Rare carotid-vertebrobasilar anastomoses with notes on the differentiation between proatlantal and hypoglossal arteries

Abstract

Two cases of persistent anastomoses between the carotid and vertebrobasilar systems which have only once been previously reported are described. These are a proatlantal intersegmental artery which arises from the external carotid artery and a primitive trigeminal artery with direct anastomosis to the superior cerebellar artery. Angiographic criteria for differentiation of the proatlantal and more common hypoglossal arteries, as well as the rare persistent cervical intersegmental artery are also presented.

Primitive hypoglossal artery: demonstration with digital subtraction-, MR- and CT angiography

“…However, sometimes there is confusion about the exact classification. Some pitfalls are pointed out by Anderson and Sondheimer [18]. The most reliable finding to establish the diagnosis of a PHA is the vessel's course through the anterior condyloid foramen, which can be enlarged up to 18 mm [19].…”

Internal carotid and ipsilateral type II proatlantal artery stenoses causing simultaneous hemispheric and vertebrobasilar transient ischemia

“…According to embryological development, persistence of carotid basilar anastomosis is often associated with hypoplasia or agenesis of vertebral arteries as noted in this case. 3,4 According to the Lasjaunias classification, there are two types of proatlantal intersegmental artery. Type I corresponds to the first segmental artery and arises from the cervical ICA.…”

Incidental Finding of a Proatlantal Intersegmental Artery

“…A higher origin is expected for the hypoglossal artery. The typical origin of the PIA is at the level of C2 or C3, whereas the hypoglossal artery usually leaves the ICA at the level of C1 vertebra or C1-C2 interspace 13 . The suboccipital horizontal course is characteristic of vertebral and PIA.…”

“…It is important to discriminate between the type I PIA and the more common hypoglossal artery that requires careful analysis because of their similar origin from the ICA 13 . A higher origin is expected for the hypoglossal artery.…”