ABSTRACT NUMBER: ESOC2026A1012 A CASE OF BILATERAL ACUTE WATERSHED INFARCTS DUE TO MOYAMOYA ANGIOPATHY, GRAVES’ DISEASE AND DOWN SYNDROME

Abstract Background and aims Moyamoya angiopathy is a progressive cerebrovascular disorder characterised by stenosis of the terminal carotid arteries leading to the development of a delicate network of collateral cerebral blood vessels prone to hypoperfusion or haemorrhage. Thyrotoxicosis due to Graves’ Disease can impact on Moyamoya angiopathy through haemodynamic and vascular effects. We present a case of the rare association of Graves’ disease in patients with concurrent Moyamoya syndrome and Down Syndrome. Methods A 16 year old male with Down Syndrome presented with recurrent left limb weakness and dysarthria. CTBrain showed no acute infarct. CT Angiogram reported bilateral ICA, MCA and ACA stenosis. MR brain and angiogram revealed bilateral acute watershed infarcts with bilateral occlusive disease. Dual antiplatelet therapy was initiated. Cerebral angiography confirmed Moyamoya angiopathy. Acetazolamide imaging showed preservation of cerebrovascular reserve. Persistent sinus tachycardia prompted thyroid function tests which revealed a thyrotoxic pattern. Results Interdisciplinary team members included Stroke and Endocrinology physicians, Neurosurgery and multidisciplinary stroke rehabilitation therapists. Free T4 >40pmol/L, T3 >30pmol/L, TSH <0.01mIU/L, Anti-TPO Ab +, TRAB +, without evidence of thyroid eye disease, goitre, tremor or weight loss. Carbimazole was immediately commenced with symptoms settling over time. Definitive surgical therapy is planned on stabilisation of thyroid function. Conclusions Recognition of the association of Moyamoya angiopathy and Graves’ Disease with Down Syndrome and an interdisciplinary approach was important to the management of this young onset stroke patient. Early optimisation of thyroid function is essential to stabilise the disease process, reduce the risk of stroke recurrence and facilitate timely surgical intervention. Conflict of interest Dr Deirdre McCartan: Nothing to disclose. Dr Mergani Abdelwhab: Nothing to disclose. Dr Caoimhe Casey: Nothing to disclose. Dr Barry Moynihan: Nothing to disclose.