Direct Bypass Surgery for Moyamoya and Steno-occlusive Vasculopathy: Clinical Outcomes, Intraoperative Blood Flow Analysis, Long-term Follow-up, and Long-term Bypass Patency in a Single Surgeon Case Series of 162 Procedures.

BACKGROUND: Cerebral extracranial-intracranial (EC-IC) direct bypass is a commonly used procedure for the treatment of cerebral hypoperfusion secondary to chronic steno-occlusive vasculopathy. We sought to determine clinical outcomes, intraoperative blood flow analysis, long term follow up, and long term patency rates from a single surgeon's series of direct cerebral bypass for moyamoya disease, moyamoya syndrome, and steno-occlusive disease. METHODS: We reviewed clinical, demographic, operative and neuroimaging records for all patients who underwent a direct EC-IC bypass by the senior author between August 1999 and November 2020. Primary outcomes analyzed were functional long-term outcomes (by modified Rankin score [mRS]), surgical complications, and short-term and long-term bypass patency. RESULTS: A total of 162 revascularization procedures in 124 patients were performed. Mean clinical follow up time was 2 years 11 months. The combined immediate and long term postoperative stroke and/or intracerebral hemorrhage rate was 6.2%. There were 17 bypasses (10%) that were found to be occluded at long-term follow-up, all but one were asymptomatic. Long-term graft occlusion was correlated with presence of complete collateralization on preoperative angiography but not cut flow index (CFI). Overall, patients had a significant clinical improvement with a mean mRS score 1.8 preoperatively and 1.2 postoperatively. CONCLUSIONS: In our consecutive series of patients treated with direct EC-IC cerebral bypass, there was significant improvement in functional outcome as measured by the mRS. The long term patency rate was 90%. There was a statistically significant correlation between complete or incomplete angiographic collateralization patterns and long-term bypass occlusion. There was no correlation between bypass type, clinical syndrome, or CFI and long-term occlusions. The role of bypass surgery and the need for surgical expertise remain strong in the treatment of moyamoya variants and a select group of atherosclerotic steno-occlusive patients.