Agenesis of the Internal Carotid Artery
- Rare congenital anomaly (< 0.01% of population). 3:1 left-sided predominance.
- Usually asymptomatic, although can develop symptoms related to cerebrovascular insufficiency.
- Key Diagnostic Features: Absent ICA with an absent carotid canal, which differentiates it from a chronic arterial occlusion. There is well developed
collateral circulation via posterior communicating artery and anterior communicating artery. As there is increased flow through
the patent ICA and communicating arteries, the radiologist should always evaluate for for intracranial saccular aneurysms.
- Three vascular abnormalities associated with agenesis of ICA:
- High degree of intracranial aneurysms (24%–34%)
- Abnormal arterial collateral channels, including persistent embryonic vessels (like persistent trigeminal artery)
- Transcraneal supply to pial vessels from ECA (autosynangiosis)
- Three vascular abnormalities associated with agenesis of ICA:
- DDx:
- Hypoplasia of ICA: small patent vessel with a small carotid canal
- Complete thrombotic occlusion of ICA: normal-sized carotid canal
- Rx: None. Only associated lesions require treatment, if necessary.
March 12, 2015 Case 2
A 14-year-old boy with acute occipital headache, vomiting, and syncope
