2026 Proffered Presentations
S011: OPTIMIZING THE TRANSORBITAL NEUROENDOSCOPIC (TONES) APPROACH TO THE CAVERNOUS SINUS: A VOLUMETRIC ANALYSIS AND QUANTITATIVE ASSESSMENT OF SURGICAL EXPOSURE AND MANEUVERABILITY
Sonia Ajmera, MD1; Rachel Blue, MD1; Kamila Bond, MD, PhD1; Reinier Alvarez, MD2; Patrick Hosokawa, MS2; A. Samy Youssef, MD, PhD2; 1University of Pennsylvania Health System; 2University of Colorado
Background: The cavernous sinus (CS) poses a unique surgical challenge due to its complex neurovascular anatomy. The transorbital neuroendoscopic (TONES) approach offers a minimally invasive corridor to the CS. This study quantitatively compares volumetric surgical exposure and maneuverability through two TONES corridors, the infratrochlear/Parkinson’s (IT) and anteromedial/Mullen’s (AM) triangles, using a cadaveric model.
Objective: To evaluate the ideal access triangle to the CS by comparing the surgical accessibility, maneuverability, and volumetric exposure through the IT and AM triangles using endoscopic transorbital approaches, with and without orbitotomy.
Methods: Ten sides of five formalin-fixed, latex-injected cadaver heads underwent TONES dissection, with neuronavigation guidance and standard endoscopic instrumentation. Both triangles were dissected with and without lateral orbitotomy. Surgical freedom, horizontal and vertical angles of attack were measured. Volumetric exposure was assessed through neuronavigation-based point acquisition and 3D segmentation. Data were analyzed using Wilcoxon signed-rank and Mann-Whitney U tests.
Results: The AM triangle demonstrated significantly greater surgical freedom (19.4 mm² vs. 13.5 mm², p = 0.0035), horizontal (16.0° vs. 12.9°, p = 0.0056), and vertical angles (19.5° vs. 16.4°, p = 0.0215) of attack compared to the IT triangle. Orbitotomy conferred a significant improvement in maneuverability metrics across both triangles: for IT triangle, surgical freedom increased by 8.4 mm² (p = 0.0079) and horizontal angle of attack increased by 8.0° (p = 0.0079) while for AM triangle surgical freedom increased by 12.9 mm² (p = 0.0317) and horizontal angle of attack by 11.3° in (p = 0.0159), however, vertical angle of attack was not significantly affected by orbitotomy in either triangle. Mean volumetric exposure was significantly higher through the AM compared to IT triangle (1.79 cm³ vs. 0.95 cm³, p < 0.01).
Conclusion: Both IT and AM triangles are viable TONES corridors to the cavernous sinus. However, the AM triangle provides superior maneuverability and volumetric exposure, particularly enhanced by orbitotomy. These findings inform optimal corridor selection for cavernous sinus lesions and support the role of TONES as one of the lesser invasive approaches to complex skull base pathology.
Figure 1. Cadaveric dissection (right side) of the bony exposure in the TONES approach FZS- Fronto-zygomatic Suture, LO- Lateral orbital wall, S- Sphenoid bone
Figure 2. A) Cadaveric dissection (right side) of the extradural exposure for the TONES approach: GWS- Greater wing of sphenoid, TD- Temporal dura, FD- Frontal dura, SOF- Superior orbital fissure, P- Periorbita, MOB- Meningo-orbital band, SC- Sagittal crest B) Cadaveric dissection (left side) of the inter-dural exposure for the TONES approach: FD-Frontal dura, ACP- Anterior clinoid process, TD- Temporal dura, T- Trochlear nerve, GG- Gasserian ganglion, TD- Temporal dura, GSPN- Greater superficial petrosal nerve, ICA- Internal carotid artery
Figure 3. Cadaveric dissection (right side) of the transcavernous exposure via the Mullens and Parkinson’s triangles via the TONES approach: A- Abducens nerve, ICA- Internal carotid artery, T- Trochlear nerve
Figure 4. Volumetric segmentation of the Anteromedial (Mullen’s) Triangle (A) and Infratrochlear (Parkinson’s) Triangle (B)