Your browser does not support javascript:   Search for gard hereSearch for news-and-events here.


Genetic and Rare Diseases Information Center (GARD)

Print friendly version

Internal carotid agenesis

Other Names for this Disease
  • Agenesis of the internal carotid artery
  • Internal carotid artery agenesis
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.

Your Question

Do you have any information about internal carotid agenesis?

Our Answer

We have identified the following information that we hope you find helpful. If you still have questions, please contact us.

What is internal carotid agenesis?

Internal carotid agenesis occurs when one of the blood vessels which supply blood to the brain does not develop (agenesis).  It is rare, occurring in less than 0.01% of people.[1]  Usually there is a pair of internal carotid arteries, one on the left side and one on the right side; agenesis occurs on the left side three times more frequently than on the right side.[2]  Individuals with this condition may not have any symptoms because there are several blood vessels transporting blood to the brain such that if one does not develop, the others can function in its place.  However, if symptoms occur, they may include headache, blurred vision, paralysis of some of the nerves in the head (palsy), epilepsy, or muscle weakness on one side of the body (hemiparesis).[2]  The main concern with internal carotid agenesis is the increased risk for enlargement of the other blood vessels (aneurysm), which can occur in up to 67% of people with this condition (compared to 2-4% of individuals without this condition).[3]
Last updated: 3/17/2011

What causes internal carotid agenesis?

The cause of this condition is currently unknown.  Most of the time, it is thought to occur by chance.  However, there have been a few instances where individuals with internal carotid agenesis also had another condition, leading to questions about a possible association between the two.[4]
Last updated: 3/17/2011

How is internal carotid agenesis diagnosed?

Internal carotid agenesis is diagnosed when the absence of the internal carotid artery is noted on tests used to visualize the blood vessels and surrounding bones such as angiography, computed tomography scanning (CT scan), and magnetic resonance imaging (MRI).[4] [3]  Once internal carotid agenesis is diagnosed, these tests are done periodically to monitor the other blood vessels and check for aneurysms.[4]
Last updated: 3/17/2011

  • Afifi, AK, Goersky JC, Menezes A, Smoker WR, Bell WE, and Jacoby CG. Cerebral Hemiatrophy, Hypoplasia of Internal Carotid Artery, and Intracranial Aneurysm: A Rare Association Occuring in an Infant. Arch Neurol. 1987; 44:232-235. Accessed 3/14/2011.
  • Florio F, Balzano S, Nardella M, Strizzi V, Cammisa M, Bozzini V, Catapano G, and D'Angelo V. Congenital Absence of the Internal Carotid Artery. Vardiovasc Intervent Radiol. 1999; 22:74-78. Accessed 3/14/2011.
  • Lee JH, Oh CW, Lee SH, and Han DH. Aplasia of the internal carotid artery. Acta Neruochin. 2003; 145:117-125. Accessed 3/14/2011.
  • Claros P, Bandos R, GIlea I, Claros Jr A, Capdevila A, Gardia Rodrigues J, Claros A. Major congenital anomalies of the internal carotid artery: agenesis, aplasia and hypoplasia. Int J Pediatr Otorhinolaryngol. 1999; 49:69-76. Accessed 3/14/2011.