Direct Bypass Reduces the Risk of Recurrent Hemorrhage in Moyamoya Syndrome, But Effect on Functional Outcome Is Less Certain

See related article, p 1415.This important study by Miyamoto et al1 provides the strongest and best evidence to date that direct revascularization, via external carotid to internal carotid artery bypass, reduces the risk for recurrent hemorrhage in adult patients presenting with hemorrhage secondary to Moyamoya syndrome. However, surgical complication rates had to be essentially zero to achieve this benefit, and whether surgery resulted in better functional outcome is not clear from the present data.Moyamoya syndrome is characterized by idiopathic, often bilateral, often progressive occlusion of the terminal internal carotid artery and a secondary hypertrophic and proliferative response by the lenticulostriate arteries that give the condition its name.2,3 It is commonly referred to as a disease, yet it is certain that the underlying occlusive vasculopathy is multifactorial and that the proliferative response may be variable, particularly in non-Asian populations.4–6 The syndrome has a bimodal presentation in Asia, with children generally presenting with ischemic symptoms and adults with hemorrhage.7 In North America and Europe, however, the syndrome is most common in women in their third, fourth, and fifth decades, presenting with ischemic symptoms.8–11 One explanation for the difference in presentation between Asian and North …