Congenital external carotid–internal carotid artery anastomosis associated with contralateral non-bifurcating cervical carotid artery

Abstract

Dear Sir, Non-bifurcating cervical carotid artery is a rare anatomical variation of the carotid artery in which the branches of the external carotid artery (ECA) directly arise from the common carotid artery without forming a bifurcation [1,2]. In addition, cases of congenital EC-internal carotid artery (ICA) anastomosis at the cervical segment forming a large arterial ring have been reported, and it seems to be a variant of the non-bifurcating cervical carotid artery [3]. We wish to bring to your attention a patient showing not only a non-bifurcating cervical carotid artery on one side but also EC-IC anastomosis on the contralateral side. This case suggests that there is a relationship between a nonbifurcating cervical carotid artery and ring formation of the cervical carotid artery.A 71-year-old man underwent CT angiography (CTA) of the extracranial neck vessels, because anomalies of bilateral cervical carotid arteries were discovered at a medical checkup. CTA showed that the right distal common carotid artery changed in caliber at the level of the C6 vertebral body. The major branches of the proximal ECA arose separately from the terminal segment of the common carotid artery or proximal ICA without a proximal main trunk of the ECA (Fig. 1). Thereafter, the artery continued as a normal ICA in the cranial portion.The left carotid bifurcation was located at the level of the C6 vertebral body. The ICA and ECA anastomosed at midcervical level to form a large arterial ring at the proximal cervical segment (Fig. 1).Morimoto et al.[2] first used the term "non-bifurcating cervical carotid artery" as variations/anomalies at the cervical carotid artery in 1990. A non-bifurcating cervical carotid artery is rare, and the overall incidence of the anomaly detected by magnetic resonance angiography was 0.21% [4]. Two hypotheses have been proposed for the development of a non-bifurcating carotid artery [5][6][7]. The first is agenesis of the common stem of the ECA with regression failure of the hyoid artery. The second is segmental agenesis of the ICA.Embryologically, the cervical carotid arteries develop by complicated processes of regression, and the communication within the vascular network consists of the ventral aorta, dorsal aorta, aortic arches, and intersegmental arteries. The ventral aorta and dorsal aorta communicate via aortic arches. Among them, the first aortic arch (mandibular artery) further regresses, while the second aortic arch (hyoid artery) continues to the stapedial artery. It is generally thought that the ECA develops from both the ventral pharyngeal artery system and the hyoid artery system. According to Lasjaunias et al. [8], the occipital artery (OA) is formed from the proatlantal artery and arises from the primitive ICA, ECA, and vertebral artery at points determined by the sites of regression. In our case, the OAs arose from the right IC and left EC, respectively. When the

Anomalous External Carotid Artery-Internal Carotid Artery Anastomosis in Two Patients with Proximal Internal Carotid Arterial Remnants

“…There have been two hypotheses to explain the development of the NBCCA: 1) agenesis of the main trunk of the ECA and 2) agenesis of the proximal ICA segment, with persistence of the hyoid-stapedial system that connects ICA with ECA at C1 level ( Fig. 3D ) ( 1 2 4 ). However, demonstration of a remnant ICA or carotid stump in these two patients suggests that the NBCCA results from the normal development of the main ECA trunk along with agenesis or hypogenesis of the proximal ICA segment ( Fig.…”

“…The non-bifurcating cervical carotid artery (NBCCA) is a rare variant of the carotid arterial bifurcation, in which the ECA trunk directly arises from the common carotid artery without the actual bifurcation forming the ICA ( 1 2 ). Several reports have described similar anomalies showing an anomalous ECA-ICA anastomosis ( 1 2 3 4 5 ).…”

Rare variant of internal carotid artery anatomy

“…ECA gives multiple branches in the cervical and facial region, whereas ICA does not have any extracranial branch. Few reports in the literature have described the entity non-bifurcating CCA (NBCCA), wherein there is anomalous ICA-ECA anastomosis, however these cases do not have a proximal ICA stump as in our case 1 2. Embryologically, it is the third aortic arch which gives rise to ICA and then continues as dorsal root whereas ECA arises from ventral aspect of third aortic arch.…”

Anomalous external carotid-internal carotid artery anastomosis diagnosed by computed tomography angiography: a case report

“…Nonbranching CCA is a rare congenital anatomical variation of the cervical carotid artery [1 , 2] . Both nonbranching CCA and anomalous ECA-ICA anastomosis forming an arterial ring seem to be similar developmental variations [1 , 3] . Two hypotheses have been proposed to explain the causes of a nonbranching CCA [2 , 4] .…”

“…However, its etiology remains unclear [1] . A congenital anastomosis between the ECA and ICA forming an arterial ring at the cervical ICA level is exceedingly rare and seems to be a nonbranching CCA variant [3] . I herein report a case of an anomalous artery directly connecting the ECA and ICA at the level of the C2–3 intervertebral space with hypoplastic proximal cervical ICA diagnosed by computed tomography angiography (CTA).…”