Surgical Clipping for Complex Middle Cerebral Artery Aneurysm: Decision-Making Tree With Tailored Bypass Strategy

INTRODUCTION: Bypass surgery is important as an effective strategy for complex middle cerebral artery (MCA) aneurysms. Various bypass techniques were reported, but some of them were challenging and difficult to understand. The aim of this report was to propose our simple and flexible method for selecting ideal bypass option and its outcome. METHODS: The strategy of bypass surgery is modified by a consideration of the anatomical situation as follows: Is it possible to make a flow our route? Is the amount of bypass flow sufficient? How is the location of lateral lenticulostriate artery (LSA)? Is the preservation of M2 branches possible? Modality of bypass surgery consists of (1) standard superficial temporal artery (STA)-middle cerebral artery (MCA) bypass (single/double, M3/4), (2) STA-proximal MCA (single/double, M1/2), (3) high flow bypass, (4) in-situ bypass (MCA-MCA parallels), and (4) interposition bypass. Operative strategy is selected based on our decision making tree. RESULTS: Between 2015 and 2018, we experienced 280 cases (70 ruptured, 210 unruptured) of direct surgery for cerebral aneurysms. Of these cases, the MCA aneurysm accounted for 40% (112 cases). Among these, revascularization was required in 10 cases of complex anatomy. Strategy of bypass surgery included the following: STA-proximal MCA (M1) single bypass: 1 case, STA-proximal MCA (M2) single bypass: 3 cases, STA-proximal MCA (M2) double bypass: 3 cases, STA-distal MCA (M3-4): 1 case, and MCA-MCA in situ bypass: 2 cases (include combination bypass). Patency of bypass was 96% and neurological worsening that caused by surgery was 20% with no operative mortality. CONCLUSION: Our decision-making tree with tailored bypass strategy is reasonable and will help select an optimal strategy for the complex MCA aneurysm surgery.