Moyamoya disease: visualization of dilated medullary vessels by flow-compensated gadolinium-enhanced MRI

Introduction Moyamoya disease is a rare cerebrovascular occlusive disease of unknown etiology, characterized by stenosis or occlusion of both internal carotid arteries (ICAs) at the supraclinoid portion and an abnormal vascular network (moyamoya vessels)(1). 3-T MR angiography clearly shows moyamoya vessels at the base of the brain (2). Gadolinium-enhanced MRI depicts dilated pial vessels (ivy sign) (3-5). There are also a few case reports regarding dilated medullary vessels demonstrated on gadolinium-enhanced MRI (5). Harada et al. (6) reported transverse lines in the white matter (medullary streaks) demonstrated on T2-reversed MRI at 3-T and speculated that these medullary streaks may represent dilated medullary vessels with stagnant flow. However, to our knowledge, dilated medullary vessels on moyamoya disease have not been investigated in detail nor completely understood. Flow-compensation (FC) is a way to rephase the MR signals of moving spins and is useful to visualize small vessels on gadolinium-enhanced MRI. In this study, we investigated frequency of visualization of dilated medullary vessels in moyamoya disease and the effect of FC technique on the visualization of dilated these vessels.