Direct versus indirect bypasses for adult ischemic-type moyamoya disease: a propensity score-matched analysis

OBJECTIVE The optimal surgical modality for moyamoya disease (MMD) remains unclear. The aim of this study was to compare the surgical effects of direct bypass (DB) and indirect bypass (IB) in the treatment of adult ischemic-type MMD. METHODS Adult patients with ischemic-type MMD who underwent either DB or IB from 2009 to 2015 were identified retrospectively from a prospective database. Patients lost to follow-up or with a follow-up period less than 12 months were excluded. Recurrent stroke events and modified Rankin Scale (mRS) scores at the last follow-up were compared between the 2 surgical groups after 1:1 propensity score matching. RESULTS A total of 220 patients were considered, including 143 patients who underwent DB and 77 patients who underwent IB. After propensity score matching, 70 pairs were obtained. The median follow-up period was 40.5 months (range 14-75 months) in the DB group and 31.5 months (range 14-71 months) in the IB group (p = 0.004). Kaplan-Meier analysis showed that patients who received DB had a longer stroke-free time (mean 72.1 months) compared with patients who received IB (mean 61.0 months) (p = 0.045). Good neurological status (mRS score ≤ 2) was achieved in 64 patients in the DB group (91.4%) and 66 patients in the IB group (94.3%), but there was no significant difference (p = 0.512). CONCLUSIONS Although neurological function outcome was not determined by the surgical modality, DB is more effective in preventing recurrent ischemic strokes than IB for adult ischemic-type MMD.