Protrusion of the Infraorbital Nerve into the Maxillary Sinus on CT: Prevalence, Proposed Grading Method, and Suggested Clinical Implications

Axial (A), coronal (B), left parasagittal (C), and right parasagittal (D) CT images in a 72-year-old woman show bilateral protrusion of the ION (arrowheads) into the maxillary sinus. The septum attaching the IOC to the anterior wall of the sinus was measured (bracket in A) on the axial image. The distance at which protrusion begins posterior to the inferior orbital rim (bracket in C) was measured on the sagittal image.

Axial CT image in a 56-year-old man shows left-sided protrusion of the ION into the maxillary sinus (arrowhead) attached to a single posterior septum (arrow). This was the only patient with a septum attaching a protruding IOC to the posterior wall of the maxillary sinus without an additional septum attaching to the anterior wall.

Coronal (A), axial (B), and right parasagittal (C) CT images in a 58-year-old man show bilateral protrusion of the IOC into the maxillary sinus. On the coronal image, an infraorbital ethmoid (Haller) cell is seen on the right (arrowhead) just medial and superior to the protruding IOC (arrow). Bilateral protrusion is seen on the axial image (arrows), and confirmation of protrusion is seen on the sagittal image through the right maxillary sinus. The presence of a protruding IOC near an infraorbital cell is important for the endoscopic surgeon to know preoperatively, in the event that the infraorbital cell is targeted during sinus surgery.