ISSN:0899-3459    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The efficacy of intravenous (IV) and intra-arterial (IA) thrombolysis for hyperacute stroke has made “brain attack” a treatable emergency. The addition of ultrafast magnetic resonance imaging (MRI) to acute stroke investigation has both increased our knowledge of acute stroke pathophysiology and brought a tool to study how to best select patients for thrombolytic therapy. MR offers the three essential components: vascular lesion identification, delineation of injured brain tissue, and map of ischemic brain. MR angiography can demonstrate the site of major cerebral artery occlusion, providing a means to screen for IA thrombolysis. Diffusion-weighted imaging (DWI) is capable of showing acute ischemic injury within minutes of symptom onset. Perfusion-weighted imaging (PWI) shows the total area of acute ischemia, more accurately reflecting the extent of neurological dysfunction. Combining DWI and PWI immediately gives information that bears on how much tissue is injured (DWI) and how much tissue is functionally inactive but still viable (ischemic on PWI but still normal on DWI). A number of important questions remain, but current knowledge of natural history of stroke with MRI has provided a framework for comparing new therapeutic interventions. Ideally, patient treatment in the future will be tailored not to a fixed time window but to the physiological state of the ischemic tissue as defined by MRI.

ISSN:0899-3459    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) are recently developed yet steadily evolving magnetic resonance techniques. DWI and PWI typically interrogate the microscopic diffusion and microcirculatory perfusion, and they can provide early, highly sensitive, and specific delineation of ischemic tissue. These techniques also can play a role in selecting patients who may benefit from thrombolytic therapy. This article reviews physical, technical, and pathophysiological background material that can be helpful in the acquisition and interpretation of DWI and PWI.

ISSN:0899-3459    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

The roles of noncontrast computed tomography (NCCT) and CT angiographic/CT perfusion (CTA/CTP) imaging in the rapid triage of clinically suspected hyperacute stroke patients to appropriate therapy is reviewed. Contraindications to thrombolysis include NCCT hemorrhage (absolute) and significant parenchymal hypodensity (relative). The sensitivity of NCCT for early (<6 h) stroke detection, higher than that of conventional magnetic resonance imaging, is improved further by using nonstandard window and level review settings. CTA/CTP is fast and convenient, adding approximately 10 min to the NCCT examination. CTA/CTP's accuracy in diagnosing ischemia and localizing thrombus to proximal or distal intracranial vessels far exceeds that of clinical examination (including National Institutes of Health stroke scale use), facilitating triage of appropriate candidates to intra-arterial thrombolysis. The size of the ischemic CTP hypodensity (proportional to reduced cerebral blood volume) predicts final infarct volume and clinical outcome; its location can guide the decision to perform intra-arterial thrombolysis, intravenous thrombolysis, or other treatment.

ISSN:0899-3459    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

Despite a traditional perception of reliance on computed tomography and lack of acceptance of magnetic resonance imaging (MRI) for detecting acute hemorrhage, MRI appears to be used increasingly in hemorrhagic stroke. This review addresses the MRI findings of acute hemorrhagic stroke obtained using relatively new imaging techniques. These new techniques have resulted in more acute stroke patients undergoing MRI examination. New information about the frequency and appearance of hemorrhage is emerging: for example, approximately 15–26% of cases of acute cerebral infarctions appear to be complicated by intracerebral hemorrhage. The MRI appearances of hemorrhagic transformation of ischemic infarction, as well as acute hypertensive intracerebral hemorrhage, are discussed based on clinical, biochemical, and technical aspects.

ISSN:0899-3459    

出版商:OVID    

年代:2000

数据来源: OVID

摘要:

This article addresses syndromes that clinically and/or radiologically resemble acute stroke. These syndromes generally fall into four categories. (1) Patients with acute neurological deficits with nonischemic lesions and no acute abnormality on diffusion-weighted images. These patients may have peripheral vertigo, migraines, seizures, dementia, functional disorders, amyloid angiopathy, or metabolic disorders. When these patients present, we can confidently predict that they are not undergoing infarction. (2) Patients with ischemic lesions with reversible clinical deficits. Nearly 50% of patients with transient ischemic attacks have lesions with restricted diffusion. Patients with transient global amnesia may have punctate lesions with restricted diffusion in the medial hippocampus, parahippocampal gyrus, and corpus callosum. (3) Vasogenic edema syndromes that may mimic acute infarction clinically and on conventional imaging. These include eclampsia/hypertensive encephalopathy, other posterior leukoencephalopathies, human immunodeficiency virus encephalopathy, hyperperfusion syndrome following carotid endarterectomy, venous sinus thrombosis, acute demyelination, and neoplasm. These syndromes demonstrate elevated diffusion rather than the restricted diffusion associated with acute ischemic stroke. (4) Entities in which restricted diffusion may resemble acute infarction. These include pyogenic infections, herpes virus encephalitis, Creutzfeldt-Jakob disease, diffuse axonal injury, tumors with dense cell packing, and rare acute demyelinative lesions.

ISSN:0899-3459    

出版商:OVID    

年代:2000

数据来源: OVID