Bilateral internal carotid artery fenestration

We present a case of bilateral internal carotid artery fenestration that was identified incidentally in a 72-year-old man. The patient had undergone a computed tomography angiogram of his neck to evaluate a thyroid nodule. The abnormality in the bilateral carotid arteries was noted and patient was referred to vascular surgery with concern for carotid dissection (A). The patient denied stroke symptoms and had no history of prior trauma. Review of the prior imaging showed symmetric duplication of the lumen in the distal extracranial internal carotid artery with smooth luminal contour on the right and irregular atherosclerotic plaque in one of the lumens on the left side (B/Cover and C). Given the incidental nature of the findings and absence of related symptoms, no intervention was indicated. The patients consented to the reporting of this case and sharing of images. Carotid artery fenestrations are extremely rare anatomical variants that have been described previously.1Hacein-Bey L. Raghavan N. Mukundan G. Sekhon A.K. Dodrill L.K. Park T.C. Fenestration of the petrous internal carotid artery with short segment duplication mimicking an arterial dissection.Clin Radiol. 2013; 68: 972-975Abstract Full Text Full Text PDF PubMed Google Scholar However, to our knowledge this case is the first in which this finding is present bilaterally. Although the term fenestration is often used interchangeably with duplication, these are in fact two distinct anatomical variants. Arteries with a single origin that divide into two separate lumens before reconverging are considered fenestrations, whereas arteries with separate origins which run in parallel courses are considered duplications. The development of these fenestrations is believed to be related to either the persistence of the carotid duct, an embryonic vessel which connects the third and fourth aortic ducts and usually regresses during development, or failure in fusion of complex arterial channels in the early stages of development.2Chess M.A. Barsotti J.B. Chang J.K. Ketonen L.M. Westesson P.L. Duplication of the extracranial internal carotid artery.AJNR Am J Neuroradiol. 1995; 16: 1545-1547PubMed Google Scholar Their clinical significance is that they can appear radiographically very similar to dissections and may be mistaken for these. In the absence of symptoms, which could develop from stenosis or aneurysm, no treatment is indicated. Illustration by David Factor. None.