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 Magnetic Resonance Imaging Decreases Hospital Length of Stay in Patients with Ischemic Stroke

Background

Imaging modalities are important part of stroke evaluation. Noncontrast head computed tomography (CT) is the initial imaging modality in acute stroke and although important to rule out acute hemorrhage and making a decision on thrombolytic treatment, ischemic changes may not be visible on CT for up to 24 hours. Magnetic resonance imaging (MRI) brain is an invaluable tool to confirm an ischemic stroke and facilitates stroke evaluation. Objective of this study was to investigate the correlation between time to MRI and length of hospital stay.

Penumbra detection using PWI/DWI mismatch MRI in a rat stroke model with and without comorbidity: comparison of methods

Perfusion-diffusion (perfusion-weighted imaging (PWI)/diffusion-weighted imaging (DWI)) mismatch is used to identify penumbra in acute stroke. However, limitations in penumbra detection with mismatch are recognized, with a lack of consensus on thresholds, quantification and validation of mismatch. We determined perfusion and diffusion thresholds from final infarct in the clinically relevant spontaneously hypertensive stroke-prone (SHRSP) rat and its normotensive control strain, Wistar-Kyoto (WKY) and compared three methods for penumbra calculation. After permanent middle cerebral artery occlusion (MCAO) (WKY n=12, SHRSP n=15), diffusion-weighted (DWI) and perfusion-weighted (PWI) images were obtained for 4 hours post stroke and final infarct determined at 24 hours on T₂ scans. The PWI/DWI mismatch was calculated from volumetric assessment (perfusion deficit volume minus apparent diffusion coefficient (ADC)-defined lesion volume) or spatial assessment of mismatch area on each coronal slice. The ADC-derived lesion growth provided the third, retrospective measure of penumbra. At 1 hour after MCAO, volumetric mismatch detected smaller volumes of penumbra in both strains (SHRSP: 31±50 mm³, WKY: 22±59 mm³, mean±s.d.) compared with spatial assessment (SHRSP: 36±15 mm³, WKY: 43±43 mm³) and ADC lesion expansion (SHRSP: 41±45 mm³, WKY: 65±41 mm³), although these differences were not statistically significant. Spatial assessment appears most informative, using both diffusion and perfusion data, eliminating the influence of negative mismatch and allowing the anatomical location of penumbra to be assessed at given time points after stroke.     

Magnetic Resonance Imaging White Matter Hyperintensity as a Predictor of Stroke Recurrence in Patients with Embolic Stroke of Undetermined Source

Background and Purpose

This study aimed to investigate factors associated with stroke recurrence and new-onset atrial fibrillation (AF) in patients with embolic stroke of undetermined source (ESUS).

Brain Activation Evoked by Sensory Stimulation in Patients with Spinal Cord Injury : Functional Magnetic Resonance Imaging Correlations with Clinical Features

Objective

The purpose of this study is to determine whether the changes of contralateral sensorimotor cortical activation on functional magnetic resonance imaging (fMRI) can predict the neurological outcome among spinal cord injury (SCI) patients when the great toes are stimulated without notice.

Methods

This study enrolled a total of 49 patients with SCI and investigated each patient''s preoperative fMRI, postoperative fMRI, American Spinal Injury Association (ASIA) score, and neuropathic pain occurrence. Patients were classified into 3 groups according to the change of blood oxygenation level dependent (BOLD) response on perioperative fMRI during proprioceptive stimulation with repetitive passive toe movements : 1) patients with a response of contralateral sensorimotor cortical activation in fMRI were categorized; 2) patients with a response in other regions; and 3) patients with no response. Correlation between the result of fMRI and each parameter was analyzed.

Results

In fMRI data, ASIA score was likely to show greater improvement in patients in group A compared to those belonging to group B or C (p<0.001). No statistical significance was observed between the result of fMRI and neuropathic pain (p=0.709). However, increase in neuropathic pain in response to the signal change of the ipsilateral frontal lobe on fMRI was statistically significant (p=0.030).

Conclusion

When there was change of BOLD response at the contralateral sensorimotor cortex on perioperative fMRI after surgery, relief of neurological symptoms was highly likely for traumatic SCI patients. In addition, development of neuropathic pain was likely to occur when there was change of BOLD response at ipsilateral frontal lobe.     

Non-cardioembolic Mechanisms in Cryptogenic Stroke: Clinical and Diffusion-weighted Imaging Features

Background

The role of several cardiogenic risk factors, including patent foramen ovale, in patients with cryptogenic stroke has been extensively studied. However, little attention has been paid to the role of non-cardioembolic causes of cryptogenic stroke. We therefore sought to identify the characteristics of cryptogenic stroke.

Methods

We studied 832 patients with acute infarction in the middle cerebral arterial territory. We divided the patients into four subtypes: 402 with large artery atherosclerosis (LAA), 133 with cardioembolism, 182 with small arterial occlusion (SAO), and 115 with cryptogenic stroke. We compared risk factors and lesion patterns observed by diffusion-weighted imaging (DWI) between patients with cryptogenic stroke and those with stroke of other subtypes.

Results

Both risk factors and DWI lesion patterns differed between the cryptogenic and cardioembolic groups (P<0.05). Risk factors for cryptogenic stroke were similar to those for the LAA and SAO groups. Similarly, DWI lesion patterns for cryptogenic stroke were similar to LAA patients. Large cortical infarcts on DWI were more common in the cardioembolic group than in the LAA or cryptogenic groups (P<0.001). In contrast, deep, non-lacunar (OR 5.02; 95% CI 2.68~9.40; P<0.001) and superficial perforator infarcts (OR 2.23; 95% CI 1.08~4.59; P=0.029) were independently associated with the cryptogenic group.

Conclusions

Our results indicate that non-cardioembolic causes, such as macro- and microangiopathy, are important mechanisms in the pathogenesis of cryptogenic stroke.     

糖尿病患者颈动脉斑块磁共振成像特征与急性脑缺血病灶形态关系研究

目的 探讨2型糖尿病患者颈动脉斑块磁共振成像（magnetic r esonance i maging,MRI）特征与相应供血区急性脑缺血病灶形态的关系。方法 横断面研究,入组临床急性颈内动脉供血区缺血性卒中患者,排除心源性卒中,在发病一周内行颈动脉磁共振管壁成像（magnetic resonance vessel wall imaging,MR-VWI）检查和常规MRI [包括磁共振血管成像（magnetic resonance angiography,MRA）和弥散加权成像（diffusion-weighted imaging,DWI）]检查,评估症状侧颈动脉斑块负荷和成分特征以及颅内外动脉管腔狭窄度,根据DWI上梗死灶形态对急性脑缺血病灶形态和体积进行分析。结果 共入选140例急性缺血性卒中患者,其中68例（48.6%）为2型糖尿病患者,多因素回归分析显示2型糖尿病是症状侧颈动脉斑块富脂质核发生的独立危险因素[比值比（odds ratio,OR）3.35,95%可信区间（confidence interval,CI）1.33～8.43];在兼具富脂质核斑块的患者中,2型糖尿病组颈内动脉区域急性脑缺血病灶体积（[ 15.45±8.97）ml vs（9.09±8.64）ml,P=0.011]和大穿支动脉梗死发生率[34.0% vs 13.2%,P =0.024）]显著高于非糖尿病组。结论 颈动脉供血区急性缺血性卒中患者中,2型糖尿病与症状侧颈动脉动脉粥样硬化斑块MRI特征,尤其是富脂质核密切相关,且更易发生大穿支动脉的梗死,提示MR-VWI细致化分析结合糖尿病因素有助于临床对缺血性卒中风险的分层和个体化诊治。     

弥散加权成像高信号完全可逆的急性缺血性卒中病例临床及影像学特征分析

目的 分析急性缺血性卒中完全可逆性DWI高信号病例的临床与影像学特征。 方法 回顾性分析2012年1月-2015年12月的急性缺血性卒中完全可逆性DWI高信号病例9例,通过 基线与随访数据评估其临床与影像学特征。 结果 急性缺血性卒中完全可逆性DWI高信号病例基线NIHSS评分为1（1～2.5）分,基线DWI高信号 体积为0.94（0.28～2.39）mL,病变既见于皮层/皮层下,又见于深部白质,随访90 d的mRS评分为0 （0～1）分。 结论 急性缺血性卒中完全可逆性DWI高信号多见于轻型卒中,病灶梗死体积小,临床预后良好。     

磁共振测量帕金森病患者基底节区、黑质体积的研究

目的:探讨MR体积测量技术评价帕金森病(Parkinson’sdiseasePD)患者基底节区(尾状核,壳核,苍白球)、黑质体积改变的价值。方法:采用3·0TMR测量早、晚期PD患者和年龄匹配正常人对照组全脑体积、尾状核、壳核、苍白球、黑质体积。对患者进行PD统一评分量表(UPDRS)第Ⅱ、Ⅲ、Ⅴ部分评分。评分结果与患者基底节区、黑质体积行相关性分析。结果:早、晚期PD患者壳核体积较正常人分别下降12·5%(P=0·004)和26·5%(P<0·001),晚期患者较早期患者下降16·0%(P=0·002)。晚期患者苍白球体积较正常人下降19·2%(P=0·023)。PD患者壳核体积与Hoehn&Yahr分级呈负相关(r=-0·741,P<0·001)。结论:MR体积测量技术是评价PD患者基底节区、黑质体积改变的一种可靠的方法,能为PD辅助诊断提供有效的影像学指标。     

利用颅内动脉高分辨磁共振成像指导缺血性卒中的病因诊断和个体化治疗

颅内动脉病变是缺血性卒中最重要的病因之一,在高分辨磁共振成像(high resolutionmagnetic resonance imaging,HRMRI)检查应用于临床之前,还没有能够准确反应颅内动脉管壁形态和结构的影像技术。时间飞跃法磁共振血管成像(time of flight magneticresonance arteriography,TOFMRA)、数字减影血管成像(digital subtractionangiography,DSA)和计算机断层血管成像(computed tomographic angiography,CTA)只能显示动脉管腔的狭窄程度,而无法     

Impact of genetic and renovascular chronic arterial hypertension on the acute spatiotemporal evolution of the ischemic penumbra: a sequential study with MRI in the rat

Although chronic arterial hypertension (CAH) increases the risk of stroke and the severity of the resultant lesion, it is rarely integrated in preclinical studies. Here, we analyzed the impact of CAH on the acute spatiotemporal evolution of the ischemic penumbra as defined by the perfusion-weighted imaging/diffusion-weighted imaging mismatch. Sequential 7T-MRI examinations were performed from 30 minutes up to 4 hours after permanent cerebral ischemia in genetically hypertensive rats (spontaneously hypertensive rats, SHR), renovascular-hypertensive rats (RH-WKY), and their normotensive controls (Wistar-Kyoto rats, WKY). The apparent diffusion coefficient (ADC)-defined lesion was larger in hypertensive rats than in normotensive animals as early as 30 minutes after the ischemia. The ischemic penumbra was smaller in both genetically and renovascular-hypertensive rats (at 30 minutes; SHR=66±25 mm³, RH-WKY=55±17 mm³ versus WKY=117±14 mm³; P<0.008) and there was no significant difference between the perfusion deficit and ADC lesion (mismatch definition of penumbra) as early as 90 minutes after the occlusion. Genetic hypertension and induced renovascular hypertension resulted in larger lesion and smaller penumbra that vanished rapidly. These data support the need to integrate CAH in preclinical studies relative to the treatment of stroke, as failure to do so may lead to preclinical results nonpredictive of clinical trials, which include hypertensive patients.     

亚低温对急性脑卒中患者血清IL-2、IL-6、TNF-α水平的影响和临床意义

目的 探讨亚低温对急性脑卒中患者血清IL-2、IL-6、TNF-α的影响和临床意义。方法 将36例急性脑卒中患者随机分为亚低温和常规治疗组．检测入院第1天（d1）、第3～5天（d3～5）、第14天（d14）血清IL-2、IL-6、TNF-α水平并进行对照比较。结果 两组患者d1、d3～5、d14血清IL-2、IL-6、TNF-α水平均高于正常组（P〈0．05）,亚低温组出d3-5、d14血清IL-2、IL-6、TNF-α水平低于同期常规治疗组（P〈0．05）。结论 亚低温可降低急性脑卒中患者血清IL-2、IL-6、TNF-α水平．抑制脑卒中后炎症反应．保护脑神经细胞。     

Functional Connectivity Magnetic Resonance Imaging Sequences in Patients With Postsurgical Persistent Spinal Pain Syndrome Type 2 With Implanted Spinal Cord Stimulation Systems: A Safety,Feasibility, and Validity Study

BackgroundChronic pain has been associated with alterations in brain connectivity, both within networks (regional) and between networks (cross-network connectivity). Functional connectivity (FC) data on chronic back pain are limited and based on heterogeneous pain populations. Patients with postsurgical persistent spinal pain syndrome (PSPS) type 2 are good candidates for spinal cord stimulation (SCS) therapy. We hypothesize that 1) FC magnetic resonance imaging (fcMRI) scans can be safely obtained in patients with PSPS type 2 with implanted therapeutic SCS devices and that 2) their cross-network connectivity patterns are altered and involve emotion and reward/aversion functions.Materials and MethodsResting-state (RS) fcMRI (rsfcMRI) scans were obtained from nine patients with PSPS type 2 implanted with therapeutic SCS systems and 13 age-matched controls. Seven RS networks were analyzed, including the striatum.ResultsCross-network FC sequences were safely obtained on a 3T MRI scanner in all nine patients with PSPS type 2 with implanted SCS systems. FC patterns involving emotion/reward brain circuitry were altered as compared with controls. Patients with a history of constant neuropathic pain, experiencing longer therapeutic effects of SCS, had fewer alterations in their connectivity patterns.ConclusionsTo our knowledge, this is the first report of altered cross-network FC involving emotion/reward brain circuitry in a homogeneous population of patients with chronic pain with fully implanted SCS systems, on a 3T MRI scanner. All rsfcMRI studies were safe and well tolerated by all nine patients, with no detectable effects on the implanted devices.