Introduction The clival, paraclival, and craniocervical junction regions are challenging surgical targets. To approach these areas, endoscopic endonasal transclival approaches (EETCAs) and their extensions (far-medial approach and odontoidectomy) have gained popularity as they obviate manipulating and working between neurovascular structures. Although several cadaveric studies have further refined these contemporary approaches, few provide a detailed step-by-step description. Thus, we aim to didactically describe the steps of the EETCAs and their extensions for trainees.

Methods Six formalin-fixed cadaveric head specimens were dissected. All specimens were latex-injected using a six-vessel technique. Endoscopic endonasal middle and inferior clivectomies, far-medial approaches, and odontoidectomy were performed.

Results Using angled endoscopes and surgical instruments, an endoscopic endonasal midclivectomy and partial inferior clivectomy were performed without nasopharyngeal tissue disruption. To complete the inferior clivectomy, far-medial approach, and partially remove the anterior arch of C1 and odontoid process, anteroinferior transposition of the Eustachian–nasopharynx complex was required by transecting pterygosphenoidal fissure tissue, but incision in the nasopharynx was not necessary. Full exposure of the craniocervical junction necessitated bilateral sharp incision and additional inferior mobilization of the posterior nasopharynx. Unobstructed access to neurovascular anatomy of the ventral posterior fossa and craniocervical junction was provided.

Conclusion EETCAs are a powerful tool for the skull-base surgeon as they offer a direct corridor to the ventral posterior fossa and craniocervical junction unobstructed by eloquent neurovasculature. To facilitate easier understanding of the EETCAs and their extensions for trainees, we described the anatomy and surgical nuances in a didactic and step-by-step fashion.

简介 斜坡、斜坡旁和颅颈交界区是具有挑战性的手术目标。为了接近这些区域，内窥镜鼻内经斜坡入路（EETCA）及其扩展（远内侧入路和齿状突切除术）已经受到欢迎，因为它们避免了神经血管结构之间的操纵和工作。尽管一些尸体研究进一步完善了这些当代方法，但很少提供详细的逐步描述。因此，我们的目标是为受训者以教学方式描述 EETCA 的步骤及其扩展。

方法 对六具福尔马林固定的尸体头部标本进行解剖。所有标本均采用六容器技术进行乳胶注射。进行了内镜下鼻内中、下阴沟切除术、远内侧入路和齿状突切除术。

结果 使用倾斜内窥镜和手术器械，在不破坏鼻咽组织的情况下进行了鼻内镜中斜坡切除术和部分下斜坡切除术。为了完成下斜坡切除、远内侧入路以及部分切除C1前弓和齿状突，需要横断翼蝶裂组织进行咽鼓鼻咽复合体前下转位，但不需要切开鼻咽部。颅颈交界处的完全暴露需要双侧锐利切口和后鼻咽的额外下部动员。提供了对腹后窝和颅颈交界处的神经血管解剖结构的无障碍访问。

结论 EETCA 是颅底外科医生的有力工具，因为它们提供了通向腹后窝和颅颈交界处的直接通道，不受神经血管系统的阻碍。为了帮助学员更轻松地理解 EETCA 及其扩展，我们以教学和分步的方式描述了解剖学和手术的细微差别。