Stroke; a journal of cerebral circulation
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Early arterial recanalization (ER) with intravenous tissue plasminogen activator (tPA) can lead to dramatic clinical recovery, whereas some patients do not experience immediate clinical improvement. ⋯ After successful arterial ER with tPA therapy, lack of early clinical changes or worsening is relatively common (37%) and appears to be independent of time to tPA bolus or reperfusion. However, with tPA alone, at least one third of these nonresponders still achieved good outcomes at 3 months, suggesting the possibility of a "stunned brain" syndrome with delayed recovery. Several different mechanisms may potentially account for this phenomenon.
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Recently, we focused on the cerebrovascular protective effects of moderate hypothermia after traumatic brain injury, noting that the efficacy of posttraumatic hypothermia is related to the rate of posthypothermic rewarming. In the current communication, we revisit the use of hypothermia with varying degrees of rewarming to ascertain whether, in the normal cerebral vasculature, varying rates of rewarming can differentially affect cerebrovascular responsiveness. ⋯ Posthypothermic rapid rewarming caused cerebral vascular abnormalities, including a diminished response to acetylcholine, hypercapnia, pinacidil, and SNP. Our data with acetylcholine and SNP suggest that rapid rewarming most likely causes abnormality at both the vascular smooth muscle and endothelial levels.
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It is unclear whether stroke in patients with spontaneous dissection of the cervical internal carotid artery (ICAD) is due to thromboembolism or impaired hemodynamics. This study investigated the mechanism of stroke in ICAD by examining brain imaging and cerebrovascular findings of such patients. ⋯ This study suggests that thromboembolism, not hemodynamic infarction, is the essential stroke mechanism in ICAD.
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Comparative Study
Therapeutic window for use of hyperbaric oxygenation in focal transient ischemia in rats.
Hyperbaric oxygenation (HBO) is an attractive procedure that has been used frequently in cerebral ischemia. However, depending on the model of cerebral ischemia and HBO protocol, different and conflicting results were obtained in the past. This study was undertaken to reevaluate the effects of single administration of HBO in 2 models of acute cerebral ischemia: transient or permanent focal ischemia in rats. A comparison of the 2 ischemia models was undertaken to search for a putative therapeutic window. ⋯ HBO is highly efficient in reducing infarct volume and improving neurobehavioral outcome in transient MCAO within the first 6 hours. HBO at later time points (>or=12 hours) is harmful by increasing infarct volume. In permanent MCAO, HBO failed to improve infarct volume and clinical outcome.