Imaging description

Moyamoya disease is an idiopathic, progressive, occlusive disorder affecting the vessels of the circle of Willis. Although first described in Japan, it is now reported from all over the world [1].

Moyamoya disease features smooth narrowing of the distal internal carotid artery (ICA), often extending to the carotid terminus and proximal portions of the anterior and middle cerebral arteries (ACA and MCA). In contrast, moyamoya syndrome refers to a phenomenon similar in clinical presentation and anatomic findings but caused by various systemic disease entities. These include a long list of potential causes including hematological disorders (sickle cell disease, SLE, aplastic anemia), congenital syndromes (neurofibromatosis, Down’s syndrome, tuberous sclerosis), and other vascular diseases (coarctation of aorta, radiation injury).

The imaging features on cross-sectional studies are dependent on the presenting features. Ischemic presentations are common in children, while adults more commonly present with hemorrhagic manifestations. CT and MRI help demonstrate the ischemic infarcts, which are commonly located in the watershed distribution between the ACA and MCA or MCA and posterior cerebral artery (PCA) territories. Infarcts of varying ages may be identified and generally related to progressive, ongoing ischemia. Generalized brain atrophy is not uncommon and occurs due to a chronic state of ischemia. On occasion, this atrophy is unilateral, if the disease is asymmetrically more advanced on one side compared to the other (Fig. 13.1).