Moyamoya disease (spontaneous occlusion of the circle of willis)

Abstract

Moyamoya is a disease affecting the cerebral arteries, which predisposes individuals to recurrent ischemic attack in association with progressive steno-occlusive change of the intracranial internal carotid arteries and their proximal branches. The disorder is typically characterized by a reduction in blood flow in the major vessels of the anterior circulation of the brain. This results in the development of a compensatory collateral vasculature around the stenosed vessels, near the apex of the internal carotid, on the cortical surface, leptomeninges, and branches of the external carotid artery and the base of the skull. In advanced cases, the posterior circulation is also involved, including the basilar and posterior cerebral arteries. While it was first described as a “hypoplasia of the bilateral internal carotid arteries,” the characteristic appearance of the network of abnormally dilated collateral vessels on conventional angiography was compared to “a puff of cigarette smoke” (Arch Neurol 20(3):288–899, 1969) or “moyamoya” in Japanese. The designation “spontaneous occlusion of the circle of Willis” was recently suggested as an alternative by the International Classification of Diseases (ICD). Moyamoya disease patients are predominantly found in Eastern Asian countries such as Japan and the Republic of Korea. Moyamoya disease patients show bimodal distribution, adult type and pediatric type. Symptom of adult moyamoya patients can be either ischemic or hemorrhagic; nevertheless, pediatric patients usually present with ischemia. In ischemic moyamoya disease, the therapeutic effect of surgical revascularization (extracranial-intracranial bypass) has been well established. Bypass surgery can improve the impaired cerebral hemodynamic state and decrease the recurrent ischemic events. Management of the hemorrhagic moyamoya disease, on the other hand, presents a serious challenge. Despite the extremely high rate of rebleeding attacks, no therapeutic method has been established until recently. In 2013, the 818 A. Yamamoto et al. Japan Adult Moyamoya (JAM) Trial, a multicentered prospective randomized controlled trial, was completed. It has been revealed that bypass surgery significantly decreases the rate of rebleeding attacks and improve the patients’ prognosis during the following 5 years. This epoch-making study is expected to establish a guiding principle for the treatment of hemorrhagic moyamoya disease.