Moyamoya Syndrome: A Window of Moyamoya Disease

Abstract

Moyamoya-like vasculopathy develops in association with various systemic diseases and conditions, which is termed moyamoya syndrome. Relatively common diseases and conditions are related to moyamoya syndrome, including neurofibromatosis type 1, Down syndrome, thyroid disease, and cranial irradiation. Moyamoya syndrome shares phenotypical characteristics with idiopathic moyamoya disease. However, they differ in other details, including clinical presentations, natural history, and treatment considerations. The study of moyamoya syndrome can provide clinicians and researchers with valuable knowledge and insight. Although it is infrequently encountered in clinical practice, moyamoya-like vasculopathy can severely complicate outcomes for patients with various underlying diseases when the clinician fails to expect or diagnose moyamoya syndrome development. Furthermore, moyamoya syndrome could be used as a doorway to more enigmatic moyamoya disease in research. More comprehensive survey and investigation are required to uncover the secrets of all the moyamoya-like phenomena.

Keywords: Down syndrome; Moyamoya syndrome; Neurofibromatosis; Radiation; Thyroid disease.

Fig. 1. Images of a boy with neurofibromatosis type 1. A : Magnetic resonance image (MRI) taken at age 7 revealed a thickened optic chiasm with gadolinium enhancement, suggesting the presence of an optic glioma. The boy experienced symptomatic progression of the optic glioma and received cranial irradiation (50.4 Gy) for treatment at age 9. B : Magnetic resonance angiography (MRA) was taken 4 years after the radiation therapy. Note the luminal narrowing of bilateral middle cerebral arteries (right side more severe) and the invisible horizontal portion of the right anterior cerebral artery. C : A markedly decreased vascular reserve in the right hemisphere was shown after infusion of diamox in single photon emission computed tomography. D : A delayed time-to-peak in the right hemisphere was also observed in a perfusion MRI. At that time, the patient was asymptomatic and no treatment was recommended. One year later, the patient began to complain of morning headaches, with increasing intensity over time. Encephaloduroarteriosynangiosis was performed on the right side. After surgery, the patient was free of headaches.

Fig. 2. A 9-year-old girl with Down syndrome had recurrent vomiting for 2 years. Examination of gastrointestinal system revealed no causes of the vomiting. A : A brain magnetic resonance image (MRI) was taken and an old small infarction was found in the left anterior watershed zone. The left middle cerebral artery trunk was invisible (not shown). B : A delayed time-to-peak in the left middle cerebral artery territory was observed in perfusion MRI. C and D : A subsequent angiography revealed a normal-looking right internal carotid artery and a near occlusion of left distal internal carotid artery with minute collateral vessel formation. Moyamoya syndrome was diagnosed. Although it was unclear that her vomiting was related to the cerebral vasculopathy, a pre-existing infarction warranted a surgical intervention. Encephaloduroarteriosynangiosis was performed on the left side. After surgery, her vomiting frequency decreased significantly. This patient illustrates the difficulty in evaluating neurological symptoms in Down syndrome patients.