Operative Techniques and Long-Term Outcomes of Radial Artery Graft Bypass for the Treatment of Moyamoya Vasculopathy: Single Institutional Experience

Introduction: Superficial Temporal Artery to Middle Cerebral Artery (STA-to-MCA) bypass is an effective treatment for Moyamoya vasculopathy (MMV). However, patients with early vasculopathy where proximal MCA stenosis is severe but not fully occluded and distal caliber is preserved, may be under-perfused by this intervention. Radial artery grafts (RAG) may provide higher flow volume for cerebral bypass revascularization compared to STA owing to its wider caliber and structure comparable to the M2 segment of the MCA.

Methods: We retrospectively reviewed all direct bypasses performed for MMV between 2005-2023 and identified a subset of patients who underwent bypass with a RAG. Selected patients were further investigated to collect data on demographics, clinical status [modified Rankin Score(mRS)] and angiographic graft status till the most recent follow-up.

Results: Between 2005-2023, 49 MMV patients were treated with 67 direct bypasses. STA was the most commonly used graft in 70% (47/67) of the cases. RAG was used in 24% (16/67) of the cases. Among patients treated with RAG bypass, the mean age was 45years (range 18-61) and all were females. The mean duration of clinical and radiological follow-up was 5years (range 1month to 15years). One patient died in the peri-operative period after suffering from malignant cerebral edema and ischemic stroke. The immediate post-operative bypass patency rate was 100% (16/16) and long-term (>12months) graft patency was 86% (12/14). For the two grafts that occluded over the long term, adequate cortical collateral perfusion had developed and the patients were asymptomatic. Baring 1 patient, no strokes were seen in the post-operative period. At last follow-up, 94% (15/16) patients had mRS 0-2.

Conclusion : This series represents the largest cohort reporting long-term outcomes of RAG bypass for the treatment of MMV patients with proximal MCA stenosis, but preserved flow and distal vessel caliber. RAG for direct bypass can provide higher flow volumes compared to STA and may be considered in patients who are anticipated to have higher flow requirements than can be met by STA-MCA bypass alone.