Magnetic resonance perfusion imaging in acute ischemic stroke using continuous arterial spin labeling

BACKGROUND AND PURPOSE: Continuous arterial spin-labeled perfusion MRI (CASL-PI) uses electromagnetically labeled arterial blood water as a diffusible tracer to noninvasively measure cerebral blood flow (CBF). We hypothesized that CASL-PI could detect perfusion deficits and perfusion/diffusion mismatches and predict outcome in acute ischemic stroke. METHODS: We studied 15 patients with acute ischemic stroke within 24 hours of symptom onset. With the use of a 6-minute imaging protocol, CASL-PI was measured at 1.5 T in 8-mm contiguous supratentorial slices with a 3.75-mm in-plane resolution. Diffusion-weighted images were also obtained. Visual inspection for perfusion deficits, perfusion/diffusion mismatches, and effects of delayed arterial transit was performed. CBF in predetermined vascular territories was quantified by transformation into Talairach space. Regional CBF values were correlated with National Institutes of Health Stroke Scale (NIHSS) score on admission and Rankin Scale (RS) score at 30 days. RESULTS: Interpretable CASL-PI images were obtained in all patients. Perfusion deficits were consistent with symptoms and/or diffusion-weighted imaging abnormalities. Eleven patients had hypoperfusion, 3 had normal perfusion, and 1 had relative hyperperfusion. Perfusion/diffusion mismatches were present in 8 patients. Delayed arterial transit effect was present in 7 patients; serial imaging in 2 of them showed that the delayed arterial transit area did not succumb to infarction. CBF in the affected hemisphere correlated with NIHSS and RS scores (P=0.037 and P=0.003, Spearman rank correlation). The interhemispheric percent difference in middle cerebral artery CBF correlated with NIHSS and RS scores (P=0.007 and P=0.0002, respectively). CONCLUSIONS: CASL-PI provides rapid noninvasive multislice imaging in acute ischemic stroke. It depicts perfusion deficits and perfusion/diffusion mismatches and quantifies regional CBF. CASL-PI CBF asymmetries correlate with severity and outcome. Delayed arterial transit effects may indicate collateral flow.     

Prognostic value of ICP, CPP and regional blood flow monitoring in diffuse and focal traumatic cerebral lesions

Forty patients with severe traumatic brain injury (GCS score 8 and less) aged 16-54 years treated in our clinic were analyzed. Correlations between clinical symptoms, CT signs of diffuse and focal traumatic lesions, intracranial hemorrhage, indices of cerebral blood flow (CBF) according to perfusion CT study, intracranial pressure (ICP) and cerebral perfusion pressure (CPP) were assessed. Main mechanism of injury in 27 of 40 (67.5%) patients was acceleration-deceleration due to traffic accidents which usually leads to diffuse axonal injury (DAI) of different severity. In the other 13 (32.5%) cases injury was associated with coup-countercoup mechanism which caused focal contusions mostly. Not only GCS score but CT-signs of DAI severity, intracranial hemorrhage and minimal levels of CPP had significant prognostic value. Results of perfusion CT studies demonstrated that in 37 of 40 (92.5%) patients cerebral blood flow decreased (below 28.6 ml/100 g/min) in one or more arterial blood distribution areas. Increase of CBF was registered in 9 cases (over 69 ml/100 g/min), in 6 of them elevation of CBF in one arterial distribution area was associated with reduction in the other. Generally, mean CBF values were higher in the middle cerebral artery circulation than in the other. The lowest CBF levels (16.3 +/- 6 ml/100 g/min) were observed in cortical and subcortical hemorrhagic foci while these values were significantly higher in the same contralateral intact zones (36.0 +/- 10.0 ml/100 g/min; p < 0.01). In 3 patients with DAI the CBF in the midbrain varied from 12.5 to 30.1 ml/100 g/min with the lowest levels in hemorrhagic focus in cerebral peduncle. It corresponded to cystic-atrophic alterations found on subsequent follow-up MRI. Thus, reduction of CBF and episodes of low CPP were the leading pathophysiological phenomena of diffuse and focal brain damages.     

Window narrowing: a new method for standardized assessment of the tissue at risk-maximum of infarction in CT based brain perfusion maps

BACKGROUND: Mapping of brain perfusion using bolus tracking methods is increasingly used to assess the amount and severity of cerebral ischemia in acute stroke. Using relative perfusion maps, however, it is difficult to identify the tissue at risk-maximum (TARM) of infarction with sufficient reliability and reproducibility. METHODS: We analysed 76 perfusion computed tomography (PCT) derived maps of cerebral blood flow (CBF), cerebral blood volume (CBV) and time-to-peak (TTP) in 40 acute stroke patients using multidetector row technology and standard software (Somatom VolumeZoom, Siemens, Germany). 'Window narrowing' of the color maps was performed until color homogenisation of the contralateral unaffected hemisphere was reached. Tissue still depictable on the affected hemisphere after sufficient window narrowing was defined as the TARM. We analysed presence and size of the TARM on PCT maps, its relative perfusion values by comparison with contralateral, mirrored tissue, and its correlation with occurrence and final size of cerebral infarction on follow-up imaging. RESULTS: An ischemic area was visible in 64, 58.9 and 72.6% on the conventional CBF, CBV and TTP maps, respectively. After window narrowing, a TARM was present in 56.8, 54.1 and 63.0% of slices comprising 11.9, 11.6 and 21.1% of the ipsilateral hemisphere (CBF, CBV and TTP), respectively. The relative perfusion values were 38.7 (CBF) and 43.0% (CBV) for the entire ischemic area and 11.3 (CBF) and 13.3% (CBV) for the TARM. Definite cerebral infarction was visible on 68.1% of the target slices comprising 23.7 +/- 22.9% of the ipsilateral hemisphere. The size of the TARM correlated slightly better with the final infarction size (r=0.74-0.82) than the entire ischemic area (r=0.61-0.79). With respect to the occurrence of cerebral infarction, the presence of a TARM on CBF maps showed the best positive (97.9%) and negative (72.7%) predictability. DISCUSSION: On PCT maps, window narrowing provides a standardized display of the TARM in peracute stroke. The severely reduced values of relative CBF and CBV suggest the TARM to indicate tissue most prone to infarction.     

Periprocedural MRI perfusion imaging to assess and monitor the hemodynamic impact of intracranial angioplasty and stenting for symptomatic atherosclerotic stenosis

We aimed to assess the clinical value of MRI perfusion imaging in the periprocedural management of intracranial atherosclerosis, analyzing if changes in mean transit time (MTT), cerebral blood volume (CBV) and cerebral blood flow (CBF) correlated with angiographic outcomes. Pre-procedural and post-procedural MRI perfusion was performed on six patients who underwent angioplasty and/or stenting for symptomatic intracranial atherosclerosis. MTT, CBV and CBF were analyzed and graded. In 83% of patients, perfusion imaging correlated with angiographic outcomes. Perfusion parameters improved to normal in two patients. Two showed marked improvement and one showed mild improvement. In one patient, the results of the post-procedural MRI perfusion prompted an angiogram, which confirmed stent occlusion. Semi-quantitative scores of MTT and CBF changed over time (p = 0.05, p = 0.03) whereas CBV did not change significantly (p > 0.05). We conclude that MRI perfusion appears a promising technique for analyzing the impact of intracranial stenosis on cerebral hemodynamics before and after treatment.     

Sickle cell disease: ischemia and seizures

Although the prevalence of seizures in children with sickle cell disease (SCD) is 10 times that of the general population, there are few prospectively collected data on mechanism. With transcranial Doppler and magnetic resonance imaging (MRI) and angiography, we evaluated 76 patients with sickle cell disease, 29 asymptomatic and 47 with neurological complications (seizures, stroke, transient ischemic attack, learning difficulty, headaches, or abnormal transcranial Doppler), who also underwent bolus-tracking perfusion MRI. The six patients with recent seizures also had electroencephalography. Group comparisons (seizure, nonseizure, and asymptomatic) indicated that abnormal transcranial Doppler was more common in the seizure (4/6; 67%) and nonseizure (26/41; 63%) groups than in the asymptomatic (10/29; 34%) group (chi2; p = 0.045), but abnormal structural MRI (chi2; p = 0.7) or magnetic resonance angiography (chi2; p = 0.2) were not. Relative decreased cerebral perfusion was found in all seizure patients and in 16 of 32 of the remaining patients with successful perfusion MRI (p = 0.03). In the seizure patients, the perfusion abnormalities in five were ipsilateral to electroencephalographic abnormalities; one had normal electroencephalogram results. These findings suggest that vasculopathy and focal hypoperfusion may be factors in the development of sickle cell disease-associated seizures.     

Accuracy of perfusion-CT inpredicting malignant middle cerebral artery brain infarction

BACKGROUND: We performed a prospective study on patients with middle cerebral artery(MCA) ischemic stroke to evaluate the accuracy of perfusion-CT imaging(PCT) to predict the development of malignant brain infarction (MBI). METHODS: 106 patients(women 37 %, mean age 65 years)underwent native cranial computed tomography (CCT), CT angiography(CTA) and PCT after a median of 2 h after stroke onset. We assessed the patency of the MCA and the area of tissue ischemia (AIT)according to cerebral blood flow(CBF), cerebral blood volume (CBV) and time-to-peak (TTP)maps. Optimum sensitivity, specificity,positive (PPV) and negative predictive values (NPV) were calculated for the end-point MBI (= midline shift > 5 mm or decompressive surgery) by means of receiver operating characteristics(ROC). RESULTS: 20 patients (19 %)developed a MBI. In these patients,a larger AIT was found in all perfusion maps as compared to the remaining patients (p < 0.001). All perfusion maps had a very high NPV (95.4-98.4 %), a high sensitivity (85-95 %) and specificity (71.6-77.9 %) and only a moderate PPV (44-47.4 %). Best prediction was found for CBF maps with AIT of > 27.9 % of the hemisphere. CONCLUSION: PCT allows the discrimination of patients without a relevant risk for MBI from those having a 50 % risk of MBI development. Due to the high sensitivity and specificity, PCT is a reliable tool in detecting MBI. Because of PCT's better availability, it is the method of choice at present for an early risk stratification of acute stroke patients.     

Transient focal cerebral ischemia as a presenting manifestation of unruptured cerebral aneurysms

Few reports have described an association between cerebral transient ischemic attacks (TIAs) and unruptured cerebral aneurysms. This study presents seven patients with TIA who had aneurysms in a vascular distribution appropriate to their clinical symptoms. In three patients, angiographic evidence of embolization was present distal to the aneurysm without another apparent cardiac or extracranial arterial source for the emboli. The most reasonable pathogenesis for TIA in a patient with an associated saccular aneurysm would be thrombosis of the aneurysmal sac with subsequent embolization. However, subarachnoid blood can cause permanent focal intracranial narrowing, and this appeared to be a factor in at least one patient. The results imply that patients with symptoms of TIA should have their intracranial arterial circulation visualized as part of the diagnostic evaluation.     

Diffusion-perfusion MR evaluation of perihematomal injury in hyperacute intracerebral hemorrhage.

BACKGROUND: It has been suggested that a zone of perihematomal ischemia analogous to an ischemic penumbra exists in patients with primary intracerebral hemorrhage (ICH). Diffusion-perfusion MRI provides a novel means of assessing injury in perihematomal regions in patients with ICH. OBJECTIVE: To characterize diffusion-perfusion MRI changes in the perihematomal region in patients with hyperacute intracerebral hemorrhage. METHOD: Twelve patients presenting with hyperacute, primary ICH undergoing CT scanning and diffusion-perfusion MRI within 6 hours of symptom onset were reviewed. An automated thresholding technique was used to identify decreased apparent diffusion coefficient (ADC) values in the perihematomal regions. Perfusion maps were examined for regions of relative hypo- or hyperperfusion. RESULTS: Median baseline NIH Stroke Scale score was 17 (range, 6 to 28). Median hematoma volume was 13.3 mL (range, 3.0 to 74.8 mL). MRI detected the hematoma in all patients on echo-planar susceptibility-weighted imaging and in all seven patients imaged with gradient echo sequences. In six patients who underwent perfusion imaging, no focal defects were visualized on perfusion maps in tissues adjacent to the hematoma; however, five of six patients demonstrated diffuse ipsilateral hemispheric hypoperfusion. On diffusion imaging, perihematomal regions of decreased ADC values were identified in three of 12 patients. All three subsequently showed clinical and radiologic deterioration. CONCLUSIONS: A rim of perihematomal decreased ADC values was visualized in the hyperacute period in a subset of patients with ICH. The presence of a rim of decreased ADC outside the hematoma correlated with poor clinical outcome. Although perfusion maps did not demonstrate a focal zone of perihematomal decreased blood flow in any patient, most patients had ipsilateral hemispheric hypoperfusion.     

Alagille syndrome associated with angiographic moyamoya

We describe the case of a 13-year-old boy with Alagille syndrome in whom intracranial imaging was performed following a seizure. The MRI and MRA revealed changes of angiographic moyamoya within both the anterior and posterior circulation. This very rare manifestation of the systemic vasculopathy in Alagille syndrome has not been previously documented in a patient without a focal neurological deficit. We discuss the potential role of routine intracranial imaging in patients with Alagille syndrome.     

Acute primary cerebral angiitis mimicking basilar artery dissection

Two patients presented with acute severe occipital headache, neck pain, nausea, vomiting and blurred vision. In both patients angiograms of the posterior circulation showed focal narrowing of the basilar artery, thus basilar artery dissection was considered. Urgent magnetic resonance imaging (MRI) was unavailable. On the basis of additional angiography of the anterior circulation and control angiograms after 4 and 6 weeks, primary cerebral angiitis was the most probable diagnosis. Treatment with corticosteroids resulted in rapid clinical and angiographic improvement. We conclude that, when MR techniques are unavailable or inconclusive, presumption of basilar dissection on the base of clinical features, Doppler studies, Duplex scanning and angiography of the vertebro-basilar system should be confirmed by additional carotid angiography in order to exclude diffuse cerebral angiitis.     

Intracranial Vessel Wall MRI in Cryptogenic Stroke and Intracranial Vasculitis

Introduction: Intracranial vasculopathies easily elude classic stroke work-up. We aim in this work to show that vessel wall-MRI could prove an efficient alternative to digital subtraction angiography for the diagnosis of intracranial vasculopathies by identifying intracranial arterial vessel walls anomalies and contrast enhancement, suggestive of angiitis of the central nervous system. Materials and methods: Clinical and imaging characteristics of stroke patients diagnosed with primary angiitis of the central nervous system based on vessel wall-MRI were retrospectively reviewed and the clinical and imaging features of angiitis associated with intracranial vessel walls anomalies and contrast enhancement detailed. Results: Twenty patients were included (mean age was 59 years old). All patients were admitted for focal neurological deficits of sudden onset that were recurrent in 13 subjects. Cognitive impairment, headache and seizures occurred in, respectively, 13, 5, and 2 patients. Cerebrospinal fluid analysis was abnormal in 15 patients. In MRI, FLAIR sequences showed ischemic infarcts in 20 patients and DWI showed acute infarct in 15 patients. Digital subtraction angiography was performed in 11 patients and disclosed proximal and distal multifocal stenosis in 10 patients along distal irregularities in different vascular territories in 7. For all of our patients, VW-MRI revealed a concentric contrast enhancement of arterial walls, localized in multiple vascular territories, suggesting angiitis. Abnormalities on digital subtraction angiography and/or MR-Angiography, and vessel wall-MRI were consistent in all patients. Conclusions: This report underlies the added value of vessel wall-MRI to the diagnosis of underlying intracranial vasculopathy, particularly primary angiitis of the central nervous system, without the use of invasive endovascular techniques and the yield of vessel wall-MRI in the work-up of cryptogenic stroke.     

Evaluation of cerebrovascular disease by combined extracranial and transcranial Doppler sonography. Experience in 1,039 patients

Results from 1,039 combined cervical and transcranial Doppler examinations are reported. Satisfactory transcranial signals were not found in 2.7% of the cases. Compared with angiography, the accuracy of transcranial criteria in assessing collateral flow over the circle of Willis was 94 and 88% for anterior and posterior circulation, respectively. The method also appeared very promising for detection of lesions of the intracranial arteries although the number of such cases with angiographic verification was limited in the present series. Arterial narrowing due to cerebral vasospasm was diagnosed with a sensitivity of 80%. In patients with ruptured intracranial aneurysms, an incidence of 93% arterial narrowing in basal cerebral arteries was found. Patients with subarachnoid hemorrhage and no aneurysm on angiography also showed arterial narrowing with an incidence of 56%. It was possible to monitor the time course and severity of cerebral vasospasm. Arteriovenous malformations were characterized by Doppler findings of high velocities and low pulsatilities. These lesions were diagnosed with an accuracy of 95%.     

VCTDSA联合CT灌注成像对急性缺血性脑卒中影像诊断价值

目的探讨容积CT数字减影血管造影VCTDSA联合CT灌注成像在急性缺血性脑卒中的诊断价值。方法对30例临床诊断为急性缺血性脑卒中的患者于发病后24h内行VCTDSA联合CT灌注成像,观察CT平扫表现及灌注图像、VCTDSA重建图像结果。测定相应区域脑血流量(CBF),脑血容量(CBV),平均通过时间(MTT)和达峰时间(TTP)。结果 25例急性缺血性脑卒中患者头部CT平扫未发现与临床症状相对应的脑缺血区,CT灌注图上可发现与临床症状相对应的脑缺血区。CT灌注成像表现为CBF下降、CBV下降、MTT延长、TTP延长或无TTP出现。VCTDSA可见23例患者相应责任血管的不同程度的狭窄,其余7例患者未检出相应责任血管狭窄。结论 CT灌注成像在急性缺血性脑卒中的早期诊断中有很重要的价值。VCTDSA能发现缺血病变的原因,为临床进一步治疗提供确切依据。     

Angiographic findings in a young man with recurrent stroke and positive fluorescent treponemal antibody (FTA)

A young man with a history of two strokes was found to have serologic evidence of a prior syphilitic infection, abnormal spinal fluid, and angiographic evidence of diffuse intracranial and extracranial angiopathy which we believe was due to tertiary syphilis, although his use of oral amphetamines cannot be ruled out as a contributing factor. This is the first reported case in which angiography has demonstrated both intracranial and extracranial disease arterial disease due to neurosyphilis. Since syphilis can produce diffuse cerebral arterial changes, this diagnosis should be considered in young patients with stroke even when non-treponemal serologic tests are negative.     

CT脑灌注与血管造影在急性缺血性脑卒中的临床应用与分析

目的探讨CT脑灌注(CTPI)与血管造影在急性缺血性脑卒中中的临床应用价值。方法选择29例急性缺血性脑卒中患者为研究对象,采用东芝Aquilion 64排CT行头颈部CTA及CTPI检查,观察两者对急性缺血性脑卒中诊断情况,分析CTPI与CTA对急性缺血性脑卒中诊断的一致性。结果①29例患者CT灌注图上发现与临床症状相对应的灌注异常区共25例,阳性率为86.2%(25/29),高于普通CT扫描的27.6%(8/29),差异具有统计学意义(P0.05)。②灌注异常区的CBF、CBV、MTT三组参数值与镜像健侧相比差异有显著统计学意义(P0.05);③CTA血管检查结果发现单纯颈内动脉狭窄5处;单纯颅内动脉狭窄10处;颈内动脉及颅内动脉均狭窄4例。④病例组CTPI联合CTA检查结果比较,病例组存在责任血管的患者CTPI检查阳性率为65.51%(19/29)高于无责任血管者的20.69%(6/29),差异具有统计学意义(P0.05)。结论 CTPI与CTA可以清晰的显示缺血性脑卒中脑内病灶及责任动脉,能够提高更多有价值的信息。     

Endovascular recanalization for subacute symptomatic intracranial arterial occlusion: a report of two cases

BACKGROUND: We hope to illustrate the feasibility of endovascular recanalization for intracranial symptomatic arterial occlusion in the subacute period without adjunctive stenting. CASE DESCRIPTION: Two patients presented with recurrent transient ischemic attacks due to subacute occlusion of intracranial vessels (left MCA M1 and basilar artery). Both had pressor-dependent ischemic symptoms referable to the occluded artery. Sustained angiographic antegrade flow was achieved following angioplasty of our first patient's occluded basilar artery. Excellent angiographic perfusion of our second patient's left hemisphere was achieved following angioplasty of her occluded M1. A Maverick 2mmx9mm balloon was employed in both cases, neither requiring chemical thrombolysis. CONCLUSION: Symptoms in both patients abated and they were weaned off pressors within 24h, underscoring the potential of angioplasty to treat fluctuating, pressor-dependent cerebral ischemia from subacute intracranial arterial occlusion. At most recent follow-up, both patients were neurologically intact, denying any transient neurologic events occurring in the interim.     

Intracranial dissection mimicking transient cerebral arteriopathy in childhood arterial ischemic stroke

Transient cerebral arteriopathy is a frequent cause of childhood arterial ischemic stroke. Differentiating this condition from intracranial carotid artery dissection is challenging but important for initial treatment. We describe 4 cases from the International Pediatric Stroke Study of intracranial carotid artery dissection, initially misdiagnosed as transient cerebral arteriopathy. Presentations were abrupt, with focal neurological deficits in 4, preceding headache in 3, and minor trauma in 1. Infarcts involved the anterior circulation, and magnetic resonance angiography showed unilateral arterial stenosis/occlusion. None had evidence of dissection. All received anticoagulation or thrombolysis. Three died from refractory intracranial hypertension. Intracranial carotid artery dissection was confirmed postmortem (n = 3) and on dedicated MR wall imaging showing intramural hematoma (n = 1). In differentiating transient cerebral arteriopathy from intracranial carotid artery dissection, routine magnetic resonance angiography is unreliable and adjunctive conventional angiography, gadolinium magnetic resonance angiography, or dedicated MRI wall imaging should be considered.     

Arterial elasticity,endothelial function and intracranial vascular health: A multimodal MRI study

Vascular dysfunctions, including arterial stiffness and endothelial dysfunction, are prevalent in hypertensive subjects. We aimed to study their relations to subclinical intracranial vascular health in this study. A total of 200 older hypertensive males without overt cardiovascular or cerebrovascular diseases were recruited. Arterial elasticity was measured as carotid-femoral pulse wave velocity (cfPWV) and endothelial function was measured as digital reactive hyperemia index (RHI). Cerebrovascular health was evaluated using MRI in four aspects: intracranial atherosclerosis, brain perfusion as cerebral blood flow (CBF), vascular rarefaction analyzed as visible arterial branches on angiography using a custom-developed analysis technique and small vessel disease measured as white matter hyperintensity (WMH). There was a significant negative association between cfPWV and CBF, suggesting a link between arterial stiffness and CBF decline. Higher cfPWV was also associated with presence of intracranial stenotic plaque and greater WMH volume. RHI was positively related to CBF, indicating that endothelial dysfunction was associated with reduced CBF. All the associations remained significant after adjustment for confounding variables. Arterial stiffness and endothelial dysfunction are associated with reduced brain perfusion in older hypertensive males. Arterial stiffness is also associated with global cerebral vascular injury, affecting both small and medium-to-large arteries.     

A case of anterior cerebral artery dissection causing hemorrhagic infarction]

A 56-year-old man presented with weakness in his right arm and leg. Throbbing headache occurred several hours prior to his weakness. Brain CT obtained on day 3 demonstrated low density areas in the medial part of the left frontal lobe. Cerebral angiography on day 14 demonstrated dilatation and narrowing of the left anterior cerebral artery (ACA) corresponding to "pearl and string sign". The diagnosis of spontaneous ACA dissection was established with clinical features, laboratory findings, and angiographic findings. Antiplatelet therapy was undertaken for the prevention of ischemic events. Serial Brain CT demonstrated hemorrhagic change in the area of infarction. However, there was no definite clinical deterioration. Antiplatelet therapy was withdrawn after hemorrhagic change was noted. Cerebral angiography on day 35 showed improvement of both dilatation and narrowing. Possible reperfusion injury caused by absorption of intramural hematoma seems to be responsible for hemorrhagic change. In patients with cerebral infarction due to dissection of intracranial arteries, antithrombotic therapy is controversial as hemorrhagic complications including hemorrhagic infarction as well as subarachnoidal hemorrhage can occur. Further accumulation of cases is required.     

Spontaneous Intracranial Arterial Dissection and Subarachnoid Hemorrhage

Spontaneous intracranial arterial dissection may cause subarachnoid or rarely intraventricular hemorrhage. The clinical presentation may resemble aneurysmal rupture. Experience using magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) in establishing the diagnosis of intracranial arterial dissection has been limited. We report three patients with intracranial arterial dissection and describe the correlation between findings on conventional angiography and MRI or MRA.