Quantitative Anatomic Comparison of Microsurgical Transcranial, Endoscopic Endonasal, and Transorbital Approaches to the Orbit and Surrounding Skull-Base Regions.

BACKGROUND AND OBJECTIVE: Microsurgical transcranial approaches (MTAs) to the orbit and surrounding skull-base region lesions have been progressively complemented by endoscopic endonasal approaches (EEAs) and endoscopic transorbital approaches (ETOAs). This study provides the first quantitative, navigation-based comparison of working volumes and exposure areas of major approaches to the orbit and surrounding skull-base regions. METHODS: Five alcohol-fixed specimens were dissected. Twenty-six subregions grouped into the orbit, midline, spheno-orbital, and cavernous regions were segmented. Nineteen approaches, including anterior MTAs, anterolateral MTAs, EEAs, and ETOAs, were performed. Exposure areas and working volumes were quantified. RESULTS: Endoscopic endonasal transpterygoid approach (EETPA) provided the greatest exposure of the optic foramen (67.98%, P = .03 vs EEA to the medial orbit). The superior eyelid approach with lateral orbitotomy achieved the widest access to the lateral orbital wall, reaching 98.56% in the middle and 99.42% in the temporal portions (P < .05 vs the orbitozygomatic approach [OZA]). The transcaruncular approach better exposed medial wall (99.41%, P = .04 vs EETPA), and the inferolateral approach gained largest orbital floor exposure (99.18%, P < .001). The extended transbasal approach maximally exposed the planum sphenoidale (99.28%, P = .03 vs orbitozygomatic approach with anterior clinoidectomy [OZA + AC]), while the EETPA the chiasmatic sulcus and the tuberculum sellae (98.76% and 96.47%, P < .001). The OZA + AC dominated most subregions, including greater wing, optic canal roof, and superior orbital fissure (98.49%, 98.18%, and 98.68%, P < .05). The superior eyelid approach with lateral orbitotomy better exposed foramen ovale at 88.89% (P < .01), foramen rotundum at 88.78% (P < .001), intracranial V3 at 92.92% (P = .04), and petrous apex at 93.85% (P < .01), while OZA + AC maximized intracranial V1 and V2 (87.94% and 90.74%, P < .05). The MTAs had largest working volumes (extended transbasal approach 59.35 cm3; OZA + AC 53.69 cm3). CONCLUSION: ETOAs provide unmatched access to the lateral orbit and cavernous regions, while EEAs excel medially and MTAs, especially OZA + AC, remain indispensable for broad spheno-orbital exposure and maximal working volumes.