Dual origin of the left vertebral artery: a rare anatomic variation

Abstract

Duplication of the vertebral artery is a very rare vascular variant. We describe a case of a duplicated left vertebral artery. Computed tomography (CT) angiography examination of the head and neck vessels of a 63-year-old man with a history of imbalance was undertaken. A duplicated left vertebral artery was incidentally noted. The medial limb directly originated from the arcus aorta between the left common carotid artery and the left subclavian artery. The lateral limb originated from the proximal left subclavian artery as the first branch and entered the transverse foramen of the C6 vertebra as usual. Prior to neck procedures requiring the anterior cervical approach and carotid endarterectomy, the awareness and diagnosis of the duplicated vertebral artery are important due to the potential risk of inadvertent vertebral artery injury. Therefore, this variation should be taken into account while evaluating cross-sectional imaging studies.

Introduction

The vertebral arteries are among the major arteries of the head and neck. They supply blood to the cervical spinal cord, brainstem, cerebellum, and posterior part of the brain. Both vertebral arteries usually originate from the proximal subclavian arteries. Developmental variations in the origin of the vertebral arteries are present in approximately 5% of individuals.

The vertebral arteries may originate from the arcus aorta, innominate artery, common carotid artery, and external carotid arteries. Among these variations, the most common is the left vertebral artery directly arising from the arcus aorta [1, 2]. Duplicated origin of the vertebral arteries is quite rare, and the majority of cases had no clinical implication.

Case report

A 63-year-old man with a history of imbalance and suspected cerebrovascular pathology was referred to our institution for computed tomography (CT) angiography examination of the head and neck vessels. On CT angiography, no hemodynamically significant lesion was noted in the head and neck vessels; however, a duplicated left vertebral artery was incidentally detected. The medial limb directly originated from the arcus aorta, between the left common carotid artery and the left subclavian artery. While ascending, the medial limb had a tortuous course posteromedially to the left common carotid artery. The lateral limb entered the transverse foramen of the C6 vertebra as usual after branching off from the proximal left subclavian artery. Both limbs united at the transverse foramen of the C4 vertebra (Figs. 1, 2). The left vertebral artery’s course was normal above that level. The right vertebral artery originated from the right subclavian artery.

Fig. 1.

Coronal maximum intensity projection (MIP) computed tomography angiography (CTA) image (a) demonstrates the lateral limb of the left vertebral artery arising from the left subclavian artery (arrows). Sagittal MIP CTA image (b) shows the medial limb of the left vertebral artery (dashed arrows) arising directly from the arcus aorta, coursing superiorly and converging with the lateral limb (black arrow). Axial multiplanar reformat CTA image (c) shows the medial (dashed white arrow) and lateral (black arrow) limbs of the left vertebral artery. The normal right vertebral artery is also shown (dashed black arrrow)

Fig. 2.

Schematic arrangements of the vessels of the neck and demonstration of the duplicated left vertebral artery with the medial limb originating from the arcus aorta and the lateral limb originating from the left subclavian artery. At the left transverse foramen of C4, both limbs show fusion. LSA left subclavian artery, RSA right subclavian artery, LVA left vertebral artery, RVA right vertebral artery

Discussion

The vertebral arteries normally arise as the first branch of the subclavian artery. Anomalous origins of the vertebral arteries are present approximately in 5% of individuals. The left vertebral artery directly arising from the arcus aorta between the left common carotid artery and left subclavian artery is the most common anomaly among those [1, 2]. However, the duplicated origin of the vertebral artery is quite rare, and the majority of these cases are found incidentally [3]. In most cases, the two limbs of the duplicated left vertebral artery arise from the arcus aorta and left subclavian artery, respectively. Rarely both limbs of the duplicated vertebral artery may arise from the left subclavian artery or both limbs may arise from the arcus aorta. Also, the limbs of the duplicated left vertebral artery arising from the thyrocervical trunk and left subclavian artery respectively were reported rarely [3, 4].

Embryologically, the vertebral artery is formed by the longitudinal anastomoses between the cervical intersegmental arteries which branched off the primitive paired dorsal aorta. The connections of the cervical intersegmental arteries to the dorsal aorta eventually regress except for the seventh cervical intersegmental artery which develops into the proximal subclavian artery containing an origin of the vertebral artery. The left vertebral artery originates from the left subclavian artery and enters the sixth transverse foramen. The persistence of the left fourth or fifth cervical intersegmental arteries and the normal origin from the seventh intersegmental artery result in a duplicated origin of the left vertebral artery. The left fourth or fifth cervical intersegmental arteries forming the medial limb of the duplicated vertebral artery originate from the aorta between the left common carotid artery and left subclavian artery [3].

The relationship between vertebral artery duplication and cerebrovascular disease has not been clearly demonstrated. But it has been suggested that the duplicated origin of the vertebral artery may lead to altered hemodynamics and predispose the patient to fenestration, kinking, dissection, and aneurysm formation [5]. Compared to subclavian artery origin, the aortic arch origin of the vertebral artery is thought to be more associated with vertebral artery dissection [6]. The medial limb of the duplicated vertebral artery arising from the aortic arch has a longer prevertebral course, and this may increase the risk of atherosclerosis affecting these segments [7]. Also, an abrupt change in the diameter of the left vertebral artery may occur at the level of anastomosis, which might be confused with hypoplasia or pathologic narrowing of the vessel [8].

Due to non-opacified blood flow from the other limb, a dual origin of the vertebral artery may mimic dissection on conventional angiography [9]. The smaller luminal diameter of the duplicated vertebral artery may affect the choice of route for endovascular procedures [10]. Because of the high entrance of the medial limb of the duplicated vertebral artery into the cervical transverse foramen, there is potential damage to the undiagnosed duplicated vertebral artery during neck procedures involving anterior cervical approach and carotid endarterectomy [11]. Therefore, it is crucial to be aware of this vascular variant prior to related surgeries and interventions.

Author contribution

VY: manuscript writing, data collection, ımage collection.

SAD: manuscript editing, ımage collection and preparation.

TH: manuscript editing, data collection, ımage collection.

Funding

The authors did not receive support from any organization for the submitted work.

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Declarations

Ethics approval

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Consent for publication

The patient has consented to the submission of the case report to the journal.

Competing interests

The authors have no relevant financial or non-financial interests to disclose.

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