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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Four cases of basilar artery occlusion with a follow-up from 7 to 12 years are reported. The first patient, a 60 year old woman, had a proximal occlusion which was revealed by an acute brain stem ischemia. The second case was a 63 year old man with an aortic aneurysm who had a single episode of vertebro-basilar insufficiency. Cerebral angiography demonstrated a lower basilar artery occlusion. The third patient, a 60 year-old woman, had been operated from right carotid artery and left vertebral artery stenosis; 8 years later, without clinical manifestations, a left carotid artery stenosis and an occlusion of the lower part of the basilar artery were discovered. The evolution was eventless after a left carotid endarterectomy. The last case was a 60 year old man who had a lower basilar artery occlusion associated with a left internal carotid occlusion. There was a full recovery after a hemiplegic stroke. From our personal cases and the review of the literature, long term survival after basilar artery occlusion may occur in occlusions restricted to the lower or middle part of the basilar artery and with a good collateral supply from carotid and cerebellar arteries.
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PMID:[Long term survival after basilar artery occlusion. 4 cases]. 259 68

The purpose of this study was to determine in subhuman primates whether hemodynamic mechanisms (as compared with embolic mechanisms) contribute to cerebral ischemia following carotid artery occlusion or stenosis. Following carotid artery occlusion there was loss of cerebral autoregulation: cerebral blood flow (CBF) measured with the xenon-133 technique became passively dependent upon the mean arterial blood pressure (MABP) over an MABP range of 30 to 110 mm Hg. By contrast, autoregulation was preserved in normal animals and in animals with a 90% carotid artery stenosis. Regional CBF was measured with carbon-14-labeled iodoantipyrine autoradiography in normotensive baboons, in hypotensive animals, and in hypotensive animals with carotid artery occlusion or stenosis. With carotid artery occlusion and hypotension, reduced levels of local CBF were seen ipsilaterally in the boundary zones between the anterior and middle cerebral arteries with 35% of the area of an anterior section through the hemisphere displaying a CBF value of less than 20 ml/100 gm/min. Comparable values with hypotension were 21% with carotid artery stenosis, 20% with no proximal vascular lesion, and 1% in normotensive animals. These areas of reduced CBF corresponded with areas of boundary-zone ischemia seen with light microscopy. The study suggests that while hemodynamic ischemia develops with carotid artery occlusion, it does not occur with even a 90% carotid artery stenosis or in normal animals.
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PMID:The hemodynamic effects of internal carotid artery stenosis and occlusion. 357 1

The retinal circulation of 35 patients (age, 30 to 71 years) with symptomatic internal carotid occlusion (22 cases) or severe inaccessible stenosis (13 cases) was studied both before and after superficial temporal to middle cerebral artery (STA-MCA) bypass surgery using ophthalmodynamometry (ODM) and intravenous fundus fluorescein angiography (IVFA). Ninety-four per cent of the patients were found preoperatively to have funduscopic findings or symptoms indicative of ocular ischemia. ODM values were abnormal preoperatively in 32 of 35 patients (91%), and improvement in ODM values for the ipsilateral eye was noted postoperatively in 25 patients (71%). ODM values obtained during the early (less than 3 months) and late (greater than 3 months) postoperative periods were significantly improved when compared to the preoperative values. IVFA values were abnormal in 25 of 29 patients (86%) preoperatively, and significant improvement was noted in 22 of 25 patients (88%) postoperatively. Preoperative patients with normal fundus examinations (10 cases) had significantly better values for IVFA and ODM than patients with venous stasis retinopathy. The findings of the study showed that STA-MCA anastomosis is beneficial in treating retinal ischemia secondary to ipsilateral severe inaccessible carotid artery stenosis or occlusion.
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PMID:Improvement in the retinal circulation after superficial temporal to middle cerebral artery bypass. 399 Sep 31

The natural history of intracranial arterial stenosis is not well understood. The lesions are pathologically quite diverse, and are subject to resolution, progression, or occlusion. The authors undertook an investigation to examine what effects, if any, extracranial-intracranial (EC-IC) bypass surgery had on the evolution of intracranial arterial stenosis in 18 patients undergoing EC-IC bypass procedures for ipsilateral hemispheric ischemia. There was inaccessible internal carotid artery stenosis in 14 patients, and middle cerebral artery stenosis in four patients. Early (within 2 weeks) and late (at 6 months) postoperative angiography was performed in all patients. During the period of the study, there was a significant change in the arterial stenosis in 50% of the patients (nine of 18). The stenotic artery became occluded in four patients while the grafts were widely patent. The occlusion occurred within a few days after the operation in three of the four cases, and was accompanied by an ischemic stroke in these patients. There was improvement or resolution of the stenotic lesion in five patients; the graft became occluded in two of these cases and was patent but showed poor cortical artery filling in the other three. All these patients remained asymptomatic and the change was detected on routine late postoperative angiograms. It is concluded that arterial stenoses should not be viewed as static or inflexible lesions, and that EC-IC bypass procedures can modify the hemodynamic parameters across stenotic lesions, predisposing them to improvement or worsening. This, in turn, may affect bypass patency. Such hemodynamic interactions are accompanied by ischemic symptoms in some patients, and contribute to the relatively higher morbidity associated with EC-IC bypass surgery in the setting of arterial stenosis.
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PMID:Changes in intracranial stenotic lesions after extracranial-intracranial bypass surgery. 670 46

Fourteen patients with severe bilateral carotid artery stenosis underwent carotid endarterectomy. Intra-operative ischemia was monitored by somatosensory evoked potentials (SSEP) bilaterally. Neuropsychological evaluations were completed within two days before operation and 4-9 days after operation. Complete loss of N1-P1 or P1-N2 components of the SSEP (seen in 4 patients) was associated with a worsening of neuropsychological abilities (p less than .01). Two of these patients subsequently had strokes (7 and 35 days after operation). No other patients in the series have had strokes. Patients whose N1-P1 or P1-N2 amplitudes decreased by 50% or more performed worse after operation than patients with less severe reductions in these amplitudes (p less than .02). Time since first ischemic symptoms, age, education, clamp time, pre-operative stroke, and interval from surgery to assessment were not statistically related to changes in neuropsychological abilities. Patients with ischemic events in the week prior to surgery tended to improve in neuropsychological abilities 4-9 days after operation (p less than .05). Recentness of ischemic episode, however, was not related to intra-operative SSEP change. Results suggest the potential utility of intra-operative SSEP monitoring and early post-operative neuropsychological assessments both for clinical and research purposes.
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PMID:Neuropsychological performance one week after carotid endarterectomy reflects intra-operative ischemia. 672 79

Eighty-eight patients with brain ischemia underwent cerebral angiography and measurement of regional cerebral blood flow (rCBF) after 133Xe inhalation. A fast compartment flow rate and an initial slope index were computed for each detector and for each hemisphere. The clinical presentation, angiographic findings, and rCBF results were then examined for significant correlations. Patients with hemispheric infarction most frequently showed bilateral diffusely decreased rCBF. In patients with transient ischemic attacks, no specific pattern emerged. Patients with unilateral internal carotid artery occlusion frequently hd bilateral diffusely decreased rCBF. Patients with severe internal carotid artery stenosis were more likely to show decreased rCBF than were patients with mild or moderate stenosis. The initial slope index seemed to be a more sensitive indicator of brain ischemia than the fast compartment flow rate. The possible pathophysiological significance and relationship to patient management of the various rCBF patterns are discussed.
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PMID:Correlation of clinical and angiographic findings in brain ischemia with regional cerebral blood flow measured by the xenon inhalation technique. 711 May 62

This study tests, the hypothesis that asymptomatic patients with hemodynamically significant internal carotid artery stenosis have a lower ipsilateral collateral cerebral vascular resistance and hence greater blood flow than their symptomatic cohorts. We measured internal carotid artery blood flow and cerebral perfusion pressures intraoperatively prior to and after carotid endarterectomy in 35 symptomatic and 10 asymptomatic patients with hemodynamically significant internal carotid artery stenosis. When the stenosis produced 30% or greater reduction in blood flow the calculated nondimensional normalized ratio of collateral cerebral vascular resistance of ipsilateral hemisphere cerebral vascular resistance was 1.15 +/- 0.83 (mean +/- SD) for the 10 asymptomatic patients and 2.98 +/- 1.89 for the 35 symptomatic patients (p = 0.0044). For the subgroup of 22 patients with 50% or greater reduction in internal carotid artery blood flow the resistance ratios were 0.782 +/- 0.541 for the 5 asymptomatic patients and 3.21 +/- 2.26 for the 17 symptomatic patients (p = 0.029). These results suggest that asymptomatic patients with hemodynamically significant internal carotid artery stenoses have a lower collateral cerebral vascular resistance than their symptomatic cohorts. The low collateral resistance may provide an adequate collateral cerebral blood flow to prevent ischemia and symptoms.
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PMID:Collateral cerebral vascular resistance in patients with significant carotid stenosis. 714 99

Brain blood flow may be compromised as severely by altered cardiovascular dynamics as by atherosclerotic flow-limiting lesions in carotid arteries. The Automated Physiologic Profile can distinguish between those clinically important mechanisms. The Automated Physiologic Profile is a concept and method and apparatus. Physiologic performance of the heart, vascular tone in systemic and pulmonary vessels, and oxygen consumption are derived and printed on a standard report form. This easy to use form identifies mechanisms and illustrates severity of patho-physiologic aberrations contributing to ischemia-inducing processes. Serial portrayal depicts effectiveness of therapeutic interventions. This report included examples of APP in patients with ventricular rhythm disturbance, sick sinus syndrome, hypovolemic low cardiac out-put, and carotid artery stenosis as contributing factors in clinical cerebrovascular insufficiency. All were accompanied by excessive systemic arteriolar resistance, implying reduced brain blood flow. Serial APPs correlated with clinical events in the case histories.
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PMID:Automated physiological profile assessment of effects of altered cardiovascular dynamics on brain blood flow. 730

By providing a non-invasive method for continuous display of mean flow velocity (Vmean) in the cerebral arteries, transcranial Doppler (TCD) ultrasound supplements evaluation of cerebral perfusion. Dynamic exercise increases middle cerebral artery (MCA) Vmean from approximately 55 to 65 cm s-1 dependent on work rate, and even more when corrected for changes of the arterial carbon dioxide tension. Evaluation of Vmean corresponds to that of cerebral blood flow as determined with the 133Xenon clearance technique, and reflects regional cortical regulation of the active muscles with important afferent nervous influence. Concomitant increases of mean arterial pressure (MAP) and heart rate is only of minor importance as illustrated during static exercise and post-exercise muscle ischaemia, where Vmean is not significantly elevated. During sustained head-up tilt, the Vmean remained unchanged at a MAP approximately 83 mmHg. Below this level, it decreased in parallel with MAP until MAP reached 50 mmHg. At an even lower MAP, Vmean seemed to approach a lower limit approximately 25 cm s-1, but at a diastolic pressure of 21 mmHg there was no flow in the MCA. Conversely, during post-exercise muscle ischemia, an increase in MAP to 140 mmHg did not influence Vmean. This is in contrast to patients operated for carotid artery stenosis and who develop ipsilateral headache. In these patients the ipsilateral MCA Vmean changed in parallel with MAP, and autoregulation was re-established only after one to two weeks. In patients with severe carotid stenosis and poor collateral circulation, the CO2-reactivity as expressed by Vmean was the lowest, and could be negative on the ipsilateral side. During carotid endarterectomy, a Vmean clamp/Vmean pre-clamp ratio below 0.6 identified patients with a cerebral blood flow below 20 ml 100 g-1 min-1. Furthermore, when the ratio was below 0.4 pathological electroenchephalographic changes developed. Thus, Vmean of the large basal cerebral arteries reflects cerebral perfusion with respect to regional flow distribution, autoregulatory response, and CO2-reactivity in normal man and patients with limited cerebral flow.
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PMID:Transcranial Doppler ultrasound for cerebral perfusion. 748 67

Since its introduction 40 years ago, the value of carotid endarterectomy has been controversial. In the early 1980s, several clinical trials were initiated to determine the efficacy of this operation in patients with carotid stenoses who were either symptomatic or asymptomatic for retinal or hemispheric ischemia. In 1991, interim results were published for the North American Symptomatic Carotid Endarterectomy Trial (NASCET) and the European Carotid Surgery Trial (ECST), both reporting efficacy for surgery in patients with symptomatic carotid artery stenosis of greater than 70%. Subgroup analyses revealed variable risk groups. The Veterans Administration (VA) Symptomatic Trial (Cooperative Studies Program 309 of the Department of Veterans Affairs) terminated early because of these results and its findings were consistent with the results of the larger trials. NASCET and ECST continue for symptomatic patients with carotid stenoses between 30% and 69%. The results of three trials in asymptomatic patients, the Mayo asymptomatic trial, the Carotid Artery Stenosis with Asymptomatic Narrowing: Operation Versus Aspirin trial, and the VA Asymptomatic Trial (Cooperative Studies Protocol 167 of the Department of Veterans Affairs), have been reported. None showed a statistically significant benefit for surgery in the prevention of stroke or death. However, none was sufficiently large to exclude such a benefit. The large Asymptomatic Carotid Atherosclerosis Study is in progress. Differences in the results and design of these trials are discussed as are restrictions in the applicability of their results.
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PMID:Carotid endarterectomy: trials and tribulations. 828 92


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