The Anatomical Study of Extracranial Hypoglossal Nerve in Relation to Common Carotid Bifurcation and its Clinical Relevance

Objectives: Hypoglossal nerve provides motor innervation to the muscles of the tongue. Damage to hypoglossal nerve is reported during carotid artery surgery. The object of this study was to investigate the surgical anatomy of the hypoglossal nerve and its relationship to the bifurcation of the Common Carotid Artery (CCA) among the North American population.
Methods: In this study, the extracranial part of hypoglossal nerve was studied in 7 formalin-embalmed adult female and male cadaver heads obtained from the Anatomy Department at the University of Detroit Mercy, School of Dentistry. The entire neck was dissected. The common carotid artery and its bifurcation were located. Then, the distance (in mm), from the Common Carotid bifurcation to the hypoglossal nerve was measured.
Results: The results of this study demonstrated that there is variation in distance from common carotid bifurcation and the hypoglossal nerve (CN-XII). The range was measured to be between 7 mm to 26 mm, with the average of 19 mm. In all specimens, the nerve was found to cross lateral to the external and internal carotid artery, superior to the bifurcation of the common carotid artery. Also, then tendon of the posterior belly of digastric muscle was superior to the course of the nerve.
Conclusions: Variations in the distance from the CCA bifurcation to the hypoglossal nerve was exhibited in the samples studied. However, a decrease in this distance will increase the probability of injury to the nerve during carotid endarterectomy. Therefore, knowledge of the location of the hypoglossal nerve pre-operatively, can minimize the risk of nerve injury at the surgical site.