OBJECTIVETo investigate the characteristics of collateral circulation in adult moyamoya disease (MMD).

METHODSThe clinical data were collected from all adult patients with MMD undergoing digital subtractive angiography (DSA) in our department from 2006 to 2016. Based on the imaging findings, the patients were divided into ischemia group and bleeding group. A double-blind analysis was conducted of the CT or magnetic resonance imaging findings and the severity of the disease was graded using the modified Suzuki score (mSS). We classified the anastomotic networks in MMD into the superficial meningeal type and deep parenchymal type. The superficial meningeal type was further classified into the leptomeningeal and the durocortical networks, and the deep parenchymal networks into subependymal networks and the inner striatal and inner thalamic networks.

RESULTSNo significant difference was found in the distribution of mSS scores between the hemorrhage group and the ischemic group (Χ=5.812, v=5, P=0.325), but the posterior communicating artery and internal carotid artery diameter ratio (Pcom/ICA ratio) was significantly greater in the hemorrhage group (t=2.119, v=108, P=0.036). The Pcom/ICA ratio differed significantly among the groups with different mSS scores (f=8.924, P=0.00), higher in groups with mSS scores of 3, 4 and 5. The incidence of anterior choroidal artery dilation differed significantly between hemorrhage and ischemic groups (Χ=11.79, P=0.001). The incidences of durocortical networks (Χ=0.327, P=0.567) and subependymal networks (Χ=0.011, P=0.917) were comparable between hemorrhage group and ischemic groups, but the incidence of leptomeningeal networks (P=0.018) and inner striatal and inner thalamic networks (Χ=7.551, P=0.006) differed significantly between the two groups.

CONCLUSIONThe collateral circulation vascular system is an important component of cerebral blood flow in MMD patients and varies from patient to patient. Patients with MMD exhibit increased Pcom/ICA ratio with abnormal expansion of the anterior choroidal artery, and the leptomeningeal networks and the inner striatal and inner thalamic networks are independent risk factors for cerebral hemorrhage.