Chronologic Evaluation of Cerebral Hemodynamics by Dynamic Susceptibility Contrast Magnetic Resonance Imaging After Indirect Bypass Surgery for Moyamoya Disease

Although indirect bypass surgery is an effective treatment option for patients with ischemic-onset moyamoya disease (MMD), the time point after surgery at which the patient's hemodynamic status starts to improve and the time point at which the improvement reaches a maximum have not been known. The objective of the present study is to evaluate the hemodynamic status time course after indirect bypass surgery for MMD, using dynamic susceptibility contrast–magnetic resonance imaging (DSC-MRI). We retrospectively analyzed the cases of 25 patients with MMD (37 sides; mean age, 14.7 years; range, 3–36 years) who underwent indirect bypass surgery and repeated DSC-MRI measurement within 6 months after the operation. The difference in the mean transit time (MTT) between the target regions and the control region (cerebellum) was termed the MTT delay, and we measured the MTT delay's chronologic changes after surgery. The postoperative MTT delay was 1.81 ± 1.16 seconds within 1 week after surgery, 1.57 ± 1.01 at weeks 1–2, 1.55 ± 0.68 at weeks 2–4, 1.32 ± 0.68 at months 1–2, 0.95 ± 0.32 at months 2–3, and 0.77 ± 0.33 at months 3–6. Compared with the preoperative value (2.11 ± 0.98 seconds), the MTT delay decreased significantly from 2 to 4 weeks after surgery (P < 0.05). The amelioration of cerebral hemodynamics by indirect bypass surgery began soon after surgery and gradually reached a maximum at 3 months after surgery. DSC-MRI detected small changes in hemodynamic improvement, which are suspected to be caused by the initiation of angiogenesis and arteriogenesis in the early postoperative period.