Hemodynamic Changes in Contralateral Unoperated Hemispheres Following Unilateral Combined Bypass Surgery in Adult Patients With Moyamoya Disease

BACKGROUND AND OBJECTIVES: Hemodynamic changes in the contralateral hemisphere after unilateral bypass surgery in patients with moyamoya disease (MMD) remain controversial. We aimed to investigate the hemodynamic changes in the contralateral hemisphere after unilateral combined bypass surgery in adult patients with bilateral MMD. METHODS: This retrospective study included 151 consecutive adult patients who underwent unilateral combined bypass surgery for bilateral MMD between August 2010 and December 2018. Clinical outcomes in the patients and hemodynamic changes in the operated and unoperated hemispheres were evaluated with the modified Rankin Scale and acetazolamide-challenged single-photon emission computed tomography, respectively, at 6 months after surgery. Posterior circulation involvement was identified in 47 operated hemispheres (31.1%) and 17 contralateral hemispheres (11.3%). Bilateral involvement was observed in 14 cases (9.3%). RESULTS: Clinical status improved 6 months after surgery (P < .001). In the operated hemisphere, basal cerebral blood flow (CBF) substantially increased across all the vascular territories (all P ≤ .006). Cerebrovascular reserve significantly increased in all territories (all P ≤ .03), except in the posterior cerebral artery territory. In the contralateral unoperated hemisphere, CBF increased significantly in some territories of the anterior, anterior middle, and posterior cerebral arteries (all P ≤ .04), with no significant change in terms of cerebrovascular reserve. CONCLUSION: CBF in the contralateral unoperated hemisphere significantly increased after surgery. These findings suggest that unilateral revascularization can improve bilateral hemodynamics. Surgical intervention should be considered selectively for the hemispheres with symptomatic manifestations and hemodynamic instability, instead of mandatory staged bilateral operations.