Abstract：
The horizontal part of the third segment (V3) of the vertebral artery (VA) is a critical anastomotic site for bypass procedures involving either donor or recipient vessels. It is rare for the V3 segment to deviate from its typical course of passing through the atlanto-transverse foramen. V3 anomaly encountered in occipital artery (OA)-V3 bypass surgery has not been previously reported. Here, we present a case involving a patient undergoing bypass surgery due to recurrent post-stent occlusion at the first segment (V1) of the left VA. During the operation, it was noted that the V3 horizontal segment could not be identified within the left VA groove, leading to initial suspicion of left V3 disuse atrophy attributed to prolonged chronic ischaemia. Consequently, there was a need to modify the operative method and to transition from an OA-V3 bypass to an OA-posterior inferior cerebellar artery bypass. Post-operative computed tomography angiography confirmed that indeed, the left V3 did not traverse through the transverse foramen of the atlas and instead entered the dural membrane between the first cervical vertebra (C1) and the second cervical vertebra (C2).
摘要：
椎动脉（VA）第三段（V3）的水平部分是涉及供体或受体血管的旁路手术的关键吻合部位。V3段很少偏离其典型的穿过寰横孔的过程。在枕动脉（OA）-V3搭桥手术中遇到的V3异常以前没有报道。这里,我们介绍一例病例,其中1例患者因左VA第一段(V1)复发性支架后闭塞而接受旁路手术.在操作过程中,注意到V3水平段无法在左VA凹槽内识别，导致最初怀疑归因于长期慢性缺血的左V3废用萎缩。因此,有必要修改手术方法,并从OA-V3分流术过渡到OA-小脑后下动脉分流术.术后计算机断层扫描血管造影证实，左侧V3没有穿过寰椎的横孔，而是进入了第一颈椎（C1）和第二颈椎（C2）之间的硬脑膜。
