Techniques and challenges of the expanded endoscopic endonasal access to the ventrolateral skull base during the “far-medial” and “extreme medial” approaches

Background: Expanding the ventrolateral skull base corridor from the midline of lower clivus to the petroclival fissure is a challenging endonasal surgical task. Resection of lytic lesions like chondrosarcoma can cause cranial nerve morbidities and injury of ICA, necessitating accurate knowledge of correlative endoscopic anatomy with stereotactic landmarks. Methods: We describe an extended endoscopic endonasal approach (EEA) for a right petroclival chondrosarcoma with the demonstration of ipsilateral surgical landmarks with contralateral normal correlates, using a stepwise comparative image-guided cadaveric dissection study. Conclusion: EEA for lytic lesions like chondrosarcomas needs to address brain shift and displacement of ICA, posing a chance for cranial nerve morbidities and ICA injury. Meticulous utilization of intraoperative stereotactic landmarks can help avoid and mitigate surgical complications.