Vertebrocarotid collateral in extracranial carotid artery occlusions: digital subtraction angiography findings

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Abstract

The internal and external carotid arteries are usually considered occluded distal to a common carotid artery occlusion but some collateral vessels may provide blood keeping the internal and external carotid arteries patent distal to the occlusion. Most common communication in such a case is diversion of blood from muscular branches of the vertebral artery to occipital branch of the external carotid artery which in turn could maintain blood flow into the internal carotid artery, a condition called carotid steal.

We encountered vertebrocarotid anastomoses maintaining the patency of carotid circulation in six patients. Patients were four females and two males, ages ranging from 40 to 67 (mean age: 56) years. Five of the patients had ischemic cerebral symptoms. The origin of the external carotid artery was occluded in two and the whole common carotid artery in the remaining four patients. Two patients had double steal, carotid and subclavian at the same time. There was also severe stenosis or occlusion of at least one other major extracranial cerebral artery in all the cases. This concomitant involvement of the second extracranial cerebral artery was thought to be the main reason for the development of vertebrocarotid collateral. In contrast to most of the previously published reports claiming the inadequacy of angiography when compared with colour Doppler ultrasonography, angiography finely depicted the distal patency of the carotid circulation and all the collaterals in detail in every case. Selective injection of the vertebral artery ipsilateral to the occlusion, is the key to demonstrate distal patency of the carotid circulation in cases of proximal carotid occlusion. Demonstration of patency of the distal circulation is very important because some of the patients might get benefit from a reconstructive surgery.

Introduction

It is well known that occlusion of an artery is often accompanied by the development of collateral circulation through the dilatation of existing anastomosis. With occlusion of the common carotid artery (CCA) or origin of the external carotid artery (ECA), flow in the ipsilateral ECA and sometimes in the ipsilateral internal carotid artery (ICA) can be maintained by collateral vessels. This can occur mainly from the ipsilateral vertebral artery (VA) to the ECA through its occipital branch, a condition called carotid steal or external carotid steal [1], [2]. Until the 1980s carotid steal was mostly reported in patients who had undergone therapeutic ligation of the CCA [3], [4]. Thereafter, spontaneously occurring cases have been reported more frequently.

We present six vertebrocarotid collaterals in patients with CCA or ECA occlusions diagnosed by CDUS and confirmed by digital subtraction angiography (DSA). All the cerebral vessels were examined by DSA in detail with particular attention to the collateral blood flow.

Section snippets

Materials and methods

Between September 1999 and November 2003, vertebrocarotid collateral vessels were seen in four patients with CCA and two patients with ECA occlusions with preservation of the patency of the ECA and/or the ICA distally. Patients were four females and two males, ages ranging from 40 to 67 (mean age: 56) years. Four patients had patent ICA and ECA distal to CCA occlusion, whereas two patients had patent ECA distal to occlusion at its origin. We have searched angiographic findings in these six

Results

Demographic data and presenting symptoms of the patients and surgical treatment, if applicable, were presented in Table 1. CDUS diagnosed the occlusion of the major arteries in all but could not demonstrate the collateral circulation in four of the patients. Angiography confirmed the diagnosis and finely depicted all the collateral blood flow. Table 2 demonstrates the distribution of occluded and stenosed arteries. Arch aortography revealed occlusion or stenosis of the origin of the main

Discussion

Occlusion of the common carotid or external carotid artery is less frequent than occlusion of the internal carotid artery. Atherosclerosis is the most common cause while collagen tissue diseases with arteritis, fibromuscular dysplasia, postradiation fibrosis and trauma are rare causes [5], [6]. The internal and external carotid arteries are usually considered to be occluded by distal propagation of clot after occlusion of the CCA. However, preservation of the patency of the ICA and ECA through

Conclusion

Vertebrocarotid collateral supplying blood into the ECA and ICA is a rare communication seen in patients with ipsilateral CCA or ECA occlusion. This collateral is mostly, if not invariably, seen in patients with multiple severe stenoses or occlusions of the extracranial cerebral arteries. Although CDUS usually diagnoses occlusion of the CCA and patency of the distal arteries, selective bilateral VA injection with delayed arterial images is the key to demonstrate the collateral flow and the

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