ISSN 2005-7881 Charles H. Tegeler Ultrasound Screening in Asymptomatic Patients Journal of Neurosonology 1(Suppl. 1):47-51, 2009 REVIEW 급성뇌졸중에서의이중초음파검사 연세대학교원주의과대학신경과학교실 김서현 Duplex Sonography in Acute Stroke Seo Hyun Kim, MD Department of Neurology, Yonsei University Wonju College of Medicine, Wonju, Korea 서론 급성허혈뇌졸중 (ischemic stroke) 환자에서내경동맥 (internal carotid artery) 협착은비교적흔하게발견되며, 1,2 이중두개외내경동맥협착의빈도는생활습관이나식습관등이서구화됨에따라높아지는추세이다. 두개외경동맥질환은이중초음파검사 (duplex sonography), 전산화단층혈관조영술 (CT angiography), 자기공명혈관조영술 (MR angiography), 고식적혈관조영술 (conventional angiography) 등을이용하여진단하게되는데, 이중초음파검사는다른검사에비해시행하기용이하고안전하므로무증상환자의선별검사뿐아니라급성뇌졸중환자의원인검사에도유용하다. 3,4 최근에는두개경유색조이중초음파검사 (transcranial color duplex sonography) 로두개내동맥질환을진단할뿐만아니라, 초음파에너지를이용하여급성허혈뇌졸중환자에혈전용해치료를시도하기도한다. 5 다음에서저자는급성허혈뇌졸중의원인인죽상경화증 (atherosclerosis), 색전증 (embolism), 동맥박리 (arterial dissection) 에의한두개외경동맥의협착및폐색에대하여기술하고자한다. 본론 1. 죽상경화증에의한경동맥의협착및폐색 죽상경화증에의한허혈뇌졸중의기전은크게두가지로나눌수있다. 첫째, 죽상경화판 (atherosclerotic plaque) 이파열되어혈전이형성되는경우에혈전으로동맥이폐색되거나색전으로원위부동맥이폐색되면혈전색전성뇌졸중 (thromboembolic stroke) 이발생할수있다. 6 둘째, 죽상경화판의진행으로동맥협착이심한경우에특정상황에서혈류감소가일어나면혈류역학뇌졸중 (hemodynamic stroke) 이발생할수있다. 7 경동맥분지 (carotid bifurcation) 부위는죽상경화판이진행되어협착이일어나기쉬운해부학적위치이다 (Fig. 1). 허혈뇌졸중및일과성허혈발작 (transient ischemic attack) 의 10~15% 는죽상경화증에의한경동맥분지부위의내경동맥협착으로발생한다고한다. 4 이전에증상을일으킨두개외내경동맥협착의정도가 50% 이상인경우에는, 협착정도가심할수록향후허혈뇌졸중발생의위험은증가한다. 8,9 North American Symptomatic Carotid Endarterectomy Trial (NASCET) 과 European Carotid Surgery Trial (ECST) 에의하면, 8,9 허혈뇌졸중이나일과성허혈발작환자의증상을 Address for correspondence: Seo Hyun Kim, MD Department of Neurology, Yonsei University Wonju College of Medicine, 162 Ilsan-dong, Wonju, Gangwon-do 220-701, Korea Tel: +82-33-741-1252, Fax: +82-33-748-1752, E-mail: s-hkim@yonsei.ac.kr 47
Journal of Neurosonology Vol. 1, Suppl. 1, 2009 A B C Fig. 1. Color Doppler-assisted duplex imaging (A), MR angiography (B), and conventional angiography (C) of carotid stenosis with ulcerative plaque. A B Fig. 2. Correlation analyses between peak systolic velocity (PSV; A)- and color Doppler-assisted duplex imaging (CDDI; B)- derived cross-sectional luminal area reduction measurements and intra-arterial digital subtraction angiography (IA) in determining the degree of internal carotid artery stenosis. The dotted line in (B) indicates first-order regression and the solid lines indicate the best-fitting higher-order regression (A, B). The correlation coefficients were R 5 = 0.85 in (A), and R 1 = 0.94, R 3 = 0.96 in (B). 일으킨두개외경동맥협착이심할경우에는뇌졸중의이차예방을위하여경동맥혈관성형술이고려되어야하므로, 경동맥협착여부를검사하는것은중요하다. 전산화단층혈관조영술, 자기공명혈관조영술, 고식적혈관조영술은좁아진동맥내강을영상으로구현하여협착을검사하지만, 경동맥이중초음파검사는회색도영상 (grayscale imaging) 으로동맥벽의영상을구현하고색조방식 (color mode) 과도플러스펙트럼분석 (Doppler spectrum analysis) 으로혈류역학정보를얻어경동맥의협착을검사한다. 50% 이상의경동맥협착을평가하는데유용한초음파파라미터 (parameter) 에는내경동맥수축기최고속도 (peak systolic velocity: PSV), 내경동맥 / 총경동맥 PSV비 (ICA/CCA PSV ratio), 회색도영상에서의협착측정치, 내경동맥이완기말속도 (end diastolic velocity: EDV) 가있다. 10 내경동맥 PSV와이외의초음파파라미터들의측정치를종합하여판독하면협착정도를좀더정확하게알수있다고한다 (Fig. 2). 11,12 여러연구결과로협착정도를판단하는파라미터들의기준치가제시되었다 (Table 1). 11 실제검사실에서경동맥을검사할때에는, 제시된기준치들을참조하여각검사실에맞게단일한기준치를정하여적용해야하겠다. 이외에혈류역학적으로심한내경동맥협착을나타내는초음파검사의간접소견으로는, 협착원위부동맥의 EDV 감소, 협착부위의색혈류 (color flow) 소견, 안동맥의혈류역전, 전교통동맥 (anterior commu- 48 신경초음파학회지제 1 권부록 1, 2009
김서현 급성뇌졸중에서의이중초음파검사 Table 1. Consensus panel grayscale and Doppler US criteria for diagnosis of ICA stenosis Primary Parameters Additional Parameters Degree of stenosis, % ICA PSV (cm/sec) Plaque Estimate (%) ICA/CCA PSV Ratio ICA EDV (cm/sec) Normal <125 None <2.0 <40 <50 <125 <50 <2.0 <40 50-69 125-230 50 2.0-4.0 40-100 70 but less than near >230 50 >4.0 >100 occlusion Near occlusion High, low, or undetectable Visible Variable Variable Total occlusion Undetectable Visible, no detectable lumen Not applicable Not applicable *Plaque estimae (diameter reduction) with grayscale and color Doppler US. Table 2. Meta-analysis of sensitivity and specificity for all stenosis groups and imaging techniques Degree of Stenosis, % Duplex sonography CT angiography MR angiography Contrast enhanced MR angiography 70-99% stenosis Sensitivity 0.89 0.77 0.88 0.94 (95% CI) (0.85-0.92) (0.68-0.84) (0.82-0.92) (0.88-0.97) Specificity 0.84 0.95 0.84 0.93 (95% CI) (0.77-0.89) (0.91-0.97) (0.76-0.97) (0.89-0.96) 50-69% stenosis Sensitivity 0.36 0.67 0.37 0.77 (95% CI) (0.25-0.49) (0.30-0.90) (0.26-0.49) (0 59-0 89) Specificity 0.91 0.79 0.91 0 97 (95% CI) (0.87-0.94) (0.63-0.89) (0.78-0.97) (0 93-0 99) 0-49% stenosis or 100% occluded Sensitivity 0.83 0.81 0.81 0 96 (95% CI) (0.73-0.90) (0.59-0.93) (0.70-0.88) (0 90-0 99) Specificity 0.84 0.91 0.88 0 96 (95% CI) (0.62-0.95) (0.74-0.98) (0.76-0.95) (0 90-0 99) nicating artery) 이나후교통동맥 (posterior communicating artery) 을통한측부혈류, 동측총경동맥의박동지수 (pulsatility index) 증가, 동측중대뇌동맥의박동지수감소등이있다. 13,14 완전히폐색된내경동맥의이중초음파검사소견으로는내경동맥내강의혈류측정불가, 이질의 (heterogenous) 물질로채워진내경동맥내강, 폐색부위에소위그루터기신호 (stump signal) 의존재, 그외에위문단에언급된초음파검사의간접소견들이있다 (Fig. 3). 15 거의폐색되었지만완전히폐색되지않은내경동맥을이중초음파검사로검사할때내경동맥이완전히폐색된것으로판독하는오류를범하는경우가종종있다. 이때파워혈류영상 (power flow imaging) 등을이용하면최소잔여혈류를예민하게검사할수있어완전히폐색된것과의감별에도움이된다. 내경동맥의협착이 70~99% 인경우에이중초음파검사는민감도가 0.89 정도이고특이도가 0.84 정도로비교적높은것으로보고된다 (Table 2). 16 단, 이중초음파검사의 결과는검사자의숙련도에따라차이가날수있으므로, 민감도와특이도를높이기위하여는검사자의충분한수련이필요하다. 동맥협착뿐아니라죽상경화판의조성도허혈뇌졸중과관련된다. 경동맥이중초음파검사는판 (plaque) 의형태학적특성을알려주는장점이있다. 내부에출혈이있거나파열이되어표면에혈전이생긴판은허혈뇌졸중이나일과성허혈발작과관련이있는불안정판 (unstable plaque) 으로알려져있다. 17-20 초음파의회색도영상에서출혈이나혈전은무반향성 (echolucent) 으로나타난다. 또한, 판에궤양이있거나, 판의일부가움직이거나, 혈관벽이종축으로박동하는경우에도혈전색전성뇌졸중을일으킬위험이있는데, 이중초음파검사로비교적용이하게검사할수있다. 17,18,20 2. 비죽상경화증 (nonatherosclerosis) 에의한경동맥의협착및폐색 49
Journal of Neurosonology Vol. 1, Suppl. 1, 2009 B A C Fig. 3. MR angiography (A) and color duplex sonography (B, C) of left internal carotid occlusion (arrow). 죽상경화증뿐아니라색전증과경동맥박리등의질환에서도경동맥이협착되거나폐색되어급성허혈뇌졸중이발생할수있다. 죽상경화증에의한폐색과달리, 심인성이나정맥성색전증에의한경동맥폐색의이중초음파검사소견은동질의저반향성 (hypoechoic) 덩어리로혈관내강이차있는것이다. 21 경동맥이폐색된소견을보이다가수일후다시재개통되는등, 색전성경동맥폐색은시간이지남에따라이중초음파검사소견이비교적빠르게변하는경향이있다. 21 경동맥박리의이중초음파검사소견에는이중내강 (double lumen), 편심성 (eccentric) 으로늘어진혈전형성, 원위부혹은근위부혈관폐색의간접소견, 미세색전 (microembolism) 신호등이있다. 22 결론 경동맥이중초음파검사는뇌졸중환자의침상에서안전하고신속하게검사할수있으며필요한경우에일정시간간격을두고반복하여검사하기쉬워, 급성허혈뇌 졸중의원인을찾고치료를결정하는데유용한검사이다. 또한숙련된검사자가검사를할경우, 비교적정확하게혈류협착이나폐색을진단할수있다는장점이있다. REFERENCES 1. Oh WS, Lee KY, Kim SH, Chung JI, Kim DI, Kim SH, et al. Characteristics of internal carotid artery stenosis in patients with acute ischemic stroke. J Korean Neurol Assoc 2003;21:121-127. 2. Suh DC, Lee SH, Kim KR, Park ST, Lim SM, Kim SJ, et al. Pattern of atherosclerotic carotid stenosis in Korean patients with stroke: Different involvement of intracranial versus extracranial vessels. AJNR 2003;24:239-244. 3. Saleem MA, Sadat U, Walsh SR, Young VE, Gillard JH, Cooper DG, et al. Role of carotid duplex imaging in carotid screening programmes - an overview. Cardiovasc Ultrasound 2008;6:34-36. 4. Fine-Edelstein JS, Wolf PA, O Leary DH, Poehlman H, Belanger AJ, Kase CS, et al. Precursors of extracranial carotid atherosclerosis in the Framingham study. Neurology 1994;44:1046-1050. 5. Eggers J. Acute stroke: Therapeutic transcranial color duplex sonography. Front Neurol Neurosci 2006;21:162-170. 6. Leys D. Atherothrombosis: A major health burden. Cerebrovasc Dis 2001;11 Suppl 2:1-4. 7. Bladin CF, Chambers BR. Frequency and pathogenesis of hemody- 50 신경초음파학회지제 1 권부록 1, 2009
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