Figure 1: Example of endoscopic endonasal resection of a chordoma via a transclival approach. a, b The 36-year-old female patient presented with sudden headaches and paresis of the oculomotor nerve. Imaging revealed a large hemorrhagic, contrast enhancing petroclival tumor with extension in suprasellar direction and into the right cerebellopontine angle. The tumor led to a significant compression of the mesencephalon and pons. During preparation for surgery, the patient developed ophthalmoplegia on the right side and a high-grade hemiparesis on the left. Because of the progredient neurological deficits, surgery was performed as an emergency intervention. c Resection of the clivus with the high-speed drill with presentation of the clival internal carotid artery and the sellar dura. In order to create enough space for microsurgical preparation, the roof of the clival carotid artery was removed on both sides and the sella was completely decompressed. d Resection of the posterior clinoid process in order to reach cranial tumor parts. e Tumor resection with the curette. f Bimanual sharp separation of the tumor capsula from the superior cerebellar artery. g Inspection of the cerebellopontine angle with the 45° optic after removal of the tumor shows the trochlear and trigeminal nerves. h Inspection in cranial direction with the 45° optic reveals the basilar tip with the efferent arteries as well as the oculomotor nerve on both sides. i Presentation of the transclival approach which was used for resection of the large chordoma. j A fat graft is glued into the clival skull base defect. k Reconstruction of the skull base with a nasoseptal flap. l The postoperative MRI shows complete tumor resection and the nasoseptal flap well supplied with blood (arrows). The neurological deficits were completely regredient soon after surgery.