Top-Down and Down-Top Ipsilateral Biportal Endoscopic Transorbital and Transmaxillary Transsphenoidal (bpTONES-EATT) Approach to the Cranio-Orbital Region and Middle Cranial Fossa: A Feasibility Volumetric Anatomical and Imaging Study

Background:: Traditional and well-established transcranial approaches to address spheno-orbital and middle cranial fossa regions guarantee optimal intracranial exposure, with additional orbital and zygomatic osteotomies allowing extra-cranial components to be resected; however, these techniques come at the cost of relevant morbidity. The recent introduction of combined endoscopic approaches and the conceptualization of the so-called multiportal strategy might provide an alternative route.

Objective:: This study aimed to assess the ex vivo feasibility of the combined biportal endoscopic transorbital and transmaxillary transsphenoidal (bpTONES-EATT) approach to the spheno-orbital and middle cranial fossa regions to address spheno-orbital and Meckel’s cave lesions compared to the uniportal EATT approach.

Methods:: A total of 5 silicon-injected adult cadaveric specimens (10 sides) and 10 radiological (20 sides) records of healthy subjects were employed in this study. Step-wise dissection was performed: (1) superior eyelid endoscopic transorbital approach (TONES) and (2) endoscopic transmaxillary transsphenoidal (EATT) technique were pursued. Measurements were repeated after each approach and during two operators, four-hand exploration of the biportal surgical corridors at the end of the dissection, focusing on pterygopalatine, infratemporal, anterior and middle cranial fossa floor exposures, Meckel’s cave and cavernous sinus access, overall posteroinferior exposure, and relevant landmarks reached. Gadolinium-enhanced head MRI and iodine-enhanced head CT scans in healthy subjects were evaluated to collect reference measurements and simulate the anatomical volume of exposure according to cadaveric findings. Imaging analysis was computed through dedicated software (3DSlicer; ITK Snap).

Results:: A qualitative overview of the surgical exposure was provided through dedicated image frames, and a tier-wise quantitative analysis was then conducted as follows: (1) linear distances from primary targets were measured; (2) “areas of exposure” of the anterior, middle, infratemporal and pterygopalatine fossa, Meckel’s cave and lateral cavernous sinus were quantified and compared; (3) “angles of exposure,” a novel reliable measurement, and angles of attack were measured for anterior clinoid process, Gasserian ganglion, superior orbital fissure, foramen ovale, rotundum and trigeminal porus; (4) “prismatoid surgical corridor volume,” a novel measurement method to assess irregularly shaped surgical routes, was computed for accessing anterior, middle, infratemporal and pterygopalatine fossa. Relevant linear measurements were repeated on coregistered head MRI-CT scans and qualitatively compared.

Conclusion:: The use of biportal trajectories through the endoscopic bpTONES-EATT approach might provide adequate exposure of the spheno-orbital region, infratemporal and middle cranial fossa, addressing significant limitations of previously investigated techniques (i.e., optic nerve decompression, hyperostotic bone resection, and infratemporal exposure) for managing large spheno-orbital and Meckel’s cave neoplasms sparing avoidable tissue injury during the exposure. The biportal corridor might provide adequate maneuverability compared to uniportal approaches with limited orbital or sinus morbidity and safe control of critical neurovascular structures compared to anterolateral open techniques. Further clinical studies are warranted to validate its safety and efficacy in a clinical setting.

Publikationsverlauf

Artikel online veröffentlicht:
05. Februar 2024