Lower Cranial Nerves in the Neck: An Anatomical Study

Objectives The aim of this anatomical study was to analyze distances and anatomical relations between the lower cranial nerves and important neck landmarks. Methods Anatomical study based on neck dissection in Thiel-embalmed cadavers. Anatomical relations and distances between the vagus (X), accessory (XI), and hypoglossal (XII) nerves and important neck landmarks were registered and compared. The relation between the emergence of the great auricular nerve and the posterior border of the sternocleidomastoid muscle and certain anatomical aspects of the ansa cervicalis were also studied. Results A total of 18 neck dissections (seven bilateral, four unilateral) were performed on 11 adult cadavers (mean (SD) age: 74.2 (12.9) years, four male, seven female). The X nerve was posterolateral to the common carotid artery and medial to the internal jugular vein (IJV) in 55.6% of the cases. In relation to the IJV, the XI nerve traveled mostly anteromedial (44.4%) at the level of the jugular foramen, posterior (50%) at the posterior belly of the digastric muscle, and posterolateral (77.8%) below the digastric muscle. The XII nerve was inferior (50%), medial (33.3%), and superior (16.7%) to the digastric tendon. The distance between the XII nerve and the carotid bifurcation was significantly superior in the male gender (mean (SD): 31.7 (6.8) mm vs. 18.5 (7.9) mm, p = .003). Also, the distance between the origin of the occipital artery and the point where it crosses the XII nerve was significantly higher in females (median (IQR): 7 (12.0) vs. 4 (4.0), p = .012). Conclusions There is a great variability in the anatomical position, course, and distances between the lower cranial nerves and traditional anatomical landmarks in the neck. The topography of the lower cranial nerves can vary even with the gender. Proper anatomical knowledge is crucial in neck surgery to prevent potential nerve injuries.