MON-353 - The Graves-Moyamoya Association: Cerebrovascular Sequelae of Thyrotoxicosis

Background

Moyamoya disease is a rare, progressive cerebrovascular disorder characterized by stenosis of the intracranial internal carotid arteries and development of collateral vessels. An association between Moyamoya disease and autoimmune thyroid disorders, particularly Graves’ disease, has been reported, with thyrotoxicosis implicated as a potential trigger for ischemic events. Recognition of this relationship is critical, as uncontrolled hyperthyroidism may accelerate cerebrovascular pathology.

Case Presentation

A 39-year-old woman with a five-year history of hyperthyroidism presented for endocrine follow-up after hospitalization for thyroid storm manifested by palpitations and severe thyrotoxicosis. She had previously been treated intermittently with antithyroid medications, including methimazole and propylthiouracil, with variable adherence due to medication intolerance. On initial evaluation, she reported palpitations, tremors, heat intolerance, insomnia, and irregular menses. Examination was notable for bilateral exophthalmos. Laboratory evaluation showed suppressed TSH ( < 0.005 uIU/mL) with elevated thyroid hormones (free T4 3.06 ng/dL), and later testing confirmed Graves’ disease with elevated TSI (7.39 IU/L) and TRAb antibodies. Thyroid ultrasound demonstrated a mildly enlarged, heterogeneous gland without nodules.

Despite adjustment of antithyroid therapy and beta-blockade, the patient developed episodic left upper-extremity numbness and heaviness several months later, prompting emergency evaluation. She was subsequently hospitalized again after recurrent paresthesias of the hands, at which time neuroimaging revealed findings concerning Moyamoya disease or prior ischemic stroke. Laboratory evaluation revealed biochemical hypothyroidism (TSH 11 µIU/mL), attributed to overtreatment with methimazole. Methimazole was discontinued. She was referred to neurology for ongoing management. Her neurologic symptoms improved, and she remains under close multidisciplinary surveillance.

Discussion

Multiple studies demonstrate a higher prevalence of Graves’ disease among patients with Moyamoya disease, suggesting a shared autoimmune or genetic predisposition. Thyrotoxicosis may exacerbate cerebral hypermetabolism and vascular instability, increasing the risk of ischemic events. Women appear disproportionately affected, and neurologic complications often occur during periods of poor thyroid control.

Conclusion

This case highlights the importance of maintaining strict biochemical control of Graves’ disease and maintaining a high index of suspicion for cerebrovascular complications in patients presenting with neurologic symptoms. Early recognition of the Graves–Moyamoya association may reduce morbidity through prompt neurologic evaluation and coordinated care.

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