Case ReportBilateral Internal Carotid Artery Segmental Agenesis: Embryology, Common Collateral Pathways, Clinical Presentation, and Clinical Importance of a Rare Condition
Section snippets
Background
Congenital absence of the internal carotid artery (ICA) is a rare congenital anomaly in common clinical practice. The terminology “absence” encompasses a spectrum of abnormalities other than agenesis. Agenesis occurs in <0.01% of the population.1, 2 Only <10% of those cases have bilateral occurrence.3 Hypoplasia is prevalent at 0.079%.
Agenesis and aplasia mean absence of the vessel. Hypoplasia is characterized by ICA narrowing along its entire course as a reflection of incomplete development.
Case Description
An 18-year-old Caucasian man presented to our hospital with occasional mild headaches. Neurologic examination revealed normal findings. Despite medical treatment, headache persisted. As a result, more advanced investigations were performed.
MRI showed no brain abnormalities, while magnetic resonance angiography, performed with both 3-dimensional (3D) time-of-flight and postgadolinium 3D-fast spoiled gradient echo sequences, showed bilateral agenesis of the cervical segments of the ICAs.
Discussion
The spectrum of ICA malformation is widely variable and can range from complete absence of the artery (agenesis or aplasia) to absence of a single section or reduction in its dimension (hypoplasia).
The ICA derives from the third aortic arch, and its formation is essential for further development of the carotid canal. Therefore the absence of the carotid canal signifies that the alteration has occurred between the third and fifth weeks of embryonic development, during which the ICA is defined,
Conclusion
Bilateral internal carotid segmental agenesis may be completely asymptomatic and harmless, but associated conditions, such as cerebral aneurysms or abnormal collateral circulation, should alert clinicians to the possibilities of subarachnoid hemorrhage or cerebral ischemia. Furthermore, human carotid rete mirabile, commonly associated with carotid hypoplasia/agenesis, even if it has no inherent pathologic significance, must be recognized because it has important implications in the surveillance
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2020, Journal of Stroke and Cerebrovascular DiseasesCitation Excerpt :The common, internal and external carotid arteries are almost formed by about the sixth week. The failure of the third distal aortic arch to develop, or its incomplete development, results in agenesis or hypoplasia of the ICA respectively.1,6 –8 The primordial ICA is well formed by the fourth embryonic week, whereas the base of the skull does not form until the fifth to sixth weeks of fetal life.
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Conflict of interest statement: None of the authors has a conflict of interest to declare, and none of them received financial support.