External Frontal Bone Transillumination for Frontal Sinus Mapping in Anterior Skull Base Surgery: Technical Note

Background: Accurate identification of frontal sinus boundaries is an important step in anterior skull base surgery, particularly when a transsinusal approach is planned, as it allows optimization of the surgical bony window and minimization of unnecessary bone removal. Objective: To describe a simple and reproducible technique of external frontal bone transillumination for intraoperative mapping of the frontal sinus. Methods: After bicoronal exposure of the frontal bone, a standard fiber-optic light cable connected to the operating room light source is applied in direct contact with the frontal squama under low ambient light. When properly applied, the frontal sinus appears as a brighter translucent area, allowing accurate delineation of its margins. Results: Between 2015 and 2024, the technique was applied in 14 patients undergoing anterior skull base surgery, including olfactory groove meningiomas, post-traumatic cerebrospinal fluid fistulas, and one case of intrasinusal osteoma. In all cases, external transillumination allowed clear identification of frontal sinus boundaries and facilitated creation of an adequate surgical window. No sinus-related complications or postoperative cerebrospinal fluid leaks were observed. Conclusion: External frontal bone transillumination is a simple and reliable method for frontal sinus mapping during anterior skull base surgery. Its ease of adoption and use of routinely available equipment make it a practical adjunct to preoperative imaging for optimizing surgical exposure.