Nonbifurcating Carotid Artery: A Case Report with a Review of Embryogenesis

A nonbifurcating cervical carotid artery with a remnant of the proximal internal carotid artery that mimicked an aneurysm on magnetic resonance angiography

PURPOSE

To describe a case of a nonbifurcating cervical carotid artery with remnant of the proximal internal carotid artery (ICA).

METHODS

A 47-year-old man with unruptured cerebral aneurysm underwent magnetic resonance (MR) angiography of the neck region and intracranial region. The MR machine was a 3-T scanner. Catheter angiography was performed for the treatment of the aneurysm by coil embolization.

RESULTS

The proximal main trunk of the left external carotid artery (ECA) was absent, and branches arose separately, indicative of a nonbifurcating cervical carotid artery. At the level of the ICA origin, aneurysmal protrusion was found on MR angiography. On catheter angiography, this protrusion was not an aneurysm but a remnant of the proximal ICA.

CONCLUSION

The configuration of the nonbifurcating cervical carotid artery lacks the proximal ECA; however, segmental agenesis of the proximal ICA forms this rare cervical arterial variation. The present case had remnants of the proximal ICA. We speculate that the ICA channel, except for the origin, was occluded after the development of EC-ICA anastomosis, and a nonbifurcating cervical carotid artery with a remnant of the ICA may have formed. Including our patient, only four cases have been reported in the relevant English-language literature.

Anomalous Cervical External Carotid Artery-Internal Carotid Artery Anastomosis Diagnosed Using Digital Subtraction Angiography: A Case Report

Anomalous external carotid artery (ECA)-internal carotid artery (ICA) anastomosis is a rare variant of cervical carotid artery formation that forms an arterial ring in the cervical segment, and its embryological mechanism is still unknown. We report a case of a 41-year-old woman who was incidentally diagnosed with this arterial variation using digital subtraction angiography. The angiography revealed the occipital artery arising from the anastomotic vessel and the ascending pharyngeal artery arising from the ICA near the anastomosis. The proximal ICA was smaller in diameter than the proximal ECA, but it was not stenotic and had sufficient caliber for the distal blood flow. It is commonly believed that the persistence of primitive vessels is the result of agenesis or hypoplasia of the proximal artery. In our case, the anomalous vessel was considered to be the remnant of a primitive anastomosis between the ECA and the ICA via the pharyngo-occipital system, and the narrowing of the proximal ICA may be the result of the remaining ECA-ICA anastomosis.

Congenital external carotid-internal carotid artery anastomosis: a report of three cases and literature review

PURPOSE

Congenital external carotid-internal carotid artery (EC-ICA) anastomosis is a cervical arterial variation that was initially reported, based on anatomic dissection, from Japan in 2000. The purpose of this report is to show the characteristic radiological findings of this extremely rare cervical arterial variation.

METHODS

We analyzed nine cases, including six previously reported cases and three cases that we recently experienced. Three of the six previously reported cases were from Japan, and the remaining three cases were from Korea. MR angiography (4), CT angiography (2), catheter angiography (2) and autopsy (1) were used as diagnostic modalities.

RESULTS

The study population included eight men and one woman. Anastomosis was seen on the left side in seven cases and the right side in two cases, and it was located at the level of the C1/2-C2/3 intervertebral space. In all cases, ECA was larger than the ICA at the level of their origins. In four cases, the ICA was extremely small in caliber. In one case, the ICA may have been occluded postnatally, and its configuration was similar to that of the nonbifurcating cervical carotid artery (CCA). With the exception of this occluded case, the carotid bifurcation and EC-ICA anastomosis formed a large arterial ring in all cases.

CONCLUSION

EC-ICA anastomosis can be regarded as a variant of the nonbifurcating CCA because if the most proximal segment of the small ICA is occluded, nonbifurcating CCA may form. EC-ICA anastomosis is located between the C1/2-C2/3 intervertebral space and may be formed by the remnants of the proatlantal artery I.

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

An anomalous anastomosis between the external and internal carotid arteries forming an arterial ring at the level of the cervical internal carotid artery is an extremely rare variant, and its embryological origin remains unclear. This report describes a rare arterial variation at the level of carotid bifurcation incidentally discovered in a 67-year-old man. Computed tomography angiography revealed an anomalous anastomosis between the external and internal carotid arteries at the level of the C2–3 intervertebral space with a small proximal cervical segment of the internal carotid artery and the occipital artery originating at this anomalous anastomosis. This report may be of embryological significance and contribute to understanding the mechanisms of carotid artery formation.