Investigation of the bifurcation level of the common carotid artery and variations of the branches of the external carotid artery in human fetuses.

Variations in the position of the bifurcation of the common carotid artery (CCA) and the origin or branching pattern of the external carotid artery (ECA) are well known and documented. In this study, the bifurcation levels of the CCA and origin variations of the branches of the ECA have been extensively investigated in human fetuses. Bilaterally, 40 carotid bifurcations and 40 ECA and their branches have been examined. A latex solution, which had been diluted with water at a ratio of 25% and colored with red India ink, was injected into the aortic arch. Fetuses were kept at room temperature for 24 h before the ECA and its branches were dissected under the microsurgery microscope. Cases of variation were determined and photographed. The bifurcation level of the CCA was determined to be 55% at the C3 level, 35% at the C4 level, 10% at the C5 level on the right side and 60% at the C3 level, 40% at the C4 level on left side. The distribution of the ECA trunks was determined as follows: A linguofacial trunk was present in 20% of the cases, a thyrolingual trunk in 2.5%, a thyrolinguofacial trunk in 2.5% and an occipitoauricular trunk in 12.5%. Beyond this the ascending pharyngeal artery (APA) was observed in one fetus to originate from the internal carotid artery (ICA). Knowledge of variations in the origin and course of the ECA and its branches is of great importance in surgery and radiological examinations.