Stenosis Severity-Dependent Shrinkage of Posterior Cerebral Artery in Moyamoya Disease

Objective: The involved carotid forks in moyamoya disease (MMD) will show decreases in both luminal caliber and outer diameter. The present study aimed to clarify the changes in the outer diameter associated with luminal stenosis/occlusion of the posterior cerebral artery (PCA) in patients with MMD. Methods: The present study included 24 pediatric and 48 adult patients with MMD and 17 healthy adult controls. Using magnetic resonance angiography, the degree of PCA involvement was classified into 3 grades: grade 0, normal; grade 1, stenotic; and grade 2, occluded. Using 3-dimensional constructive interference in steady state, the outer diameters were quantified in the P2 segment. All the patients were followed up to identify the disease progression in the PCA. Results: The outer diameter of the P2 segment significantly decreased in a stepwise fashion in parallel with the severity of the luminal stenosis. In pediatric patients, the outer diameters of the P2 segments were 2.0 ± 0.26 mm, 1.5 ± 0.42 mm, and 0.87 ± 0.15 mm in those with grade 0, 1, and 2, respectively (P < 0.001). In adult patients, the outer diameters of the P2 segments were 2.0 ± 0.34 mm, 1.5 ± 0.34 mm, and 1.1 ± 0.17 mm in those with grade 0, 1, and 2, respectively (P < 0.001). We found no significant difference between grade 0 PCA of the adult patients and the PCA of the healthy controls (P = 0.92). Disease progression led to further arterial shrinkage of the P2 segment (n = 4). Conclusions: The results of our study have shown that the involved PCA demonstrates, not only luminal stenosis, but also arterial shrinkage in MMD. This finding strongly suggests that the underlying mechanism in the development of MMD is common in both the carotid fork and PCA.