Anatomical And Clinical Study Of Endonasal Endoscopic For Cranial Base Chordoma

Background: Chordomas are rare brain tumors that have puzzled even the most experienced surgeons over the last more than 100 years and continue to do so today.The deep location of skull base chordomas in the central skull base within a delicate meshwork of vital neurovascular structures makes chordomas challenging surgical targets.Surgical resection of these locally aggressive and osteoinvasive tumors is very difficult,but it is still the most effective method for treating skull base chordomas,accompanied by postoperative locally radiotherapy.The unresponsiveness of chordomas to conventional doses of radiation treatment presents an additional challenge.In recent years,the emergence and improvement of endonasal endoscopic technique has enabled surgeons to reach the entire central skull base from the frontal sinus above to the clivus below on the sagittal plane and access to the entire lateral skull base from the sellar area to the jugular foramen,occipital condyle,and parapharyngeal space on the coronal plane.In addition,the endonasal endoscopic approach(EEA)has wider and brighter surgical field,thus achieving better surgical results and improving the prognosis to a certain extent.This approach has been of special significance in the treatment of tumors in the ventral midline of skull base and has become a safe and reliable choice in the surgical approach of skull base.Methods: EEA was performed to investigate the possible behavioral patterns of skull base chordomas in frozen skull specimens with silicone perfusion into arteries and veins.Each approach was dissected from top to bottom on the sagittal plane and the coronal plane with the important anatomical markers exposed.The ipsilateral or bilateral distances of important anatomical landmarks and the maximum range of exposure were measured.A retrospective analysis with histopathologically diagnosed skull base chordoma between January 2010 and September 2020 in Tianjin Huanhu Hospital was performed.Basic demographic information,imaging data and clinical results of different surgical approaches were collected,including extent of resection,incidence of complications and evaluation of prognostic factors,such as overall survival and tumor recurrence.Results: The extended EEA can clearly expose the entire ventral structure of the midline skull base and extend laterally to bilateral cavernous sinuses,petrous bone,jugular foramen,occipital condyle,infratemporal fossa and parapharyngeal space.All the anatomical structures,especially important intradural neurovascular structures,can be observed under direct vision at a close range.By simulating the anatomy of different approaches and drilling bones,a wider exposure can be provided for safer tumor resection.In the retrospective analysis of skull base chordoma cases,compared with the endonasal microscopic approach and the transcranial lateral approach(TLA),the gross total resection(GTR)rate was significantly improved by EEA,but the incidence of related complications,such as cerebrospinal fluid leakage increased.With the improvement of intraoperative reconstruction technology and postoperative lumbar drainage,most patients recovered well.The extent of tumor resection,pathological indicators,postoperative adjuvant radiotherapy,preoperative scores and grouping of patients affect the prognosis of this disease.Our results showed that low Ki-67 index,postoperative adjuvant radiotherapy,and low preoperative score were more likely to have a good prognosis.Among them,the pathological index Ki-67 index can be considered as an independent risk factor affecting the recurrence or progression of cranial base chordomas.Conclusion: EEA provides a direct and wide surgical field for the treatment of skull base chordomas,allowing a more clear observation of the relationship between tumor and neurovascular structures,improving the GTR rate.On the other hand,the indications of the EEA should not be expanded excessively.The surgical approaches should be selected according to the tumors’ anatomical location,the relationship between the tumor and neurovascular structures,and the familiarity with endoscopy by surgeons.The EEA should be complementary with TLA;EEA and TLA can be used in combination or in stages when necessary.In addition,the learning curve of EEA is steep and lengthy.Detailed preoperative clinical scores for each patient are valuable for planning surgery and assessing prognosis.