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 o f the supraorbital nerve is by way of a notch or a foramen at the bord er of the inner to the medial third of the supraorbital rim. In contra st to several anatomic textbooks, we noticed that the exit point was r epeatedly not at the site where anticipated when implanting lid spring s for facial palsy. This gave us the idea of investigating these varia tions and how big they are, because most open and recent endoscopic fo rehead lift techniques have relied on a constant exit point of the sup raorbital nerve. A total of 507 macerated skulls (1014 orbits) from th ree anatomic collections in Austria and Germany were studied. All skul ls 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 inclu ded in the statistical analysis but in the discussion. The anatomic me asurements on the skulls were carried out with an anthropometric calli per. The examinations concentrated on the configuration (notch/foramen ) and the number of exit point(s) on the supraorbital rim, the vertica l distance from the supraorbital rim, and the distance from the nasion to the various exit point(s). Combining all of these parameters, 74 p ercent 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 latera l branch, either through a notch or a foramen, the foramen being somet imes the exit of a supraorbital canal. The average distance from the n asion 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 fa rthest exit paint was 19 mm. Other than what is cited in literature, t he variations concerning the configuration and the distance of the exi t point(s) of the supraorbital nerve were so significant that all fore head operations, especially those using endoscopic techniques, must ta ke into account these findings.