Congenital absence of the internal carotid artery
 Discussion of Congenital absence of the internal carotid artery
- Agenesis, aplasia, and hypoplasia of the internal carotid artery (ICA) are rare congenital anomalies, occurring in less than 0.01% of the population.
- Slightly more than 100 cases of congenital absence of the ICA have been reported in the literature.
- The term absence has been chosen to incorporate agenesis, aplasia, and hypoplasia of the ICA.
- The most common type of collateral flow is through the circle of Willis.
- Less commonly, collateral flow is provided via persistent embryonic vessels or from transcranial collaterals originating from the external carotid artery (ECA) system.
- Although many of these cases remain asymptomatic and go undetected, it is associated cerebral aneurysms. Also these anomalies have important implications during carotid endarterectomy and transsphenoidal hypophyseal surgery, and in the setting of thromboembolic disease.
 Imaging Findings for Congenital absence of the internal carotid artery
- Agenesis, aplasia, and hypoplasia of the internal carotid artery with collateral vessels.
Patient #1: Congenital absence of the left internal carotid artery
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 References for Congenital absence of the internal carotid artery
- Given II, Curtis A., Huang-Hellinger, Frank, Baker, Michael D., Chepuri, Neeraj B., Morris, P. Pearse. Congenital Absence of the Internal Carotid Artery: Case Reports and Review of the Collateral Circulation. AJNR Am J Neuroradiol 2001 22: 1953-1959.