Vascular remodeling of the circle of Willis in moyamoya disease

OBJECTIVES: A positive (outward) remodelling pattern in patients with typical atherosclerotic disease was recognised using magnetic resonance imaging (MRI). In this report, the outer diameter of the circle of Willis was evaluated in patients with moyamoya disease, and its remodelling pattern was verified. METHODS: A total of 18 consecutive patients with moyamoya disease were included in this analysis. The diameter of the terminal portion of the internal carotid artery (ICA) (C1), proximal portion of the middle cerebral artery (MCA) (M1) and proximal portion of the anterior cerebral artery (A1) was evaluated using fast imaging employing steady-state acquisition (FIESTA) imaging. The outer diameter was estimated using these images, and compared with the control group, and the correlation with magnetic resonance angiography (MRA) scores was calculated for patients with moyamoya disease. RESULTS: The mean diameter of the moyamoya patient group on FIESTA was significantly lower than that of the control group in the C1, M1 and A1 (P < 0.0001). The M1 diameter on the FIESTA image showed a strong correlation with the moyamoya disease MRA score (y = (0.53x+2.31; R = 0.72), whereas the C1 diameter on the FIESTA image showed only a weak correlation (y = (0.16x+2.47; R = 0.21). CONCLUSION: We found that the outer diameter of all the vessels around the C1 was generally reduced in patients with moyamoya disease. Diameter of the MCA especially decreases as the disease progresses, similar to the negative (constrictive) remodelling pattern.