2026 Proffered Presentations
S012: QUANTITATIVE ANATOMICAL COMPARISON OF MICROSURGICAL TRANSCRANIAL, ENDOSCOPIC ENDONASAL AND TRANSORBITAL APPROACHES TO THE ORBIT AND SURROUNDING SKULL BASE REGIONS
Edoardo Agosti1; Marco Valentini2; Karen Mapelli1; Barbara Buffoli1; Mario Turri-Zanoni2; Pierre-Olivier Champagne3; Vittorio Rampinelli1; A. Yohan Alexander4; Ludovico Agostini5; Maria Peris-Celda4; Marco Ravanelli1; Rita Rezzani1; Marco Maria Fontanella1; Francesco Doglietto5; 1University of Brescia; 2University of Insubria; 3Université Laval; 4Mayo Clinic; 5Fondazione Policlinico Universitario Agostino Gemelli IRCCS
Introduction: Surgical access to orbit and surrounding skull base regions (sSBRs) lesions remain challenging. Microsurgical transcranial approaches (MTAs) 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 sSBRs.
Methods: Five alcohol-fixed cadaveric heads (10 sides) underwent high-resolution CT and three-dimensional segmentation of 26 subregions grouped into the orbit (OR), midline (MR), spheno-orbital (SOR), and cavernous regions (CR) (Figure 1).
Nineteen approaches, including anterior MTAs, anterolateral MTAs, EEAs and ETOAs, were performed in modular fashion (Figure 2).
An optical neuronavigation system (Polaris Vicra®; NDI, Waterloo, Ontario, Canada) coupled with GTx-Eyes II was used to quantify the maximum surgical volume with the highest surgical maneuverability (i.e. “non-crossing” modality) and the largest exposure obtained with straight instruments (i.e. “crossing” modality). Exposure areas and working volumes were computed in real time and reviewed on axial, coronal, sagittal, and 3D planes (Figure 3).
Statistical analysis was performed using linear mixed models with random intercepts for each specimen to account for intra-sample variability. Surface area exposure and working volume were compared across approaches. Statistical significance was set at p < 0.05, and confidence intervals were estimated using bootstrap resampling (1,000 iterations).
Results: Endoscopic endonasal transpterygoid approach (EETPA) provided the greatest exposure of the optic foramen at 67.98%, significantly surpassing the endoscopic endonasal approach to the medial orbit (Δ=13.06%, p=0.03). The superior eyelid endoscopic transorbital approach with lateral orbitotomy (SETOA+LO) achieved the widest access to the lateral orbital wall, reaching 98.56% in the middle and 99.42% in the temporal portions (both p<0.05 versus the orbitozygomatic approach, OZA). Transcaruncular approach (TCETOA) offered the most complete exposure of the medial wall at 99.41% (p=0.04 versus EETPA) and the inferolateral approach yielded the largest orbital floor exposure at 99.18% (p<0.001). The extended transbasal approach (ETBA) maximally exposed the planum sphenoidale at 99.28% (p=0.03 versus OZA with anterior clinoidectomy, OZA+AC), while EETPA achieved the highest values for the chiasmatic sulcus at 96.47% (p<0.001) and the tuberculum sellae at 98.76% (p<0.001). OZA+AC dominated most subregions including the greater wing at 98.49%, optic canal roof at 98.18%, and superior orbital fissure at 98.68% and maxillary strut at 95.12% (all p<0.05). SETOA+LO provided superior exposure of the foramen ovale at 88.89% (p<0.01), foramen rotundum at 88.78% (p<0.001), cavernous sinus lateral wall at 94.66%, intracranial V3 at 92.92% (p=0.04) and petrous apex at 93.85% (p<0.01), while OZA+AC maximized intracranial V1 and V2 at 87.94% and 90.74% (Figure 4 summarize the exposures of CR).
MTAs offered the largest working volumes (ETBA 59.35 cm³; OZA+AC 53.69 cm³).
Conclusion: ETOAs provide unmatched access to the lateral orbit and CR, EEAs excel medially and MTAs, especially OZA+AC, remain indispensable for broad spheno-orbital exposure and maximal working volumes. This quantitative map supplies evidence-based guidance for selecting the optimal approach in complex orbital and skull base surgery.