Improvement in cognitive decline after indirect bypass surgery in adult moyamoya disease: implication of 15O-gas positron emission tomography

Purpose To investigate the characteristics of patients with moyamoya disease (MMD) who show improvement in their cognitive decline after bypass surgery by analyzing the hemodynamic and metabolic parameters of O-15-gas positron emission tomography (PET). Materials and methods We retrospectively analyzed adult patients with MMD who were evaluated with PET and cognitive tests before and approximately one year after indirect bypass surgery. The PET parameters of the left Rolandic area were compared between patients who did and did not show improvement in their cognitive decline. Results Of the 19 patients analyzed, fourteen (74%) showed improvement in either the verbal or performance intelligence quotient (VIQ or PIQ). Three out of four patients with perioperative infarction experienced significant cognitive decline. The preoperative oxygen extraction fraction (OEF) was significantly higher in patients who showed improvement in their cognitive decline in terms of the PIQ than in those patients who did not (P = 0.03). The postoperative increase in the cerebral metabolic rate of oxygen (CMRO2) was significantly higher in patients who showed improvement in their cognitive decline in terms of the VIQ than in those who did not (P = 0.02). Conclusion Adult patients with MMD might show improvement in their cognitive decline after successful indirect bypass surgery if they have a severely increased regional OEF before the surgery and an increased regional CMRO2 after the surgery.