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

The density of perfused capillaries (dCAP), defined as capillaries that transport glucose, as well as the volume fraction of these capillaries in the vascular bed (fCAP), and the mean transit time of blood through the capillaries (tCAP), were calculated from hemodynamic variables obtained in vivo by positron tomography of brains of six patients affected by stroke. Each patient was studied twice, within 38 hrs of the insult, and one week later. 38 ischemic and 38 contralateral mirror regions were compared. The metabolic rate for glucose (CMRglc) was determined on the basis of regional calculations of the lumped constant. No significant change of the lumped constant was observed in any region. In normal regions, no significant differences of any variables existed between the first and second studies. In the infarct regions of the first study, CMRglc and CMRO2 (cerebral metabolic rate for oxygen) were 30-50% of control (deactivation) and CBF (cerebral blood flow), capillary density, and the capillary diffusion capacity for fluorodeoxyglucose (K1) were similarly reduced, although the oxygen/glucose ratio was only 3.75 in the ischemic regions. While fCAP decreased, tCAP doubled. One week after the first study, blood flow returned to normal in the infarct regions despite continued depression of metabolism. Capillary density and diffusion capacity remained low, indicating absent recruitment of nutrition vessels (perfusion capillaries).
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PMID:Absent recruitment of capillaries in brain tissue recovering from stroke. 767 79

Female reproductive hormones are considered to be protective agents in atherosclerotic vascular disease and stroke. The present study determined if there are unique cerebrovascular responses in female animals to global cerebral ischemia and if 17 beta-estradiol is important to postischemic outcome in brain. Three groups of anesthetized, sexually mature rabbits were treated with normotensive four-vessel occlusion (6 min) and 3 h of reperfusion: females chronically instrumented with 17 beta-estradiol implants (EFEM; n = 8, plasma estradiol level = 365 +/- 48 pg/ml), untreated females (FEM; n = 8, estradiol = 13 +/- 3 pg/ml), and untreated males (M; n = 8, estradiol < limit of radioimmunoassay). CBF (microspheres) and somatosensory evoked potential (SEP) amplitude were measured during ischemia/reperfusion. Baseline hemispheric blood flow and regional flow distribution were not altered by chronic estradiol treatment. Hemispheric blood flow was equivalently reduced during ischemia in FEM and M (6 +/- 1 and 9 +/- 2 ml min-1 100 g-1, respectively); however postischemic hyperemia was greater in FEM than M (CBF = 257 +/- 27 and 183 +/- 27 ml min-1 100 g-1. However, EFEM experienced higher CBF during ischemia (e.g., 13 +/- 2 ml min-1 100 g-1) and less hyperemia (134 +/- 4 ml min-1 100 g-1 in hemispheres) in numerous brain regions than FEM. CBF at 3 h reperfusion was not different among the groups. Recovery of SEPs was incomplete and similar in all groups. We conclude that chronic exogenous 17 beta-estradiol treatment increases CBF during global incomplete ischemia and ameliorates postischemic hyperemia in the female animal.
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PMID:Postischemic cerebral blood flow recovery in the female: effect of 17 beta-estradiol. 779 Apr 16

A study was performed in order to investigate how infarcts located in the white matter of the right hemisphere may affect processing of spatial and perceptual abilities. A battery of neuropsychological tests was applied to 7 right-handed patients with CT-verified infarcts of the right internal capsule or periventricular white matter. Examinations were performed 1-3 weeks post stroke and 3-7 months later. The patients were assessed by neurological examinations, EEG, and cortical regional cerebral blood flow (rCBF) measurements. This study suggested that deep white matter infarcts of the right hemisphere may result in persistent spatial impairment in the absence of decreased cortical rCBF. Perception was disturbed in cases of low mean cortical CBF of both hemispheres.
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PMID:Spatial and perceptual impairment related to cortical cerebral blood flow and EEG in deep white matter infarcts of the right hemisphere. 779 41

Experimental models of focal cerebral ischemia have provided important data on early circulatory and biochemical changes, but typically their correspondence with metabolic and hemodynamic findings in stroke patients has been poor. To fill the gap between experimental studies at early time points and rather late clinical studies, we repeatedly measured CBF, CMRO2, oxygen extraction fraction (OEF), cerebral blood volume (CBV), and CMRglc in six cats before and up to 24 h after permanent middle cerebral artery (MCA) occlusion (MCAO), using the 15O steady state and [18F]fluorodeoxy-glucose methods and a high-resolution positron emission tomography (PET) scanner. Likewise, three sham-operated control cats were studied during the same period. Final infarct size was determined on serial histologic sections. In the areas of final glucose metabolic depression that were slightly larger than the histologic infarcts, mean CBF dropped to approximately 40% of control values immediately on arterial occlusion. If further decreased to < 20% during the course of the experiment. This progressive ischemia was most conspicuous in border zones. CMRO2 fell to a lesser degree (55%), eventually reaching approximately 25% of its control level. At early stages, OEF increased mainly in the center of ischemia. With time, areas of increased OEF moved from the center to the periphery of the MCA territory. Concurrently, progressive secondary decreases in OEF in conjunction with further reductions of CBF and CMRO2 indicated the development of central necrosis. The findings are highly suggestive of a dynamic penumbra. In five cats with complete MCA infarcts, CBF decreased and OEF increased in the contralateral hemisphere after 24 h, suggesting whole-brain damage. This effect may be explained by the widespread brain edema found histologically in addition to the nonspecific CBF reductions and OEF elevations observed also in the sham-operated controls after 1 day in the experimental condition. In one cat, cortical OEF increased only transiently. Normal CMRO2 and CMRglc were eventually restored, and the final infarct was small. This study demonstrates that acute regional pathophysiologic changes can be repeatedly assessed by multivariate PET in cats. Viable tissue can be detected up to several hours after MCA occlusion, and the transition of misery-perfused regions into necrosis or preserved tissue can be followed over time. The present results support the concept of a dynamic penumbra, in which for up to 24 h tissue damage spreads progressively from the center to the periphery of ischemia. Sequential high-resolution PET provides insight into the dynamics of regional pathophysiology and may thus further the development of rational therapeutic strategies.
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PMID:Dynamic penumbra demonstrated by sequential multitracer PET after middle cerebral artery occlusion in cats. 792 54

The relationship between local cerebral blood flow (ICBF) and local cerebral glucose metabolism (ICGU) at the chronic stage of focal cerebral ischaemia was assessed in young stroke-prone spontaneously hypertensive rats (SHRSP) following occlusion of the distal middle cerebral artery (MCA). On day 7 following this occlusion, ICBF and ICGU were measured by autoradiographic methods using 14C-iodoantipyrine and 14C-2-deoxyglucose (2DG), respectively. The infarct was limited to the ipsilateral cerebral cortex. A narrow band of increased uptake of 14C-2DG was observed in the border zone at the periphery of infarcted areas. The ICBF in the ischaemic cortex revealed a graded reduction from the ischaemic centre to the surrounding tissues. A significant reduction in ICGU coupled to CBF was also observed in 4 of 13 selected noninfarcted regions ipsilateral to the MCA occlusion. The ischaemic regions had a significant increase in water content. The region with ischaemic oedema was limited to a narrow area compared with the findings regarding ICBF and ICGU. The SHRSP strain has more severe cerebral ischaemia, oedema formation, and metabolic derangement at the chronic stage of focal ischaemia, compared to normo-tensive animals.
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PMID:Local cerebral blood flow and glucose metabolism in chronic focal ischaemia of stroke-prone spontaneously hypertensive rats. 798 61

Single photon emission computed tomography (SPECT) with acetazolamide challenge has increasingly been used for evaluating hemodynamic reserve in stroke patients. The accuracy of this test, however, has not been validated with positron emission tomography (PET). In 14 patients who had occlusive disease of the internal carotid artery or the trunk of the middle cerebral artery (MCA) with minimal or no infarction on computed tomography (CT) and magnetic resonance imaging (MRI), we compared acetazolamide reactivity on SPECT with N-isopropyl-p-[123I]-iodoamphetamine to hemodynamic parameters determined with gas inhalation labeled 15O steady-state PET studies. The asymmetry index (AI)--i.e., the percentage of the activity rate of the ischemic MCA territory versus the contralateral one, was determined by SPECT. Acetazolamide reactivity expressed as delta AI, or change in AI after acetazolamide challenge, was significantly lower in seven patients than -8.4%, the lower limit of the 95% confidence interval for the normal reactivity. Values of ipsilateral CBF, cerebral blood volume (CBV)/CBF, and oxygen extraction fraction (OEF) and contralateral OEF were significantly different between patients with normal and reduced acetazolamide reactivity. Values of delta AI were correlated with OEF (r = -0.87; p < 0.001) and CBV/CBF (r = -0.56; p < 0.05). All patients with OEF > 0.52, the mean + 2 SD calculated from five normal volunteers, also had reduced acetazolamide reactivity, while the patients with normal OEF values had normal reactivity. The present study has demonstrated that SPECT studies with an acetazolamide challenge can detect the Stage II hemodynamic failure.
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PMID:Acetazolamide reactivity on 123I-IMP single photon emission computed tomography in patients with major cerebral artery occlusive disease: correlation with positron emission tomography parameters. 806 72

We reported a case of subacute stroke which showed high uptake of 99mTc-d,l-hexamethylpropyleneamine oxime (HMPAO) in the reperfused infarct corresponding to slightly decreased perfusion by 133Xe inhalation CBF measurement. In the chronic stage, both SPECT images of 99mTc-HMPAO and 133Xe showed low perfusion in the affected lesion. It was, therefore, considered that the high uptake of 99mTc-HMPAO had represented luxury perfusion. In the subacute stage of stroke, high uptake of 99mTc-HMPAO may imply luxury perfusion but not always hyperperfusion. It is suggested that the fractional fixation of 99mTc-HMPAO temporarily change in the affected lesion and it is essential to take into consideration the clinical stage for the interpretation of SPECT images.
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PMID:[A case of subacute stroke with high uptake of 99mTc-HMPAO in the reperfused infarct corresponding to low perfusion area]. 807 34

We studied whether administration of nitric oxide (NO) donors reduces the ischemic damage resulting from middle cerebral artery (MCA) occlusion in spontaneously hypertensive rats (SHRs). In halothane-anesthetized and ventilated SHRs, the MCA was occluded. CBF was monitored using a laser-Doppler flowmeter. Three to five minutes after MCA occlusion, the NO donors sodium nitroprusside (SNP; 3 mg/kg/h) or 3-morpholino-sydnonimine (SIN 1; 1.5-6 mg/kg/h) were administered into the carotid artery for 60 min. As a control, the effect of papaverine (3.6 mg/kg/h), a vasodilator that acts independently of NO, was also studied. The hypotension evoked by these agents was counteracted by intravenous infusion of phenylephrine. At the end of the infusion, rats were allowed to recover. Stroke size was determined 24 h later in thionin-stained sections. In sham occluded rats, SNP (n = 5), SIN 1 (n = 5), and papaverine (n = 5) produced comparable increases in CBF (p > 0.05 from vehicle). After MCA occlusion, SNP (n = 5) and SIN 1 (n = 5), but not papaverine (n = 5), enhanced the recovery of CBF (p < 0.05 from vehicle) and reduced the size of the infarct by 28 +/- 12 and 32 +/- 7%, respectively (mean +/- SD; p < 0.05 from vehicle). To determine whether NO donors could act by inhibiting platelet aggregation, we studied the effect of SNP on collagen-induced platelet aggregation. Intracarotid administration of SNP (3 mg/kg/h for 60 min) did not affect platelet aggregation to collagen, suggesting that the protective effect of NO donors was not due to inhibition of platelet function. We conclude that NO donors increase CBF to the ischemic territory and reduce the tissue damage resulting from focal ischemia. The protective effect may result from an increase in CBF to the ischemic territory, probably the ischemic penumbra. These findings suggest that NO donors may represent a new therapeutic strategy for the management of acute stroke.
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PMID:Nitric oxide donors increase blood flow and reduce brain damage in focal ischemia: evidence that nitric oxide is beneficial in the early stages of cerebral ischemia. 811 18

A multicenter study was performed in seven European centers comparing 99mTc-bicisate with 133Xe as a means of evaluating bicisate as a tracer of CBF distribution in humans. The same type of single photon emission computed tomography (SPECT) instrument (Tomomatic) was used in all centers. A total of 115 cases were collected, and of these 105 were considered technically adequate, comprising 18 normal subjects, 18 senile dementia, eight epilepsy, one brain tumor, eight chronic head trauma, and 52 stroke cases. As expected, bicisate gave better spatial resolution than Xe. Agreement between the results of the two methods was noted in 98 cases, but not in the remaining 7, all belonging to the stroke group. These seven all suffered from a subacute stroke (11-23 days after onset), and the disagreement in all cases consisted of bicisate showing low count rate in the area of the infarct and Xe a normal or elevated flow (luxury perfusion) as sign of spontaneous thrombolysis with reperfusion; in fact, these seven cases comprised all the reperfusion cases in the series. The results validate bicisate as a tracer of CBF in normal humans and in chronic brain diseases. Only in a subgroup of subacute stroke cases does bicisate not follow CBF, as it fails to show reperfusion hyperemia. This suggests the usefulness of bicisate in stroke cases, particularly in the subacute phase, where other SPECT methods often present difficulties due to reflow masking the size and the severity of the lesion.
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PMID:99mTc-bicisate reliably images CBF in chronic brain diseases but fails to show reflow hyperemia in subacute stroke: report of a multicenter trial of 105 cases comparing 133Xe and 99mTc-bicisate (ECD, neurolite) measured by SPECT on same day. 826 71

To evaluate the cerebral distribution of 99mTc-ethyl cysteinate dimer (99mTc-ECD) at blood flow levels beyond the normal range, we investigated postischemic reperfusion and acetazolamide (Diamox) activation test in stroke patients. The postischemic reperfusion was studied in 10 patients who showed a postischemic hyperperfusion area on other single photon emission computed tomography (SPECT) studies using N-isopropyl-rho-[123I]iodoamphetamine ([123I]IMP), 99mTc-hexamethyl propyleneamine oxime (99mTc-HMPAO), or 133Xe. 99mTc-ECD SPECT demonstrated a hyperactive area in one case, an isoactive area in four, and a hypoactive area in five. Correlations with CT findings revealed hyperactive areas without any abnormality, isoactive areas with perifocal rim, perifocal edema, or diffuse cerebral edema, and hypoactive areas with an infarct core. The Diamox activation test was studied in eight other patients with atherothrombotic stroke, and a limitation in vasodilative capacity was classified into three grades: Gr. 0 (none to minimal), Gr. I (mild), and Gr. II (moderate). [123I]IMP SPECT showed Gr. II and limitation in all eight cases. However, 99mTc-ECD showed Gr. II in three cases and Gr. I in five, and 99mTc-HMPAO revealed Gr. II in two cases, Gr. I in three, and Gr. 0 in three. We suggest that a lack of retention of 99mTc-ECD in a postischemic reperfusion area indicates the severity of the initial brain damage. Although the limitation in vasodilative capacity under Diamox-activated conditions was underestimated using 99mTc-labeled CBF tracers as compared with [123I]IMP, a retention of 99mTc-ECD in the unaffected area with an increased CBF under Diamox activation could be relatively superior to 99mTc-HMPAO.
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PMID:Assessment of postischemic reperfusion and diamox activation test in stroke using 99mTc-ECD SPECT. 826 72


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