Abstract 66: Prevalence Of Shunting In Patients With Moyamoya

Moyamoya (MMD) is a rare progressive stenosis of anterior cerebral circulation of unknown etiology that occurs at higher prevalence in patients with neurofibromatosis 1, trisomy 21, sickle cell disease (SCD), and East Asians. We hypothesized that vasoactive substances, normally inactivated in the lungs, may escape inactivation through right-to-left shunting and contribute to the development of MMD in at-risk groups. We compared the prevalence of shunting in MMD patients versus controls without MMD. In an IRB-approved, retrospective study we identified 67 MMD patients who had echocardiograms between 1991-2018 and compared the prevalence of potential right-to-left shunting with that of a control group of 123 patients without MMD or stroke from a prior study. In the MMD group, 32 (48%) had potential shunting identified on echocardiogram (23 (34%) intracardiac and 9 (13%) intrapulmonary) versus 29 (24%) potential shunting in our control group (P=0.0006). We also evaluated our MMD patients considering possible bias regarding SCD patients and increased prevalence of pulmonary shunting. In the 43 MMD patients without SCD, 21 (49%) had potential shunting identified on echocardiogram versus 29 (24%) potential shunting in our control group (P=0.0018). In conclusion, these observations support our hypothesis that shunting could contribute to MMD development, possibly through unknown vasoactive substances escaping lung inactivation, subsequently inducing vascular changes in patients with predisposing conditions. This has potential mechanistic and therapeutic implications and will need to be verified in larger prospective studies.