Introduction: Conventional extracranial-intracranial bypass for direct revascularization of anterior cerebral artery (ACA) territory is technically challenging, owing to anatomic complexity and lack of a single surgical corridor for achieving proximal and distal control. Furthermore, the use of superficial temporal artery (STA) as donor poses a unique conundrum due to its lateral location and insufficient graft length, requiring the harvest and use of interposition grafts, e.g. radial artery. This study attempted to address these shortcomings by harvesting the STA with its frontal division and using the parietal STA branch as an interposition graft to revascularize the A3 segment.
Methods: Ten cadaveric specimens were prepared for surgical simulation. The STA was microsurgically dissected, preserving its frontal and parietal branches. An anterior interhemispheric approach was used with a paramedian craniotomy to identify the middle inferior frontal branch (MIFA) of A3. Following this, the parietal division was transected and used an interposition graft between the frontal STA and MIFA. Lengths and calibers of the main trunk of STA and its frontal and parietal branches were measured. The distance from STA at the zygomatic root to MIFA and the caliber of MIFA at the anastomotic site were also noted.
Results: The average caliber of MIFA was 1.4mm, which matched with the caliber of frontal and parietal branches of STA(1.3 mm). The mean distance from STA to MIFA was 145.5±7.4mm and the mean harvested donor graft length with parietal branch interposition was 204.2± 27.9mm. This bypass construct could provide approximately 58% excess graft length for an STA-A3 bypass.
Conclusions: Using an extended unilateral STA donor graft with a parietal division interposition to MIFA (A3 segment) is a reasonable bypass model for direct revascularization of ACA complex. The advantages of this technique over existing approaches include use of a single skin incision, sufficient length for tension-free anastomosis and enhanced technical feasibility.
Patient Care: This novel bypass technique from STA to A3 segment using a parietal branch interposition graft will allow for direct revascularization of ACA territory with a single skin incision. This procedure can be used for prevention of cerebral ischemia in moyamoya disease or for management of distal ACA aneurysms (A2-A5 segments).
Learning Objectives: 1. To understand the current limitations of reveasculariztion options for anterior cerebral artery territory
2. To understand the anatomy of superficial temporal artery (STA) and the potential for using the parietal branch of STA as an interposition graft
3. To get an overview of technique for insitu EC-IC bypass using STA as a donor vessel, with the parietal branch of STA as an interposition graft