Cuvinciuc, Victor

Lovblad, Karl-Olof

Scheffler, Max

Vargas, Maria Isabel

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A 68-year-old female presenting with gait instability andvertigo for six months was referred to our institution for cranialmagnetic resonance imaging (MRI) to rule out acoustic neuromaor stroke. Her past medical history was noteworthy forhypertension, hypercholesterolemia, obesity, and diabetes. Theneurological examination revealed no focal neurological deficit. Magnetic resonance imaging of the head and the vessels of theneck was performed on a 1.5 Tesla machine (Magnetom Espree;Siemens, Germany) with acquisition sequences comprising axialT1 weighted imaging, axial T2 weighted imaging, coronal fluidattenuated inversion recovery (FLAIR), axial gradient echo T2,axial diffusion weighted imaging, axial three-dimensional (3D)time of flight MRI angiography, and coronal MRI angiographyof the supraaortic vessels after injection of 23 ml ofparamagnetic gadolinium-based contrast media (Dotarem;Guerbet, Roissy, France). Multiplanar maximum intensity pixeland 3D reconstructions were performed. The MRI revealed neither an anomaly of the patient's internalauditory canals, nor signs of recent stroke. However, particularlywell seen on the angiographic 3D reconstructions, was aduplication of the right extracranial internal carotid artery (ICA)starting 1.8 cm above the common carotid bifurcation withextension to the base of the skull and the beginning of thepetrous portion of this artery, where the two lumens reunited(Figures 1, 2). The diameter of the two rounded lumens wasequal, and the distance between them too great for a diagnosis ofdissection to be entertained (Figure 2). The course of theduplicated ICA was within normal limits, the two branchesparallel. Just caudal to their reunification, a small 3.5 mmaneurysm was seen arising from the more medial of the twobranches (Figure 1). Several variations may occur in carotid anatomy, in thecourse of the common carotid artery (CCA) and the ICA, as wellas in the position of the carotid sinus1. Persistent embryologicarteries comprise the trigeminal artery, the hypoglossal artery,otic and proatlantal intersegmental arteries1. Duplication of theextracranial ICA is a rarely seen anatomic variant. Duplicationmust be differentiated from dissection as well as fenestration, thelatter referring generally to a shorter segment. In the scientificliterature, ICA duplication has been described by Killien et al in19802, and then by Chess et al in 19953, and McEachen et al in2008, in association with other developmental anomalies4. In the human embryo, vasculogenesis commences on day 17in the yolk sac mesoderm, and on day 18 in the embryonic disc,where endothelial cell precursors form so-called “angioblasticcords”5. These “angioblastic cords” coalesce to form a networkof angioblastic plexuses, the base of the circulatory system of theembryo5. On day 19, vascular elements form in the cardiogenicTHE CANADIAN JOURNAL OF NEUROLOGICAL SCIENCES 423Duplication of the Extracranial Internal Carotid Artery Analyzed by MRI  Max Scheffler, Victor Cuvinciuc, Karl-Olof Lovblad, Maria Isabel Vargas Can J Neurol Sci. 2013; 40: 423-425BRIEF COMMUNICATIONSregion, the endocardial tubes. At the same time, paired dorsalaortae develop in the dorsal part of the embryo. The endocardialtubes form the primitive heart tube, with the truncus arteriosislocated at its outflow end5. Figure 1: 3D-reconstructed gadolinium-enhanced T1-weighted echo-gradient angio-MRI of a 68-year-old woman showing right extracranialICA duplication associated with a subcranial aneurysm (arrowhead). From the Departments of Radiology (MS), Neuroradiology (VC, KOL, MIV),University of Geneva and Geneva University Hospitals, Geneva, Switzerland.RECEIVED SEPTEMBER 12, 2012. FINAL REVISIONS SUBMITTED DECEMBER 11, 2012.Correspondence to: Maria Isabel Vargas, Service de neuroradiologie, HôpitauxUniversitaires et Université de Genève, 4 Gabrielle-Perret-Gentil, 1211 Genève 14,Switzerland. Email: maria.i.vargas@hcuge.ch.https:/www.cambridge.org/core/terms. https://doi.org/10.1017/S0317167100014414Downloaded from https:/www.cambridge.org/core. University of Basel Library, on 30 May 2017 at 17:51:00, subject to the Cambridge Core terms of use, available atThe great vessels of the upper thorax and the neck in humansarise from the branchial arch system, a remnant of the branchialrespiratory system in agnathan fish. During the fourth and fifthweeks of gestation (4-5 mm embryonal stage), five branchialarches develop on each side of the pharynx, out of mesenchymalcondensations with mesodermal and endodermal components, ina craniocaudad sequence5. Initially, these arches contain multiplearterial channels, the aforementioned angioplastic plexuses,connecting (anastomosing) the aortic sac extension of thetruncus arteriosus (ventral aorta) with the dorsal aorta.Subsequently, with ongoing angiogenesis, aortic arch arteries 1,2, 3, 4, and 6 form in remodeling processes, arch 5 remainingrudimentary or non-existant in human development1. Theentirety of these arteries conveys, initially, oxygenated blood tothe paired dorsal aorta. The first two arches form between days 22 and 24 andinvolute in humans without significant remains apart fromstapedian and maxillary arteries3. Arches 3, 4, and 6 developbetween days 26 and 29. On either side, the proximal, extra-cranial portion of the ICA is a derivative of the proximal portionof the third aortic arch, also known as “carotid arch“, whereasthe intracranial portion of the ICA is formed by the distal portionof the third aortic arch and the ipsilateral cranial dorsal aorta. By35 days of embryonic age, the segments connecting arches 3 and4 of the dorsal aortae, the “trunci carotici”, disappear byregression. The CCA also develop out of the third aortic arches5,with contribution of the ventral aortic sac1. Branches of the latteralso form the external carotid arteries1. The left fourth aortic archforms a part of the normal adult aortic arch and the sixth aorticarches finally develop into the pulmonary arteries and the ductusBotalli1. Embryogenic vasculogenesis is thus a process comprisingregression, remodeling, and fusion/anastomosis of primitivevessels or plexuses. Regression affects mainly the right side ofthe aortic arch system5. Most vascular malformations result fromthe failure of some primitive elements to undergo regression5.In the case here described, the duplication seems to be due toa developmental abnormality of the right-sided third aortic arch,possibly in the form of an incomplete consolidation of the thirdarch's plexiform arterial channels described above into thenormal vessels. In our case, the finding was associated with asmall aneurysm of one of the two lumens, just below the skullbase. It remains unclear whether this aneurysm existed from theoutset, as an associated congenital anomaly, or whether itdeveloped secondarily due to altered blood flow dynamics andperhaps an altered vascular media. To our best knowledge, this isthe first case of an aneurysm described in association withextracranial ICA duplication. Other vascular variants have been described in combinationwith aneurysms, such as fenestration of vertebral arteries andsupraclinoid ICA fenestration. Several cases of middle cerebralartery duplication have been described with concomitantaneurysms6,7. Duplication of the extracranial ICA on the otherhand has been reported in association with severe stenosis8,posing the question of an increased risk for the formation ofatherosclerotic lesions. In conclusion, we report a case of duplication of theextracranial ICA, a rare anatomic variant, usually incidentallydiscovered and requiring no particular treatment. Its importancelies in differentiating it from carotid dissection. It also needs tobe inscribed in the patient's medical record in case of possiblefuture neck or carotid surgery or angioplasty. Moreover, in ourcase an aneurysm was associated with the duplication,warranting follow-up imaging. THE CANADIAN JOURNAL OF NEUROLOGICAL SCIENCES424Figure 2: Transverse reconstruction of gadolinium-enhanced T1-weighted echo-gradient angio-MRI showing rightcervical ICA duplication (white arrowhead). Note left normal cervical ICA (black arrowhead), external carotidarteries (black arrows), and vertebral arteries (white arrows). https:/www.cambridge.org/core/terms. https://doi.org/10.1017/S0317167100014414Downloaded from https:/www.cambridge.org/core. University of Basel Library, on 30 May 2017 at 17:51:00, subject to the Cambridge Core terms of use, available atREFERENCES1. Dungan DH, Heisermann JE. The carotid artery. Embryology,normal anatomy, and physiology. Neuroimag Clin N Am. 1996;4:789-99. 2. Killien FC, Wyler AR, Cromwell LD. Duplication of the internalcarotid artery. Neuroradiology. 1980;19:101-2. 3. Chess MA, Barsotti JB, Chang JK, Ketonen LM, Westesson PL.Duplication of the extracranial internal carotid artery. Am JNeuroradiol. 1995;16:1545-7. 4. McEachen JC, Obrzut M, Bokhari SJ. A rare combination of carotidartery congenital abnormalities: understanding the embryologyand clinical associations. Emerg Radiol. 2009;16:411-4. 5. Larsen WJ. Human embryology. 3rd ed. Philadelphia: ChurchillLivingstone; 2001. 6. Kai Y, Hamada J, Morioka M, Yano S, Kudo M, Kuratsu J.Treatment of unruptured duplicated middle cerebral arteryaneurysm: case report. Surg Neurol. 2006;65:190-3. 7. Hori E, Kurosaki K, Matsumura N, et al. Multiple aneurysmsarising from the origin of a duplication of the middle cerebralartery. J Clin Neurosci. 2005;12:812-5. 8. Kung DK, Lui W, Smoker WR, Hasan DM. Duplication of theinternal carotid artery presenting with severe artheroscleroticstenosis. J Clin Neurosci. 2011;18:982-3. LE JOURNAL CANADIEN DES SCIENCES NEUROLOGIQUESVolume 40, No. 3 – May 2013 425https:/www.cambridge.org/core/terms. https://doi.org/10.1017/S0317167100014414Downloaded from https:/www.cambridge.org/core. University of Basel Library, on 30 May 2017 at 17:51:00, subject to the Cambridge Core terms of use, available at

Duplication of the Extracranial Internal Carotid Artery Analyzed by MRI

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Duplication of the Extracranial Internal Carotid Artery Analyzed by MRI

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