Computed tomography in acute cerebral ischemia

Summary Computed tomography (CT) is the first step in the radiological diagnostics of brain emergencies. We intend to study which pathophysiological changes are detected by CT and how CT contributes to prognosis and patient management in acute cerebral ischemia. We review recent publications about the role of CT in acute cerebral ischemia. Ischemic brain edema is associated with a decreased X-ray attenuation. Computed tomography is thus highly sensitive in detecting irreversibly damaged ischemic brain tissue. Patients showing large volumes of ischemic edema, exceeding one third of the middle cerebral artery territory, do not benefit from thrombolysis and have an increased risk of brain hemorrhage. The brain territory at risk from ischemia can be detected by CT angiography. To combine CT with CT angiography is a pragmatic approach which enables carefully directed treatment in acute cerebral ischemia.      

Perfusion MRI in cerebral infarction

Purpose: To investigate the hemodynamic changes in patients with acute cerebral stroke by perfusion MRI. Materials and methods: In 12 patients with acute stroke in the territory of the middle cerebral artery, perfusion MRI was performed. Peak time, mean transit time, regional cerebral blood volume and regional cerebral blood flow were calculated in the infarction, the peri-infarction area and the contralateral hemisphere. Results: In the infarction the mean blood flow was 29 ml/100 g/min, compared to about 40 ml/100 g/min in the peri-infarction area and the contralateral hemisphere. In two patients increased cortical blood flow was found in the infarction due to luxury perfusion. The cerebral blood volume was reduced in the infarction, but significantly increased, to 7.3 ml/100 g, in the peri-infarction tissue. Conclusion: Perfusion MRI allows one to differentiate various patterns of perfusion disorders in patients with acute cerebral stroke. The resulting data may be helpful in describing the pathophysiologic mechanisms of compensation.      

碱性成纤维细胞生长因子对大鼠局灶性脑缺血的保护作用与bax表达

目的 观察动脉内溶栓与碱性成纤维细胞生长因子（bFGF)联合治疗对大鼠缺血性脑梗死面积的影响,并探讨bFGF的保护机制。方法 将50只雄性Wistar大鼠,用血栓栓塞法制备大脑中动脉缺血模型,于缺血4h后随机分为：1、单纯溶栓组;2．溶栓与bFGF联合治疗组。分别在治疗后不同时间点观察大鼠神经功能缺陷的和MRI T2WI显示病变面积的变化,采用免疫组化法检测各时间点bax的表达,结果 在单纯溶栓组,脑缺血再灌注3h时,bax表达开始增加,再灌注12h时达到高峰;与单纯溶栓组比较,溶栓与bFGF联合治疗6h后,MRI T2WI显示病变面积显著缩小（P＜0．05）,bax表达明显减弱（P＜0．05）。结论 bFGF对大鼠局灶性缺血具有保护作用,可降低bax表达,抑制细胞凋亡可能是其作用机制之一。     

Acute stroke magnetic resonance imaging: current status and future perspective

Cerebral stroke is one of the most frequent causes of permanent disability or death in the western world and a major burden in healthcare system. The major portion is caused by acute ischemia due to cerebral artery occlusion by a clot. The minority of strokes is related to intracerebral hemorrhage or other sources. To limit the permanent disability in ischemic stroke patients resulting from irreversible infarction of ischemic brain tissue, major efforts were made in the last decade. To extend the time window for thrombolysis, which is the only approved therapy, several imaging parameters in computed tomography and magnetic resonance imaging (MRI) have been investigated. However, the current guidelines neglect the fact that the portion of potentially salvageable ischemic tissue (penumbra) is not dependent on the time window but the individual collateral blood flow. Within the last years, the differentiation of infarct core and penumbra with MRI using diffusion-weighted images (DWI) and perfusion imaging (PI) with parameter maps was established. Current trials transform these technical advances to a redefined patient selection based on physiological parameters determined by MRI. This review article presents the current status of MRI for acute stroke imaging. A special focus is the ischemic stroke. In dependence on the pathophysiology of cerebral ischemia, the basic principle and diagnostic value of different MRI sequences are illustrated. MRI techniques for imaging of the main differential diagnoses of ischemic stroke are mentioned. Moreover, perspectives of MRI for imaging-based acute stroke treatment as well as monitoring of restorative stroke therapy from recent trials are discussed.     

急性脑梗塞动脉内溶栓治疗时间窗选择与疗效分析

目的探讨急性脑梗塞动脉内溶栓治疗时间及梗塞部位等因素对疗效的影响。方法288例脑梗塞患者均在CT检查及血管造影基础上接受选择性动脉溶栓治疗,其中在6h以内溶栓者76例,6~24h溶栓者212例。统计2组患者的血管再通率和90d后预后情况。结果脑血管造影发现血管闭塞245例,其中颈内动脉系统闭塞173例,椎基底动脉(VBA)闭塞72例;溶栓后再通分别为112例、38例。治疗后90d恢复良好者180例,预后差108例。颅内出血2例。不同治疗时间2组患者治疗后90d预后良好率分别为80.35%和71.43%,血管再通率分别为67.86%和59.26%,血管再通中位时间分别为68min和73min。结论动脉溶栓治疗脑梗塞,动脉内溶栓时间窗与多种因素密切相关。     

Reperfusion injury following cerebral ischemia: pathophysiology,MR imaging,and potential therapies

Introduction Restoration of blood flow following ischemic stroke can be achieved by means of thrombolysis or mechanical recanalization. However, for some patients, reperfusion may exacerbate the injury initially caused by ischemia, producing a so-called “cerebral reperfusion injury”. Multiple pathological processes are involved in this injury, including leukocyte infiltration, platelet and complement activation, postischemic hyperperfusion, and breakdown of the blood–brain barrier. Methods/results and conclusions Magnetic resonance imaging (MRI) can provide extensive information on this process of injury, and may have a role in the future in stratifying patients’ risk for reperfusion injury following recanalization. Moreover, different MRI modalities can be used to investigate the various mechanisms of reperfusion injury. Antileukocyte antibodies, brain cooling and conditioned blood reperfusion are potential therapeutic strategies for lessening or eliminating reperfusion injury, and interventionalists may play a role in the future in using some of these therapies in combination with thrombolysis or embolectomy. The present review summarizes the mechanisms of reperfusion injury and focuses on the way each of those mechanisms can be evaluated by different MRI modalities. The potential therapeutic strategies are also discussed.     

Reactive thymic hyperplasia following treatment of ACTH-producing tumors

Summary Surgical or conservative treatment of ACTH-producing tumors results in acute drop of the previously excessively high cortisol levels. The following associated pathophysiological changes also occur in the organism's recovery from stress, such as trauma, operation or chemotherapy of tumors. Both cases result in a regeneration of the immune system, which might even be exalted. The corresponding radiographic feature is the ”rebound” enlargement of the thymus occuring about six months after remission of hypercortisolism. Histological examination reveals benign thymus hyperplasia. Especially in cases of still unkown primary tumor the appereance of this anterior mediastinal mass can lead to misdiagnosis. We present the cases of two patients with diffuse thymic hyperplasia following surgical and medical correction of hypercortisolism. One patient suffered from classic Cushing's disease responding to transsphenoidal resection of an ACTH-secreting pituitary microadenoma. Six months later CT of the chest incidentally demonstrated an anterior mediastinal mass known as thymic hyperplasia. The second patient presented with an ectopic, still unkown source of ACTH-production. Six months after medical correction of hypercortisolism CT of the thorax showed an enlargement of the anterior mediastinum. Thymectomy was performed in order to exclude thymus carcinoid. Histological examination revealed benign thymus hyperplasia with negative immunostaining. Conclusion: Radiologists and clinicians should be familiar with the pathophysiological changes resulting from precipitously dropping cortisol levels in order to prevent diagnostic errors and unnecessary operations. Eingegangen am 26. Mai 1997 Angenommen am 26. August 1997     

大鼠脑缺血再灌注后血脑屏障通透性的改变

 目的探讨大鼠脑缺血再灌注后血脑屏障(BBB)通透性的改变.方法采用线栓法制备大鼠局灶性脑缺血再灌注模型,通过测定脑组织中伊文蓝(EB)含量及免疫组化法来观察血脑屏障通透性的改变.结果缺血2 h再灌注3 h,BBB通透性开始增加,24 h达高峰,72 h后明显减弱.结论缺血再灌注后BBB的通透性在24 h内逐渐增加,提示脑梗死超早期给予溶栓是可行的.     

Intra-arterial thrombolysis using rt-PA in patients with acute stroke due to vessel occlusion of anterior and/or posterior cerebral circulation

Introduction The aim of our study was to evaluate the safety and efficacy of intra-arterial (IA) thrombolysis using recombinant tissue plasminogen activator (rt-PA) in patients with acute stroke due to occlusion in the anterior or posterior circulation. Methods We retrospectively analyzed the clinical and radiological data of 88 consecutive patients with acute ischemic stroke who underwent emergency cerebral angiography for the purpose of subsequent IA thrombolysis. The neurological deficit on admission and discharge was graded using the National Institutes of Health Stroke Scale (NIHSS) score. Baseline computer tomography (CT) scans were examined for any signs indicative of cerebral ischemia. The angiographic findings were classified according to the Thrombolysis in Myocardial Infarction (TIMI) score for myocardial infarction. Follow-up CT scans were examined for hemorrhagic complication. Results Of the 88 patients who underwent IA thrombolysis, 63 presented with complete or partial arterial occlusion in the suspected perfusion area. In these 63 patients, the median NIHSS score dropped from 15 points on admission to 10 points at discharge. The recanalization rate was 52.6% for partial and complete reperfusion. In-hospital mortality was 20.6% (9.1% for carotid, 44.4% for basilar territory occlusion). Intracerebral bleeding (ICB) occurred in 38.6% of the patients with occlusion in the anterior circulation, resulting in these patients presenting a worse clinical outcome than those without ICB. Only minor extracranial bleedings occurred in 20.6% of patients. Patients with ICB had a significantly higher frequency of ischemic signs on the baseline CT scan. Conclusion Occlusion of a cerebral artery is present in about 75% of the patients eligible for thrombolytic therapy. Intra-arterial thrombolysis using rt-PA in patients with acute ischemic stroke can achieve re-vascularization, although ICB remains the major risk factor affecting its efficacy.     

Acute peripheral arterial occlusion: solving a clinical problem

This paper gives an overview of the endovascular treatment of acute limb ischemia. Clinical findings and selection criteria will be discussed briefly. The advantages and disadvantages as well as the clinical success rates and complications of pharmacologic and mechanical thrombolysis and aspiration thromboembolectomy will be covered.     

Brain perfusion-CT in acute stroke patients

The role of neuro-imaging in the evaluation of acute stroke has changed dramatically in the past decade. Previously, neuro-imaging was used in this setting to provide anatomic imaging that indicated the presence or absence of acute cerebral ischemia and excluded lesions that produce symptoms or signs mimicking those of stroke, such as hemorrhage and neoplasms. More recently, the introduction of thrombolysis has changed the goals of neuro-imaging from providing solely anatomic information to providing physiologic information that could help to determine which patients might benefit from therapy. In particular, significant emphasis has been placed on the delineation of the ischemic penumbra, also called tissue at risk. Modern CT survey, consisting of three indissociable elements: noncontrast CT (NCT) of course, perfusion-CT (PCT) and CT-angiography (CTA), fulfill all the requirements for hyperacute stroke imaging. CTA can define the occlusion site, depict arterial dissection, grade collateral blood flow, and characterize atherosclerotic disease, whereas PCT accurately delineates the infarct core and the ischemic penumbra. CT offers a number of practical advantages over other cerebral perfusion imaging methods, including its wide availability. Using PCT and CTA to define new individualized strategies for acute reperfusion will allow more acute stroke patients to benefit from thrombolytic therapy.     

Brain perfusion-CT in acute stroke patients

The role of neuro-imaging in the evaluation of acute stroke has changed dramatically in the past decade. Previously, neuro-imaging was used in this setting to provide anatomic imaging that indicated the presence or absence of acute cerebral ischemia and excluded lesions that produce symptoms or signs mimicking those of stroke, such as hemorrhage and neoplasms. More recently, the introduction of thrombolysis has changed the goals of neuro-imaging from providing solely anatomic information to providing physiologic information that could help to determine which patients might benefit from therapy. In particular, significant emphasis has been placed on the delineation of the ischemic penumbra, also called tissue at risk. Modern CT survey, consisting of three indissociable elements: noncontrast CT (NCT) of course, perfusion-CT (PCT) and CT-angiography (CTA), fulfill all the requirements for hyperacute stroke imaging. CTA can define the occlusion site, depict arterial dissection, grade collateral blood flow, and characterize atherosclerotic disease, whereas PCT accurately delineates the infarct core and the ischemic penumbra. CT offers a number of practical advantages over other cerebral perfusion imaging methods, including its wide availability. Using PCT and CTA to define new individualized strategies for acute reperfusion will allow more acute stroke patients to benefit from thrombolytic therapy.     

Evaluation of a new Spin-echo diffusion-weighted sequence on a 0.35 T open magnetic resonance imaging (MRI)-system: first experiences within 3 h after acute stroke

In acute stroke, diffusion-weighted magnetic resonance imaging helps to select patients who are eligible for thrombolysis, but is almost exclusively implemented on closed-bore scanners, which make monitoring of patients difficult. We developed and tested a cardiac gated Spin-echo diffusion-weighted sequence with prescan finetrim and motion correction on an open system with 0.35 T. Nineteen stroke patients appropriate for thrombolytic therapy by clinical criteria were enrolled in a prospective study on an intention-to-treat basis. In all but one patient, computed tomography and magnetic resonance imaging including the new diffusion-weighted sequence were performed within 3 h after symptom onset. Images were evaluated for acute cerebral ischemia and hemorrhage by two radiologists blinded to clinical information. Magnetic resonance imaging required a mean total acquisition time of 26 min. Sensitivity for early infarction was 94% in diffusion-weighted imaging and 73% in computed tomography. Six patients were excluded from thrombolysis due to an infarct size of more than 1/3 of the territory of the middle cerebral artery exclusively diagnosed with diffusion-weighted imaging. Hemorrhage was recognised by both, magnetic resonance imaging and computed tomography. We conclude that in acute stroke, diffusion-weighted imaging with an open system at 0.35 T is practicable. The implemented sequence reliably demonstrated the size of the infarction and improved the selection of patients who are eligible for thrombolysis.     

Imaging of stroke: Part 2, Pathophysiology at the molecular and cellular levels and corresponding imaging changes

OBJECTIVE: Stroke is the third leading cause of death and the leading cause of severe disability. During the "decade of the brain" in the 1990s, the most promising development was the treatment of acute ischemic stroke. It is thought to result from a cascade of events from energy depletion to cell death. In the initial minutes to hour, clinical deficit does not necessarily reflect irreversible damage. The final outcome and residual deficit will be decided by how fast reperfusion is achieved, which in turn depends on how early the diagnosis is made. This article explains the pathophysiology of stroke at the molecular and cellular levels with corresponding changes on various imaging techniques. CONCLUSION: The pathophysiology of stroke has several complex mechanisms. Understanding these mechanisms is essential to derive neuroprotective agents that limit neuronal damage after ischemia. Imaging and clinical strategies aimed at extending the therapeutic window for reperfusion treatment with mechanical and pharmacologic thrombolysis will add value to existing treatment strategies. Acute ischemic stroke is defined as abrupt neurologic dysfunction due to focal brain ischemia resulting in persistent neurologic deficit accompanied by characteristic abnormalities on brain imaging. Knowledge of the pathophysiologic mechanisms of neuronal injury in stroke is essential to target treatment. Neuroprotective and thrombolytic agents have been shown to improve clinical outcome. Physiologic imaging with diffusion-weighted imaging (DWI) and perfusion CT and MRI provide a pathophysiologic substrate of evolving ischemic stroke.     

静脉溶栓桥接Solitaire支架取栓治疗急性缺血性脑卒中的效果分析

目的探讨静脉溶栓桥接Solitaire支架取栓开通颅内闭塞大血管的疗效。 方法回顾我院2014年6月—2015年10月采用桥接模式接受血管内治疗的15例急性缺血性脑卒中患者资料。分析大血管开通情况,术中、术后并发症发生情况,早期神经功能改善情况以及随访90 d时mRS情况。 结果15例患者中,大脑中动脉闭塞9例,颈内动脉颅内段合并大脑中动脉闭塞2例,椎基底动脉系统闭塞4例。所有患者大血管均获得开通。2例患者出现颅内出血,1例为颞叶出血、1例为丘脑出血。死亡2例。入院NIHSS评分(14.83±5.65)与3天后NIHSS评分(6.82±5.53)比较,差异有统计学意义。90 d随访临床结果优良患者9例(mRS<2)。 结论静脉溶栓桥接Solitaire支架动脉取栓能使大血管获得较好的再通率,显著改善急性缺血性脑卒中患者的预后。     

Interventional MR imaging: state of the art and future perspectives

Summary The concept of MR guidance of invasive diagnostic and minimally invasive therapeutic procedures is based on the excellent morphologic and functional properties of MR imaging. Prerequisites are adequate patient monitoring and adherence to safety guidelines. Fast and ultrafast sequences, temperature quantification, visualization of intravascular devices, thermal stability of contrast media and thermosensitive contrast media are discussed. The spectrum of clinical applications includes biopsies, thermal ablation modalities, vascular applications, MR endoscopy and intraoperative MR imaging. The development of interventional MR imaging is still in its infancy. In the future, MR imaging may play an important role in interventional radiology and minimally invasive therapy.      

Imaging techniques in the diagnosis of coronary heart disease

Summary Coronary heart disease is the leading cause of death and disability worldwide. Coronary angiography makes it possible to visualize coronary artery stenosis and can be used for angioplasty and stent implantation; however, it does not allow the assessment of changes in myocardial microcirculation. The severity of an angiographically evaluated coronary stenosis does not always correspond to the extent of myocardial ischemia. Noninvasive techniques are needed to re-examine our reliance on coronary angiography and to explore the clinical value of the physiological assessment of coronary artery stenoses. Such noninvasive techniques might become important tools in the future following an overal evaluation of coronary morphology, myocardial function and perfusion ascertained by all available methods. Eingegangen am 8. Januar 1997 Angenommen am 9. Januar 1997     

Diffusion and perfusion MR imaging in stroke

Magnetic resonance imaging (MRI) in stroke makes it possible to visualize the initial infarct in cases of acute cerebral ischemia. Perfusion MRI serves to determine which tissues are additionally at risk of infarction due to persistent hypoperfusion. MRI also allows those examiners with limited experience to reliably confirm an infarct. The most important differential diagnosis of cerebral ischemia, intracerebral hemorrhage, can likewise be recognized with certainty using MRI. Although diffusion and perfusion MRI only demonstrate the pathophysiology of cerebral ischemia approximately, the method is suited for identifying those patients who would profit from reperfusion therapy. Whether MRI is also appropriate as an aid to reaching a prognosis on the risk of secondary hemorrhage has not yet been resolved.     

Imaging strategies in focal hepatic disease

Introduction: Advanced therapies are improving significantly the survival of patients with malignant focal liver disease. For efficient implementation of these surgical and interventional techniques a clear concept of the diagnostic procedere is mandatory. Methods: Based on a review of the current literature, the different imaging modalities, including ultrasound, computed tomography, magnetic resonance tomography, nuclear medicine and angiography, are discussed and evaluated for their diagnostic efficacy in focal hepatic disease. Results: Considering clinical, diagnostic, and economical appropriateness, recommendations for diagnostic strategies in different clinical scenarios regarding focal hepatic disease are presented. Conclusion: If the power of specific imaging methods and relevant clinical information is known, problem-based diagnostic strategies help to avoid unnecessary, expensive and time-consuming studies in the work-up of focal liver lesions.      

Telemedicine – possibilities and perspectives

Summary The discussion about the implementation of telemedicine and teleresourcing and its consequences has been under way for some time now. The rate at which telemedical applications are being developed, leaves little time for consideration of the economic, scientific and social aspects. There is a need for integration of all the existing fragments into one coherent telemedical concept. Different aspects of telemedical concepts are discussed. Eingegangen am 20. Januar 1997 Angenommen am 19. Februar 1997