2025 Proffered Presentations
S342: QUANTITATIVE ANATOMICAL COMPARISON OF MICROSURGICAL TRANSCRANIAL, ENDOSCOPIC ENDONASAL, AND ENDOSCOPIC-ASSISTED TRANSORBITAL APPROACHES TO THE ORBIT AND SURROUNDING SKULL BASE REGIONS
Edoardo Agosti1; Marco Valentini2; Mario Turri-Zanoni2; Marco Ravanelli1; Barbara Buffoli1; Marco Maria Fontanella1; Francesco Doglietto3; 1University of Brescia; 2Insubria University; 3Policlinico Gemelli Roma
Introduction: During the decades the orbit has evolved from surgical target to serving as a corridor to various skull base regions. Several surgical approaches have been developed to access and pass through the orbit, including microsurgical orbitotomies (MOs), cranio-orbitotomies (MCOs), endoscopic transorbital (ETOAs), and endoscopic endonasal approaches (EEAs). However, there is no consensus on the best approach for specific orbital portions and surrounding skull base regions. This study aims to quantitatively compare these approaches in a preclinical setting.
Methods: Six formalin-fixed, latex-injected cadaveric head specimens were dissected, performing the following approaches in each specimen: ETOAs (preseptal lower eyelid approach, lateral cantotomy, precaruncular approach, and superior eyelid crease approach), EEAs (transethmoidal sphenoidotomy to the medial orbital wall and optic canal, and medial maxillectomy to the inferior orbital wall), Caldwell-Luc approach, MOs (lateral cantotomy orbitotomy), and MCOs (fronto-orbital and orbito-zygomatic approaches) (Figures 1,2,3). High-resolution CT scans were obtained for all specimens, and ITK-Snap software rendered the target regions. An optic neuronavigation system (ApproachViewer, part of GTx-Eyes II, University Health Network, Toronto, Canada) quantified the working volume and exposed area for each approach. Statistical analyses were conducted using mixed linear models with random intersections.
Results: Twenty-four target regions of the orbit and surrounding skull base areas were identified. MOs provided direct access to the lateral orbital wall and superior orbital fissure, offering the maximum exposure of the lateral orbital wall (78%; p = 0.02) compared to ETOAs (55%). MCOs extended this access, allowing a broader view of the orbital apex and posterior orbit, including the superior and inferior orbital fissures, with significantly greater exposure compared to MOs (84% vs. 62%; p = 0.01).
ETOAs provided access to the medial and inferior orbital walls, offering a minimally invasive route to the lamina papyracea and optic canal, with a 25% gain in exposure compared to MCOs (67% vs. 42%; p = 0.03). ETOAs also facilitated exposure of the anterior cranial fossa, including the planum sphenoidale and cribriform plate, with a 32% gain in exposure compared to EEAs (74% vs. 42%; p = 0.02). Additionally, ETOAs enabled access to the sphenoid sinus and lateral recess of the sphenoid, critical for addressing lesions in the parasellar region, with a significant gain compared to MOs (63% vs. 28%; p = 0.01).
EEAs uniquely facilitated access to the medial orbit and optic canal, particularly useful for decompression procedures, providing 55% exposure of the optic canal compared to 32% by ETOAs (p = 0.04), though they provided limited access to lateral orbital structures. Each approach had distinct advantages: MOs and MCOs excelled in lateral (78% vs. 55%; p = 0.02) and posterior orbital exposure (84% vs. 62%; p = 0.01), while ETOAs and EEAs were superior for accessing medial (67% vs. 42%; p = 0.03) and deep orbital structures (55% vs. 32%; p = 0.04).
Conclusion: MOs and MCOs are preferred for lateral and posterior orbital exposure and lateral skull base interventions, while ETOAs and EEAs are superior for accessing medial and deep orbital structures and medial skull base.
