24 research outputs found
Cerebral Collateral Circulation in Carotid Artery Disease
Carotid artery disease is common and increases the risk of stroke. However, there is wide variability on the severity of clinical manifestations of carotid disease, ranging from asymptomatic to fatal stroke. The collateral circulation has been recognized as an important aspect of cerebral circulation affecting the risk of stroke as well as other features of stroke presentation, such as stroke patterns in patients with carotid artery disease. The cerebral circulation attempts to maintain constant cerebral perfusion despite changes in systemic conditions, due to its ability to autoregulate blood flow. In case that one of the major cerebral arteries is compromised by occlusive disease, the cerebral collateral circulation plays an important role in preserving cerebral perfusion through enhanced recruitment of blood flow. With the advent of techniques that allow rapid evaluation of cerebral perfusion, the collateral circulation of the brain and its effectiveness may also be evaluated, allowing for prompt assessment of patients with acute stroke due to involvement of the carotid artery, and risk stratification of patients with carotid stenosis in chronic stages. Understanding the cerebral collateral circulation provides a basis for the future development of new diagnostic tools, risk stratification, predictive models and new therapeutic modalities. In the present review we discuss basic aspects of the cerebral collateral circulation, diagnostic methods to assess collateral circulation, and implications in occlusive carotid artery disease
Intra-Arterial Treatment Methods in Acute Stroke Therapy
Acute revascularization is associated with improved outcomes in ischemic stroke patients. It is unclear which method of intra-arterial intervention, if any, is ideal. Promising approaches in acute stroke treatment are likely a combination of intravenous and endovascular revascularization efforts, combining early treatment initiation with direct clot manipulation and/or PTA/stenting. In this review, we will discuss available thrombolytic therapies and endovascular recanalization techniques, beginning with chemical thrombolytic agents, followed by mechanical devices, and a review of ongoing trials. Further randomized studies comparing medical therapy, intravenous and endovascular treatments are essential, and their implementation will require the wide support and enthusiasm from the neurologic, neuroradiologic, and neurosurgical stroke communities
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Direct Visualization of Arterial Emboli in Moyamoya Syndrome
Background: Hemodynamic insufficiency is often considered the cause of ischemic stroke in patients with moyamoya syndrome. While high-intensity transient signals (HITS) on transcranial Doppler (TCD) have been reported in this population, the relationship between these signals and ischemic symptoms is not clearly established. Accordingly, current treatment is directed at improving perfusion. Clinical presentation We present two patients with symptoms of cerebral ischemia and angiographic findings of moyamoya syndrome. In each case, ischemia may have been caused by either hypoperfusion or embolization. Patient A presented with multifocal right middle cerebral artery (MCA) territory infarctions and angiographic findings consistent with moyamoya disease. She underwent right superficial temporal artery–MCA bypass. Intra-operatively, embolic material was observed and recorded traveling through the recipient MCA branch artery on two occasions. Postoperative TCD demonstrated HITS that resolved with uptitration of antiplatelet therapy. Patient B presented with multifocal, embolic-appearing left MCA infarctions, and unilateral angiographic moyamoya syndrome. She was found to have HITS in the left MCA, which eventually resolved with a combination of antiplatelets and anticoagulation. Conclusion: Hemodynamic compromise may not be the only cause of brain infarction in patients with moyamoya syndrome. Observations from these two patients provide both direct visualization and TCD evidence of embolization as a potential etiology for brain ischemia. Future investigations into the role of antithrombotic agents should be considered
Neuroprotection and Stroke Rehabilitation: Modulation and Enhancement of Recovery
Recent advances in research are modifying our view of recovery after nervous system damage. New findings are changing previously held concepts and providing promising avenues for treatment of patients after stroke. This review discusses mechanisms of neuronal injury after brain ischemia and the attempts to study neuroprotection options based on such mechanisms. It also considers measures available at present to improve outcome after stroke and presents new areas of research, particularly stimulation techniques, neurogenesis and trophic factors to enhance recovery. In order to improve outcomes, medications that may be detrimental to recovery should be avoided, while symptomatic therapy of problems such as depression, pain syndromes and spasticity may contribute to better results. Continued surveillance and early treatment of complications associated with acute stroke, along with supportive care remain the mainstay of treatment for stroke patients in the recovery phase. Present research on limiting brain damage and improving recovery and plasticity enhance the prospects for better clinical treatments to improve recovery after stroke
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Detection of Microemboli by Transcranial Doppler Ultrasonography in Aneurysmal Subarachnoid Hemorrhage
Abstract OBJECTIVE: To determine the frequency and characteristics of microembolic signals (MES) in subarachnoid hemorrhage (SAH). METHODS: Twenty-three patients with aneurysmal SAH were monitored with transcranial Doppler ultrasonography for the presence of MES and vasospasm. Each middle cerebral artery was monitored for 30 minutes three times each week. Patients were excluded if they had traumatic SAH or cardiac or arterial sources of emboli. Monitoring was initiated 6.3 days (1–16 d) after SAH and lasted 6.6 days (1–13 d). Eleven individuals without SAH or other cerebrovascular diseases who were treated in the same unit served as control subjects. Each patient underwent monitoring of both middle cerebral arteries a mean of three times; therefore, 46 vessels were studied (a total of 138 observations). Control subjects underwent assessment of each middle cerebral artery once, for a total of 22 control vessels. RESULTS: MES were detected for 16 of 23 patients (70%) and 44 of 138 patient vessels (32%) monitored, compared with 2 of 11 control subjects (18%) and 2 of 22 control vessels (9%) (P < 0.05). MES were observed for 83% of patients with clinical vasospasm and 54% of those without clinical vasospasm. Ultrasonographic vasospasm was observed for 71 of 138 vessels monitored; MES were observed for 28% of vessels with vasospasm and 36% of those without vasospasm. Aneurysms proximal to the monitored artery were identified in 38 of 138 vessels, of which 34% exhibited MES, which is similar to the frequency for vessels without proximal aneurysms (31%). Coiled, clipped, and unsecured aneurysms exhibited similar frequencies of MES. CONCLUSION: MES were common in SAH, occurring in 70% of cases of SAH and one-third of all vessels monitored. Although MES were more frequent among patients with clinical vasospasm, this difference did not reach statistical significance. We were unable to demonstrate a relationship between ultrasonographic vasospasm and MES, and the presence of a proximal secured or unsecured aneurysm did not alter the chance of detection of MES. Further studies are required to determine the origin and clinical relevance of MES in SAH