Maxillary Artery to Middle Cerebral Artery Bypass: A Novel Technique for Exposure of the Maxillary Artery Kaan Ya  gmurlu, M. Yashar S. Kalani, Nikolay L. Martirosyan, Sam Safavi-Abbasi, Evgenii Belykh, Avra S. Laarakker, Peter Nakaji, Joseph M. Zabramski, Mark C. Preul, Robert F. Spetzler - OBJECTIVE: To define the maxillary artery (MaxA) anatomy and present a novel technique for exposing and preparing this vessel as a bypass donor. - METHODS: Cadaveric and radiologic studies were used to define the MaxA anatomy and show a novel method for harvesting and preparing it for extracranial to intracranial bypass. - RESULTS: The MaxA runs parallel to the frontal branch of the superficial temporal artery and is located on average 24.8  3.8 mm inferior to the midpoint of the zygomatic arch. The pterygoid segment of the MaxA is most appro- priate for bypass with a maximal diameter of 2.5  0.4 mm. The pterygoid segment can be divided into a main trunk and terminal part based on anatomic features and use in the bypass procedure. The main trunk of the pterygoid segment can be reached extracranially, either by following the deep temporal arteries downward toward their origin from the MaxA or by following the sphenoid groove downward to the terminal part of the pterygoid segment, which can be followed proximally to expose the entire MaxA. In comparison, the prebifurcation diameter of the superficial temporal artery is 1.9  0.5 mm. The average lengths of the mandibular and pterygoid MaxA segments are 6.3  2.4 and 6.7  3.3 mm, respectively. - CONCLUSIONS: The MaxA can be exposed without zygomatic osteotomies or resection of the middle fossa floor. Anatomic landmarks for exposing the MaxA include the anterior and posterior deep temporal arteries and the pterygomaxillary fissure. INTRODUCTION E xternal carotid to internal carotid artery bypass surgery has been used to treat complex aneurysms that require parent vessel occlusion, 1-4 skull base tumors that involve the major vessels, 5 moyamoya angiopathy, 6,7 iatrogenic injury to intracranial vessels, and ischemic disease refractory to maximal medical therapy. 8 Bypass procedures for cerebral revascularization are divided into 2 categories depending on their flow volume: low-flow bypass (50 mL/minute) and high-flow bypass (>50 mL/minute). 9 Cerebral revascularization techniques are also divided into 2 types depending on graft materials: pedicled arterial grafts (e.g., superficial temporal artery [STA], occipital artery, and middle meningeal artery [MMA]), which are generally used in low-flow bypass proced- ures, or free venous or arterial grafts (e.g., radial artery or saphenous vein), which are used in high-flow bypass proced- ures. 9 The STA may, in some cases, be a robust conduit and provide more flow than a classic low-flow graft. The STA is a workhorse for extracranial to intracranial (EC-IC) bypass surgery because of its ease of exposure and proximity to the circle of Willis. However, the size of the STA and previous surgery resulting in STA sacrifice may require an alternative bypass donor to be identified. The maxillary artery (MaxA) has been proposed as an alternative bypass donor for EC-IC bypass surgery. 10,11 Although neurosurgeons are familiar with the Key words - Aneurysm - Bypass - Ischemia - Maxillary artery - Revascularization Abbreviations and Acronyms EC-IC: Extracranial to intracranial MaxA: Maxillary artery MCA: Middle cerebral artery MMA: Middle meningeal artery STA: Superficial temporal artery Department of Neurosurgery, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, Phoenix, Arizona, USA To whom correspondence should be addressed: Robert F. Spetzler, M.D. [E-mail: Neuropub@dignityhealth.org] Citation: World Neurosurg. (2017) 100:540-550. http://dx.doi.org/10.1016/j.wneu.2016.12.130 Supplementary digital content available online. Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2017 Elsevier Inc. All rights reserved. 540 www.SCIENCEDIRECT.com WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2016.12.130 Technical Note