Superficial Temporal Artery-Middle Cerebral Artery Bypass Combined with Pedicled Temporoparietal Fascial Flap Onlay for Moyamoya Disease: Technical Anatomy and Extended Cohort Outcomes

Background Pedicled temporoparietal fascial flap (TPFF) onlay has been used as an indirect component of combined revascularization for moyamoya disease (MMD). We describe the technical anatomy and evaluate an extended institutional cohort. Methods We retrospectively studied adults admitted from 2018 to 2024 with angiographically confirmed MMD, Suzuki stage III or IV, and modified Rankin Scale (mRS) score of 3 or less. Fifty-five patients underwent superficial temporal artery-middle cerebral artery bypass with TPFF onlay; 23 who declined surgery received medical management as a self-selected observational comparison. All completed at least 24 months of follow-up. Results Direct bypass patency was 54 of 55 (98%). At 1 week, perfusion-weighted imaging was qualitatively classified as improved in 51 patients (93%) by integrated visual assessment of mean transit time, time to peak, cerebral blood flow, cerebral blood volume, and color maps. On each patient's latest follow-up angiogram, 47 (85%) had Matsushima grade A collateralization after repeat review by 2 senior neurosurgeons. In the nonrandomized comparison, non-surgical management was associated with a higher observed stroke hazard (adjusted hazard ratio, 7.12; 95% confidence interval, 2.61-19.42; P < 0.001). mRS scores improved after surgery. The 12-patient hemorrhagic subgroup was underpowered for equivalence assessment. No perioperative deaths occurred. Conclusions In this selected retrospective cohort, combined bypass and TPFF onlay was associated with high patency, later indirect collateral formation, and favorable functional outcomes. The self-selected comparison does not establish a causal treatment effect, and superiority over other combined techniques was not evaluated.