Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied the diagnostic and prognostic value of diffusion- and perfusion-weighted magnetic resonancce imaging (DWI and PWI) for the initial evaluation and follow-up monitoring of patients with stroke that had ensued less than 6 hours previously. Further, we examined the role of vessel patency or occlusion and subsequent recanalization or persistent occlusion for further clinical and morphological stroke progression so as to define categories of patients and facilitate treatment decisions. Fifty-one patients underwent stroke magnetic resonance imaging (DWI, PWI, magnetic resonance angiography, and T2-weighted imaging) within 3.3 +/- 1.29 hours, and, of those, 41 underwent follow-up magnetic resonance imaging on day 2 and 28 on day 5. In addition, we assessed clinical scores (on the National Institutes of Health Stroke Scale, Scandinavian Stroke Scale, Barthel Index, and Modified Rankin Scale) on days 1, 2, 5, 30, and 90 and performed volumetric analysis of lesion volumes. In all, 25 patients had a proximal, 18 a distal, and 8 no vessel occlusion. Furthermore, 15 of 43 patients exhibited recanalization on day 2. Vessel occlusion was associated with a PWI-DWI mismatch on the initial magnetic resonance imaging, vessel patency with a PWI-DWI match (p < 0.0001). Outcome scores and lesion volumes differed significantly between patients experiencing recanalization and those who did not (all p < 0.0001). Acute DWI and PWI lesion volumes correlated poorly with acute clinical scores and only modestly with outcome scores. We have concluded on the basis of this study that early recanalization saves tissue at risk of ischemic infarction and results in significantly smaller infarcts and a significantly better clinical outcome. Patients with proximal vessel occlusions have a larger amount of tissue at risk, a lower recanalization rate, and a worse outcome. Urgent recanalization seems to be of utmost importance for these patients.
 ...
PMID:Stroke magnetic resonance imaging within 6 hours after onset of hyperacute cerebral ischemia. 1131 Jun 23

Diffusion (DWI) and perfusion (PWI) magnetic resonance imaging are relatively new methods of clinical imaging that probably can detect infarcted (DWI) and hypoperfused but still salvageable tissue (PWI) in acute human stroke. Forty-six acute stroke patients were imaged within 24 h of ictus, on the second day and after a week. SPECT was also performed on 23 patients in the acute phase (first or second day). On the first day, mean volume of hypoperfused tissue was significantly greater (P<0.001) than the infarcted tissue. The initial hypoperfusion volume correlated significantly with the final infarct size (P<0.001). The initial perfusion-diffusion mismatch correlated significantly with the infarct growth (P< or =0.001). The hypoperfusion volumes measured from PWI and SPECT correlated significantly (P<0.001). In conclusion, combined DWI and PWI is a powerful tool in evaluating the hemodynamics of acute ischemic stroke and can predict the infarct growth during 1 week.
 ...
PMID:Diffusion and perfusion MR imaging in acute ischemic stroke: a comparison to SPECT. 1137 34

Contrast agent free time-of-flight magnetic resonance angiography (TOF-MRA) was applied to the intraluminal thread occlusion model of experimental stroke in rat. It was combined with perfusion- and diffusion-weighted imaging (PWI and DWI) sequences to correlate occlusion and reopening of the middle cerebral artery with alterations in these well-established magnetic resonance sequences. Since TOF-MRA can be repeated without limitations, the time course of vascular patency is demonstrated during an experimental period of up to 8 h (2 h control, 1 h ischemia, 3-6 h reperfusion). With an acquisition time of 10 min, TOF-MRA proved to be suitable to analyze the vascular state of occlusion and reperfusion repetitively in longitudinal studies. Spatial resolution was sufficient to observe neurovascular structural details. In eight out of 10 animals complete vessel occlusion by the intraluminal thread could be validated by an entirely extinguished signal of the ipsilateral middle cerebral artery (MCA) in the angiograms. This was in accordance with a perfusion deficit in the MCA vascular territory detected by PWI (reduction to 30.4 +/- 7.4% relative to contralateral side) and a disturbance of water ion homeostasis monitored by DWI in this area. One animal showed a delayed occlusion after 30 min of MCA occlusion, in another animal vessel occlusion failed. In seven out of the eight successful occlusion experiments there was immediate reperfusion after withdrawal of the thread. One animal showed a delayed reperfusion after suture retraction. Remarkable hemispheric differences in vascular branching of the MCA could be recognized in three out of 10 animals. In conclusion, TOF-MRA is considered a helpful method to survey even in small laboratory animals the correct time course of vascular occlusion and reopening in experimental ischemia, and provides complementary information to the tissue perfusion status monitored by PWI and the ischemic lesion territory detected by DWI.
 ...
PMID:MR angiographic investigation of transient focal cerebral ischemia in rat. 1147 49

Thrombolysis is an effective but potential deleterious therapy and should therefore be limited to patients with acute intracerebral vessel occlusion and salvageable tissue. MRI currently develops towards the new diagnostic standard for the selection of stroke patients eligible for acute thrombolytic treatment and acute stroke studies. Diffusion- and perfusion-weighed MRI provides diagnostic information not available from the neurological assessments or from CCT and conventional spin-echo MRI. As high-speed DWI and PWI protocols become standardized, a 15-minute integrated stroke protocol of employing echo-planar imaging (EPI) can be outinely performed in the setting of acute clinical stroke. The combination of these MR techniques is suitable to define tissue at risk of infarction that is potentially salvageable brain tissue (an estimate of the ischemic penumbra) and may respond to early recanalization even beyond 3 hours after stroke onset. The extension of the therapeutic window for thrombolytic therapy towards 6 hours in a subpopulation of acute stroke patients might open the way for the successful reperfusion therapy in more stroke patients.
 ...
PMID:CT and MRI in the diagnosis of acute stroke and their role in thrombolysis. 1156 80

Based on earlier findings that the presence of word comprehension impairment (a deficit in the meaning of words, or lexical semantics) in acute stroke was strongly associated with the presence of hypoperfusion or infarct in Wernicke's area, we tested the hypothesis that the severity of word comprehension impairment was correlated with the magnitude of delay in perfusion of Wernicke's area on magnetic resonance perfusion-weighted imaging. Eighty patients were prospectively studied within 24 hours of onset or progression of acute left hemisphere stroke symptoms, with diffusion-weighted imaging, perfusion-weighted imaging, and detailed language tests. For 50 patients without infarct in Wernicke's area, we found a strong Pearson correlation between the rate of errors on a word comprehension test and the mean number of seconds of delay in time-to-peak concentration of contrast in Wernicke's area, relative to the homologous region on the right. These results add further evidence for the crucial role of Wernicke's area (Brodmann's area 22) in word comprehension and indicate that the magnitude of delay on PWI may be a gross indicator of tissue dysfunction.
 ...
PMID:Hypoperfusion of Wernicke's area predicts severity of semantic deficit in acute stroke. 1170 59

99mTc-ECD SPECT is valuable for the evaluation of cell viability and function. The purpose of the present study was to evaluate the significance of 99mTc-ECD brain SPECT in ischemic stroke. We compared 99mTc-ECD brain SPECT with perfusion and diffusion weighted images (PWI, DWI). Ten patients with acute and early subacute ischemic stroke were included in this prospective study. T2-weighted images (T2WI), DWI, PWI and 99mTc-ECD SPECT were obtained during both the acute/early subacute and late subacute stages. In the case of PWI, time to peak (TTP) and regional cerebral blood volume (rCBV) maps were obtained. The rCBV map and 99mTc-ECD SPECT images were compared in 8 lesions using DeltaAI. The asymmetry index (AI) was calculated as (Ci - Cc) X 200 / (Ci + Cc); where Ci is the mean number of pixel counts of an ipsilateral lesion and Cc is the mean number of pixel counts of the normal contralateral hemisphere. DeltaAI was defined as AIacute - AIsubacute in the ischemic core and periphery. PWI and 99mTc-ECD SPECT detected new lesions of the hyperacute stage or of evolving stroke more accurately than T2WI and DWI. 99mTc-ECD SPECT was able to localize the infarct core and peri-infarct ischemia in all lesions in both the acute and the subacute stages. DeltaAI was higher in the rCBV map than in the 99mTc-ECD SPECT images in the ischemic core (p = 0.063) and in the periphery (p = 0.091). In the 99mTc-ECD SPECT images, DeltaAI was higher in the ischemic core than in the periphery (p = 0.028). During the subacute stage, 99mTc-ECD SPECT detected all the lesions without the pseudonormalization seen in the MR images of 5/11 lesions. Based on this study, 99mTc-ECD SPECT is comparable to PWI in terms of its ability to detect acute stroke and is more useful than PWI in the case of subacute infarction.
 ...
PMID:Significance of 99mTc-ECD SPECT in acute and subacute ischemic stroke: comparison with MR images including diffusion and perfusion weighted images. 1197 Dec 15

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.
 ...
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.
 ...
PMID:The very acute stroke treatment: fibrinolysis and after. 1245 Feb 34

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.
 ...
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.
 ...
PMID:Early magnetic resonance imaging prediction of arterial recanalization and late infarct volume in acute carotid artery stroke. 1257 55


<< Previous 1 2 3 4 5 6 7 Next >>