Moyamoya Disease Associated with Graves' Disease and Down Syndrome: A Case Report and Literature Review.

Background: Moyamoya vessels are cerebral vasculopathies characterized by net-like collateral vessel formation at the cerebral basal area and stenosis of the terminal internal carotid artery, proximal middle cerebral artery, and anterior cerebral artery. A diagnosis of Moyamoya disease depends on the bilateral presence of Moyamoya vessels. Moyamoya disease associated with Graves' disease has rarely been reported to be a cause of ischemic events due to hyperthyroidism. However, there are extremely rare cases of Moyamoya disease with concurrent Graves' disease and Down syndrome. We aimed to report such a case, and to compare these cases' clinical features, pathogenesis, and treatment effects to those of the cases of concurrent Moyamoya disease and Graves' disease alone.

Methods: We performed an English literature search using the PubMed database and the keywords Moyamoya, quasi-Moyamoya, Graves' disease, thyrotoxicosis, Down syndrome, and trisomy 21.

Results: Only five cases of Moyamoya disease with Graves' disease and Down syndrome have been reported, including our own. Four patients were female (80%), and all underwent antithyroid therapy and experienced ischemic episodes, including transient ischemic attacks. At the time of their vascular accident, two patients were in a thyrotoxic state; only our patient was in a euthyroid state. The mean age was 15.6 years (standard deviation: 6.1), which was younger than the mean age of 31.4 years (standard deviation: 13) in patients with Moyamoya disease and Graves' disease alone. Down syndrome is commonly associated with abnormal vascular networks due to increased endostatin concentrations or immunological abnormalities such as those that occur in Graves' disease. Graves' disease accelerates the progression of Moyamoya disease and ischemic attacks due to atherosclerosis, enhances sympathetic nervous system activity and immunological changes. As compared to Moyamoya disease patients, patients with concurrent Graves' disease only and Moyamoya disease patients with concurrent Graves' disease and Down syndrome may experience accelerated disease progression or more frequent ischemic attacks.

Conclusion: Early imaging follow-ups and strict control of thyroid function are necessary in such cases; if ischemic attacks have already occurred, revascularization surgery may be effective.