Objective: Moyamoya syndrome (MMS) is a subset of moyamoya disease (MMD) with a systemic comorbidity. Due to the lack of direct comparisons between various MMS subgroups and their MMD counterparts, we aimed to analyze differences in stroke-related outcomes between MMS subgroups and patients with MMD through propensity score matching (PSM).

Methods: We analyzed the National Inpatient Sample (NIS) from 2011 to 2020 for patients with MMD and common MMS-related comorbidities: Down syndrome (DS), sickle-cell disease (SCD), and type 1 neurofibromatosis (NF1). PSM was performed to match patients of each MMS subgroup to patients with MMD only, controlling for stroke risk factors. Rates of ischemic strokes, hemorrhagic strokes, and transient ischemic attacks (TIAs) were evaluated after matching.

Results: A total of 10,652 patients with a moyamoya diagnosis were identified: 7971 with MMD only, 2202 with MMS-SCD, 162 with MMS-NF1, and 317 with MMS-DS. PSM for MMD only and MMS-SCD resulted in 630 matched pairs. After matching, univariate analysis showed that patients with MMS-SCD had significantly lower rates of ischemic strokes (8.9% vs. 17.9%; P = 0.001), hemorrhagic strokes (5.1% vs. 8.1%; P = 0.031), and TIAs (2.2% vs. 4.6%; P = 0.020) than did patients with MMD only. For the MMS-DS subgroup, 92 matched pairs showed significantly lower rates of TIAs than did patients with MMD only (0% vs. 6.5%; P = 0.013). Comparing 54 matched pairs of patients with MMD only and patients with MMS-NF1 showed no significant differences in stroke-related outcomes.

Conclusions: Patients with MMS-SCD had significantly lower rates of acute ischemic stroke, hemorrhagic stroke, and TIA compared with patients with MMD only. Future research should consider the source of these differences in improving stroke prevention in patients with MMD.