Background: A few cases of moyamoya syndrome associated with thyrotoxicosis have been reported. However, studies on the association of hyperthyroidism with moyamoya syndrome are insufficient.

Case Report: Here we report a case of hyperthyroidism associated with moyamoya syndrome in a 41-year-old woman with aphasia and right side weakness. Brain imaging revealed acute cerebral infarction of left middle cerebral artery territory and occlusion of bilateral distal internal carotid arteries.

Conclusion: Antithyroid medication stabilized the patient’s neurologic deterioration, suggesting that thyrotoxicosis could aggravate acute cerebral infarction caused by moyamoya syndrome.

Acute stroke in Moyamoya disease caused by Grave's disease