Delano’s Classification of Optic Nerve Canal to Posterior Paranasal Sinuses: A Retrospective Study in Eastern District, KSA

Background: The Delano classification categorizes the re-lationship between the sphenoid sinus and optic nerve into four types. This classification helps understand the location of the optic nerve and posterior paranasal sinuses, especially for endo-scopic sinus surgical procedures in which the proximity of the optic nerve to the sphenoid sinus can pose risks. Aim of Study: This study aimed to determine the relation-ship between the optic nerve canal (ONC) and posterior parana-sal sinuses and their types, incidence, and prevalence among a study population in the eastern district of the Kingdom of Saudi Arabia (KSA). Key Points paranasal sinuses CT; Delano’s clas-sification; optic nerve canal; optic nerve dehiscence; pneumati-zation of anterior clinoid process. Patients and Methods: This retrospective study included 300 patients who were referred to our CT unit for paranasal sinus for the planning of functional endoscopic sinus surgery. Results: This study found that the most common type was type 1, whereas the second most common was type 2. Types 3 and 4 were least common. Delano type 3 was more common on the right side, and type 4 was more common on the left, where-as types 1 and 2 occurred most frequently bilaterally. This il-lustrates the significance of Delano’s classification according to side, with a p-value of <0.001. We found a significantly higher frequency of dehiscence and positive pneumatization of anteri-or clinoid process (PACP) in Delano type 3 on both sides. Conclusion: Optic nerve dehiscence and PACP were asso-ciated more frequently with Delano type 3; therefore, patients with type 3 are more predisposed to optic nerve injury during sinus surgery. Hence, we conclude that anatomical variations of the paranasal sinuses using the Delano classification of the optic nerve are very important for preoperative identification.