A new pattern of arterial rete compensation of segmental basilar agenesis associated with carotid retia mirabilia: a case report (2010: 1b)

Abstract

The carotid rete mirabile is a transdural arterial network centered at the parasellar area, in place of the intracavernous internal carotid artery (ICA), associated with hypoplasia or absence of the cervical and petrous ICA. Rare cases of vertebral rete mirabile associated with segmental agenesis of transdural vertebral arteries have been reported before. The authors present a new case of carotid rete mirabilia associated with segmental basilar agenesis compensated by a previously unknown pattern of arterial rete. Collateral flow, its efficacy and differential diagnosis are discussed.

Bilateral Carotid and Vertebral Rete Mirabile Presenting with a Prominent Anterior Spinal Artery Mimicking a Spinal Dural AV Fistula at MRI

“…To our knowledge, there are nine cases in the literature of carotid and vertebrobasilar rete mirabile in the literature (Table 1). Transdural rete formation was associated with vertebral agenesis in six cases (3, 4, 7-10), while intradural rete formation associated with basilar agenesis occurred in two cases (2, 6), and vertebrobasilar agenesis occurred in one (5). In only two of these cases, angiography demonstrated both transdural anastomosis via dilated anterior spinal or medullary arteries and intradural rete formation (3, 7).…”

“…Evaluation of the skull base for presence or absence of the carotid canal is required for distinguishing aplasia from agenesis, since the presence of the ICA precursor is a prerequisite for the development of the carotid canal at 5-6 weeks of gestation. Demonstration of a small carotid canal by CT is helpful for excluding acquired etiologies; the thin and hypoplastic carotid canal demonstrated on CT supports this theory (6). In our case, both carotid canals were demonstrated on CT even though it was very small on the right side and relatively normal on the left side.…”

“…If the absence of the ICA occur by regression after its development, the embryonic vessels are already regressed and no longer available for collateral circulation. As the CRM is not present in any human developmental state (3-6), it is probably a secondary change to ICA regression in early development (6). Evaluation of the skull base for presence or absence of the carotid canal is required for distinguishing aplasia from agenesis, since the presence of the ICA precursor is a prerequisite for the development of the carotid canal at 5-6 weeks of gestation.…”

Two Unusual Cases of the Posterior Cranial Fossa Blood Supply

“…Dural branches may also play a role in supplementing the posterior circulation [5,9,15]. Although rare reports of vertebral "rete mirable" have been published, to our knowledge, bilateral atresia of the vertebral arteries has not been reported [16][17].…”

Bilateral Segmental Agenesis of Carotid and Vertebral Arteries with Rete Mirabile and the Prominent Anterior and Posterior Spinal Arteries as Compensations

“…eral VAs agenesis with an abnormal arterial network of intracranial VAs, which they called "vertebral rete mirabile", supplying the distal VAs and the BA. To the best of our knowledge, only ten cases of vertebrobasilar rete have been reported in the literature, and all of them were also associated with carotid rete (Table 1) 3,6,[7][8][9][10][11][12][13][14] . Among those cases, bilateral segmental agenesis of ICAs was observed in all; six cases had bilateral transdural VAs agenesis with transcranial rete formation, one had rete formation at the proximal segment of the right intracranial VA and duplication of the left VA, and four had segmental agenesis of the BA with various types of intradural rete.…”