Reply to the Comment on the Article “Selective-Targeted Extra-Intracranial Bypass Surgery in Complex Middle Cerebral Artery Aneurysms

Abstract

Bypass surgery plays a very important role in the management of complex middle cerebral artery (MCA) aneurysms not amenable to selective clipping, coiling, or other endovascular procedures. The goal of a bypass is the preservation of blood flow in the territory fed by the vessel that needs to be occluded for final aneurysm treatment.1 Identification of the correct bypass recipient could be obtained by microsurgical dissection of both the perianeurysmal angioanatomy and the sylvian fissure.2 When dissection of the sylvian fissure is considered at risk or when a superficial cortical recipient artery (namely an M4 segment of the MCA) is preferred as the recipient, it is very important that the cortical recipient artery represents a distal branch of the trapped vessel. Angioanatomic landmarks and neuroimaging, neuronavigation, and stereotactic modalities represent useful tools3,4 for identifying the correct recipient; however, the risk of revascularization into a wrong territory still exists, with possible subsequent severe ischemic effects.1,3 We recently reported the feasibility and efficiency of a technique for selective-targeted revascularization, namely for the identification and targeting of the cortical recipient in extracranial-to-intracranial bypass surgery for the treatment of complex MCA aneurysms.1 The technique is based on the use of microscope-integrated near-infrared indocyanine green video angiography. We have reported our clinical experience in 7 consecutive patients treated for complex MCA aneurysms. This technique allowed the correct identification of the cortical recipient arteries (cortical branches of the trapped MCA segment) in all patients and eliminated the risk of erroneous revascularization of uninvolved territories. Patients underwent successful treatment of their aneurysm, including a cortical bypass; no ischemic complications were reported, and a favorable clinical outcome was achieved in all patients (The modified Rankin Scale score at follow-up was less than or equal to the preoperative modified Rankin Scale score). This technique can be applied in the treatment of both proximal and distal complex MCA aneurysms.1 We thank Dr Andreas Gruber (Vienna, Austria), Drs Duke Samson and Kim Rickert (Dallas, Texas), and Dr Laligam N. Sekhar (Seattle, Washington) for their comments on and contributions to our article.1 From part of Dr Sekhar’s comment, we realized that the illustrations of the case example 2 (see the original publication) may have been somewhat misleading. Dr Sekhar stated that “in the case example 2, we decided to accept the sacrifice of the anterior temporal artery, even with the knowledge that it will lead to infarction of that portion of the brain.” In fact, we did not sacrifice the anterior temporal artery. We only occluded it temporarily to perform a provocative indocyanine green video angiography to avoid the selection of a cortical recipient representing a branch of the anterior temporal artery itself. This step was useful for extra verification and represents an application of the technique to identify “uninvolved” cortical arteries. To better illustrate the treatment strategy applied in this case, we supply this letter with a new schematic drawing (Figure).FIGURE: A, drawing illustrating the partially thrombosed giant middle cerebral artery (MCA; M1) bifurcation aneurysm and the perianeurysmal angioanatomy. B, the same drawing after placement of a temporary clip on the anterior temporal artery to perform a provocative indocyanine green video angiography to identify “uninvolved” cortical arteries (namely perisylvian fissure cortical arteries not representing distal branches of the artery that need to be occluded for the final aneurysmal treatment). C, the same drawing after removal of the temporary clip on the anterior temporal artery and placement of a temporary clip on the M2 segment of the MCA to perform a provocative indocyanine green video angiography to identify the correct cortical recipient (a cortical artery representing a branch of the artery that needs to be occluded for the final aneurysmal exclusion). D, the same drawing illustrating the permanent clips used for final aneurysm exclusion and the role of the bypass in revascularizing vessels coming from the permanently occluded aneurysmal branch. The anterior temporal artery was preserved.Disclosure The authors have no personal financial or institutional interest in any of the drugs, materials, or devices described in this article. Acknowledgment We thank Peter Roth (Department of Neurosurgery, University Hospital Zurich, Zurich, Switzerland) for the drawings in the Figure.