The Orbitosellar Line: An Anatomical Guide in Accessing the Sellar and Suprasellar Regions

Background: Expanded endoscopic endonasal (EEA) approaches to the sellar and suprasellar regions may pose a risk in damaging vital structures, such as the optic nerve or internal carotid artery (ICA), especially when directly accessing these compartments through the sphenoid sinus. Specially, under certain circumstances such as the presence of Onodi cells or bony dehiscence over the above-mentioned structures, it may result in a fatal complication, if not properly addressed. Utilizing a lateral to medial trajectory may prevent such difficulties.

Objective: To anatomically describe the orbitosellar line (OSL), which is a landmark that connects the orbit to the sellar region.

Methods: Five formalin-fixed and injected cadaveric heads were dissected to be able to describe the OSL in a step-wise manner.

Results: We define the OSL as a line drawn from anterolateral to posteromedial and from superior to inferior along the following three adjacent structures, from distal to proximal: (1) the diagonal of the rectangular region of the LP, which is bordered between the fovea ethmoidalis superiorly, maxillary sinus roof inferiorly, and the lateral border of the sphenoid sinus posteromedially; (2) optic canal (OC) protuberance; and (3) medial opticocarotid recess (MOCR; [Fig. 1]). Measurements along its three segments were made (in cm): 2.822 ± 0.531 (LP segment), 0.903 ± 0.131 (OC segment), and 0.342 ± 0.093 (MOCR segment). The same concept was applied in surgery for endoscopic optic nerve decompression to better illustrate the methodology ([Fig. 2]).

Conclusion: The OSL serves as a reliable guide in the gradual and sequential exposure of the lamina papyracea (LP), optic canal (OC) and medial opticocarotid recess (MOCR) from a lateral to medial trajectory. We consider it as a guideline when working in the ventral anteromedial (extending from frontal sinus to dorsum sellae) and anterolateral (extending from lamina papyracea to pterygoid) corridors to avoid neurovascular damage to the optic nerve or the ICA, by providing a step-by-step exposure of those structures.

No conflict of interest has been declared by the author(s).