Disruption of Cortical Arterial Network is Associated with the Severity of Transient Neurologic Events After Direct Bypass Surgery in Adult Moyamoya Disease.

Objective: Transient neurologic events (TNEs) frequently occur after revascularization in adult moyamoya disease (MMD). In the present study, we hypothesized that cortical arterial network disruption may be associated with TNE severity after bypass surgery.

Methods: This retrospective study included 76 hemispheres in 45 consecutive adult patients with MMD who underwent direct revascularization surgery at our institution. We classified cortical arterial network disruption grade (NDG) into the following 4 categories based on angiography: NDG 0, >90% of suprasylvian cortical branches of the middle cerebral artery showed anterograde filling; NDG 1, 50%-90%; NDG 2, <50%; and NDG 3, none. TNE severity was assigned 1 of 4 grades based on symptom duration and clinical features: grade 0, none; grade 1, mild; grade 2, moderate; and grade 3, severe. We evaluated multiple clinical characteristics, including NDG, to identify factors that have a significant association with TNE severity.

Results: Of the 73 hemispheres without perioperative ischemic or hemorrhagic complications, the following degrees of TNEs were developed: grade 0, 33%; grade 1, 30%; grade 2, 22%; and grade 3, 15%. We determined that NDG and left-side surgery were significantly associated with TNE severity (P < 0.01 and P = 0.04, respectively). The NDG had excellent interobserver reliability (weighted κ value = 0.96). There were no significant correlations between TNE severity and other clinical backgrounds.

Conclusions: NDG is useful for the prediction of severity of TNEs after revascularization. Disturbed bypass flow spreading may lead to the development of TNEs in adult MMD.