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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The ischaemic penumbra was described for the first time in the late 1970s as a ring of hypoperfused zone surrounding the region of complete infarction. The penumbral zone is a functionally silent tissue which is able to regain its function if promptly reperfused. This implies that the ischaemic penumbra is not a static but a "dynamic" and "time-dependent" concept. In this paper we describe the role of neuroimmaging tecniques such as single photon emission tomography (SPET), positron emission tomography (PET), and diffusion-weighted and perfusion-weighted magnetic resonance imaging (DWI and PWI) in the study of ischaemic penumbra. These functional imaging techniques have the advantage of giving "in vivo" quantitative estimate of cerebral blood flow (CBF) as well as information on how the ischaemic tissue metabolic changes develop. It follows that, as therapeutic options for treating acute stroke evolve, neuroimaging strategies are assuming an increasingly important role in the initial evaluation and management of the acute ischaemic patient. In this regard, a wide range of therapeutic approaches have been investigated for either ameliorating the perfusion, or interfering with the pathobiochemical cascade leading to ischaemic neuronal damage, or improving endogenous neuroprotection pathways. The "time windows" required for these treatments to be effective varies being rather short for reperfusion and longer for neuroprotection. Salvaging more penumbra would enhance recovery and thereby allow the most appropriate candidate for therapeutic trials to be selected.
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PMID:Ischaemic penumbra: highlights. 1245 Feb 27

Thrombolytic therapy with rt-PA given within 3 h after stroke onset to patients with ischemic stroke significantly improves outcome after stroke. There are some evidences that thrombolysis may also work up to 6 h after stroke onset in carefully identified patients, but the three most important trials, which used 0-6 h time-windows, combined with CT-scans to define the ischemic areas, failed individually to produce statistical benefits for the rt-PA-treated patients. In order to enlarge the time-window there is a need for additional information about the functionality of the affected brain area. There is a growing interest in the use of Diffusion Weighted (magnetic resonance) imaging (DWI) and Perfusion Weighted (magnetic resonance) imaging (PWI) in the assessment of patients with acute ischemic stroke. These magnetic resonance techniques are powerful methods for identifying the extent and location of early cerebral ischemia.
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PMID:The very acute stroke treatment: fibrinolysis and after. 1245 Feb 34

To evaluate and review the clinical spectrum of anterior cerebral artery (ACA) territory infarction, we studied 48 consecutive patients who admitted to our stroke unit over a 6-year period. We performed magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) in all patients, and diffusion magnetic resonance imaging (DWI) in 21. In our stroke registry, patients with ACA infarction represented 1.3% of 3705 patients with ischemic stroke. The main risk factors of ACA infarcts was hypertension in 58% of patients, diabetes mellitus in 29%, hypercholesterolemia in 25%, cigarette smoking in 19%, atrial fibrillation in 19%, and myocardial infarct in 6%. Presumed causes of ACA infarct were large-artery disease and cardioembolism in 13 patients each, small-artery disease (SAD) in the territory of Heubner's artery in two and atherosclerosis of large-arteries (<50% stenosis) in 16. On clinico-radiologic analysis there were three main clinical patterns depending on lesion side; left-side infarction (30 patients) consisting of mutism, transcortical motor aphasia, and hemiparesis with lower limb predominance; right side infarction (16 patients) accompanied by acute confusional state, motor hemineglect and hemiparesis; bilateral infarction (two patients) presented with akinetic mutism, severe sphincter dysfunction, and dependent functional outcome. Our findings suggest that clinical and etiologic spectrum of ACA infarction may present similar features as that of middle cerebral artery infarction, but frontal dysfunctions and callosal syndromes can help to make a clinical differential diagnosis. Moreover, at the early phase of stroke, DWI is useful imaging method to locate and delineate the boundary of lesion in the territory of ACA.
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PMID:Spectrum of anterior cerebral artery territory infarction: clinical and MRI findings. 1245 77

Atherosclerotic disease of the extracranial vessels is a frequent cause of cerebral ischemia and stroke. Many natural history studies and prospective treatment trials with large patient samples have focused on optimal patient assessment in regard to medical or interventional measures. Clinical decision making nowadays is largely based on the identification, visualization, and grading of the local stenosis, and the identification of neurologic symptoms related to carotid artery stenosis. MRI already has contributed considerably as many surgeons no longer require preoperative conventional contrast angiography but may use the combination of duplex ultrasound studies and MRA for visualization of the pathology. Besides MRA improvements, DWI and PWI are increasingly used in addition to conventional MR contrasts (PD, T2-, T1-weighted MRI) in attempts to gather information on tissue status and the pathophysiology of hemodynamic compromise and cerebral ischemia in patients with carotid artery stenosis. Obtaining background information using this array of MR data may eventually become a basis for optimal risk-benefit assessment in patients with carotid artery stenosis.
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PMID:Diffusion and perfusion MRI for the assessment of carotid atherosclerosis. 1248 27

In patients with acute ischemic stroke, early recanalization may save tissue at risk for ischemic infarction, thus resulting in smaller infarcts and better clinical outcome. The hypothesis that clinical and diffusion- and perfusion-weighted imaging (DWI, PWI) parameters may have a predictive value for early recanalization and final infarct size was assessed. Twenty-nine patients were prospectively enrolled and underwent sequential magnetic resonance imaging (1) within 6 hours from hemispheric stroke onset, before thrombolytic therapy; (2) at day 1; and (3) at day 60. Late infarct volume was assessed by T2 -weighted imaging. At each time, clinical status was assessed by the National Institutes of Health Stroke Scale (NIHSS). Twenty-eight patients had arterial occlusion at day 0 magnetic resonance angiography (MRA). They were classified into two groups according to day 1 MRA: recanalization (n = 18) versus persistent occlusion (n = 10). Any significant differences between these groups were assessed regarding (1) PWI and DWI abnormality volumes, (2) relative and absolute time-to-peak (TTP) and apparent diffusion coefficient within the lesion on DWI; and (3) day 60 lesion volume on T2 -weighted imaging. Univariate and multivariate logistic regression analysis showed that the most powerful predictive factors for recanalization were lower baseline NIHSS score and lower baseline absolute TTP within the lesion on DWI. The best predictors of late infarct size were day 0 lesion volume on DWI and day 1 recanalization. Early PWI and DWI studies and day 1 MRA provide relevant predictive information on stroke outcome.
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PMID:Early magnetic resonance imaging prediction of arterial recanalization and late infarct volume in acute carotid artery stroke. 1257 55

In industrialized nations, stroke is the most common cause of permanent disability and need of care. Causal treatment is possible only during the first few hours following the stroke, in the form of systemic fibrinolysis. An exact diagnosis of the causative pathology must be made before starting the therapy, and this must happen in the shortest possible period of time. Using imaging techniques, the whole spectrum of differential diagnoses of cerebral ischemia must be covered, including above all intracerebral and subarachnoid hemorrhage. Although computed tomography (CT) is excellently suited for determining hemorrhage, infarct can be recognized with much better contrast using diffusion-weighted magnetic resonance (MR) imaging (DWI). Stroke MR imaging additionally allows the representation of vital "tissue at risk"of infarction using perfusion images as well as the recognition of vessel occlusion using MR angiography. This paper is intended to define the usefulness of DWI in comparison to CT techniques and to elucidate the use of diffusion coefficients for differentiating the various stages of infarction. Besides presenting an explanation of the basic principles of modern stroke MR imaging, typical results of MR perfusion measurements and the appearance of hemorrhages on MR will be explained.
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PMID:[Modern magnetic resonance techniques in stroke]. 1266 41

Diffusion- and perfusion-weighted magnetic resonance imaging (DWI and PWI, respectively) are novel imaging modalities that can detect brain ischemia early in its full extent, can be performed in minutes, can be repeated easily, and allow for follow-up of the ischemic lesion size over time with good spatial and temporal resolution. We have used DWI and PWI in evaluating novel therapeutic approaches for ischemic stroke in numerous studies in the rat and lately in humans. It is now clear that DWI and PWI offer a good combination for safe and reliable evaluation of novel drugs on the size and tissue characteristics of brain ischemia. After inducing focal brain ischemia in the rat, one can first detect the presence and extent of ischemia by DWI and hypoperfusion by PWI, calculate the volume of ischemic brain tissue, and then follow the development of the ischemic lesion over time for several hours during treatment, thus detecting in vivo effects of the novel drug on brain ischemia. Successful reperfusion (either mechanically or as a result of thrombolytic therapy) can also be detected easily. DWI and PWI when performed before starting treatment can also exclude the pretreatment bias, a potential reason for false-positive studies in which proper imaging studies are not employed. Thus we can determine the in vivo efficacy (or lack of efficacy) of new therapeutic regimens (both neuroprotective and thrombolytic) rapidly, safely, and reliably by using a small sample size only, and adapt the same strategy to clinical trials.
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PMID:Use of diffusion- and perfusion-weighted magnetic resonance imaging in drug development for ischemic stroke. 1276 5

There is doubt as to whether acute haemorrhage is visible on MRI. We carried out MRI within 6 h of symptom onset on five patients with minor (low Hunt and Hess grades 1 or 2) subarachnoid haemorrhage (SAH) diagnosed by CT to search for any specific pattern. We used our standard stroke MRI protocol, including multiecho proton density (PD)- and T2-weighted images, echoplanar (EPI) diffusion- (DWI) and perfusion- (PWI) weighted imaging, and MRA. In all cases SAH was clearly visible on PD-weighted images with a short TE. In four patients it caused a low-signal rim on the T2*-weighted source images of PWI, and DWI revealed high signal in SAH. In the fifth patient SAH was perimesencephalic; susceptibility effects from the skull base made it impossible to detect SAH on EPI DWI and T2*-weighted images. Perfusion maps were normal in all cases. MRA and conventional angiography revealed an aneurysm in only one patient. Stroke MRI within 6 h of SAH thus shows a characteristic pattern.
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PMID:MRI in acute subarachnoid haemorrhage; findings with a standardised stroke protocol. 1465 34

Sixteen patients with acute middle cerebral artery stroke were studied to correlate neuroinflammatory markers with perfusion- and diffusion-weighted magnetic resonance imaging (MRI) lesion volumes (PWI and DWI). At arrival (less than 6 hours), plasmatic matrix metalloproteinase (MMP)-9, MMP-2, interleukin (IL)-6, IL-8, intercellular adhesion molecule (ICAM)-1, and tumor necrosis factor (TNF)-alpha were serially measured (by ELISA), and MRI was performed. In cerebral ischemia, tissue destruction seems related to matrix metalloproteinases expression because baseline MMP-9 was the only predictor of the infarct volume measured as a DWI lesion (lineal regression: b = 0.50, 0.25-0.74; P < 0.001). Moreover, the extent of hypoperfused brain area (PWI) was associated with a proinflammatory cytokine release in the next hours (TNF-alpha and IL-6).
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PMID:Plasmatic level of neuroinflammatory markers predict the extent of diffusion-weighted image lesions in hyperacute stroke. 1466 35

We carried out baseline and short-term follow-up MRI, including perfusion-weighted imaging (PWI) and tests of neurologic and cognitive function on 15 consecutive patients with large-vessel ischemic stroke who showed a persistent large perfusion-diffusion mismatch at enrollment up to seven days after the onset of symptoms. Of these, ten underwent induced blood pressure elevation with phenylephrine and oral medications (in eight) or intravenous fluids (in two) with the goal of improving perfusion; five had no such treatment. Significant functional improvement was defined by a reduction of 3 or more points on the NIH stroke scale (NIHSS). Significant improvement in perfusion was defined by a reduction in the volume of hypoperfused brain by 30 cc on PWI using time-to-peak (TTP) maps, without enlargement of the infarct. There was a strong, statistically significant association between improved function and improved perfusion: six (75%) of eight patients who improved in function, but none of the seven who did not, showed a reduction in volume of hypoperfused brain. All six patients who met the perfusion goal, and only two (22%) of nine who did not showed significant functional improvement (Fisher's exact: P < 0.01). There were no differences between patients who improved functionally and those who did not with respect to age, initial volume of abnormality on DWI or PWI, initial NIHSS, or changes on DWI. These findings indicate that reduction in volume of hypoperfused brain on PWI is a marker of response to treatment to improve perfusion even in subacute stroke and that partial reperfusion of regions of salvageable but dysfunctional tissue is a mechanism of improved function associated with induced blood pressure elevation.
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PMID:Perfusion-weighted MRI as a marker of response to treatment in acute and subacute stroke. 1467 53


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