Abstract WP61: A Novel Application of Four-dimensional Magnetic Resonance Angiography Using Arterial Spin Labeling for Assessment of Postoperative Cerebral Hemodynamic Changes in Moyamoya Disease

Introduction: Recently, four-dimensional magnetic resonance angiography without contrast enhancement using arterial spin labeling (ASL-4D MRA) has become available to visualize the intracranial arteries. However, few reports are available about the efficacy of ASL-4D MRA in moyamoya disease (MMD). Hypothesis: We hypothesized that postoperative hemodynamic changes in MMD patients could be evaluated using ASL-4D MRA. Methods: This study included 26 hemispheres of 21 patients who underwent combined direct and indirect revascularization for MMD. ASL-4D MRA was serially performed before and after surgery. We assessed the time phases where signals of the arteries were detected on ASL-4D MRA in order to analyze perioperative changes in cerebral hemodynamics. Results: The signals of the anastomosed arteries on ASL-4D MRA were detected and disappeared at significantly earlier time phase after surgery than before. This change in acute period was moderated in chronic period after surgery. Postoperative hyperperfusion was observed in 12 of 26 hemispheres within 7 days after surgery. The signals of the arteries were detected significantly earlier in hemispheres with hyperperfusion than those without. In cases with hyperperfusion, ASL-4D MRA demonstrated high intensity of peripheral middle cerebral artery (MCA) around anastomosed region in early time phase (Figure). This “early hyperintensity of MCA” was observed in all cases with hyperperfusion and corresponded to the timing of the occurrence of hyperperfusion. Furthermore, this hyperperfusion-specific sign could not be detected by routine TOF MRA. Conclusions: Noninvasive ASL-4D MRA successfully evaluated perioperative dynamic changes of cerebral blood flow and the effect of surgical revascularization in MMD. This next generation modality could also visualize cerebral hemodynamics in cases with postoperative hyperperfusion and would be quite useful for appropriate postoperative management.