Microsurgical Technique and Long-term Outcomes of Selective Pedicled Pericranial Flaps for Salvage of Direct Bypasses in Patients with Moyamoya Disease or Syndrome

Introduction: Direct extracranial-to-intracranial (EC-IC) bypass is the preferred initial treatment for Moyamoya Disease (MMD) and Syndrome (MMS). However, direct bypasses may become inadequate, resulting in recurrent symptoms. Such cases are often treated with supplemental indirect bypass using pedicled omental flaps, wide arterial sparing encephalo-duro-arteriosynangiosis, temporoparietal fascial flaps, and pericranial flaps.

Methods: We retrospectively reviewed all MMD/MMS patients treated by a single surgeon between 2005 and 2023 and identified patients who received salvage indirect bypass for recurrent ischemia after direct bypass. Demographic, clinical and radiological data was collected. Cerebral ischemia was confirmed by angiographic blood flow studies. The surgical technique involves plastic surgery and creation of carefully planned skin flap, elevation of vascularized pericranial or muscle flap, microsurgical opening of arachnoid membrane over the ischemic areas, and approximation of the flap on the cortical surface.

Results: Between 2005 and 2023, 54 patients with MMD/MMS were treated with EC-IC bypass in 63 cerebral hemispheres. Fifteen percent of patients (8/54) were treated subsequently for recurrent ischemia with indirect bypass using vascularized muscle or pericranial flaps (mean age 41, 63% females). The most common symptoms included headache, dizziness, weakness and numbness. The median time to clinical improvement after indirect bypass was 10 months (range 1-84, n=9) and the median time to radiographic improvement was 7 months (range 4-9, n=7). Postoperatively there was symptomatic improvement in 89% (8/9) of cases. On radiographic follow-up, 71% of patients (5/7) showed improved perfusion on angiographic and CT perfusion studies. There was one peri-operative stroke resulting in aphasia, which improved with speech therapy. There were no hemorrhagic complications.

Conclusion : Our series shows that salvage revascularization using muscle or pericranial flaps for inadequate direct bypass in MMD and MMS provides effective revascularization with excellent long-term outcomes. Collaboration with plastic surgery is crucial for salvage revascularization with indirect bypass flaps.