Dr. Walter Jr. Boim Araujo
Cirurgia Vascular e Endovascular
Radiologia Intervencionista e Angiorradiologia
Adriano Carvalho Guimarães;
Thaís Duarte Baião Pessoa;
Ricardo Herkenhoff Moreira;
Walter Junior Boim de Araujo.
The cervical and cerebral arterial system undergoes many transformations during the process of embryonic development before arriving at its final form in the fetus. Development of this system is modulated by countless molecular factors and failures in these pathways can cause anatomic variants and a range of different clinical repercussions. The primitive aorta has six arches that are organized into the different branches known. The third arch gives rise to the common carotids and the proximal segments of the internal carotids. The distal segments are derived from the dorsal aorta between the first and third primitive arches. The external carotids emerge from the common carotids. This development pattern occurs in approximately 65% of the population; anomalies are observed in the remainder.
Anomalies result from abnormal persistence or disappearance of segments of the arch of the primitive aorta. In 22% of the population, the left common carotid artery originates from the brachiocephalic trunk, rather than the aortic arch, also known as the “bovine aortic arch”. In this case, the brachiocephalic trunk gives rise to the right subclavian artery and the left and right common carotid arteries, while the left subclavian artery originates from the aortic arch, as normally expected. This variant accounts for 73% of all anomalies of the arch. Many other variants have been described, all of which occur in less than 3% of the population.
Agenesis of the internal carotid was described for the first time in 1787, post-mortem, and in vivo for the first time in 1954, after an angiography examination. This is a rare anomaly with incidence of less than 0.01% and, in the majority of cases, it is asymptomatic because anastomoses are present. However, it can be linked with complications, primarily when other anatomic abnormalities or severe atherosclerotic disease are present.
The patient was a 63-year-old female with hypertension and diabetes. She had no history of smoking or heart disease. She had undergone surgery to clip a cerebral aneurysm 3 years previously and the treating neurosurgeon responsible at the time had reported difficulty with catheterization of cervical arteries. She was examined with Doppler ultrasonography of carotid and vertebral arteries, which showed that the left common carotid artery had a smaller caliber than the right ( Figure 1 ), the left carotid bifurcation could not be observed, and the left common carotid artery only led to the left external carotid artery ( Figure 2 ). Angiotomography was ordered, showing agenesis of the left internal carotid artery ( Figure 3 ). The patient remains asymptomatic and attends regular follow-up consultations.
Figure 1 Mode B ultrasonography images showing the left common carotid artery () with a smaller caliber than the right common carotid artery (RIGHT CCA).
Figure 2 Mode B ultrasonography images showing the left common carotid artery () with a smaller caliber than the right common carotid artery (RIGHT CCA).
Figure 3 Angiotomography showing a patent left common carotid artery (LEFT CCA) (white arrow) leading to the left external carotid artery (LEFT ECA) (yellow arrow) and agenesis of the left internal carotid artery (LEFT ICA).