[Indications for Extracranial-Intracranial Bypass Surgery].

Previous randomized clinical trials have so far failed to establish the efficacy of extracranial-intracranial(EC-IC)bypass in the prevention of secondary ischemic strokes. For patients with a recent transient ischemic attack or ischemic stroke ipsilateral to a stenosis or occlusion of the middle cerebral or carotid artery, EC-IC bypass is not recommended as per the American heart association/American stroke association guidelines(Class III, Level of Evidence A). However, patients with severe hemodynamic impairment(misery perfusion)are at high risk of developing stroke, and EC-IC bypass is recommended as per the Japan stroke guideline 2021, provided that the patients show cerebral blood flow less than 80% from baseline and cerebral vascular reserve less than 10%. Perioperative management is also important in preventing ischemic complications and hyperperfusion. Some adjunctive drugs, including minocycline and edaravone, have been reported to be effective against brain damage from hyperperfusion. Regarding Moyamoya disease, EC-IC bypass has been established as a recommended strategy for ischemic presentation, hemorrhagic presentation, hemodynamic impairment, and choroidal anastomosis. EC-IC bypass is also necessary for specific types of aneurysms, including fusiform and thrombotic, as well as in the dissection of aneurysms that are difficult to clip.