Effect of thin-split encephalomyosynangiosis on transient neurological events in revascularization surgery for pediatric patients with moyamoya disease

OBJECTIVE Transient neurological events (TNEs) are among the most important events after revascularization surgery in pediatric patients with moyamoya disease (MMD). Although hemodynamic changes and crying are representative factors of TNEs, brain compression by encephalomyosynangiosis (EMS) is another important cause of TNEs. Therefore, the authors assumed that making the EMS as thin as possible reduces the frequency of TNEs. However, thin-split EMS can lead to insufficient development of collateral vessels. This study aimed to evaluate the effects of thin-split EMS in combined revascularization surgery on postoperative outcomes in pediatric patients with MMD. METHODS The authors retrospectively included 56 consecutive combined revascularization surgeries in the anterior cerebral circulation in pediatric patients with MMD. These surgeries were classified into the former group and thin-split EMS group. The temporal muscle was halved in the former EMS group and split as thinly as possible in the thin-split EMS group. The authors performed between-group comparisons of postoperative stroke events and TNEs during the acute period and the development of collateral flow and stroke events during the chronic period. RESULTS Former and thin-split EMS procedures were performed in 37 and 19 patients, respectively. TNEs without crying or hemodynamic changes were observed significantly less frequently in the thin-split EMS group than in the former EMS group (0 [0.0%] in the thin-split EMS group vs 9 [24.3%] in the former EMS group, p = 0.021). There were no significant between-group differences in the development of indirect bypass during the chronic period (good: 34 [91.9%] and poor: 3 [8.1%] in the former EMS group vs good: 16 [84.2%] and poor: 3 [15.8%] in the thin-split EMS group; p = 0.397). Additionally, there were no significant between-group differences in the incidence of chronic clinical events, including death or stroke. CONCLUSIONS Thin-split EMS can reduce TNEs that do not accompany crying or hemodynamic changes. Furthermore, the procedure has sufficient prevention effects against stroke events during the chronic postoperative period in pediatric patients with MMD.