CTP联合CTA对慢性脑缺血患者血流动力学的评价

目的：利用CT灌注（CTP）和CT血管成像（CTA）探讨慢性脑缺血患者脑血流动力学变化及其与脑供血动脉狭窄、血管性认知功能障碍之间的关系。方法：对55例临床拟诊为慢性脑缺血的患者行常规头颅CT平扫、CTP及CTA检查,应用简易智能状态检查（MMSE）量表评定受试者的智能状态。结果：根据平均通过时间（MTT）、达峰时间（TTP）图灌注延迟范围将灌注表现分为3型：Ⅰ型为大脑中动脉和/或大脑前动脉供血区广泛性低灌注22例;Ⅱ型为分水岭区局限性低灌注21例;Ⅲ型为灌注正常12例。颈内动脉（ICA）或大脑中动脉（MCA）的重度狭窄或闭塞所致脑灌注异常（Ⅰ、Ⅱ型）明显高于轻中度狭窄者（χ^2=29.49,P〈0.01）,Ⅲ型未见ICA或MCA的重度狭窄或闭塞。ICA或MCA狭窄程度与脑灌注异常之间呈正相关（Spearman′sr=0.74,P〈0.01）。脑灌注Ⅰ、Ⅱ型患者MMSE评分均低于正常值（P〈0.01）,且以Ⅰ型为著（P〈0.01）,Ⅲ型MMSE评分正常。结论：慢性脑缺血患者脑血流低灌注与ICA或MCA狭窄程度密切相关,在血管性认知功能障碍的发病机制中起着重要作用。     

Long-term follow-up of asymptomatic patients with major artery occlusion: rate of symptomatic change and evaluation of cerebral hemodynamics

BACKGROUND AND PURPOSE: The natural history of asymptomatic major cerebral artery occlusive disease is unclear. Rate of symptomatic change, appearance of new lesions on MR images, and cerebral hemodynamics were analyzed for patients with asymptomatic major cerebral artery occlusion. METHODS: This prospective study included asymptomatic patients who had occlusive disease between 1992 and 1995. MR imaging and MR angiography were used to detect internal carotid artery (ICA) or middle cerebral artery (MCA) occlusion in 3965 neurologically asymptomatic patients and for follow-up of affected patients for 67 to 105 months (mean, 79 months). Regional cerebral blood flow and cerebrovascular reserve capacity were examined by xenon-enhanced CT at rest and after the administration of acetazolamide, respectively. RESULTS: Eighteen patients had MCA occlusion and 17 had ICA occlusion. During the follow-up period, five patients became symptomatic (four with MCA occlusion and one with ICA occlusion), with no significant difference (P = .332) in the rate of symptomatic change. Among these five patients, new infarction occurred on the ipsilateral side in three patients, contralateral side in one, and bilateral sides in one. New stenotic or occlusive changes occurred in three patients. The patients were divided into groups: group A, without new lesions on MR images (n = 23), and group B, with new lesions (n = 12). There was no significant difference in regional cerebral blood flow value between groups A and B in the whole hemisphere, anterior cerebral artery territory, or MCA territory. There was a significant difference in cerebrovascular reserve capacity between groups A and B between the affected side (P = .00051 and P = .00068, respectively) and the contralateral side (P = .00101 and P = .00115, respectively) for the whole hemisphere and MCA territory, and the difference was more severe on the affected side in both regions. CONCLUSION: These pilot data suggest that asymptomatic MCA occlusion has a worse prognosis than does ICA occlusion. Silent events are common bilaterally. This may be because of hemodynamic factors or perhaps MCA occlusion is a marker for a more progressive type of atherosclerosis. A prospective study involving assessment of hemodynamics and baseline stroke risk factors in patients with MCA occlusion is indicated.     

Comparison of cerebral perfusion reserve and collateral circulation in patients with internal carotid artery disease

Summary The cerebral hemodynamics in patients with carotid disease is influenced by a network of extra- and intracranial collaterals. The purpose of this study was to compare the findings of regional cerebral perfusion reserve (rCPR) with angiographically proven collateral circulation. In 41 patients (28 men, 13 women, age 63 ± 10 years) with angiographically proven carotid stenoses or occlusions (30 stenoses, 11 occlusions) 24 ^{99 m}Tc-HMPAO-SPECT and 25 dynamic Xe-CT investigations were conducted, both before and after acetazolamide stimulation. rCPR was quantified as the ratio (1) of the absolute rCBF values obtained by Xe-CT and (2) of the count density measured by HMPAO-SPECT of the acetazolamide administration. A rCPR of less than 95 % in a vascular territory was classified as compromised rCPR. A recent CT examination was available in all cases. According to the angiographic findings the patients could be classified into (1) group A (n = 9) with residual carotid perfusion, (2) Group B (n = 8) with collateralization via the circle of Willis, and (3) group C (n = 24) with leptomeningeal or ophthalmic artery collateral circulation. The rCPR values were significantly different in groups B and C with both methods, Xe-CT (P = 0.0035) and HMPAO-SPECT (P = 0.0014). rCPR was decreased in 13/14 group C patients investigated with Xe-CT and in 11/14 examined with HMPAO-SPECT. All patients in group B showed normal rCPR according to Xe-CT and HMPAO-SPECT. In group A, six of seven revealed decreased rCPR on Xe-CT, while rCPR values were normal in all four group A-patients examined with HMPAO-SPECT. The cerebral hemodynamics depend on a collateralization network and not only on the degree of internal carotid artery (ICA) stenosis. A decreased CPR in a vascular territory ipsilateral to an ICA stenosis or occlusion correlates strongly with the angiographic finding of leptomeningeal or ophthalmic artery collateral circulation.      

氙CT脑血流成像在颞浅动脉-大脑中动脉搭桥术中的应用价值

目的:探讨氙CT脑血流成像评价缺血性脑血管病颅内外血管搭桥术的价值。方法:10例颈内/大脑中动脉闭塞患者实施颞浅动脉-大脑中动脉搭桥术前、术后均行氙CT检查,其中8例于术前行乙酰唑胺负荷试验。对药物负荷前后以及手术前后脑血流量(CBF)进行定性和定量比较分析。结果:10例患者术前病变侧CBF均有降低,行乙酰唑胺负荷试验的8例患者用药后4例CBF降低更明显,其余4例CBF无明显变化或仅轻度增加。术后复查氙CT有8例患者CBF较术前增加,2例CBF较术前降低,手术前后病变区CBF值有显著性差异(P<0.05)。结论:氙CT脑血流成像能够定性、定量评价颈内/大脑中动脉闭塞的脑血流情况和脑血管储备能力,对指导颅内外血管搭桥术和评价疗效具有重要价值。     

The effect of EC-IC bypass surgery on resting cerebral blood flow and cerebrovascular reserve capacity studied with stable Xe-CT and acetazolamide test

Summary Cerebral blood flow (CBF) and cerebrovascular reserve capacity (CRC) were measured by stable xenon computerized tomography (Xe-CT) and acetazolamide test in 15 patients with cerebrovascular disease before and after extracranial-intracranial (EC-IC) bypass surgery for minor stroke, reversible ischemic neurological deficit or transient ischemic attack. All had angiographically shown occlusive lesions of the major arterial trunk. In the present series, global analysis showed that the bypass did not increase the resting rCBF, but did increase the rCRC. We divided the patients into four groups according to the preoperative resting rCBF and rCRC. All 3 patients with normal resting rCBF and reduced rCRC showed postoperative improvement of rCRC. Of 6 patients with reduced CBF and reduced CRC, three had postoperative increase in resting CBF and four had increased CRC. One of two patients with reduced CBF and normal CRC showed only an increase in CRC. We propose that reduced CRC or reduced CBF with reduced CRC are criteria for selection of candidates for bypass surgery. We conclude that Xe-CT with the Diamox test is a useful and simple method for evaluating cerebral hemodynamics. Preoperative grouping with a combination of preoperative resting cCBF and preoperative rCRC is useful for predicting the effect of EC-IC bypass surgery.     

Assessment of blood flow velocity and diameter of the middle cerebral artery during the acetazolamide provocation test by use of transcranial Doppler sonography and MR imaging

BACKGROUND AND PURPOSE: Our purpose was to show changes in the diameter of the M1 segment of the middle cerebral artery (MCA) by using high-resolution MR imaging in patients with chronic internal carotid artery occlusion after IV administered acetazolamide challenge. Changes in blood flow velocity of the basal cerebral arteries are thought to correlate with changes of cerebral blood flow. Changes in the diameter of the basal cerebral arteries, however, might influence the validity of transcranial Doppler measurements. METHODS: Eight patients with internal carotid artery occlusion who were undergoing acetazolamide testing for assessment of cerebrovascular vasomotor reactivity were included in the study. Blood flow velocities of both MCAs were measured with transcranial Doppler sonography before and 25 minutes after the administration of acetazolamide. Before and 15 minutes after the administration of medication, MR imaging was performed contralateral to the occlusion side. A T2-weighted turbo-gradient spin-echo sequence was chosen to show a cross section of the M1 segment in high resolution (pixels, 0.27 x 0.29 mm). Based on interpolated data, the smallest and greatest MCA diameters were determined. RESULTS: We did not find changes in the diameter of the MCA after acetazolamide provocation testing with high-resolution MR imaging in patients with occlusive extracranial carotid artery disease. CONCLUSION: The results of our study support the hypothesis that changes in MCA flow velocity measured by transcranial Doppler sonography reflect relative changes in cerebral blood flow after acetazolamide provocation testing.     

Solitaire AB型支架用于急性脑动脉闭塞取栓术31例

目的探讨Solitaire AB型支架用于急性脑动脉闭塞动脉取栓术的效果及安全性。方法 2010年5月至2011年5月采用Solitaire AB型支架用于急性脑动脉闭塞的动脉取栓术,共31例,其中颈内动脉闭塞6例,大脑中动脉闭塞12例,基底动脉闭塞9例,合并大脑中动脉及基底动脉闭塞1例,颈内动脉末段合并大脑中动脉闭塞3例。回顾性分析其即时取栓效果,术后出血情况,并比较其随访90 d时的MRS评分情况。结果大脑中动脉和基底动脉闭塞患者均成功再通,颈内动脉有6例(6/9)获再通。12例患者因为再通后仍存在管腔狭窄而放置支架。术后颅内出血4例(12.9%),死亡8例(25.8%)。在死亡患者中,5例责任动脉在颈内动脉,3例在基底动脉。从发病到获得再通时间超过8 h者8例,其中死亡2例,均为颈内动脉闭塞患者。90 d随访患者中,出院MRS评分预后良好(<2)的有15例(48.4%)。结论用Solitaire AB型支架进行动脉取栓对于大脑中动脉及基底动脉闭塞患者能获得较高的再通率,改善临床结局,但对颈内动脉闭塞患者效果不理想,再通率低,死亡率高。     

容积穿梭80 mm CT脑灌注成像及动态四维CT血管成像诊断颈内动脉系统血管狭窄和闭塞

目的 探讨利用容积穿梭扫描模式(volume shuttle)的80 mm CTP)及80 mm动态4D-CTA诊断大脑Willis环血管狭窄或闭塞.方法 55例大脑中动脉(MCA)或颈内动脉(ICA)重度狭窄或闭塞患者,行CT平扫、脑CTP和头颈部CTA检查,CTP检查获得脑血流量(CBF)、脑血容量(CBV)、平均通过时间(MTT)、达峰时间(TTP)等参数,同时获得80 mm(0.625 mm×128)扫描覆盖范围内动态4D-CTA.采用K Independent Samples分析ICA或MCA狭窄或闭塞者脑血流灌注参数CBF、CBV、MTT、TTP.结果 40例单侧MCA或ICA重度狭窄或闭塞患者中4例脑血流灌注未见显著异常改变,36例患者TTP和MTT均发现与临床症状相对应的灌注延迟区,病变侧MTT(7.18±1.34)s、TTP(19.65±1.81)s与健侧MTT(5.22±1.14)s、TTP(17.62±1.65)s比较,差异有统计学意义(X~2值分别为30.833、25.817,P值均<0.017);CBV、CBF未见明显异常.15例双侧MCA或ICA重度狭窄或闭塞患者,5例责任病灶侧与非责任病灶侧比较,脑血流灌注未见明显差异.10例责任病灶侧与非责任病灶侧比较,可见明显的脑血流灌注异常区,TTP和MTT较非责任病灶侧延迟,责任病灶侧 CBF(42.85±6.09)ml·100 g~(-1)·min~(-1)、CBV(2.63±0.42)ml·100 g~(-1)、MTT(11.27±1.43)s、TTP(21.07±1.44)s和对照组CBF(71.20±6.30)ml·100 g~(-1)·min~(-1)、CBV(2.29 ±0.15)ml·100 g~(-1)、MTT(3.38±0.61)s、TTP(17.64±1.70)s比较,差异具有统计学意义(X~2值分别为17.314、5.913、17.334、13.834,P值均<0.017).应用容积穿梭扫描模式获得80 mm动态Willis环4D-CTA图像,27例单侧MCA重度狭窄或闭塞患者中右侧MCA狭窄患者13例,左侧MCA狭窄患者9例;单侧MCA闭塞患者5例,其中右侧1例,左侧4例.9例双侧MCA重度狭窄或闭塞患者4D-CTA图像显示双侧MCA狭窄.4D-CTA图像与常规CTA、DSA显示Willis环血管狭窄或闭塞结果一致.结论 64层CT容积穿梭扫描模式可同时获得80 mm脑血流灌注和80 mm动态Willis环4D-CTA,对MCA或ICA狭窄或闭塞不仅能确定脑灌注异常范围,而且能够进行病因诊断,指导临床医师选择治疗方案及评价疗效,有广泛的临床应用前景.     

颈动脉狭窄或闭塞患者数字记忆的功能磁共振成像研究

目的:探讨左侧颈内动脉/大脑中动脉狭窄和闭塞患者与正常人数字工作记忆的激活脑区差异及其记忆障碍的脑加工机制。方法:对12例左侧颈动脉狭窄/闭塞患者(其中左侧颈内动脉狭窄4例,左侧颈内动脉闭塞2例,左侧大脑中动脉狭窄5例,左侧大脑中动脉闭塞1例,24例正常对照组进行数字记忆任务的功能磁共振成像,采用AFNI软件进行数据分析和脑功能区活动图像。结果:左侧颈内动脉/大脑中动脉狭窄和闭塞患者的反应时间较对照组显著延长(P0.05),正确率较对照组明显降低(P0.05)。脑激活图显示数字工作记忆的编码期、保持期、提取期患者组的脑激活明显少于正常对照组,而且脑激活的左侧半球优势减弱,右侧半球出现代偿性激活,其中提取期最为明显。结论:左侧颈动脉狭窄/闭塞患者数字记忆任务的脑激活区存在损害,功能磁共振成像研究能为早期诊断认知障碍提供影像学依据。     

大脑中动脉分布区脑梗死模式的分析研究

目的：探索影像学梗死模式在判定动脉粥样硬化性大脑中动脉分布区梗死的责任血管及发生机制中的临床价值。 方法：选取2015年1月—2016年12月在我院神经内科住院的缺血性脑卒中患者105例,分为颈内动脉（ICA）梗死组68例,大脑中动脉（MCA）梗死组37例,比较两组患者的临床资料及病变血管的狭窄程度,并对不同狭窄程度下的脑梗死模式进行统计分析。 结果：ICA梗死组的低密度脂蛋白水平高于MCA梗死组,差异具有统计学意义[（2.34±0.70）mmol/L vs.（2.08±0.49）mmol/L,t=2.00,P<0.05];两组间的临床病史、侧支循环情况、单双侧梗死、单发及多发梗死、三酰甘油、高密度脂蛋白、同型半胱氨酸、血压的差异均无统计学意义。105例脑梗死患者共累及108支血管。其中37支为MCA病变所致,71支为ICA病变所致。ICA组中轻度狭窄血管的比例高于MCA组,差异有统计学意义（42.3% vs. 8.1%,P<0.05）;两组中、重度狭窄和闭塞血管的比例差异无统计学意义。ICA梗死组和MCA梗死组发生大面积梗死分别为1/0例,散在皮层梗死2/2例,单独内分水岭梗死3/13例,单独外分水岭梗死7/9例,单独穿动脉梗死7/13例,散在皮层及内分水混合梗死4/16例,穿动脉及内分水岭混合梗死4/8例,穿动脉、散在皮层及内分水岭混合梗死9/10例;轻度、中度及重度狭窄程度的ICA与MCA两组间梗死模式差异无统计学意义;闭塞的MCA组中发生穿动脉梗死的比例高于闭塞的ICA组（4/13 vs. 0/16,P=0.03）,差异有统计学意义。 结论：影像学梗死模式在临床判定责任血管的价值依赖于后期更严谨的研究设计,此类依靠管腔狭窄程度作为分组指标的方法可能是影响研究结果的重要因素。     

Relationship between circle of Willis morphology on 3D time-of-flight MR angiograms and transient ischemia during vascular clamping of the internal carotid artery during carotid endarterectomy

BACKGROUND AND PURPOSE: A potential source of complication at carotid endarterectomy (CEA) is cerebral ischemia caused by hypoperfusion during clamping of the carotid artery. Configuration of primary collateral pathways may be a major risk factor for development of transient cerebral ischemia during clamping. We investigated whether circle of Willis morphology on 3D time-of-flight (TOF) MR angiograms can reliably predict transient ischemia during vascular clamping of the internal carotid artery (ICA) in patients undergoing CEA. METHODS: Three-dimensional TOF MR angiography and CEA were performed in 117 patients. Patients had unilateral stenosis (n = 86), unilateral stenosis with contralateral occlusion (n = 21), or bilateral severe stenosis (n = 10) of the ICA. Circle of Willis morphology on preoperative 3D TOF MR angiograms was analyzed and correlated with intraoperative history of ischemia during vascular clamping of the ICA. RESULTS: Patients with unilateral stenosis or bilateral severe stenosis experienced transient ischemia during clamping of ICA at a low rate (11 [11%] of 96). In these groups, we found no specific circle of Willis patterns associated with development of intraoperative ischemia. However, patients with contralateral ICA occlusion experienced ischemia frequently during clamping of the ICA (12 [57%] of 21). In this group, incompleteness of the circle of Willis was significantly related to the risk of intraoperative ischemia (P =.005). CONCLUSION: In patients without contralateral ICA occlusion, circle of Willis morphology on 3D TOF MR angiograms cannot predict the development of intraoperative ischemia. However, in patients with contralateral ICA occlusion, incompleteness of the posterior part of the circle of Willis is a significant risk factor for development of ischemia during vascular clamping of the ICA.     

多期相超短回波四维MRA在评估颅内血管狭窄中的应用价值

目的:探讨多期相超短回波四维磁共振血管成像(mUTE 4D MRA)在评估颅内血管狭窄中的应用价值.方法:前瞻性收集59例脑血管病患者的临床及影像资料,受试者均先行3D时间飞跃法MR血管成像(3D TOF MRA)和mUTE 4D MRA扫描,然后在同一天行CT血管成像(CTA)检查.由2位神经影像医师采用双盲法对血管...     

Topographic distribution of misery perfusion in relation to internal and superficial borderzones

BACKGROUND AND PURPOSE: Whether misery perfusion (MP) commonly accompanies brain borderzones (BZs) in patients with major cerebral artery occlusion remains unclear. We elucidated topographic patterns of chronic hemodynamic failure in such patients. METHODS: Twenty-four patients with unilateral occlusion or severe stenosis (>75% in diameter) of the internal carotid artery (ICA) or middle cerebral arterial (MCA) trunk with minimal or no infarct underwent PET with (15)O-labeled gas inhalation. Mean cerebral blood flow (CBF), cerebral blood volume (CBV), cerebral metabolic rate of oxygen, oxygen extraction fraction (OEF), and CBV/CBF ratio were determined in the superficial BZs, internal BZ, and MCA territory excluding BZs. Values in BZs were standardized and compared with those in controls. Topographic distributions of regions with OEF greater than that in controls were determined. RESULTS: Values in patients and controls were not significantly different. Topographic distributions included matched perfusion in 10 patients, MP in only the ipsilateral internal BZ in four, MP in both ipsilateral internal and superficial BZs in two, MP in the ipsilateral MCA territory including BZs in one, MP in the ipsilateral MCA territory including BZs and contralateral BZs in two, and MP in the ipsilateral MCA territories including BZs in five. CONCLUSION: Only 25% of the patients had MP localized in affected BZs Although localized MP more frequently accompanied the internal BZ than other regions, no patient had elevated OEF in the superficial BZ alone. These results are inconsistent with clinical observations that 80% of BZ infarctions develop superficially. Thus, hemodynamic mechanisms may not cause most superficial BZ infarctions.     

MR动脉血质子自旋标记与波谱成像在颈内动脉系统狭窄或闭塞的应用研究

目的 探讨MR动脉血质子自旋标记(ASL)与氢质子磁共振波谱成像(1H-MRS)在颈动脉系统狭窄或闭塞的应用价值. 资料与方法 28例单侧颈内动脉(ICA)/大脑中动脉(MCA)重度狭窄或闭塞患者行ASL 和1H-MRS检查.对ASL后处理的相对脑血流量(CBF) 图进行定性和定量分析;对1H-MRS测量病变侧和对侧脑组织的氮-乙酰天门冬氨酸(NAA)、胆碱(Cho)、肌酸(Cr)的波峰下面积,比较两侧各代谢物峰下面积比值(NAA/Cho、NAA/Cr、Cho/Cr)的差异,并观察是否出现乳酸(Lac)峰. 结果 28例CBF图显示18例病变侧灌注较对侧降低,10例未见明显异常;1H-MRS显示病变侧的NAA/Cho、NAA/Cr低于对侧,差异有统计学意义(P<0.01),Cho/Cr高于对侧,差异有统计学意义(P<0.01),3例于病变侧检测到Lac峰. 结论 ASL 能够早期发现颈动脉系统狭窄或闭塞患者的CBF改变,1H-MRS能够显示缺血脑组织的代谢异常.     

Redistribution of cerebropetal blood flow in patients with carotid artery stenosis measured non-invasively with fast cine phase contrast MR angiography

The purpose was to evaluate the blood flow redistribution in the neck vessels of patients with internal carotid artery (ICA) stenosis. Eighty-six patients with ICA stenosis underwent contrast-enhanced magnetic resonance angiography (CEMRA) and fast 2D phase contrast (2D-PC) sequence to measure the mean blood flow (MBF) of ICA, basilar artery (BA) and middle cerebral artery (MCA). CEMRA revealed 53 severe stenoses, 45 moderate stenoses and 3 occluded vessels. Patients with a unilateral severe ICA stenosis had a significantly reduced MBF of the ICA compared to the control group; the MBF reduction of the severely stenosed ICA was less conspicuous if associated with a controlateral severe stenosis. The MBF of the BA increased significantly in the presence of the bilateral severe ICA stenosis and in the ICA occlusion. The MBF of the MCA was unchanged in the presence of various degrees of ICA stenosis. Measurement of MBF with fast PC MRA permits cerebropethal blood flow assessment and gives additional information in grading ICA stenosis. The reduced MBF of a severe ICA stenosis has to be considered with caution since it depends also on the status of the controlateral ICA and may be considered a confident parameter only in case of unilateral carotid stenosis.     

Influence of the site of arterial occlusion on multiple baseline hemodynamic MRI parameters and post-thrombolytic recanalization in acute stroke

In this prospective MRI study, we evaluated the impact of the site of occlusion on multiple baseline perfusion parameters and subsequent recanalization in 49 stroke patients who were given intravenous tissue plasminogen activator (tPA). Pretreatment magnetic resonance angiography (MRA) revealed an arterial occlusion in 47 patients: (1) internal carotid artery (ICA) + M1 middle cerebral artery (MCA) occlusion (n=12); (2) M1 MCA occlusion (n=19); (3) M2 MCA, distal branches of the MCA and anterior cerebral artery (ACA) occlusion (n=16). Patients with ICA occlusion had significantly larger DWI, PWI and mismatch lesion volume on pretreatment MRI compared to patients with other sites of occlusion. The differences in cerebral blood flow (CBF) and peak height were significantly higher in patients with ICA occlusion compared to patients with other sites of occlusion (P=0.03 and P=0.04, respectively). Day 1 MRA showed recanalization in 28 patients (60%). The rate of recanalization was significantly different depending on the site of occlusion: 33% in ICA + M1 MCA occlusion, 63% in M1 MCA occlusion and 81% in either M2 MCA, distal branches of the MCA or ACA occlusion (P=0.002). Our data suggest that CBF and peak height are the most relevant MRI parameters to assess the severity of hemodynamic impairment in regard to the site of occlusion.     

Hyperacute ischemic stroke: middle cerebral artery susceptibility sign at echo-planar gradient-echo MR imaging

PURPOSE: To evaluate the accuracy of echo-planar T2*-weighted magnetic resonance (MR) sequences in detection of acute middle cerebral artery (MCA) or internal carotid artery (ICA) thrombotic occlusion. MATERIALS AND METHODS: Forty-two consecutive patients with stroke involving the MCA territory underwent MR imaging within 6 hours after clinical onset. MR examination included echo-planar T2*-weighted, diffusion-weighted (DW), and perfusion-weighted (PW) imaging and MR angiography. Presence or absence of the susceptibility sign on echo-planar T2*-weighted images, which is indicative of acute thrombotic occlusion involving MCA or ICA, was assessed in consensus by two observers blinded to clinical information and other MR imaging data. Differences in lesion volume on DW and PW images between patients with and those without the susceptibility sign were evaluated with the Mann-Whitney test. P <.05 was considered to indicate a significant difference. RESULTS: Thirty patients (71%) had a positive susceptibility sign that correlated with MCA or ICA occlusion at MR angiography in all cases (sensitivity, 83%; specificity, 100%). Mean lesion volume on PW images was higher in patients with a positive susceptibility sign (P =.01), but no significant differences were found in mean lesion volume on DW images. Cases in which the susceptibility sign was identified proximal to MCA divisional bifurcation (27 patients) showed a mean perfusion deficit of 83.9% of the total MCA territory (range, 50%-100%). CONCLUSION: Presence of the susceptibility sign proximal to MCA bifurcation provides fast and accurate detection of acute proximal MCA or ICA thrombotic occlusion.     

Clinical significance of cerebrovascular reserve in acetazolamide challenge —comparison with acetazolamide challenge H2O-PET and Gas-PET—

OBJECTIVE: The response of cerebral blood flow (CBF) to acetazolamide (ACZ) challenge is frequently determined in clinical settings to evaluate cerebrovascular reserve (CVR). A reduced CVR can indicate patients with occlusive cerebrovascular disease and compromised hemodynamics who may be at increased risk of cerebral ischemia. However, how precisely ACZ reflects cerebral hemodynamic impairment remains obscure. The present study aims to clarify the pathological significance of CVR in patients with occluded carotid arteries. METHODS: We recruited seventeen patients with occlusive lesions in the internal carotid artery (ICA) or middle cerebral artery (MCA). We assessed these patients in terms of resting cerebral blood flow (CBF) and the CVR response to ACZ challenge using H20 positron emission tomography (PET). In addition, we evaluated hemodynamic parameters including oxygen extraction fraction (OEF) using Gas-PET. RESULTS: We identified a significant negative correlation between the CVR and OEF or the cerebral blood volume (CBV)/CBF ratio, as a potential index of cerebral perfusion pressure. Although the CVR values were reduced in all regions with elevated OEF (Stage II), these values were highly variable regardless of the CBV/CBF ratios. The cut-off value of CVR alone could not detect Stage II, but when combined with resting CBF, misery perfusion accompanied by increased OEF was detected with high sensitivity (6/7) and specificity (61/62). CONCLUSION: CVR could be applied as an index reflecting both autoregulatory capacity and OEF. The present study also supported the notion that SPECT with ACZ challenge can be clinically applied to detect misery perfusion.     

Internal carotid artery stent implantation in 25 patients with acute stroke: preliminary results

PURPOSE: To evaluate retrospectively the outcome for patients with acute ischemic stroke in the territory of the middle cerebral artery (MCA) who had undergone stent implantation in the proximal segment of the internal carotid artery (ICA) in addition to intraarterial thrombolysis (IAT). MATERIALS AND METHODS: Stent implantation and retrospective analysis of clinical and radiologic data were approved by the institutional ethical committee. Endovascular treatment was performed after obtaining informed consent from patients or their closest relatives. Informed consent for retrospective review was not required. After pharmacologic and/or mechanical IAT, 25 consecutive patients (seven women, 18 men; mean age, 59 years +/- 14 [standard deviation]) underwent stent implantation in the proximal segment of the ICA (endovascular group). The clinical and radiologic characteristics (ie, interval from symptom onset to arrival at the emergency department, prevalence of vascular risk factors, causes of stroke, stroke severity, early signs of cerebral ischemia, duration of endovascular intervention, type of occlusion, and prevalence of leptomeningeal collateral vessels), recanalization rates, and clinical outcomes for patients in the endovascular group were compared with those for patients in the medical group (10 women, 21 men; mean age, 62 years +/- 12) who experienced ischemic stroke in the territory of the MCA as a result of ICA occlusion and who received antithrombotic treatment only. Differences between groups were assessed by using the chi2 test. A logistic regression analysis was performed to assess the effect of clinical and radiologic factors on recanalization rates and outcome. RESULTS: ICA recanalization was successful in 21 patients. Good recanalization of the MCA was achieved in 11 patients. In nine of these patients, recanalization of the MCA was achieved by using mechanical IAT only. In the remaining 12 patients, administration of intraarterial urokinase was performed in addition to mechanical thrombolysis. Two patients from the endovascular group experienced symptomatic intracerebral hemorrhage. At 3 months, 56% of the endovascular group and 26% of the medical group had a favorable outcome. Mortality was 20% in the endovascular and 16% in the medical group. CONCLUSION: IAT and stent implantation in the proximal segment of the ICA seem to improve the outcome for patients with ischemic stroke caused by occlusion of the cervical portion of the ICA.     

Carotid perfusion CT with balloon occlusion and acetazolamide challenge test: feasibility

Carotid balloon test occlusion (BTO) is used to assess the collateral circulation and cerebrovascular reserve in patients in whom carotid artery occlusion is contemplated. Eight patients in whom the test was successful were evaluated with perfusion computed tomography (CT) in the resting state and after acetazolamide challenge. Three of the patients showed symmetric blood flow and normal response to acetazolamide. One of them underwent permanent carotid occlusion and did not develop any delayed ischemic stroke. The remaining five patients showed asymmetric blood flow. One of them had markedly low blood flow and abnormal response to acetazolamide. The patient developed ipsilateral hemispheric stroke following permanent carotid occlusion after the superficial temporal artery to middle cerebral artery bypass graft occluded. In the other four patients, the steal phenomenon was seen in ipsilateral and contralateral hemispheres. Although definitive quantitative values for perfusion CT are not yet standardized, it may be feasible to predict that the patients with symmetric blood flow and normal acetazolamide-enhanced challenge test results will do well after permanent carotid occlusion. Patients with asymmetric blood flow and abnormal response to the acetazolamide challenge test may require a revascularization procedure to protect them from delayed ischemic stroke.