Abstract MP9: Incidence and Outcomes of Posterior Circulation Involvement in Moyamoya Disease

Moyamoya disease (MMD) is a progressive, occlusive disease of the internal carotid arteries and their proximal branches, with the subsequent development of an abnormal vascular network of small, weak blood vessels that are prone to rupture. Steno-occlusive changes in the posterior cerebral arteries (PCA) may contribute to worse outcomes in MMD patients, however, there is a paucity of information on the incidence and natural history of MMD patients with PCA disease. We retrospectively reviewed the charts of patients with MMD treated between 1987 and 2019. Demographics, peri-operative outcomes, and radiological phenotypes were recorded for 450 patients. PCA disease was scored as either 0 (no disease), 1 (mild), 2 (moderate), or 3 (severe, or occluded). Out of 450 patients, 164 (34.4%) had concurrent PCA disease. In patients with PCA disease, the extent of occlussion was mild in 56 (34%), moderate in 41 (25%), and severe in 67 (40.9%) patients. In total, there were 319 females (70.9%), with a higher proportion of female MMD patients having severe or moderate PCA disease (p=0.038). Patients with severe and moderate PCA disease had higher Suzuki grades (p Over a mean follow-up of 6.94±4.16 years, 28 patients (8.86%) developed new or progressive PCA disease. Bilateral disease was present in 66 patients (14.7%) and was associated with higher Suzuki grades (p PCA disease involvement is associated with higher rates of ischemic peri-operative complications and poor functional outcomes likely due to reduced collateral flow. Progression of PCA disease is not uncommon. Future studies are needed to assess the impact of PCA disease progression on long-term outcomes.