Endoscopic Endonasal Accessibility and Maneuverability Around the Internal Carotid Artery from Distal Dural Ring to Foramen Lacerum: Cadaveric Study

Background: Expanded-endoscopic endonasal approaches (eEEA) to surgical targets around the internal carotid artery (ICA) remain inspiring and necessitate a special learning curve. Methods: Six formalin-fixed heads were dissected to study the 360° accessibility and manoeuvrability around ICAs from the distal dural ring (DDR) to the foramen lacerum (FL) on each side (n=12) via eEEA. The ICA course was divided into three segments: ICA in cavernous sinus (CS-ICA), paraclival-ICA and lacerum-ICA. Following total exposure of each ICA, the three-dimensional (3D= medial/lateral, superficial/deep and above/below) anatomical targets (n= 35) around each ICA were evaluated. The data were collected and analyzed. Results: Distinctively, we included 35 anatomical targets (pertinent to CS-ICA, paraclival-ICA and lacerum-ICA were 16, 10, and 9, respectively) in 360° around every ICA (n=12) from the DDR to FL. Although reasonable visual validation was possible for all targets, micro-dissections were safely achievable for 19 targets (54.3%) through full or limited surgical freedom in 73.7% and 26.3%, respectively. In the remaining 45.7%, the accessibility to targets was abandoned due to hazardous manipulation. The most unreachable targets were around the lacerum-ICA (55.6%) with extremely restricted maneuverability (75%). Though, favorable accessibility (60%) and full surgical freedom (100%) were around the paraclival-ICA. Conclusion: This study delivers a distinctive view to appreciate the degree of complexity and invasiveness in relation to the degree of surgical freedom around ICA via eEEA. Illustrating these details for skull base surgeons can lead them to tailor their approach. It delivers prospective feedback for our operative theatre.