The cranio-orbital foramen, the groove on the lateral wall of the human orbit, and the orbital branch of the middle meningeal artery.

The cranio-orbital foramen, a foramen in the lateral wall of the orbit, contains an anastomosis between the anterior branch of the middle meningeal artery and the lacrimal artery. Previous workers have speculated that the groove starting either from the cranio-orbital foramen or the lateral extremity of the superior orbital fissure contains the anastomotic artery. We investigated the cranio-orbital foramen and the groove on the lateral wall of the orbit in a series of 170 dried adult human skulls, and the course of the orbital branch of the middle meningeal artery in 74 specimens from 37 cadavers. We observed the cranio-orbital foramen in 141 skulls (82.9%). It was unilateral in 55 (32.4%) and bilateral in 86 (50.6%) skulls. The groove on the lateral wall of the human orbit was observed in 122 skulls (71.8%). It was unilateral in 40 (23.5%) and bilateral in 82 (48.2%). The groove on the lateral wall of the orbit started from the cranio-orbital foramen in 20 skulls (11.8%). The orbital branch of the middle meningeal artery was found in 48 cadaveric specimens (64.9%): 32 (43.2%) passed through the cranio-orbital foramen and 12 (16.2%) passed through the superior orbital fissure. In four specimens (5.4%), orbital branches of the middle meningeal artery passed through both the superior orbital fissure and the cranio-orbital foramen. The anatomy of the cranio-orbital foramen and the course of the orbital branch should be well known by surgeons reconstructing the anterior base of the skull, the orbit after orbital base surgery, and during excision of meningiomas.