Air spaces neighbouring the infraorbital canal

The infraorbital canal (IOC) courses through the roof of the maxillary sinus (MS). Different grading systems concerning the topography of the IOC have been proposed. Further, it has been suggested that a transantral IOC would be morphologically related to Haller's cells (HCs). However, we hypothesized that this is not necessarily the case. Hence, we aimed to study the anatomical possibilities of the air spaces located medially to the IOC.

The cone-beam computed tomography (CBCT) files of 40 adult patients were retrospectively evaluated.

The transantral type of IOC was found in 32.5% of patients. The infraorbital recesses of the MS were found medial to the IOC in 20% of patients. As referred to the nasolacrimal canal, these recesses were either prelacrimal (appearing as false isolated air cells) or retrolacrimal (appearing as false HCs). True HCs were found in 10% of patients. They were located medial to the IOC and they drained into the ethmoidal infundibulum (EI), which was distinct from the MS drainage. In 15% of patients, aerated nasolacrimal ducts (NLDs) were found anterior to the EI and medial to the antral angle. They were capable of masquerading either a HC or an infraorbital recess of the MS.

Previous classifications of the IOC, which related it to HCs, were reviewed and the evidence was found to be insufficient to assess the HC-related topography of the IOC. Therefore, to achieve the accurate anatomical identification of the air spaces neighbouring the IOC, the infraorbital recesses of the MS, the HCs, and the aerated NLDs should be carefully discriminated within the antero-supero-medial antral angle.