Asymptomatic Moyamoya Disease

Abstract

Moyamoya disease is an uncommon cerebrovascular disorder that is characterized by progressive stenosis of the supraclinoid internal carotid arteries and its main branches within the circle of Willis. This occlusion results in the formation of a fine vascular network (the moyamoya vessels) at the base of the brain. Moyamoya vessels are the dilated perforating arteries and function as collateral pathways. Recent investigations have rapidly developed our knowledge on basic and clinical aspects in moyamoya disease, including its etiology, pathophysiology, surgical results, and long-term prognosis. Thus, recent epidemiological and genetic studies have suggested the involvement of some genetic factors in its pathogenesis. The potential contribution of infections has also been pointed out, although specific pathogens have not been identified. Pediatric patients with moyamoya disease often develop transient ischemic attacks (TIA) or cerebral infarction, while adult patients also suffer intracranial bleeding. Surgical revascularization such as superficial temporal artery to middle cerebral artery (STA–MCA) anastomosis and indirect bypass improves their cerebral hemodynamics and prevents further ischemic attacks. An on-going multicenter randomized clinical trial is being performed to examine whether surgical revascularization including STA–MCA anastomosis reduces hemodynamic stress on the dilated moyamoya vessels and contributes to prevent further intracranial bleeding [1].