Neurophysiological and anatomical variability of the greater auricular nerve

Objective - To study the normal variation in greater auricular nerve (GAN) conduction and anatomical course. Materials and methods - GAN nerve conduction was studied in 77 healthy adults while 17 GANs were dissected in 10 cadavers. Results - The largest sensory nerve action potentials (SNAP) were recorded when the stimulator was placed 6 or 7 cm from the external acoustic meatus (EAM). Amplitude decreased significantly with age (P = 0.001). The dissected GANs entered the subcutaneous layer between 55 and 105 mm (median 68 mm) from EAM. The postauricular branch was found in 13 of 17 cases. Conclusion - A large variation was observed both anatomically and by way of electrical stimulation. SNAP variation does probably reflect the anatomical variation in GAN course, branching, and terminal distribution. The best sites for stimulation were found 6 and 7 cm from EAM at the posterior sternocleiodomastoid border. The maximal amplitude, right:left amplitude ratio, and distal latency may be useful variables in GAN conduction studies.