Retrograde Transillumination: A Reliable Guide for Frontal Sinus Opening in Endoscopic Sinus Surgery.

To describe and assess the feasibility of a simple, low-cost retrograde transillumination technique for identifying and confirming the frontal sinus opening during endoscopic frontal sinus surgery in a small series of patients. This single-center descriptive surgical series, conducted between November 2024 and January 2025, included five patients who underwent endoscopic frontal sinus surgery. The technique's five steps were standardized: angled endoscopic view (45°) of the frontal recess, probing the probable opening with angled instruments, darkening the room, placing the light source of the endoscope superomedial to the eyebrow, and observing a retrograde endonasal glow at the true ostium. In all cases, localization of the frontal opening was achieved by retrograde transillumination and independently verified with neuronavigation. Representative scenarios included nasal polyposis, pansinusitis, revision surgery (Draf III), and a pediatric patient with complicated sinusitis with epidural abscess. Retrograde transillumination enabled identification of the frontal sinus opening in all five cases and guided the extent of surgery (Draf IIa-b/III as indicated). It proved especially helpful when landmarks were distorted or when frontal recess cell variants obscured the pathway. In this limited series, retrograde transillumination appeared to be a pragmatic, cost-effective adjunct that complemented anatomical expertise, surgical experience, and neuronavigation for intraoperative localization of the frontal sinus opening. Larger comparative studies are needed to further evaluate its accuracy and generalizability.