Abstract
Background: Extracranial-Intracranial (EC-IC) bypass is increasingly used for treatment of hemodynamic failure in Moya-Moya disease (MMD) or syndrome (MMS). No specific imaging parameter has been established to determine bypass patency in these patients. We sought to determine if vasomotor reactivity (VMR) testing could be correlated with pre-operative angiographic data and predict bypass patency.
Methods: All available pre-operative VMRs and diagnostic angiograms (DSA) in patients with EC-IC direct bypass surgeries performed at our institution from 2007-2019 were reviewed to determine the degree of pre-procedural hemispheric failure (by VMR to the inhalation of carbon dioxide and hyperventilation, abnormal defined by less than 70%) and collateral compensation (categorized as complete vs. incomplete collaterals by DSA). Bypass patency was assessed on follow-up imaging (either immediate in post-op angiogram and delayed subsequent CTA or DSA).
Results: Of the 113 bypass surgeries performed, 68 had pre-operative VMR and DSA. A total of 52 patients were included, in which 16 had both hemispheres operated on (median age 46 [IQR 25], 74% women, 60% with Moya-Moya disease, 51% presented with ischemic stroke, 37% TIA, 10% intracerebral hemorrhage and 1% headache). Pre-operatively, 97% had an abnormal VMR, 24% had incomplete collateralization. A total of 79% had bypass patency (87% immediate, 76% delayed, median time 1 year 8 months [IQR 1 year and 6 months)) on follow up. Patients with patent bypass had significantly lower VMR (27 [SD ± 18.8] vs. mean 36 [SD ± 14.5], p=0.005) and higher likelihood of incomplete collateralization pre-operatively (mean 25.1 [SD ± 16.4] vs. mean 39.2 [SD ± 18.8], p=0.013) as compared to non-patent bypass patients. In multivariate analysis low pre-operative VMR was a significant predictor for bypass patency adjusting for age, presenting stroke type and gender (p=0.01).
Conclusion: Vasomotor reactivity is a non-invasive, low-cost test which predicted angiographic vessel collateralization and bypass patency. Bypass patency remains important predictor of outcomes in this population.