The small foramina of the orbit and periorbital region: assessment with multi detector computed tomography.

BACKGROUND

Familiarity with the variants of the foramina of the orbit and periorbital region is important in planning anesthesiological blocks and during orbital and maxillofacial surgery to avoid damage to nerves and vessels.

PURPOSE

To assess the visibility and the incidence of variants of the small foramina of the orbit by multidetector computed tomography (MDCT).

MATERIAL AND METHODS

The MDCT scans of 400 orbits from 200 patients were evaluated retrospectively. Slice thickness of the reconstructed images were in the range of 0.5-1.0 mm. The visibility and the variants of the foramen supraorbitale, the foramen infraorbitale, the foramen zygomaticofaciale, the foramen ethmoidale anterius et posterius, and the foramen cranio-orbitale were assessed using three-dimensional reconstruction tools.

RESULTS

The foramen infraorbitale (100%; n = 400), foramen supraorbitale (99.5%, n = 398), foramen zygomaticofaciale (76.5%; n = 307), and foramen zygomatico-orbitale (74.5%; n = 298) were most reliably detected by MDCT, while the foramen ethmoidale anterius (58.7%; n = 235) et posterius (56.7%; n = 225) were depicted less frequently. The foramen cranio-orbitale could not be identified in any case. Doubling was found for the foramen supraorbitale in 3.25% (n = 13), the foramen infraorbitale in 1.75% (n = 7), the foramen zygomaticofaciale in 16% (n = 64), and the foramen zygomatico-orbitale 14% (n = 56). Three foramina zygomatico-orbitale and foramina infraorbitale were found in 1.5% (n = 6) and in 0.5% (n = 2) of orbits, respectively.

CONCLUSION

The foramina supraorbitale, infraorbitale, zygomatico-orbitale, and zygomaticiofaciale and their variants are well visible on MDCT. Knowledge of the exact number of these small foramina is relevant for preoperative evaluation.