Introduction: To review the indications and applications of the 45º endoscope in skull base surgery, compare the visualization advantages over the 0º endoscope, and describe the technical nuances of its surgical use
Methods: Five latex injected high-quality specimens were used to perform expanded endonasal approaches and compare the anatomical structures viewed with the 0º and 45º endoscopes. The results were correlated with the accumulated experience of +400 endoscopic skull base cases performed in the last 2 years.
Results: In the transcribiform approach, the 45º endoscope allows for visualization of the anterior surface of the frontal lobe and bridging veins, and for lateral expansion of the surgical field through a supero-medial orbitotomy. At the level of the planum sphenoidale, it facilitates the access to the medial, inferior, and superior aspects of the optic canal. In the suprasellar infrachiasmatic region the angled endoscope improves the identification of oculomotor nerve, posterior communicating artery, and perforating branches; in the retrosellar retroinfundibular region it provides direct view of the posterior perforated substance and ventral hypothalamic surface. Within the sella, the 45º endoscope augments medio-lateral inspection and access to the cavernous sinus. When approaching the gland from an infrasellar trajectory, it provides direct access to the intermediate and posterior pituitary lobes without crossing the anterior lobe. The transclival approach can be expanded laterally behind the paraclival carotid artery to identify the petroclival fissure and medial petrous apex, Dorello´s canal, and the abducens nerve entrance into the cavernous sinus.
Conclusions: The 45º endoscope implements the visualization of structures that are at the limit of the wide-angle view provided by 0º endoscope. This improvement, when combined with extensive bony resection for instrumental access, allows for safer and more effective dissection, and provides the basis for the extension of the endonasal endoscopic approaches beyond current limitations.
Patient Care: It will help to clarify the right place and time of the use of the 45º endoscope during the expanded endonasal aproaches to the skull base.
Learning Objectives: Indications of the use of the 45º endoscope compared with the 0º endoscope