Encephalomyosynangiosis (EMS) is a surgical procedure performed most commonly in children with moyamoya disease as a form of indirect revascularization to bypass the occlusive terminal internal carotid and/or circle of Willis vessels .
It entails dissecting strips of vascularized temporalis muscle and subjacent galeal flap and laying them directly onto the pial surface of the brain. Revascularization occurs as a result of angiogenesis driven by local hypoperfusion and ischemia .
Encephaloduroarteriomyosynangiosis (EDAMS) differs from EMS in so far as it also includes branches of the superficial temporal artery, whereas encephaloduroarteriosynangiosis (EDAS) only entails laying branches of the superficial temporal artery onto the brain .
In EMS, EDAS and EDAMs, and unlike superficial temporal artery to middle cerebral artery (STA-MCA) bypass, no direct anastomosis is created.