Negative Remodeling of Carotid Canal during Spontaneous Disease Progression in Moyamoya Disease

Objective This study was designed to observe the changes in the carotid canal over time by measuring the carotid canal diameter longitudinally in adult patients with moyamoya disease in whom disease stage progressed spontaneously. Methods Of 70 adult patients with moyamoya disease, 10 adult patients on 15 sides with spontaneous progression of the disease stage during conservative follow-up were included in this study. Another 10 moyamoya cases on 15 sides were selected as the controls without disease progression. All patients were followed up for at least 60 months after the progression of disease stage was confirmed. In addition, 5 patients who underwent microvascular decompression were included as healthy controls. The carotid canal diameter was measured with bone window computed tomography (CT) and source images of time-of-flight magnetic resonance angiography at initial presentation, and then were serially monitored with the latter. Results There was a significant correlation between the values obtained from CT and magnetic resonance imaging (R2 = 0.992, P < 0.001). The carotid canal diameter in moyamoya disease at initial presentation was 4.29 ± 0.61 mm, being smaller than 5.20 ± 0.51 mm in healthy controls (P < 0.01). In response to disease progression, the carotid canal diameter started to decrease at 6 months after disease progression was confirmed, and reduced to about 85% of the original level during 60 months (P < 0.01). The phenomenon was not observed in patients without disease progression. Conclusions The carotid canal diameter can decrease in response to disease progression even in adult moyamoya disease. “Negative” bone remodeling may play a key role in this unique phenomenon.