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External frontal bone transillumination for frontal sinus mapping in anterior skull base surgery: technical note
1Department of Neurosurgery, ASST Lecco - Ospedale "Alessandro Manzoni", Via dell'Eremo 12/14, Lecco, 23900, Italy. l.fiori@asst-lecco.it.
Background:
Accurate identification of frontal sinus boundaries is a critical step in anterior skull base surgery, particularly in transsinusal approaches, as it allows optimization of the surgical bony window while minimizing unnecessary bone removal.
Objective:
To describe a simple and reproducible technique of external frontal bone transillumination for intraoperative frontal sinus mapping.
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 conditions. When properly applied, the frontal sinus appears as a brighter translucent area, allowing accurate delineation of its margins. Postoperative CT imaging was retrospectively reviewed to assess correspondence between the intraoperatively identified margins and the actual anatomical boundaries.
Results:
Between 2015 and 2024, the technique was applied in 14 consecutive patients undergoing anterior skull base surgery, including olfactory groove meningiomas, post-traumatic anterior skull base cerebrospinal fluid fistulas, and one case of intrasinusal osteoma. In all cases, external transillumination enabled clear identification of frontal sinus boundaries and facilitated creation of an adequate surgical window. Postoperative imaging confirmed correspondence between the planned opening and the actual anatomical extent of the frontal sinus opening. No sinus-related complications or postoperative cerebrospinal fluid leaks were observed.
Conclusion:
External frontal bone transillumination is a simple, fast, and reliable method for intraoperative frontal sinus mapping during anterior skull base surgery. Its ease of adoption and use of routinely available equipment make it a useful adjunct to preoperative imaging for optimizing surgical exposure.
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