The frontotemporal peripheral nerves. Topographic variations of the supraorbital, supratrochlear and auriculotemporal nerves and their possible clinical significance.

The peripheral topography of the supraorbital (SON) and supratrochlear (STN) nerves and the superficial temporal branch of the auriculotemporal nerve (ATN) was investigated in 10 cadavers. The aim was to define the optimal locations for anaesthetic nerve blocks, as well as to help surgeons prevent nerve injuries. Specific measurements on the nerve "exits" in relation to defined landmarks are presented. The variability of the supraorbital notches and peripheral branching of the dissected nerves suggests several methods for anaesthetic blocks in cases of surgical and clinical head pain. The optimum injection site for a selective SON block is 20-30 mm from the midline (range 15-33 mm); reinjection at 30-50 mm from the midline might complete inefficient nerve block. For selective SON block the distance between the main SON and STN branches (mean 15.3 mm) should also be considered. The ATN is best blocked at a point located at the level with and 10-15 mm (range 8-20 mm) anterior to the upper origin of the helix. Separate exits for the medial and lateral SON branches were observed in eight of the 20 nerves examined. Twenty of the 28 exits were foraminae completed by bony or connective tissue. In many cases both the SON and STN ascended close to the associated artery: in six cases a tissue band covered the nerve and vessel at the orbital exit. Some of the observed structures associated with the nerve might be pain-generators, however the present study does not provide any evidence for such a hypothesis.