An Anatomic Study to Define A Ratio to Locate the Great Auricular Nerve

Goals/Purpose: Injury to the great auricular nerve (GAN) is the most common nerve injury with a facelift procedure, occurring at a 6-7% rate. Previous studies have indicated absolute measurements that can be used to predict the location of the GAN, however these estimates can vary greatly depending on patient size. Our aim was to find a ratio based on clear anatomic landmarks to more accurately predict the location of the GAN thus avoiding injury during flap elevation and dissection.

Methods/Technique: Eleven fresh cadaver specimns were dissected under loupe magnification. All dissections were performed in a 45 degree position (facelift position) with a mid-sternocleidomastoid (SCM) incision. Measurements were taken from multiple bony and soft tissue landmarks to the GAN that operating surgeons could easily ascertain preoperatively and intraoperatively. Measurements from the bony mastoid process, bony external auditory canal, external jugular vein and anterior border of the SCM to the GAN were taken in each cadaver.

Results/Complications: The GAN has a consistent course over the mid-body of the SCM before bifurcating into anterior and posterior branches and terminal arborization. Depending on the length of the SCM, the GAN at its most superficial location was found consistently at a ration of 1/3 the distance from the superior aspect of the SCM when measuring from either the bony mastoid process or the bony external auditory canal. The range of the distance of the GAN from the EAC was 5.8-7.4cm, with an average distance of 6.5cm +/-0.9cm.

Conclusion: Despite previous descriptions of nerve location, injury to the GAN still carries significant morbidity in terms of high incidence and functional sequelae. Knowledge of the anatomy and course of the GAN in relation to the SCM (1/3 ratio) may reduce the risk of injury to the GAN with facelift procedures.