External Carotid Artery

42 External Carotid Artery

F. Goetz, A. Giesemann

42.1 Bifurcation of the Common Carotid Artery

The division of the common carotid artery has often been related to the larynx. The height of the larynx is age-dependent, resulting in different heights of division of the common carotid artery according to age. It is more reliable to relate the bifurcation to the vertebral column to avoid age dependency. Differences of up to the height of one cervical vertebra have been described between the right and left side. Arch-like divisions are more common in higher divisions and divisions at acute angles more frequent in lower divisions.¹^–³

The references are given for anomalies of the carotid arteries in general²^,⁴^–¹⁰ (see also Figs. 2.3–2.28) and for the branches and trunks of the external carotid artery. Many studies deal with more than one branch.¹^,²^,¹¹^–¹³

Fig. 42.1 Bifurcation of the common carotid artery. Schematic (a) and X-ray angiography, unsubtracted image, lateral view, common carotid artery injection (bifurcation at the level of C3) (b). 1 Internal carotid artery; 2 external carotid artery; 3 common carotid artery.

42.2 Superior Thyroid, Lingual, and Facial Arteries

42.2.1 Separate Origins (80%)

Fig. 42.2 All three arteries originate from the external carotid artery (50%). Schematic (a) and X-ray angiography, lateral view, common carotid artery injection (b). 1 Facial artery; 2 lingual artery; 3 inferior thyroid artery.

Fig. 42.3 The superior thyroid artery originates from the bifurcation of the common carotid artery (20%). This variation is more common on the left side than on the right side. Schematic (a) and X-ray angiography, lateral view, common carotid artery injection; note ectasia of the superior thyroid and occipital arteries (b). 1 Internal carotid artery; 2 internal maxillary artery; 3 occipital artery; 4 facial artery; 5 inferior thyroid artery.

Fig. 42.4 The superior thyroid artery originates from the common carotid artery (10%). This variation is considerably more common on the left side than on the right side, and it is more common in women than in men. Schematic (a), X-ray angiography, lateral view, left common carotid artery injection (b), and X-ray angiography, lateral view, left common carotid artery injection with origin of the superior thyroid from the common carotid and origin of a linguofacial trunk at the bifurcation level (c). 1 Internal maxillary artery; 2 facial artery; 3 lingual artery; 4 inferior thyroid artery.

Fig. 42.5 The superior thyroid and lingual arteries originate from the common carotid artery (<1%). Schematic.

42.2.2 Trunk Formation (20%)

Fig. 42.6 Linguofacial trunk (always from the external carotid artery) (18%). The superior thyroid artery might derive from the common carotid artery. Schematic.