EC-IC bypass function in Moyamoya disease and non-Moyamoya ischemic stroke evaluated by intraoperative indocyanine green fluorescence angiography.

Indocyanine green (ICG) emits near-infrared fluorescence when it is excited by near-infrared light. The near infrared fluorescence of ICG was applied to the imaging of cerebral vessels during neurosurgical operations such as clipping of aneurysms. In this study, ICG angiography was applied to extracranial-intracranial (EC-IC) bypass surgery to evaluate the hemodynamic changes induced by bypass in moyamoya disease (MD) and non-moyamoya ischemic diseases (non-MD). These patients underwent superficial temporal artery-middle cerebral artery (STA-MCA) anastomosis. We compared the cortical areas where the bypass supplied blood flow between MD and non-MD. ICG angiography clearly demonstrated the bypass blood flow from the anastomosed STA to the cortical vessels including arteries, capillaries, and veins in both MD and non-MD. Interestingly, the anastomosed STA supplied blood flow to a larger cortical area in MD than non-MD. The bypass supplied greater extent of blood flow to the ischemic brain in MD than in non-MD. This difference might be caused by the fact that the perfusion pressure was lower in MD than in non-MD.