Anatomical study of the carotid bifurcation and origin variations of the ascending pharyngeal and superior thyroid arteries.

BACKGROUND Human anatomy texts in current use have very little precise information as to the frequency of variations in the bifurcation of the common carotid artery, and a clear description of the relation between external and internal carotid arteries as well as the variation of the origin of the ascending pharyngeal and superior thyroid arteries is limited. MATERIAL AND METHODS Sixty common carotid arteries in the sagittal section of the head and neck of 30 human adult cadavers were obtained from the Anatomy Department of King Abdulaziz University. The data collected were analysed using the Chi square-test. RESULTS The carotid bifurcation was at the level of the superior border of the thyroid cartilage in 48.3% of cases, 25% were opposite the hyoid bone, and 18.3% were at the level between the thyroid cartilage and the hyoid bone. The bifurcation appeared at a lower level than the superior border of the thyroid cartilage in 5% of cases, while in 3.3% of cases the bifurcation level was seen higher than the hyoid bone. The usual anteromedial position of the external carotid artery to the internal carotid artery was found in 51.7% of cases, whereas it was medial to the internal carotid artery in 36.7% of cases. In 10% it was seen in an anterior position and only in 1.7% the external carotid artery was lateral to the internal carotid artery. In 93.3% of the cases the ascending pharyngeal artery originated from one root, while in the remaining 6.7% of cases it originated from two roots. In 80% of cases the superior thyroid artery arose from the external carotid artery. In 18.3% of cases it originated from the common carotid artery, and in 1.7% it arose from a thyrolingofacial trunk. CONCLUSIONS The carotid bifurcation can occur as high as the hyoid bone, or as low as the cricoid cartilage. The anteromedial position of the external carotid artery (ECA) in relation to the internal carotid artery (ICA) was the most common anatomical position. The origins and configurations of the ascending pharyngeal artery and the superior thyroid artery are variable.