摘要目的:研究颅底凹陷合并寰枢椎脱位患者椎动脉V3段的危险变异类型和发生率，探讨不同类型椎动脉V3段患者的内固定策略。方法:回顾性分析2017年1月至2019年1月首都医科大学宣武医院神经外科采用内固定融合手术重建颅颈交界区稳定性的56例颅底凹陷合并寰枢椎脱位患者的临床和影像学资料。对于不合并椎动脉解剖变异的患者，采取寰椎侧块螺钉联合枢椎椎弓根螺钉行内固定治疗；对于椎动脉骨外段变异患者，术中尽可能采取枕骨螺钉替代寰椎侧块螺钉；对于高跨椎动脉(骨内段变异)患者，采用枢椎椎板螺钉或者峡部螺钉代替椎弓根螺钉。所有患者术后均常规行颈椎X线平片和头颈部CT检查评估内固定器械的位置以及是否发生后循环缺血梗死。结果:56例患者中，不合并椎动脉变异患者18例(32.1%)；椎动脉骨外段变异20例(35.7%)，包括永存第一节间椎动脉16例，椎动脉开窗和硬膜外起源小脑后下动脉各2例；高跨椎动脉28例(50.0%)。其中，骨外段变异合并高跨椎动脉变异10例(17.9%)。56例患者在置入枢椎螺钉时均未出现椎动脉损伤情况。1例椎动脉开窗患者术中显露寰椎侧块和寰枢椎关节时，开窗椎动脉下干损伤大出血，术中给予电凝闭塞止血。所有患者术后X线平片及CT检查均显示螺钉位置良好，CT检查未见明显后循环脑梗死征象。结论:颅底凹陷合并寰枢椎脱位患者椎动脉V3段解剖变异发生率较高，术前需充分评估椎动脉解剖走行，根据患者不同的椎动脉解剖变异情况制定个体化的手术方案。

abstractsObjective:To evaluate the anomalies of V3 in patients with basilar invagination (BI) and atlantoaxial dislocation and to discuss the surgical strategies of BI patients according to V3 anatomy.Methods:The clinical and imaging data of 56 patients with BI and atlantoaxial dislocation who underwent posterior instrumentation surgery of the craniovertebral junction (CVJ) at the Department of Neurosurgery, Xuanwu Hospital of Capital Medical University from January 2017 to January 2019 were retrospectively reviewed. For patients without V3 anomalies, lateral mass screws combined with axial pedicle screws were used for internal fixation. For patients with extraosseous V3 anomalies, occipital screws were used instead of lateral mass screws. For patients with high-riding vertebral artery (HRVA), C 2 laminar screws or isthmus screws were used instead of pedicle screws. X-ray and CT examinations were routinely performed in all patients after surgery to assess the location of internal fixation devices and the occurrence of posterior circulation infarction. Results:Of the 56 patients, there were 18 cases (32.1%) without any V3 anomalies. There were 20 cases (35.7%) with extraosseous V3 anomalies, including 16 cases of persistent first intersegmental artery (FIA), 2 cases of fenestrated vertebral artery (FVA) and 2 cases of posterior inferior cerebellar artery (PICA) with epidural origin. There were 28 cases (50.0%) of HRVA. There were 10 cases (17.9%) with extraosseous V3 anomalies combined with HRVA. None of the 56 patients had vertebral artery injury during the C 2 screw implantation. A patient with FVA developed massive hemorrhage due to inferior trunk damage during exploration of atlantoaxial joint and implantation of lateral mass screw, and coagulation was performed to stop bleeding during the operation. In all patients, X-ray and CT examinations showed that the screw positions were good, and CT did not show any obvious signs of posterior circulation infarction. Conclusions:V3 anomalies are common in patients with BI. Therefore, preoperative radiological studies should be performed to identify V3 segment anomalies to reduce the risk of iatrogenic VA injury during posterior CVJ instrumentation. To avoid disastrous complications associated with VA injury, the strategy of posterior CVJ instrumentation surgery should be decided according to the V3 anomalies in patients with BI.