Type II proatlantal artery

Case contributed by Dr James Harvey


ICU admission with refractory seizures on background of epilepsy.

Patient Data

Age: 45 years
Gender: Male

A large vessel (type II proatlantal artery) arises from the left external carotid artery immediately distal to the carotid bifurcation. The left vertebral artery is aplastic and this proatlantal artery enters the foramen magnum. It joins a hypoplastic right vertebral artery to form the basilar artery.

A bovine aortic arch (normal variant) is also noted.

Case Discussion

Proatlantal arteries, also called proatlantal intersegmental arteries, are carotid-vertebrobasilar anastamosis that persists beyond the embryonic period.

These vessels are frequently associated with anomalies of the ipsilateral vertebral artery, as in this case. In the above case the proatlantal artery is the main supply of the posterior circulation.

Two types of proatlantal artery exist: type I arises from the internal carotid artery and type II arises from the external carotid artery or common carotid artery. The vessels usually obliterate at the 7-12mm embryonic stage.

While proatlantal arteries are normal variants, they are important to identify prior to carotid endarterectomy, as clamping of the proximal carotid artery may lead to posterior circulation infarct.

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Case information

rID: 70820
Published: 5th Sep 2019
Last edited: 5th Sep 2019
Inclusion in quiz mode: Included

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