Neuroradiology nuggets: Non bifurcating carotid

Shriram Varadharajan1, Meena Nedunchelian2

1Senior Consultant – Neuroradiology, Kauvery Hospital, Radial Road, Chennai

2Junior Consultant – Neuroradiology, Kauvery Hospital, Radial Road, Chennai

Introduction

Knowledge of anatomical variations is crucial in the correct diagnosis and management. The cervical carotid artery normally bifurcates at the level of C3/4 vertebral bodies. Non bifurcating carotid artery is a rare anomaly of the cervical carotid, with absence of carotid bifurcation. A single carotid artery arising from the aortic arch is seen to continue intracranially along the course of internal carotid artery, as well as giving off various branches which normally would be expected to arise from the external carotid artery.

Previous studies report an incidence of 0.21% with less than 20 cases worldwide in available existing literature. We report a very rare case report of a patient presenting with stroke and demonstrating a non-bifurcating carotid, with contralateral ICA occlusion.

Case Presentation

A 75-year-old male brought to ER with complaints of drowsiness for 1 week, with progressively increasing symptoms and decreased movement in left upper and lower limb. Non contrast stroke protocol Magnetic Resonance Imaging (MRI) was performed on a 3T Philips Elition system.

Protocol for limited stroke imaging includes Diffusion Weighted Imaging (DWI), Fluid Attenuated Inversion Recovery (FLAIR) and Susceptibility Weighted Imaging (SWI) with non-contrast MR Angiography of neck and brain. Incorporation of neck MRA in all Stroke protocols is mandatory for complete vascular assessment. If possible high resolution arch to vertex coverage should be obtained.

Imaging Findings 1

Fig (1) & (2): DWI images show acute right hemispheric infarcts

Image Finding 2

(3)

Fig (3): MR Angiogram shows, Non visualisation of the complete right ICA with absent flow signals from region of the cervical bifurcation, suggestive of steno-occlusion.

Image Finding 3

Fig (4) & (5): Contralateral left carotid artery shows non bifurcating pattern with CCA continuing as a single trunk (ICA) with occipital, linguofacial and internal maxillary branches.

Clinical implications

  • Atherosclerosis has been reported in cases with an anomalous non bifurcating carotid artery, challenging the theory of flow diversion as the major etiological factor for plaque predilection at the carotid bifurcation.
  • Carotid stenosis can be treated with carotid endovascular stenting, which requires a distal protection device to reduce the risk of thromboembolic events. Knowledge of the variant anatomy and branching pattern helps in selecting the suitable distal protection device.
  • Remnant ICA could be mistaken for an aneurysmal sac.
  • Arterial dissection in non-bifurcating artery might be common due to the longer extracranial course than the normal ICA and the vulnerable area is longer.

Embryological Hypothesis and Conclusions

Few hypotheses have been put forward to explain non bifurcating pattern

  1. Non bifurcating carotid Hypogenesis / agenesis of proximal ICA with anastomosis of the proximal ECA and distal ICA – With / without proximal ICA stump
  2. Agenesis of ECA with its branches arising from the terminal segment of the CCA or proximal ICA.

Knowledge of variation thus helps in treatment planning and preventive strategies.

References

  • Rodriguez HE, Ziauddin MF, Podbielski FJ, Durham JR, Clark ET. Congenital absence of the external carotid artery: atherosclerosis without a bifurcation. J Vasc Surg. 2002;35(3):573-575.
  • Yuan C, Duan H, Yi Z, Zhang Y, Zhang J. Stenting for Middle Cerebral Artery Stenosis Associated with a Nonbifurcating Cervical Carotid Artery: Case Report and Naming Consideration. World Neurosurg. 2019;125:170-174.
  • Lourenco P, Heran M. Asymptomatic non-bifurcating carotid artery. A case report and literature review. Neuroradiol J. 2014;27(4):393-396.
  • Nas OF, Karakullukcuoglu Z, Hakyemez B, Erdogan C. Dissection of a non-bifurcating cervical carotid artery. Neuroradiol J. 2016;29(3):213-215.
  • Murono S, Nakanishi Y, Minami T, Matsui O, Furukawa M, Yoshizaki T. Case report. Intra-arterial chemotherapy for laryngeal cancer via a non-bifurcating carotid artery. Br J Radiol. 2009 Oct;82(982):e197-9.
  • Yoshida S, Ota T. Carotid Endarterectomy for Atherosclerotic Stenosis Associated with Non-bifurcating Cervical Carotid Artery: A Case Report. NMC Case Rep J. 2016;3(3):59-62. Published 2016 May 12.

 

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