Transcranial Doppler Markers of Diffusion-Perfusion Mismatch

BACKGROUND AND PURPOSE: During the evaluation of acute ischemic stroke with diffusion- and perfusion-weighted magnetic resonance imaging (DWI and PWI, respectively), the presence of salvageable brain tissue is suggested by the occurrence of a perfusion-diffusion "mismatch." DWI and PWI, however, are not universally available and have inherent inconveniences, which justify a search for practical diagnostic alternatives. The purpose of this study is to investigate whether there are transcranial Doppler (TCD) markers of mismatch. METHODS: Retrospective analysis of 22 patients with acute ischemic stroke affecting the middle cerebral artery (MCA) territory, who had a TCD performed within 24 hours of magnetic resonance imaging (MRI) with DWI and PWI. RESULTS: MRI and TCD were performed on average 10.8 +/- 9.2 hours apart. Time from symptom onset to MRI and TCD completion were 1.6 +/- 1.6 and 2 +/- 1.9 days, respectively. MCA and intracranial internal carotid artery (ICA) cerebral blood flow velocity (CBFV) asymmetry, together with a large ICA-to-MCA gradient, were associated with the presence of mismatch. The combined use of 2 TCD parameters (MCA CBFV asymmetry of > or = 30% and ICA-to-MCA gradient > or = 20 cm/sec) had a sensitivity of 75%, specificity of 80%, positive predictive value of 82%, and negative predictive value of 73% at detecting mismatch cases. CONCLUSIONS: Diffusion-perfusion mismatch appears to be associated with interhemispheric asymmetry between MCA and ICA CBFVs, and a large CBFV gradient between the ICA and MCA on the affected side. Prospective studies are required to verify these observations and to determine whether TCD can be used to follow patients with mismatch.     

Diffusion- and perfusion-weighted imaging in vasospasm after subarachnoid hemorrhage

BACKGROUND AND PURPOSE: Better measures of cerebral tissue perfusion and earlier detection of ischemic injury are needed to guide therapy in subarachnoid hemorrhage (SAH) patients with vasospasm. We sought to identify tissue ischemia and early ischemic injury with combined diffusion-weighted (DW) and hemodynamically weighted (HW) MRI in patients with vasospasm after SAH. METHODS: Combined DW and HW imaging was used to study 6 patients with clinical and angiographic vasospasm, 1 patient without clinical signs of vasospasm but with severe angiographic vasospasm, and 1 patient without angiographic spasm. Analysis of the passage of an intravenous contrast bolus through brain was used to construct multislice maps of relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF), and tissue mean transit time (tMTT). We hypothesize that large HW imaging (HWI) abnormalities would be present in treated patients at the time they develop neurological deficit due to vasospasm without matching DW imaging (DWI) abnormalities. RESULTS: Small, sometimes multiple, ischemic lesions on DWI were seen encircled by a large area of decreased rCBF and increased tMTT in all patients with symptomatic vasospasm. Decreases in rCBV were not prominent. MRI hemodynamic abnormalities occurred in regions supplied by vessels with angiographic vasospasm or in their watershed territories. All patients with neurological deficit showed an area of abnormal tMTT much larger than the area of DWI abnormality. MRI images were normal in the asymptomatic patient with angiographic vasospasm and the patient with normal angiogram and no clinical signs of vasospasm. CONCLUSIONS: We conclude that DW/HW MRI in symptomatic vasospasm can detect widespread changes in tissue hemodynamics that encircle early foci of ischemic injury. With additional study, the technique could become a useful tool in the clinical management of patients with SAH.     

Lesion development and reperfusion benefit in relation to vascular occlusion patterns after embolic stroke in rats

Vascular occlusion sites largely determine the pattern of cerebral tissue damage and likelihood of subsequent reperfusion after acute ischemic stroke. We aimed to elucidate relationships between flow obstruction in segments of the internal carotid artery (ICA) and middle cerebral artery (MCA), and (1) profiles of acute ischemic lesions and (2) probability of subsequent beneficial reperfusion. Embolic stroke was induced by unilateral intracarotid blood clot injection in normotensive (n=53) or spontaneously hypertensive (n=20) rats, followed within 2 hours by magnetic resonance (MR) angiography (MRA), diffusion- (DWI) and perfusion-weighted magnetic resonance imaging (MRI) (PWI). In a subset of animals (n=9), MRI was repeated after 24 and 168 hours to determine the predictive value of the occlusion pattern on benefit of reperfusion. The extent of cerebral perfusion and diffusion abnormality was related to the pattern of flow obstruction in ICA and MCA segments. Hypertensive animals displayed significantly larger cortical perfusion lesions. Acute perfusion-diffusion lesion mismatches were detected in all animals that subsequently benefitted from reperfusion. Yet, the presence of an angiography-diffusion mismatch was more specific in predicting reperfusion benefit. Combination of DWI, PWI, and MRA exclusively informs on the impact of arterial occlusion profiles after acute ischemic stroke, which may improve prognostication and subsequent treatment decisions.     

急性脑梗死散在和单一弥散加权成像病损与其供血动脉狭窄的关系

目的 探讨急性脑梗死弥散加权磁共振成像(DWI)上大脑中动脉(MCA)供血区散在性或单一性缺血性病损与其脑供血动脉狭窄或闭塞的关系.方法 回顾性分析73例连续积累的DWI显示一侧MCA供血区脑梗死的病例,入组病例均排除心源性栓塞性脑梗死,所有患者均在发病24 h内进行MRI和MRA等检查,7例患者并进行DSA.采用DWI急性缺血性病损分类方法 分为散在病损组和单一病损组,比较两组的病灶同侧MCA、颈内动脉(ICA)颅内段和颅外段狭窄或闭塞的发生率.结果 散在病损组42例,单一病损组31例.在病损同侧ICA颅外段和MCA闭塞或重度狭窄方面两组差异有统计学意义(28.6%与0,x2=10.6,P=0.001).在病损同侧ICA颅内段并MCA轻中度狭窄方面,两组间差异具有统计学意义(31.0%与9.7%,x2=4.717,P=0.03).散在病损与MCA和(或)ICA严重或多发狭窄呈正相关(OR值为13.7,95%CI:3.6～52.5).在MRA或DSA未发现颅内外大血管狭窄方面,两组间差异具有统计学意义(11.9%与32.3%,x2=4.526,P=0.033).散在病损组与无明显血管狭窄呈负相关(OR值为0.284,95%CI:0.09～0.94).结论 (1)脑梗死急性期DWI显示的MCA区散在性病损患者,MCA和ICA狭窄、甚至闭塞的可能性较大,以ICA颅外段闭塞较为常见;(2)DWI显示单一病损时提示脑供血动脉狭窄程度较轻,范围较局限,小血管病变的可能性相对较高,很少为严重的ICA颅外段狭窄或闭塞.

Abstract：

Objective To investigate the relationship between scattered or single lesion of acute cerebral infarction in middle cerebral artery territory on diffusion-weighted imaging (DWI) and stenosis of middle cerebral artery (MCA) or internal carotid artery (ICA). Methods With exclusion of cardioembolism, 73 consecutive patients with acute cerebral infarction of the unilateral MCA territory on DWI were analyzed. All patients got magnetic resonance imaging (MRI) and angiography (MRA) within 24 hours after onset, and 7 patients also had digital subtraction angiography (DSA). The patients were classified into single lesion group or scattered lesions group according to the DWI findings. The incidence of stenosis or occlusion of ipsolateral MCA, intracranial and extracranial ICA were compared between the two groups. Results 42 patients had scattered lesions and 31 patients had single lesion. The scattered-lesions group had a high incidence of ipsilateral extracranial ICA or MCA occlusion or severe stenosis ( 25.6%versus 0, x2 = 10.6, P = 0.001 ) and a high incidence of ipsilateral intracranial ICA or MCA moderate or mild stenosis (31.0% versus 9.7% ,x2 =4.717, P =0.03 ). A positive correlation was found between the scattered lesions and severe or multifocal stenosis of ipsilateral ICA and MCA ( OR: 13.7, 95% CI: 3.6 to 52.5). There was a low incidence of absence of extra- and intracranial stenosis on MRA or DSA in the scattered-lesions group ( 11.9% versus 32.3%, x2= 4.526, P = 0.033 ). A negative correlation was found between the scattered lesions and absence of large-artery stenosis ( OR: 0.284, 95% CI: 0.09 to 0.94).Conclusions ( 1 ) Patients with acute cerebral infarction and scattered lesions on DWI were more likely to suffer from stenosis or occlusion of ICA or MCA, especially over the extracranial ICA. (2) Patients with single lesion were less likely to have severe or multiple stenosis of MCA and ICA, indicating the relevance of small-vessel pathogenesis.     

Pathophysiological topography of acute ischemia by combined diffusion-weighted and perfusion MRI.

BACKGROUND AND PURPOSE: Combined echoplanar MRI diffusion-weighted imaging (DWI), perfusion imaging (PI), and magnetic resonance angiography (MRA) can be used to visualize acute brain ischemia and predict lesion evolution and functional outcome. The appearance of a larger lesion by PI than by DWI quantitatively defines a mismatch of potential clinical importance. Qualitative lesion variations exist in the topographic concordance of this mismatch. We examined both the topographic heterogeneity and relative frequency of mismatched patterns in acute stroke using these MRI techniques. METHODS: Acute DWI, PI, and MRA studies of 34 prospectively recruited patients with supratentorial ischemic lesions scanned within 24 hours of stroke onset (range 2.5 to 23.3 hours, 12 patients <6 hours) were analyzed. RESULTS: Ischemic lesions were predominantly in the middle cerebral artery (MCA) territory (94%), with DWI lesions most commonly affecting the insular region. Mismatched patterns with PI lesion larger than DWI lesion occurred in 21 patients (62% overall), in all 4 patients imaged within 3 hours, and in 44% of patients imaged after 18 hours. A patient with a large PI but no DWI lesion and severe clinical deficit at 2.5 hours after stroke onset recovered completely. Regional variations in DWI and PI lesion loci were found, inferring site of proximal MCA occlusion, embolic pathogenesis, and regional arterial reperfusion. CONCLUSIONS: Analysis of the topographic concordance of PI and DWI lesions in acute stroke reveals regional PI lesions without concomitant DWI lesions, which do not necessarily progress to infarction but may suggest stroke pathogenesis and site of current arterial occlusion. Location of DWI lesions may suggest an earlier site of arterial occlusion and regions of maximal perfusion deficit.     

Diffusion/perfusion-weighted magnetic resonance imaging after carotid angioplasty and stenting

Abstract. Background and purpose: Carotid angioplasty and stenting, a so far non-validated procedure, may be an alternative to surgery in patients with a high surgical risk. However, it carries also a risk of cerebral embolic events. The purpose of this study was to evaluate tissue signal abnormalities in the brain before and after carotid angioplasty and stenting by means of diffusion- (DWI) and perfusion (PWI) weighted magnetic resonance imaging (MRI). Methods: We performed cerebral MRI before and after carotid angioplasty in 22 consecutive patients, with 23 treated high-grade carotid stenoses. The lesions were located at the origin of the internal carotid artery (ICA) in 20 patients, and at the origin of the common carotid artery (CCA) in 2. MRI was performed the day before, and repeated within 24 hours after the procedure, and examined by two neuroradiologists. Results: All stent implantations were successful but 4 patients developed an acute neurological deficit within 24 hours after carotid angioplasty. On PWI, Time To Peak (TTP) values ipsilateral to the carotid stenosis were increased before the procedure in 15 patients, and had remained normal in 6 and were not assessable in 1. After the procedure, TTP values were normal in 12 patients, increased in 8 and not assessable in 2. On DWI, new ipsilateral lesions were detected in 2 patients: 1 with an acute neurological deficit and 1 symptom free. Conclusion: Perfusion deficits may be present in severe carotid stenosis and be improved within 24 hours by carotid angioplasty and stenting. Asymptomatic infarcts may occur.     

ABCD~2评分结合DWI和PWI对TIA后发生脑梗死的预测价值

目的观察ABCD~2评分联合核磁共振弥散加权成像(DWI)和灌注加权成像(PWI)对短暂性脑缺血发作(TIA)后7 d和30 d内发生脑梗死风险的预测价值。方法 247例TIA患者发病后72 h内分别行ABCD~2评分联合头部DWI和PWI检查,随访发病后7 d和30 d脑梗死发生率。结果 247例TIA患者中,7 d和30 d内脑梗死发生率分别为21例(8.5%)和27例(14.8%);ABCD~2危险度分层7 d和30 d内脑梗死发生率低危组中危组高危组(均P0.05);DWI和PWI阳性且ABCD~2≥4分组显著高于DWI、PWI阴性组且ABCD~24分(均P0.05);DWI和PWI阳性组与DWI和PWI阴性组在各ABCD~2评分因素方面差异均有统计学意义(P0.05);Logistic回归分析表明ABCD~2评分中高危、DWI阳性和PWI阳性为TIA后发生脑梗死的独立危险因素。结论 ABCD~2联合DWI和PWI评分对预测TIA后7 d和30 d内脑梗死的发生风险具有重要的价值。     

Detection of the ischemic penumbra using pH-weighted MRI.

The classic definition of the ischemic penumbra is a hypoperfused region in which metabolism is impaired, but still sufficient to maintain cellular polarization. Perfusion- and diffusion-weighted MRI (PWI, DWI) can identify regions of reduced perfusion and cellular depolarization, respectively, but it often remains unclear whether a PWI-DWI mismatch corresponds to benign oligemia or a true penumbra. We hypothesized that pH-weighted MRI (pHWI) can subdivide the PWI-DWI mismatch into these regions. Twenty-one rats underwent permanent middle cerebral artery occlusion and ischemic evolution over the first 3.5 h post-occlusion was studied using multiparametric MRI. End point was the stroke area defined by T(2)-hyperintensity at 24 h. In the acute phase, areas of reduced pH were always larger than or equal to DWI deficits and smaller than or equal to PWI deficits. Group analysis showed that pHWI deficits during this phase coincided with the resulting infarct area at endpoint. Final infarcts were smaller than PWI deficits (range 65% to 90%, depending on the severity of the occlusion) and much larger than acute DWI deficits. These data suggest that the outer boundary of the hypoperfused area showing a decrease in pH without DWI abnormality may correspond to the outer boundary of the ischemic penumbra, while the hypoperfused region at normal pH may correspond to benign oligemia. These first results show that pHWI can provide information complementary to PWI and DWI in the delineation of ischemic tissue.     

弥散成像和血流灌注成像磁共振诊断急性缺血性脑血管病的意义

目的评价弥散成像（DWI）、血流灌注成像（PWI）磁共振对急性缺血性脑血管病的诊断价值。方法用DWI、PWI诊断急性脑缺血,并与常规MRI结果比较。结果经MRI检查证实的急性缺血性脑血管病患者共22例。其中发病后90分钟至6小时检查者11例,其CT及常规MRI未见异常,3例短暂性脑缺血发作（TIA）患者的DWI、PWI正常;其余8例脑梗死患者经DWI、PWI检查,均发现相对应的病灶,且6例灌注减低体积（PWIv）＞弥散异常体积（DWIv）,2例PWIv＝DWIv。起病在6－12小时5例,4例行PWI检查,3例PWIv＞DWIv,1例PWIv＝DWIv。起病在12－48小时6例,2例行PWI检查,PWIv＝DWIv。8例陈旧病灶在DWI上表现为低信号,所有新病灶在DWI上均为高信号。结论DWI、PWI可超早期诊断脑梗死,并可帮助了解缺血半暗带。T2加权像和DWI结合可以鉴别新旧梗死灶。     

Significance of early CT signs in acute stroke. A CT scan-diffusion MRI study.

OBJECTIVE: To study the pathophysiology of early CT signs. BACKGROUND: Early CT signs, due to an increase in tissue water content, are commonly attributed to cytotoxic edema and development of irreversible injury. This may have important implications for thrombolysis. METHODS: In patients with acute ischemic stroke in the middle cerebral artery territory, the areas of early CT signs and diffusion weighted imaging (DWI) hypersignal were independently assessed and drawn on a standardized atlas. Then, patients were classified into three groups (early CT signs larger than, similar to or smaller than DWI hypersignal) and compared with perfusion weighted imaging (PWI). RESULTS: Of 16 patients, CT scanning was performed with a median time of 3 h after onset and early CT scan signs were recorded in 10/16 patients (62.5%). DWI signal hyperintensity was present in 15/16 (94%) patients. In 7/16 (43%) patients, the area with early CT scan signs was larger than the DWI lesion ('CT-larger group'). Only in 2/16 (12%) patients were the areas matching ('matching group'). In 7/16 (43%) the DWI lesion was larger than the early CT scan signs area ('DWI-larger group'). When compared with PWI, the areas of early CT signs were larger than DWI hypersignal and were matching with PWI abnormalities (rMTT) in 2 cases, suggesting that they may represent a reversible process. CONCLUSIONS: Early CT signs might have a potential dual fate: infarction or reversibility. Other techniques of recognizing reversible ischemic damage, such as DWI-PWI, are needed to improve acute stroke diagnosis and management.     

Diffusion- and perfusion-weighted MRI. The DWI/PWI mismatch region in acute stroke.

BACKGROUND AND PURPOSE: Diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) are relatively new MR techniques increasingly used in acute stroke. During the first hours of stroke evolution, the regions with abnormal perfusion are typically larger than the DWI lesions, and this mismatch region has been suggested to be "tissue at risk." The aim of this study was to evaluate the PWI/DWI mismatch region in acute stroke patients and find parameters indicative of both infarct progression and functional impairment. METHODS: Twenty patients with nonlacunar ischemic stroke were imaged with DWI, PWI, and conventional MRI within 24 hours of symptom onset and after 1 week; in addition, the European Stroke Scale (ESS) score was recorded. With PWI, the volumes of regions with "time-to-peak" (TTP) delays of >/=2, 4, 6, 8, and 10 seconds were measured; these volumes were compared with the acute DWI lesion volumes, final infarct size, and ESS score. RESULTS: In 80% of patients the acute DWI lesion was surrounded by regions with abnormal TTP delays (PWI>DWI lesion). A TTP delay of >/=6 s in the mismatch region was found to be associated with lesion enlargement between the initial and follow-up MRI scans. Lesions increased in 9 of 12 patients (75%) in whom the area with TTP delay >/=6 s was larger than the DWI lesion, but they increased in only 1 of 8 (12.5%) of the remaining patients, in whom the area with a TTP delay >/=6 s was smaller than the DWI lesion. The volume of the regions with TTP delays of >/=4 s correlated better with ESS (r=-0.88, P<0.001) than other PWI (or DWI) volumes, which indicated that a TTP delay of approximately 4 s might be the threshold for functional impairment of brain tissue. CONCLUSIONS: Only patients with severe perfusion deficits in the PWI/DWI mismatch (TTP delays of >/=6 s) are at high risk of lesion enlargement. Functionally, more moderate perfusion deficits (TTP delays >/=4 and <6 s) appear to also contribute to the acute clinical deficit.     

Magnetic resonance imaging and clinical patterns of patients with 'spectacular shrinking deficit' after acute middle cerebral artery stroke

BACKGROUND: Rapid resolution of neurological deficits after severe middle cerebral artery (MCA) stroke has been coined spectacular shrinking deficit (SSD). We studied clinical and MRI patterns in patients with SSD. METHODS: Patients with acute MCA stroke <6 h were examined by stroke MRI (perfusion- and diffusion-weighted imaging (PWI, DWI), MR angiography (MRA)) at admission, day 1 and day 7. SSD was defined as a > or =8-point-reduction of neurological deficit in the National Institute of Health Stroke Scale (NIHSS) to a score of < or =4 within 24 h. PWI and DWI lesion volumes were measured on ADC (ADC < 80%) and time to peak maps (TTP > +4 s). Recanalization was assessed by MRA after 24 h. Final infarct volumes were defined on T2 weighted images at day seven. Outcome was assessed after 90 days using modified Rankin Scale (mRS) and Barthel Index (BI). RESULTS: SSD was present in 14 of 104 patients. Initial DWI and PWI lesion volumes were smaller in SSD patients - ADC < 80%: 8.9 (4.3-20.5) vs. 30 (0-266.7) ml; TTP > +4 s: 91.6 (29.7-205.8) vs. 131.5 (0-311.5) ml. Early recanalization was associated with SSD resulted in smaller final infarct volumes (11.9 (2.4-25.9) vs. 47.7 (1.2-288.5)). All SSD patients were independent at day 90 (mRS 0 (0-2); BI 100). CONCLUSION: The clinical syndrome of SSD is reflected by a typical MRI pattern with small initial DWI and PWI lesion volumes, timely recanalization and small final infarct volumes.     

MR灌注与弥散加权成像不同匹配与急性脑梗死降纤治疗效果的关系

目的 探讨MR灌注加权成像(PWI)与弥散加权成像(DWI)(PWI/DWI)不同匹配与急性脑梗死降纤治疗效果的关系.方法 给38例急性脑梗死患者行巴曲酶降纤治疗,在治疗前予以MR PWI及DWI检查,在治疗前和治疗后进行美国国立卫生研究院卒中量表(NIHSS)评分并评定疗效.比较PWI/DWI不同匹配患者治疗前后的N...     

Combined diffusion and perfusion MRI with correlation to single-photon emission CT in acute ischemic stroke. Ischemic penumbra predicts infarct growth.

BACKGROUND AND PURPOSE: More effective imaging methods are needed to overcome the limitations of CT in the investigation of treatments for acute ischemic stroke. Diffusion-weighted MRI (DWI) is sensitive in detecting infarcted brain tissue, whereas perfusion-weighted MRI (PWI) can detect brain perfusion in the same imaging session. Combining these methods may help in identifying the ischemic penumbra, which is an important concept in the hemodynamics of acute stroke. The purpose of this study was to determine whether combined DWI and PWI in acute (<24 hours) ischemic stroke can predict infarct growth and final size. METHODS: Forty-six patients with acute ischemic stroke underwent DWI and PWI on days 1, 2, and 8. No patient received thrombolysis. Twenty-three patients underwent single-photon emission CT in the acute phase. Lesion volumes were measured from DWI, SPECT, and maps of relative cerebral blood flow calculated from PWI. RESULTS: The mean volume of infarcted tissue detected by DWI increased from 46.1 to 75.6 cm(3) between days 1 and 2 (P<0.001; n=46) and to 78.5 cm(3) after 1 week (P<0.001; n=42). The perfusion-diffusion mismatch correlated with infarct growth (r=0. 699, P<0.001). The volume of hypoperfusion on the initial PWI correlated with final infarct size (r=0.827, P<0.001). The hypoperfusion volumes detected by PWI and SPECT correlated significantly (r=0.824, P<0.001). CONCLUSIONS: Combined DWI and PWI can predict infarct enlargement in acute stroke. PWI can detect hypoperfused brain tissue in good agreement with SPECT in acute stroke.     

Relationship between severity of MR perfusion deficit and DWI lesion evolution

OBJECTIVE: To assess whether a quantitative analysis of the severity of the early perfusion deficit on MRI in acute ischemic stroke predicts the evolution of the perfusion/diffusion mismatch and to determine thresholds of hypoperfusion that can distinguish between critical and noncritical hypoperfusion. METHODS: Patients with acute ischemic stroke were studied in whom perfusion-weighted imaging (PWI) and diffusion-weighted imaging (DWI MRI) were performed within 7 hours of symptom onset and again after 4 to 7 days. Patients with early important decreases in points on the NIH Stroke Scale were excluded. Maps of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT) were created. These hemodynamic parameters were correlated with the degree of recruitment of the baseline PWI lesion by the DWI lesion. RESULTS: Twelve patients had an initial PWI > DWI mismatch of >20%. A linear relationship was observed between the initial MTT and the degree of recruitment of the baseline PWI lesion by the DWI lesion at follow-up (R(2) = 0.9, p < 0.001). Higher CBV values were associated with higher degrees of recruitment (rho = 0.732, p < 0.007). The volume of MTT of >4 (R(2) = 0.86, p < 0.001) or >6 seconds (R(2) = 0.85, p < 0.001) predicted final infarct size. CONCLUSION: Among patients who have had an acute stroke with PWI > DWI, who do not have dramatic early clinical improvement, the degree of expansion of the initial DWI lesion correlates with the severity of the initial perfusion deficit as measured by the mean transit time and the cerebral blood volume.     

Etiology of Perfusion-Diffusion Magnetic Resonance Imaging Mismatch Patterns

BACKGROUND AND PURPOSE: Diffusion-and perfusion-weighted magnetic resonance imaging (DWI and PWI) are useful tools for the assessment of brain ischemia. Discrepancies between the extent of DWI and PWI abnormalities are thought to depend pre dominantly on time from symptom onset to magnetic resonance imaging (MRI) examination. However, underlying ischemic stroke etiology can also be important. A mismatch may indicate the presence of tissue at risk for infarction, whereas the relevance of other DWI/PWI patterns is uncertain. The authors therefore investigated the etiology of brain ischemia in patients with different DWI/PWI patterns. METHODS: Retrospective study of 130 patients with acute brain ischemia and detailed stroke workup, including MRI within a week after symptom onset (40 +/- 39 hours). Patients were divided into the following groups: mis-match (PWI > DWI), reverse mismatch (DWI > PWI), and match (<25% difference between PWI and DWI). RESULTS: Mismatch occurred in 49% of patients, whereas 22% had reverse mis-match and 29% matched lesions. Time from symptom onset to MRI examination was similar between the 3 groups. Largeartery atherosclerosis increased by almost 4-fold the odds of mismatch (odds ratio: 3.89, 95% confidence interval: 1.72-8.78; P < .001), whereas patients with reverse mismatch were likely to have cryptogenic stroke. Patients with matched lesions were similarly distributed among different stroke subtypes. CONCLUSIONS: Ischemic stroke etiology appears to influence the development of specific DWI/PWI patterns. Prospective studies are needed to confirm these observations.     

Early motor evoked potentials in acute stroke: adjunctive measure to MRI for assessment of prognosis in acute stroke within 6 hours

BACKGROUND: In acute stroke, a magnetic resonance (MR) perfusion-weighted imaging (PWI) and diffusion-weighted imaging (DWI) mismatch (PWI>DWI mismatch) may indicate tissue at risk for infarction and poor prognosis. However, different to early enthusiasm about this surrogate marker, its validity has shown several drawbacks in individual patients. Rather than relying on imaging, we evaluated motor evoked potentials (MEP) as a measure of cerebral function in the acute stroke setting. METHODS: Thirteen patients with acute hemiparetic stroke underwent time to peak PWI and DWI within 6 h after onset as well as recordings of early MEP of first dorsal interosseous muscles. Outcome was assessed by the Unified Neurological Stroke Scale and Barthel Index at day 42. RESULTS: Of 8 patients with PWI>DWI mismatch, 4 patients with normal MEP had a good clinical outcome and 4 patients with absent or pathological MEP had an unfavourable outcome (p < 0.05, Fisher's exact test). In all patients without PWI>DWI mismatch, MEP findings predicted clinical outcome. Normal MEP at day 0--but not PWI/DWI findings--significantly correlated with a good clinical outcome. CONCLUSIONS: Early MEP recordings in acute stroke patients provide valid prognostic information; they may become more useful for specific treatment decisions than presently available MRI surrogate parameters.     

116例大脑中动脉病变患者脑梗死类型分布和脑灌注异常分析

目的 应用神经影像检查,分析大脑中动脉闭塞性疾病(MCAOD)患者梗死类型分布和脑灌注异常. 方法 对经CT血管造影(CTA)证实的116例MCAOD患者的CT平扫、CT灌注成像(CTP)和CTA的影像资料进行回顾性分析,确定其脑梗死类型分布和脑灌注改变. 结果 116例患者中,CTA共检出133条大脑中动脉(MCA)狭窄或闭塞,其中单侧者99例,双侧者17例.其中MCA闭塞25条,重度狭窄39条,中、轻度狭窄69条.CT或MRI显示腔隙性脑梗死(LIS)45例,各型分水岭脑梗死(CWSI)38例,流域性脑梗死26例,纹状体内囊梗死(SCI)10例,未检出梗死病灶14例.CTP显示MCA供血区内脑血流灌注异常96例,其中58例有MCA供血区的大范围血流灌注减低.未检出血流灌注异常者37例. 结论 由于MCA狭窄的部位、程度和发病机制的不同以及侧支循环的建立,MCAOD可造成不同类型的脑梗死和血流灌注异常.     

Feasibility and safety of intrathecal nimodipine on posthaemorrhagic cerebral vasospasm refractory to medical and endovascular therapy

OBJECTIVE: The effectiveness of balloon angioplasty and intra-arterial infusion of vasodilating agents for patients suffering from severe vasospasm following aneurysmal subarachnoid haemorrhage (SAH) is often unsatisfying and there is still demand for further last resort treatment strategies. In the current prospective study, we attempted the intrathecal lavage administration of nimodipine in cases of severe cerebral vasospasm that were refractory to medical and endovascular therapy. METHODS: Eight of 146 patients with aneurysmal SAH were included in the prospective study, which had been approved by the local ethics committee. Treatment was instituted by intraventricular nimodipine bolus (0.4mg), followed by a continuous lumbar intrathecal infusion (0.4mg/h). Effectiveness was monitored angiographically, with transcranial Doppler (TCD), perfusion CT (pCT), and by neurological examination during treatment course and follow-up. RESULTS: The neurological condition improved directly in three patients and remained unchanged in four patients. Seventeen (70.8%) CT perfusion analyses revealed improved perfusion. A reduction of vasospasm was seen angiographically by digital subtraction angiography (DSA) in seven (66.6%) investigations. Additional ischaemic infarction after onset of the intrathecal therapy was documented in two (25%) patients. There were no serious adverse effects observed. CONCLUSION: The present study has for the first time demonstrated the feasibility and safety of intrathecal nimodipine lavage in patients with severe vasospasm resistant to the established medical and endovascular treatment strategies. The results of the study are therefore encouraging, and further experimental and clinical trials should be carried out so as to investigate the efficacy of intrathecal nimodipine lavage in vasospasm therapy.     

Cerebral infarction secondary to vasospasm after perimesencephalic subarachnoid hemorrhage

Perimesencephalic subarachnoid hemorrhage (pSAH) has been described as a distinct form of subarachnoid hemorrhage (SAH) associated with good outcomes. We report a 48-year-old female who developed cerebral infarction due to severe diffuse vasospasm following pSAH. The patient presented with non-aneurysmal pSAH and was discharged home on day 5. However, one week later she developed an acute onset of right hemiparesis. A brain MRI showed acute infarctions on diffusion weighted imaging and her cerebral angiogram showed diffuse vasospasm. The patient received intra-arterial diltiazem and hypervolemic-hypertensive-hemodilution therapy with resulting resolution of the vasospasm and hemiparesis. While not as common as in SAH, there is a potential for the occurrence of cerebral infarction due to vasospasm after pSAH.