High bifurcation of the common carotid artery and looping of the external carotid artery â a case reportCorrespondence Address :
Department of Anatomy,
Chettinad, Hospital And Research Institute,
Chettinad, University,Kelambakkam ,Tamil Nadu-603103, India.
Phone : +919962069025
During the routine dissection of the anterior triangle of the neck in a 65-year old female cadaver at Chettinad Hospital and Research centre, a bilateral high bifurcation of the common carotid artery and looping of the external carotid artery on the left side was observed. A high bifurcation of the common carotid arteries on both sides above the level of the angle of the mandible was found. The âSâ shaped loop of the external carotid artery was observed on the left side. The branching pattern of the external carotid artery was normal on the right side, but on the left side, the superior thyroid artery was found to arise from the common carotid artery
Bifurcation, common carotid, Looping, External carotid artery, Kinking
Common carotid arteries (CCA) are large arterial vessels of head and neck surgery, which are important landmarks which define the plane of dissection during radical neck surgery (1). Conventional angiography is considered as the most accurate technique for the diagnosis of carotid bifurcation diseases such as stenosis(2). Variations in the origin and branching of the external carotid artery are well known and they have been documented. As already has been discussed by Susan Standing (3), the common carotid artery of both the sides diverges laterally behind the sterno-clavicular join to the level of the upper border of the thyroid cartilage of the larynx (C3-4 junction), where it divides into the external and the internal carotid arteries and the external carotid artery runs within the substance of the parotid gland and behind the neck of the mandible. It divides into two terminal branches, the superficial temporal and the maxillary arteries. These variations are of importance for surgical approaches in the head and neck region (4). Coiling (or looping) of an artery is a rare morphological entity, which has been most frequently described in the internal carotid artery as a single cause of cerebrovascular insufficiency or in combination with carotid atherosclerosis (5),(6),(7),(8). The term âDolicho-arteriopathiesâ has been applied to the coiling, kinking, and the tortuosity of the carotid arteries (9). The incidence of coiling and kinking of the internal carotid artery has been estimated to be from 10% to 16% in the general population. Its respective clinical significance still remains the ground of controversy (10).
The variations in the level of bifurcation of the common carotid artery and in the branching pattern of the external carotid artery was seen during the routine dissection of the anterior triangle of the neck in a 65-year old female cadaver in the Department of Anatomy, Chettinad Hospital and Research Institute. The common carotid artery bilaterally bifurcated above the level of the angle of the mandible. The course and the branching pattern of the external Case Reportcarotid artery were normal on the right side. The left superior thyroid artery arose from the common carotid artery, 1.8 cm below the carotid bifurcation and its other branches and the course of the external carotid artery were normal on the left side. The left external carotid artery, at its commencement, formed an âSâ shaped looping, which is a characteristic feature that was noticed (Table/Fig 1).
The common carotid artery bifurcates commonly at the level of the upper border of the thyroid cartilage, as has been described in the standard text books of anatomy (11),(12).The lower division of the common carotid artery has been recorded to be as frequent as 30% (11),(12).
The common carotid artery has no significant branches, but it may give rise to the vertebral artery, the superiorthyroid artery, laryngeal branches or ascending pharyngeal arteries (12).The origin of the superior thyroid artery from the common carotid artery has been previously reported by many authors (13),14].The origin of the superior thyroid artery from the common carotid artery was found only in 5% of the cases among the Swiss and in 45% cases among the Americans (11).Recent reports have also stated the same to be 30% and 52.3% (15),(16). The hypoglossal nerve was closer in relation to the common carotid artery bifurcation (15). In this present case also, the superior thyroid artery originated from the common carotid artery on the left side while the hypoglossal nerve lay on the origin of the external carotid artery (Table/Fig 1). On the right side, the superior thyroid artery originated from the external carotid artery. Other branches of the external carotid artery from both the sides were normal.
The mode of classification of the variations of the internal carotid artery can also be applied to classify the variations in the external carotid artery (17).
The frequency of the common carotid bifurcation at the C3 and C3-4 vertebrae was 38.8% and 22.5%. Terminations which were higher than the C3/C3-4 levels were found in 25% of the vessels. The higher bifurcation was at the level of C2 in 12.5% of the cases (18) and the bifurcation at the level of C3 was 50% on the right side and 55% on the left side (19) respectively. A study on human foetuses showed the maximum CCA bifurcation at the level of C3 in 60% of cases on the left side and in 55% on the right side. A high division of CCA on both the sides 1cm above the greater cornu of the hyoid bone and 2 cm above the superior border of the lamina of the thyroid cartilage was reported (20),(21).There was a report that the common carotid bifurcation was noted bilaterally at the level of C2 (22).The present case also showed the bilateral higher bifurcation of the common carotid, but it was above the angle of the mandible (C2), that is 3.6cm above the superior border of the thyroid cartilage.
The third aortic arches are the precursors of the carotid system. It forms the CCA and the cranial segment of the ICA. The caudal segment of the ICA is formed by the dorsal aorta and the external carotid artery sprouts from the third aortic arch (23). The embryological reason for the kinking of the external carotid artery may be the descent of the heart and the incomplete straightening of the vessels during the shifting of the origin from the aortic sac to the third aortic arch.
The âSâ shaped looping on the left side was observed at the level of origin of the external carotid artery (24).Variations like elongations, tortuosity, coiling, kinking or looping may be congential. The kinking may be associated with arteriosclerosis, stenosis, vasculitis, atrophic dilation, loss of elasticity and dissection in the context of fibro muscular dysplasia (25). The carotid coils occur conversely in adults and most frequently in the elderly, in whom atherosclerosis is also frequently seen. The coiling of the external carotid artery may be acquired from the excessive elongation of the artery with age, and the elongated artery may have thinning of the media and fragmentation of the elastic lamina (7).
Knowledge of the vascular anatomy is essential for the interpretation of diagnostic and interventional vascular procedures.When there is a need for a more accurate interpretation in radiological examinations during precutaneous carotid angiography, external anatomical land marks turn out to be useful. Radiologists should take these variations into consideration. Looping may be associated with degenerative changes in the vessel wall and it may predispose to atherosclerotic stenosis. The hypoglossal nerve lies closer to the CCA bifurcation, which is more vulnerable.
There is no grant support.We thank the Chettinad hospital and research institute for permitting us to carry out this study.
DECLARATI ON ON COMPETING INTERESTS:
No competing Interests.
Date of Submission: Jun 10, 2011
Date of Peer Review: Aug 22, 2011
Date of Acceptance: Aug 22, 2011
Date of Publishing: May 01, 2012
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