Anatomical Landmarks and Branching Patterns of the Greater Auricular Nerve.

Abstract

Descriptive cross-sectional study. Background: The greater auricular nerve (GAN) courses over the sternocleidomastoid muscle (SCM) to supply the area of skin over the parotid gland (PG), the lower auricle and over the mastoid. It is vulnerable to injury during rhytidectomies and parotidectomies, resulting in sensory losses and pain. Although previous studies have identified suitable landmarks, injury to the GAN in the Kenyan setting still occurs. This study therefore aimed at identifying specific landmarks for the GAN and describing its branching pattern. Objective: To determine the anatomical landmarks of the GAN and its branching patterns. Methods: Forty six nerves were studied. The skin and fascia of the neck was carefully dissected to reveal the platysma muscle, which was reflected to expose the GAN. The distance of the emergence of the GAN on the posterior border of the sternocleidomastoid muscle as measured from the mastoid process (MP) was measured. Its perpendicular distance from the tragus to the point of branching was also measured. Its distance to the external jugular vein (EJV) was taken using a ruler and a pair of dividers. Finally, the nerve was described according to McKinney's point. The pattern of branching was described as either type 1 (no branching), type 2 (2 branches) or type 3 (3 branches). The position of branching was classified as either anterior, posterior or middle. Collected data was coded into SPSS software (Version 21.0, Chicago, Illinois), and means ± standard deviation were calculated. Representative photos were taken. Results: The mean distance of the point of emergence of the nerve was 9.13 cm +/- 1.66 cm from the MP, while its distance from the tragus was 6.93 cm +/- 1.55. It was also located at a distance of 1.67 cm from the EJV. It mainly bifurcated into two branches (55.6%) and trifurcated in 4.4% of the cases. It remained undivided in 40% of the cases. In our study, the nerve mainly bifurcates in the anterior third of the SCM (22.2%). Conclusions: The GAN in our population mainly bifurcates, and it is more likely to divide closer to the parotid gland. The data presented in the study may be helpful in avoiding its iatrogenic injury.