Endoscopic trans-orbital approaches to anterior and middle cranial fossa: exploring the potentialities of a modified lateral retro-canthal approach.

Abstract Background Among the new perspectives to revolutionize skull base surgery, there are the trans-orbital neuro-endoscopic (TONES) approaches to reach the anterior and middle cranial fossa (ACF and MCF). We conceived to explore the potentialities of a modified superiorly and medially extended lateral retro-canthal (LRC) approach. Methods Six head specimens were dissected. Applying the established conic model and the key surgical landmark of spheno-frontal suture, we tested the feasibility of a modified LRC to reach ACF and MCF; CT scans were performed before and after dissection to obtain a morphometric analysis of the surgical corridors employing a polygonal surfaces model. Results Through our anatomical study, we were able to identify and explore 3 different surgical corridors to reach the ACF and MCF: the supero-medial, the supero-lateral, and the infero-lateral. The superomedial corridor appeared most suitable to reach the medial part of the ACF and the optic-carotid region, whereas through the superolateral and inferolateral corridors it was possible to reach and explore the lateral part of ACF and MCF. The mean volumes of the three surgical corridors calculated on post-dissection CT scans were: 12.72 ± 1.99, 5.69 ± 0.34, and 6.24 ± 0.47 cm3, respectively. Conclusions The development of TONES approaches has not replaced the traditional open or endoscopic approach, nonetheless identification of surgical corridors and the possibility to combine them represent a major breakthrough. Clinical studies are necessary to demonstrate their validity and test the effectiveness, safety and reproducibility of TONES approaches in managing lesions harboring in the ACF and MCF.