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Interest in endoscopic transnasal access has increased with continued technological advances in endoscopic technology. The goals of this study were to review the normal anatomy in transnasal endoscopic neurosurgery and outline the anatomical basis for an expanded surgical approach. Defining anatomical aspects of surgical endoscopy helps guide the surgeon by defining normal anatomy of the access vector. This anatomic study was conducted on 15 adult male cadaver specimens using various microsurgical tools and endoscopic instruments and 1 intraoperative case. The vasculature was injected with colored silicone to aid visualization. Different transnasal approach techniques were used, with angles of endoscope access at 0°, 30°, 45°, and 70° accordingly for extensive anatomical mapping. The proximity of critical structures is different in each approach degree. A full understanding of the possible structures to be met during transnasal access is described. As a result of the study, anatomical aspects and important structures were outlined, and a surgical protocol was defined for minimal risk access in respect to normal anatomy of the area. Thorough knowledge of topographic anatomy of the craniovertebral junction is required for performing minimal-risk surgical intervention in this region. It is important to know all anatomical aspects of the transnasal approach in order to reduce the risk of damage to vital structures. Transnasal endoscopic surgery of the craniovertebral junction is a relatively new direction in neurosurgery; therefore, anatomical studies such as the one described in this article are extremely important for the development of this access method. [ABSTRACT FROM AUTHOR]

Objective To present the basic topographic and anatomic features of the clivus and adjacent structures with an objective of possible improvements and optimization of the extended endoscopic endonasal posterior (transclival) approach when removing tumors of the clivus and anterior regions of the posterior cranial fossa. Materials and Methods A craniometric study was conducted on 125 human skulls. A topographic anatomic study was conducted on 25 cadaver head specimens with arterial and venous beds stained with colored silicone, according to the method developed by us, to visualize its features and individual variability. Results The most important anatomic features of the external and internal regions of the clivus and the adjacent neural and vascular structures were analyzed. An accessible zone for the most effective transclival approach to the posterior cranial fossa is also specified. Conclusion The endoscopic endonasal transclival approach can be used to obtain access to centrally located tumors of the posterior cranial fossa. It is an alternative to transcranial approaches in the surgical treatment of tumors of the clivus. Highlights • We present our results of craniometric study on 125 human skulls. A topographic anatomical study was conducted on 25 cadaver head specimens. • The anatomical landmarks of a number of anatomical structures, necessary to perform the endoscopic endonasal posterior approach are described. • Upper, middle and lower transclival approaches provide access to the anterior surface neurovascular complexes of the posterior cranial. [ABSTRACT FROM AUTHOR]

Introduction Intraoperative identification of cranial nerves is crucial for safe surgery of skull base tumors. Currently, only a small number of published papers describe the technique of trigger electromyography (t-EMG) in endoscopic endonasal removal of such tumors. Objective To assess the effectiveness of t-EMG in preventing intraoperative cranial nerve damage in endoscopic endonasal surgery of skull base tumors. Materials and Methods Nine patients were operated on using the endoscopic endonasal approach within a 1-year period. The tumors included large skull base chordomas and trigeminal neurinomas localized in the cavernous sinus. During the surgical process, cranial nerve identification was carried out using monopolar and bipolar t-EMG methods. Assessment of cranial nerve functional activity was conducted both before and after tumor removal. Results We mapped 17 nerves in 9 patients. Third, fifth, and sixth cranial nerves were identified intraoperatively. There were no cases of postoperative functional impairment of the mapped cranial nerves. In one case we were unable to get an intraoperative response from the fourth cranial nerve and observed its postoperative transient plegia (the function was normal before surgery). Conclusion t-EMG allows surgeons to control the safety of cranial nerves both during and after skull base tumor removal. [ABSTRACT FROM AUTHOR]