Does the great auricular nerve predict the size of the main trunk of the facial nerve? A clinical and cadaveric study.

There seems to be only individual clinical experience and some anecdotal evidence about a relation between the width of the great auricular nerve (GAN) and the size of the main trunk of the facial nerve during parotidectomy. To our knowledge no anatomical studies have been published. In this cadaveric and clinical study we measured the widest point of the GAN as it crosses the sternomastoid muscle before it divides, and the main trunk of the facial nerve before it bifurcates. Measurements were obtained from 16 patients who required formal superficial parotidectomies with identification of the facial nerve, and from 21 cadavers (16 formalin-fixed and 5 fresh frozen) where both sides were dissected. We recorded the results and the side of dissection. The mean (SD) width of the GAN and facial nerve from all the dissections was 2.75 (0.53)mm and 2.83 (0.54)mm, respectively. There was a strong correlation between the width of the nerves from both sides (left: r=0.934, p<0.001; right: r=0.940, p<0.001). The nerves did not differ significantly in size in patients or cadavers (GAN: right, p=0.873; left, p=0.486; facial nerve: right, p=0.931; left, p=0.691). We have found that the GAN accurately predicts the width of the main trunk of the facial nerve. This is particularly useful surgically as a narrow GAN can alert the surgeon to expect a small facial nerve.