Stroke; a journal of cerebral circulation
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Comparative Study
Carotid diameter and blood flow velocities in cerebral circulation in hypertensive patients.
The recent development of noninvasive techniques for the evaluation of the carotid arteries has focused attention on the study of arterial wall thickness to identify early lesions of vessels in patients at high risk for atherosclerosis, such as those with hypercholesterolemia, diabetes mellitus, and hypertension. ⋯ These results indicate that in addition to the degenerative changes of the common carotid wall, the diameter of the carotid artery and the relation to parietal stress show an early impairment in patients with uncomplicated hypertension.
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Comparative Study
Transcranial Doppler sonography and magnetic resonance angiography in the assessment of collateral hemispheric flow in patients with carotid artery disease.
The aim of this investigation was to compare the respective efficacy of transcranial Doppler sonography (TCD) and magnetic resonance angiography (MRA) for the assessment of intracranial hemodynamics in patients with extracranial occlusion or severe stenosis of the internal carotid artery (ICA). ⋯ TCD and MRA should be considered complementary techniques. Combining the findings of both examinations may help to better understand the changes in intracranial hemodynamics produced by extracranial carotid occlusion. The contribution of the ophthalmic pathway, although important for the intraorbital structures, is probably of limited functional significance to the hemispheric blood supply.
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Transient cerebral ischemia in rats results in selective loss of neuronal viability, eg, hippocampal CA1 neurons. The neurochemical variables responsible for this selective vulnerability to ischemia/reperfusion (IR) appear to involve excitatory amino acids. In brain IR, excitatory amino acid toxicity may be modulated by endogenous nitric oxide (NO.) gas. To investigate NO. in global brain IR, we measured the effects of NO. synthase (NOS) inhibition on interstitial excitatory amino acids in rats. Changes in postischemic cerebral blood flow and blood-brain barrier function also were evaluated. ⋯ NOS inhibition did not attenuate extracellular glutamate accumulation during ischemia and increased its concentration on reperfusion. The elevated glutamate concentration after IR in L-NAME-treated rats did not appear to be due to either a decrease in cerebral blood flow response after ischemia or increases in local blood-brain barrier permeability. For the most part, the blood-brain barrier was spared in the immediate postischemic period by L-NAME treatment. These data suggest that NO. production may oppose synaptic excitatory amino acid accumulation and presumably excitotoxicity during IR.
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Free radical scavengers enhance neuronal survival in some models of transient forebrain ischemia. Recent experiments have suggested that N-acetylcysteine prevents cellular injury after a reperfusion injury. No information is available regarding the neuroprotective potential of the free radical scavenger N-acetylcysteine after transient forebrain ischemia. In this study we evaluated the potential of N-acetylcysteine to improve hippocampal neuronal survival after transient forebrain ischemia in the rat. ⋯ N-Acetylcysteine partially improved neuronal survival when administered before or after ischemia following transient cerebral ischemia (mean arterial blood pressure, 45 mm Hg) but not with a more severe ischemic insult of 10 minutes of transient cerebral ischemia with a mean arterial blood pressure of 30 mm Hg.
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Acute ischemia in the territory of the carotid artery can lead to massive cerebral edema with raised intracranial pressure and progression to coma and death due to uncal, cingulate, or tonsillar herniation. Thus far, only anecdotal experience with supratentorial ischemia treated by decompressive craniectomy has been reported; and there are no published experimental data dealing with this kind of therapy in acute supratentorial stroke. In this study, we present our results on the effect of decompressive craniectomy in an endovascular model of cerebral infarction in rats. ⋯ Our results suggest that decompressive craniectomy for cerebral ischemia not only reduces mortality but also significantly improves outcome and reduces infarction size, probably because of increased perfusion pressure through leptomeningeal collaterals. This experimental study suggests that a controlled study of decompressive craniectomy in patients with acute internal carotid or middle cerebral artery occlusion would be worthwhile. By performing decompressive craniectomy in a small, selected group of patients, neurosurgeons may play an important role in the management of these patients.