Cerebral Bypass Surgery: Level of Evidence and Grade of Recommendation

BACKGROUND AND AIMS Cerebral bypasses are categorized according to function (flow augmentation or flow preservation) and to characteristics: direct, indirect or combined bypass, extra-to-intracranial or intra-to-intracranial bypass, and high-, moderate- or low-capacity bypass. We critically summarize the current state of evidence and grades of recommendation for cerebral bypass surgery. METHODS The current indications for cerebral bypass are discussed depending on the function of the bypass (flow preservation or augmentation) and analyzed according to level of evidence criteria. RESULTS Flow-preservation bypass plays an important role in managing complex intracranial aneurysms (level of evidence 4; grade of recommendation C). Flow-preservation bypass is currently only very rarely indicated in the treatment of cerebral tumors involving major cerebral arteries (level of evidence 5; grade of recommendation D). The trend has evolved in favor of partial resection and radiotherapy. To preserve the flow, the bypass is always a direct bypass.Flow-augmentation bypass is currently recommended for Moyamoya patients with ischemic symptoms and compromised hemodynamics (level of evidence 4; grade of recommendation C) and patients with hemorrhagic onset (level of evidence 1B; grade of recommendation A). Flow-augmentation bypass is currently not recommended for patients with recently symptomatic carotid artery occlusion, even in the setting of compromised cerebral hemodynamics (level of evidence 1A; grade of recommendation A), but may be considered in patients with hemodynamic failure and recurrent medically refractory symptoms as a final resort (level of evidence 5; grade of recommendation D). CONCLUSIONS The results of recent randomized clinical trials narrow the indication for cerebral bypass in the setting of ischemic cerebrovascular disease. However, cerebral bypass is still very useful for managing complex intracranial aneurysms (not amenable to selective clipping or endovascular therapies) and is the only treatment option for managing symptomatic patients with Moyamoya vasculopathy and impaired brain hemodynamics

Quantitative assessment of renal perfusion and oxygenation by invasive probes: basic concepts

Renal tissue hypoperfusion and hypoxia are early key elements in the pathophysiology of acute kidney injury of various origins, and may also promote progression from acute injury to chronic kidney disease. Here we describe basic principles of methodology to quantify renal hemodynamics and tissue oxygenation by means of invasive probes in experimental animals. Advantages and disadvantages of the various methods are discussed in the context of the heterogeneity of renal tissue perfusion and oxygenation.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by a separate chapter describing the experimental procedure and data analysis

Quantitative Magnetic Resonance Venography is Correlated With Intravenous Pressures Before and After Venous Sinus Stenting: Implications for Treatment and Monitoring.

BACKGROUND: Endovascular stenting is an effective treatment for patients with clinically significant cerebral venous sinus stenosis. Traditionally, stenting is indicated in elevated intravenous pressures on conventional venography; however, noninvasive monitoring is more desirable. Quantitative magnetic resonance angiography is an imaging modality that measures blood flow noninvasively. Established in the arterial system, applications to the venous sinuses have been limited. OBJECTIVE: To examine quantitative magnetic resonance venography (qMRV) in the measurement of venous sinus flow in patients undergoing endovascular stenting and to identify a relationship with intravenous pressures. METHODS: Five patients with intracranial hypertension secondary to venous sinus stenosis underwent cerebral venous stenting between 2009 and 2013 at a single institution. Preoperatively, venous sinus flow was determined by using qMRV, and intravenous pressure was measured during venography. After stenting, intravenous pressure, qMRV flow, and clinical outcomes were assessed and compared. RESULTS: A mean prestenotic intravenous pressure of 45.2 mm Hg was recorded before stenting, which decreased to 27.4 mm Hg afterward (Wilcoxon signed rank test P = .04). Total jugular outflow on qMRV increased by 260.2 mL/min. Analysis of the change in intravenous pressure and qMRV flow identified a linear relationship (Pearson correlation r = 0.926). All patients displayed visual improvement at 6 weeks. CONCLUSION: Venous outflow by qMRV increases after endovascular stenting and correlates with significantly improved intravenous pressures. These findings introduce qMRV as a potential adjunct to measure venous flow after stenting, and as a plausible tool in the selection and postoperative surveillance of the patient who has cerebral venous sinus stenosis