Case Report of a Saphenous Vein Graft Aneurysm after Graft Occlusion for Intracranial High-flow Bypass

We report a case of high-flow bypass (HFB) using a saphenous vein graft (SVG) for a giant cavernous carotid artery aneurysm in which the graft was occluded and the anastomosis with the middle cerebral artery (MCA) became an aneurysm.The patient was a 70-year-old woman. She underwent internal carotid artery (IC) ligation and HFB [external carotid artery (EC)-SVG-middle cerebral artery (MCA)] for bilateral giant cavernous carotid aneurysms. First, left IC ligation and HFB (EC-SVG-MCA) were performed. Six months later, right IC ligation and HFB (EC-SVG-MCA) were performed. One year and 4 months after the second surgery, we confirmed occlusion of the right HFB and blind-end anastomosis between the HFB and MCA. Four years after the occlusion, neck clipping of the SVG aneurysm (SVGA) was performed because the blind end of the SVG slowly enlarged and changed the aneurysm.Pathological observation of the SVG showed concentric thickening of the intima and tunica media, and marked lumen narrowing. Reactive fibrous thickening of the outer membrane was also observed, indicating that the SVG intima underwent atherosclerotic changes, possibly due to mechanical stimulation during anastomosis and exposure to arterial pressure.In this case, the SVG used for the HFB was occluded, and the blind end of the anastomosis with the MCA changed the aneurysm. If the SVG is occluded during follow-up, knowing that the anastomosis with the MCA may become an aneurysm is necessary.