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 conduct ion was studied in 77 healthy adults while 17 GANs were dissected in 10 cad avers. Results - The largest sensory nerve action potentials (SNAP) were re corded when the stimulator was placed 6 or 7 cm from the external acoustic meatus (EAM). Amplitude decreased significantly with age (P = 0.001). The d issected 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. Conc lusion - A large variation was observed both anatomically and by way of ele ctrical stimulation. SNAP variation does probably reflect the anatomical va riation in GAN course, branching, and terminal distribution. The best sites for stimulation were found 6 and 7 cm from EAM at the posterior sternoclei odomastoid border. The maximal amplitude, right:left amplitude ratio, and d istal latency may be useful variables in GAN conduction studies.