Variations of the frontal exit of the supraorbital nerve: an anatomic study

Until now, it has been taken for granted that the point of emergence of the supraorbital nerve is by way of a notch or a foramen at the border of the inner to the medial third of the supraorbital rim. In contrast to several anatomic textbooks, we noticed that the exit point was repeatedly not at the site where anticipated when implanting lid springs for facial palsy. This gave us the idea of investigating these variations and how big they are, because most open and recent endoscopic forehead lift techniques have relied on a constant exit point of the supraorbital nerve. A total of 507 macerated skulls (1014 orbits) from three anatomic collections in Austria and Germany were studied. All skulls were adult European skulls gathered from the prehistoric age up to the twentieth century. Additionally, 18 fixed cadavers (36 orbits) and 25 fresh cadavers (50 orbits) were studied. These data were not included in the statistical analysis but in the discussion. The anatomic measurements on the skulls were carried out with an anthropometric calliper. The examinations concentrated on the configuration (notch/foramen) and the number of exit point(s) on the supraorbital rim, the vertical distance from the supraorbital rim, and the distance from the nasion to the various exit point(s). Combining all of these parameters, 74 percent of the skulls showed asymmetric findings between the right and left orbits. In 15 percent of both orbits, the supraorbital nerve left the orbital cavity already in its two branches, the medial and lateral branch, either through a notch or a foramen, the foramen being sometimes the exit of a supraorbital canal. The average distance from the nasion to the frontal notch/foramen was 25 mm on both orbits (range 16 to 55 mm) and to the supraorbital notch/foramen 31 mm (range 20 to 49 mm). The largest vertical distance from the supraorbital rim to its farthest exit point was 19 mm. Other than what is cited in literature, the variations concerning the configuration and the distance of the exit point(s) of the supraorbital nerve were so significant that all forehead operations, especially those using endoscopic techniques, must take into account these findings.