(jīng)配對(duì)t檢驗(yàn)，兩者間差異有統(tǒng)計(jì)學(xué)意義(t=2.868，P=0.009)。結(jié)論較大的分叉角易患分叉動(dòng)脈瘤，是評(píng)估分叉動(dòng)脈瘤形成風(fēng)險(xiǎn)的客觀指標(biāo)。

大腦中動(dòng)脈；顱內(nèi)動(dòng)脈瘤;CT血管成像

顱內(nèi)動(dòng)脈瘤破裂是最常見的非創(chuàng)傷性蛛網(wǎng)膜下腔出血(SAH)的原因，SAH的致死和致殘率非常高。大腦中動(dòng)脈瘤位于側(cè)裂池內(nèi)，據(jù)報(bào)道，動(dòng)脈瘤破裂后形成側(cè)裂血腫，病殘率高達(dá)36%～58%，對(duì)于Hunt-Hess分級(jí)Ⅳ及Ⅴ級(jí)的病例，若不手術(shù)治療，病死率幾乎為100%[1-2]。大腦中動(dòng)脈瘤發(fā)病率約為25%，僅次于前后交通動(dòng)脈瘤，其破裂率約為50%，占破裂動(dòng)脈的36%左右[3-4]。鑒于大腦中動(dòng)脈瘤的高發(fā)病率、高破裂率及高危險(xiǎn)性，尋找和控制危險(xiǎn)因素，預(yù)防其發(fā)生顯得尤為重要。三維CT血管造影(3D-CTA)有著很高的靈敏度和特異度，逐漸成為顱內(nèi)動(dòng)脈瘤常用的檢查方法，目前尚少見相關(guān)研究報(bào)道，本文基于3D-CTA就分叉大腦中動(dòng)脈瘤的分叉角進(jìn)行研究。

1　材料與方法

1.1納入標(biāo)準(zhǔn)和排除標(biāo)準(zhǔn)納入標(biāo)準(zhǔn)：(1)2012年1月至2013年6月在銅仁市人民醫(yī)院行64排螺旋CTA檢查的雙側(cè)大腦中動(dòng)脈的M1段分支為雙干型，其中一側(cè)伴分叉動(dòng)脈瘤的患者；(2)經(jīng)過三維數(shù)字減影血管造影(3D-DSA)或手術(shù)確診為大腦中動(dòng)脈M1段分叉動(dòng)脈瘤的。排除標(biāo)準(zhǔn)：(1)雙側(cè)大腦中動(dòng)脈的M1段分叉動(dòng)脈瘤的；(2)大腦中動(dòng)脈的M1段分叉有腫瘤或其他占位性病灶，對(duì)測(cè)量血管產(chǎn)生壓迫推移的；(3)大腦中動(dòng)脈的M1段分叉血管走行扭曲，測(cè)量角度困難的；(4)研究動(dòng)脈有明顯狹窄的；(5)CTA效果不佳的；(6)患者配合欠佳者。按照上述標(biāo)準(zhǔn)，共有24例患者納入本次研究，所有病例均有SAH，發(fā)病年齡45～75歲，平均(55.5±7.30)歲，41～70歲23例(95.8%)，70歲以上1例(4.2%)；男9例(37.5%)，女15例(62.5%)，男女比例3∶5；病灶在左側(cè)14例(58.3%)，右側(cè)10例(41.7%)。所有納入患者均經(jīng)患者或家屬知情同意并簽署知情同意書，整個(gè)過程都在倫理審查委員會(huì)監(jiān)督下進(jìn)行。

1.2CT檢查

1.2.1一般準(zhǔn)備檢查前詢問患者有無藥物過敏史，預(yù)約檢查時(shí)交待患者檢查前禁食；上檢查床前交待注意事項(xiàng)，機(jī)器有什么樣的運(yùn)動(dòng)和聲音，屬患者檢查時(shí)保持安靜。

1.2.2CT掃描及圖像處理(1)檢查設(shè)備64排螺旋CT(Lightspeed VCT，GE Healthcare)，雙筒高壓注射器(Milwaukee，Wis)；(2)CTA掃描：使用數(shù)字減影法，準(zhǔn)直器寬度64×0.625 mm，螺距0.516，轉(zhuǎn)速為0.5 s每轉(zhuǎn)，F(xiàn)OV為240 mm，矩陣512×512，掃描范圍頸2椎體至頭頂。管電壓120 kV，管電流400 mA，重建層厚及層間距均為0.625 mm，算法為標(biāo)準(zhǔn)算法。按照上述參數(shù)先掃描一組平掃數(shù)據(jù)，再掃一組增強(qiáng)數(shù)據(jù)。增強(qiáng)掃描的觸發(fā)方式為timing bolus法。造影劑為非離子碘對(duì)比劑(碘海醇，370 mg/mL)，流速為4.5～5.0 mL/s，總劑量75～100 mL。(3)圖像重建，把所有圖像發(fā)送至后處理工作站(AW4.5，GE Healthcare)進(jìn)行后處理，在血管VR圖像上使用三維角度測(cè)量工具測(cè)量患側(cè)與健側(cè)分叉角大小，患側(cè)記為γ1，健側(cè)為γ2(圖1)。測(cè)量角度時(shí)，在分叉處及目標(biāo)血管上放置3個(gè)點(diǎn)，不同角度旋轉(zhuǎn)圖像確保點(diǎn)和線落在目標(biāo)血管上，每組數(shù)據(jù)測(cè)量3次，取平均值。

2　結(jié)　　果

患側(cè)分叉角的角度大于健側(cè)，發(fā)病部位：左側(cè)14例(58.3%)，右側(cè)的10例(41.7%)，雙側(cè)發(fā)病率差異無統(tǒng)計(jì)學(xué)意義(χ2=0.667，P=0.414)。γ1平均值為(129.48±22.38)°，γ2平均值為(111.33±20.90)°；γ1與γ2配對(duì)t檢驗(yàn)，：γ1-γ2=(18.15±3.10)°，差異有統(tǒng)計(jì)學(xué)意義(t=2.868，P=0.009)，見圖2。

α、β、γ分別代表M1段及其分支之間的夾角。

圖1角度測(cè)量示意圖

患側(cè)(B)分叉角明顯大于健側(cè)(A)。

圖2左側(cè)大腦中動(dòng)脈瘤M1段分叉動(dòng)脈瘤患者CT圖

3　討　　論

顱內(nèi)動(dòng)脈瘤好發(fā)于willis環(huán)及大腦中動(dòng)脈。目前認(rèn)為顱內(nèi)動(dòng)脈瘤形成與血管解剖結(jié)構(gòu)、遺傳等先天性因素及吸煙、高血壓等后天因素有關(guān)[5]。有系統(tǒng)評(píng)價(jià)指出，顱內(nèi)動(dòng)脈瘤家族史是其形成的高風(fēng)險(xiǎn)因素，但它卻不能準(zhǔn)確地預(yù)測(cè)顱內(nèi)動(dòng)脈瘤形成。然而，除了上述的遺傳因素和后天因素，血流動(dòng)力學(xué)被認(rèn)為在顱內(nèi)動(dòng)脈瘤形成中起著重要的作用，它可觸發(fā)血管壁局灶性變性[6]。血流動(dòng)力學(xué)因素(如WSS和壁應(yīng)力)受血管分支的幾何形態(tài)影響。因此，本研究選取大腦中動(dòng)脈瘤患者的患側(cè)和健側(cè)大腦中動(dòng)脈分叉角作為研究對(duì)象，以盡量減少可能的遺傳及其他易感因素，如高血壓、吸煙及其他危險(xiǎn)因素。本研究表明，大腦中動(dòng)脈瘤的形成與分叉角增大顯著相關(guān)。因此，本研究提示解剖結(jié)構(gòu)影響血流動(dòng)力學(xué)改變，可為評(píng)估高危患者顱內(nèi)動(dòng)脈瘤形成和生長(zhǎng)的危險(xiǎn)分級(jí)提供客觀指標(biāo)。

在以往的研究中，大多集中于前交通動(dòng)脈和后交通動(dòng)脈動(dòng)脈瘤，他們研究指出周圍血管的形態(tài)學(xué)和幾何學(xué)特征是動(dòng)脈瘤形成的重要因素[7-10]。有研究表明前交通動(dòng)脈動(dòng)脈瘤的形成與A1～A2段直徑比呈正相關(guān)[9]，存在優(yōu)勢(shì)A1段具有高發(fā)病率[10]。同樣，關(guān)于后交通動(dòng)脈動(dòng)脈瘤的研究發(fā)現(xiàn)顱內(nèi)動(dòng)脈瘤與頸內(nèi)動(dòng)脈(ICA)床突上段較短有關(guān)，并且動(dòng)脈瘤的形成與ICA、后交通動(dòng)脈的夾角有關(guān)[11]。本研究結(jié)果顯示，較大MCA分叉角易患動(dòng)脈瘤，而有研究顯示，較小ICA、后交通動(dòng)脈夾角易發(fā)生動(dòng)脈瘤，兩者正好相反。然而，如果患者有確定的風(fēng)險(xiǎn)因素(如女性、年齡、吸煙、高血壓)，則動(dòng)脈瘤形成的可能性更大[5]，這與它們的解剖和血流特點(diǎn)有關(guān)。為控制上述的復(fù)雜風(fēng)險(xiǎn)因素，本研究選擇同一組患者的患側(cè)與健側(cè)對(duì)比。

從解剖結(jié)構(gòu)上來說，分叉動(dòng)脈瘤位于M1段分叉處的遠(yuǎn)端隆突。大腦中動(dòng)脈瘤分叉角影響血流速度及血流方向，從而影響壁剪切力、壁壓力以及渦流狀態(tài)。壁剪切力在動(dòng)脈瘤發(fā)病機(jī)制中起重要作用，與動(dòng)脈瘤發(fā)生呈正相關(guān)[12]。動(dòng)脈瘤形狀及分叉部夾角具有降低動(dòng)脈流動(dòng)耗能和減小血流對(duì)管壁的剪切力的作用。有研究最早提出了最小耗能最優(yōu)化原則[13-14],最佳角度分別符合下列公式：cosφ1=(r04+r14-r24)/2r02r12，Cosφ2=(r04+r24-r14)/2r02r12，cos(φ1+φ2)=(r04+r14-r24)/2r12r22。Ingebrigtsen等[14]雖然發(fā)現(xiàn)健側(cè)大腦中動(dòng)脈分支角確實(shí)遵循最優(yōu)化原則，但在多因素分析中，這些最優(yōu)化原理參數(shù)并不能獨(dú)立預(yù)測(cè)大腦中動(dòng)脈瘤形成[14]。然而，他們發(fā)現(xiàn)動(dòng)脈瘤組的分叉角顯著增大，這也證實(shí)了本研究的發(fā)現(xiàn)。分叉角越大分支動(dòng)脈作用會(huì)相互抵消，那么它們將補(bǔ)償?shù)牧κ┘釉趧?dòng)脈的頂端[15]。高WSS和動(dòng)脈瘤形成的關(guān)系早已有研究證明，剪切損傷的增加，將會(huì)導(dǎo)致血管內(nèi)皮損傷、內(nèi)彈性膜退化以及中膜平滑肌細(xì)胞變薄，是動(dòng)脈瘤形成的早期征兆[6,16-18]。此外，一些研究也表明，更大的分叉角可能會(huì)導(dǎo)致較低的WSS，它可引起內(nèi)皮細(xì)胞增殖和凋亡，從而使血管內(nèi)皮功能障礙和動(dòng)脈瘤形成[19-20]。

總之，本研究方法簡(jiǎn)單、方便，為非侵入性研究，很大程度減少了性別、高血壓、酗酒、激素等危險(xiǎn)因素的影響，其結(jié)果與實(shí)驗(yàn)研究的結(jié)果相當(dāng)[13]，具有操作性強(qiáng),方便適用的特點(diǎn)。本研究的樣本量相對(duì)較小，未能進(jìn)行多因素邏輯回顧分析，將在后續(xù)研究中完善。

[1]Prat R,Galeano I.Early surgical treatment of middle cerebral artery aneurysms associated with intracerebral haematoma[J].Clin Neurol Neurosurg,2007,109(5):431-435.

[2]Rinne J,Hernesniemi J,Niskanen M,et al.Analysis of 561 patients with 690 middle cerebral artery aneurysms:anatomic and clinical features as correlated to management outcome[J].Neurosurgery,1996,38(1):2-11.

[3]Millon D,Derelle AL,Omoumi P,et al.Nontraumatic subarachnoid hemorrhage management:evaluation with reduced iodine volume at CT angiography[J].Radiology,2012,264(1):203-209.

[4]Lu L,Zhang LJ,Poon CS,et al.Digital subtraction CT angiography for detection of intracranial aneurysms:comparison with three-dimensional digital subtraction angiography[J].Radiology,2012,262(2):605-612.

[5]Vlak MH,Algra A,Brandenburg R,et al.Prevalence of unruptured intracranial aneurysms,with emphasis on sex,age,comorbidity,country,and time period:a systematic review and meta-analysis[J].Lancet Neurol,2011,10(7):626-636.

[6]Singh PK,Marzo A,Howard B,et al.Effects of smoking and hypertension on wall shear stress and oscillatory shear index at the site of intracranial aneurysm formation[J].Clin Neurol Neurosurg,2010,112(4):306-313.

[7]CanA,MouminahA,HoAL,etal.Effect

of vascular anatomy on the formation of basilar tip aneurysms[J].Neurosurgery,2015,76(1):62-66.

[8]Mehinovic A,Isakovic E,Delic J.Variations in diameters of vertebro-basilar tree in patients with or with no aneurysm[J].Med Arch,2014,68(1):27-29.

[9]Flores BC,Scott WW,Eddleman CS,et al.The A1-A2 diameter ratio may influence formation and rupture potential of anterior communicating artery aneurysms[J].Neurosurgery,2013,73(5):845-853.

[10]Tarulli E,Fox AJ.Potent risk factor for aneurysm formation:termination aneurysms of the anterior communicating artery and detection of A1 vessel asymmetry by flow dilution[J].AJNR Am J Neuroradiol,2010,31(7):1186-1191.

[11]Yu M,Huang Q,Hong B,et al.Morphological differences between the aneurysmal and normal artery in patients with internal carotid-posterior communicating artery aneurysm[J].J Clin Neurosci,2010,17(11):1395-1398.

[12]Alfano JM,Kolega J,Natarajan SK,et al.Intracranial aneurysms occur more frequently at bifurcation sites that typically experience higher hemodynamic stresses[J].Neurosurgery,2013,73(3):497-505.

[13]Murray CD.The physiological principle of minimum work applied to the angle of branching of arteries[J].J Gen Physiol,1926,9(6):835-841.

[14]Ingebrigtsen T,Morgan MK,Faulder K,et al.Bifurcation geometry and the presence of cerebral artery aneurysms[J].J Neurosurg,2004,101(1):108-113.

[15]Karino T,Goldsmith HL.Particle flow behavior in models of branching vessels Ⅱ Effects of branching angle and diameter ratio on flow patterns[J].Biorheology,1985,22(2):87-104.

[16]Li SY,Gomelsky M,Duan J,et al.Overexpression of aldehyde dehydrogenase-2 (ALDH2) transgene prevents acetaldehyde-induced cell injury in human umbilical vein endothelial cells:role of ERK and p38 mitogen-activated protein kinase[J].J Biol Chem,2004,279(12):11244-11252.

[17]Inci S,Spetzler RF.Intracranial aneurysms and arterial hypertension:a review and hypothesis[J].Surg Neurol,2000,53(6):530-540.

[18]Bau PF,Bau CH,Rosito GA,et al.Alcohol consumption,cardiovascular health,and endothelial function markers[J].Alcohol,2007,41(7):479-488.

[19]Arjmandi TO,Razavi SE.Numerical investigation of pulsatile blood flow in a bifurcation model with a non-planar branch:the effect of different bifurcation angles and non-planar branch[J].Bioimpacts,2012,2(4):195-205.

[20]Meng H,Tutino VM,Xiang J,et al.High WSS or low WSS Complex interactions of hemodynamics with intracranial aneurysm initiation,growth,and rupture:toward a unifying hypothesis[J].AJNR,2014,35(7):1254-1262.

The relationship of the bifurcation angle size with aneurismal occurrence in the horizontal section of middle cerebral artery

LiuYuanzao1,WangLin2△

(1.DepartmentofRadiology,People′sHospitalofTongrenCity,Tongren,Guizhou554302,China；2.TheOfficeofPublicityandTechnicalGuidanceonPopulationandFamilyPlanningofTongrenCity,Tongren,Guizhou554300,China)

ObjectiveTo investigate the relationship of the aneurismal occurrence with bifurcation angle in the horizontal section(M1) of middle cerebral artery.MethodsTotally 24 cases which were diagnosed as one-side aneurysm in bifurcation angle of middle cerebral artery with 3D-CTA were studied retrospectively and confirmed by 3D-DSA or surgery from January 2012 to June 2013.The measurement of daughter-to-daughter branch angles with the ill and the normal side were performed on the workstation.The size of the ill and normal side were expressed as γ1and γ2,respectively.Statistical analysis was performed using SPSS20.0 for windows.ResultsThe mean value of γ1was (129.48±22.38)°,while γ2was (111.33±20.90)°.The mean value of γ1-γ2was (18.15±3.10)°.There was significant difference between the ill side and normal side (t=2.868,P=0.009).ConclusionLarger daughter-to-daughter branch angles are associated with the presence of middle cerebral artery bifurcation aneurysms.This easily measurable parameter may provide objective metrics to assess aneurysm formation.

middle cerebral artery;intracranial aneurysm;computed tomography angiography

劉元早(1978-)，主治醫(yī)師，碩士，研究方向?yàn)樯窠?jīng)系統(tǒng)及頭頸部影像學(xué)。

10.3969/j.issn.1671-8348.2016.07.021

R743.3

A

1671-8348(2016)07-0929-02

2015-09-15

2015-11-28)