Moyamoya Disease: Current Concepts

Moyamoya disease is a disease of the cerebral vessels, which is characterized by narrowing of the intracranial vessels as they emerge from the base of the skull, and hypertrophy of fine collateral vessels in response to this vessel narrowing. Moyamoya means the puff of smoke in Japanese, and refers to the appearance of the abnormal fine collateral vessels appearing on cerebral angiography in patients with this condition. The most commonly affected vessels are located in the anterior circulation and include the distal intracranial internal carotid artery, proximal middle cerebral artery, and proximal anterior cerebral artery. Moyamoya disease is progressive and the underlying cause is unknown. The stenotic and occlusive process often begins unilaterally, but true moyamoya disease inevitably progresses to involve the cerebral vessels bilaterally. Patients usually present to medical attention in two distinct age groups. One group of patients presents in childhood and the other group presents in adulthood. There are also two distinct clinical presentations. One group of patients presents with intracranial hemorrhage, most commonly in the basal ganglia or in the ventricles, and sometimes in the subarachnoid space. The other group of patients presents with ischemic symptoms with either transient ischemic attacks or with cerebral infarctions. These infarctions can either be deep perforating artery infarctions, watershed infarctions, or large arterial branch infarctions. Silent infarctions can also be found in some patients at the time of initial presentation, and occasionally patients can present with decreased cognitive function. The condition was first described in Japan, and much of the published literature describing the condition and what is known about it to date, has been published by Japanese investigators. It has subsequently been recognized that moyamoya disease is a cause of stroke and intracerebral hemorrhage in Western as well as in Asian populations. Treatment of the condition usually consists of one of two types of revascularization surgery which are termed indirect and direct revascularization. Indirect revascularization involves placing vascularized tissue fed by the external carotid system on to the surface of the brain to allow collateral networks to form and reroute blood flow around the obstructed vessels at the base of the brain. Direct revascularization most commonly utilizes direct microvasular anastomosis between the superficial temporal and the middle cerebral artery (STA-MCA) in moyamoya patients. This paper reviews the current state of knowledge about the disease and also discusses current management strategies. Categories: Neurosurgery