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

Cerebral misery perfusion diagnosed using hypercapnic blood-oxygenation-level-dependent contrast functional magnetic resonance imaging: a case report

Introduction Cerebral misery perfusion represents a failure of cerebral autoregulation. It is animportant differential diagnosis in post-stroke patients presenting with collapses in the presence of haemodynamically significant cerebrovascular stenosis. This is particularly the case when cortical or internal watershed infarcts are present. When this condition occurs, further investigation should be done immediately. Case presentation A 50-year-old Caucasian man presented with a stroke secondary to complete occlusion of his left internal carotid artery. He went on to suffer recurrent seizures. Neuroimaging demonstrated numerous new watershed-territory cerebral infarcts. No source of arterial thromboembolism was demonstrable. Hypercapnic blood-oxygenation-level-dependent-contrast functional magnetic resonance imaging was used to measure his cerebrovascular reserve capacity. The findings were suggestive of cerebral misery perfusion. Conclusions Blood-oxygenation-level-dependent-contrast functional magnetic resonance imaging allows the inference of cerebral misery perfusion. This procedure is cheaper and more readily available than positron emission tomography imaging, which is the current gold standard diagnostic test. The most evaluated treatment for cerebral misery perfusion is extracranial-intracranial bypass. Although previous trials of this have been unfavourable, the results of new studies involving extracranial-intracranial bypass in high-risk patients identified during cerebral perfusion imaging are awaited. Cerebral misery perfusion is an important and under-recognized condition in which emerging imaging and treatment modalities present the possibility of practical and evidence-based management in the near future. Physicians should thus be aware of this disorder and of recent developments in diagnostic tests that allow its detection