Abstract Number ‐ 250: Case Series of Moyamoya Patients Diagnosed on Hyperacute Imaging

Abstract

Introduction Moyamoya disease is the idiopathic bilateral progressive stenosis of the anterior circulation arteries at the skull base, followed by the compensatory formation and proliferation of collateral small vessel arteries typically in the lenticulostriate region. The clinical diagnosis is made by neurovascular imaging with digital subtraction angiography being the gold standard of diagnosis. The term moyamoya syndrome is used when the formation of collateral arteries occur after unilateral vasculopathy or if the progressive stenosis occurs in the setting of known associated conditions such as sickle cell disease or prior cranial radiation treatment. For patients who have undiagnosed moyamoya syndrome, stroke symptoms may be the first presentation of the underlying disease. Methods We present a case series of 15 patients who arrived to our tertiary care hospital from December 2014 to July 2022. Results The majority of the patients were women with the average age of 43 years old. Patients were admitted with NIHSS ranging from 0 to 14, and two patients presented with signs suggestive of MCA syndrome. Including major ischemic stroke risk factors, five patients also had differentials of antiphospholipid antibody syndrome, connective tissue disorder, vasculitis, and congenital rubella as possible underlying conditions promoting the vasculopathy. Morbidity was high for moyamoya patients, with an average modified Rankin scale of 2 at discharge. Eleven patients had unknown moyamoya history at time of arrival and were identified based on hyperacute diagnostic CT angiography during stroke evaluation. Five patients were initially diagnosed as large vessel occlusion on CT angiography. Given the speed at which IV thrombolysis and mechanical thrombectomy decisions are made, patients with moyamoya vasculopathy require rapid and accurate interpretation of CT findings that distinguish them from standard large vessel occlusion patients and prevent the potentially catastrophic consequences of inappropriate treatment. Conclusions The pathophysiology leading to moyamoya disease is not well understood, but the stenosis process of major arteries is thought to be secondary to irregular hyperplasia of the tunica media, followed by compensatory growth of small collateral vessels. This collateralization leads to micro‐aneurysm formation in the small perforator branches. Moyamoya patients are at an increased risk of hemorrhage, representing a contraindication to IV thrombolysis, and, if mechanical thrombectomy is attempted, risk of possible large vessel rupture. In our case series, the 15 patients did not receive IV thrombolysis or mechanical thrombectomy based on appropriate diagnosis of moyamoya vasculopathy at time of emergency CT angiography, subsequently confirmed by elective, catheter cerebral angiography.