Elsevier

The Lancet Neurology

Volume 12, Issue 10, October 2013, Pages 989-998
The Lancet Neurology

Review
Posterior circulation ischaemic stroke and transient ischaemic attack: diagnosis, investigation, and secondary prevention

https://doi.org/10.1016/S1474-4422(13)70211-4Get rights and content

Summary

A fifth of all strokes and transient ischaemic attacks occur in the posterior circulation arterial territory. Diagnosis can be challenging, in part because of substantial overlap in symptoms and signs with ischaemia in the anterior circulation. Improved methods of non-invasive imaging of the vertebrobasilar arterial tree have been used in recent prospective follow-up studies, which have shown a high risk of early recurrent stroke, particularly when there is associated vertebrobasilar stenosis. This finding emphasises the importance of urgent secondary prevention, and the role of stenting for vertebral stenosis is being investigated.

Introduction

A fifth of all transient ischaemic attacks (TIAs) and ischaemic strokes are in the territory of the vertebrobasilar (also known as posterior) circulation.1 Despite their importance, ischaemic events in this location have received much less attention than those in the carotid artery territory. Recent studies have shown that they are associated with a high risk of early recurrent stroke (see later) and therefore effective secondary prevention is important. Such an approach needs accurate clinical diagnosis, detection of the underlying cause, including arterial stenosis, and effective medical and surgical or neurointerventional treatments. Posterior circulation ischaemia presents particular challenges in diagnosis, investigation, and treatment, but recent research and ongoing studies are improving our understanding in this area. In this Review, we focus on the diagnosis, investigation, and secondary prevention of posterior circulation ischaemic stroke and TIA and highlight recent insights and advances. We will not cover management of acute stroke or basilar artery thrombosis, which has recently been reviewed.2

Section snippets

Anatomy of posterior circulation

The vertebral artery usually arises as the first branch of the subclavian artery and occasionally directly from the aortic arch (figure 1). It is conventionally divided into four segments.3 The first (V1) is from the origin of the vertebral artery to where it enters the foramen in the transverse process of the fifth or sixth cervical vertebra. The second segment (V2) is the part that courses cranially through the transverse foramina, until the artery emerges beside the lateral mass of the

Disease mechanisms

The most common causes of posterior circulation ischaemia are cardioembolism, large artery atherosclerosis, and small artery disease. Atherosclerosis often occurs at or near the origin of the vertebral artery.

Atherosclerosis can also occur in the distal vertebral and basilar arteries. Extracranial stenosis in the posterior circulation is less strongly associated with coronary artery disease and peripheral vascular disease than stenosis at the carotid bifurcation.11 Intracranial atherosclerosis

Clinical features

Because the vertebral and basilar arteries supply the brainstem, cerebellum, and in most cases also the inferior temporal lobe, occipital lobe, and the thalamus, posterior circulation ischaemia can give rise to a broad range of symptoms. These include not only the classic pointers to ischaemia in the posterior territory such as vertigo, ataxia, visual field defects (including hemianopia), eye movement disorders, bilateral weakness, and a reduction in consciousness, but also non-localising

Investigation

The same principles apply to investigation of posterior cerebral ischaemia as to ischaemic stroke in general, but with some important modifications. MRI is more sensitive than CT to posterior circulation infarcts, particularly in the brainstem.42 These are frequently missed on CT but are usually identified on MRI, particularly if diffusion-weighted imaging is done during the acute phase.43, 44 However, diffusion-weighted imaging can occasionally be negative for clinically definite posterior

Risk of recurrent stroke after posterior circulation stroke and TIA

In contrast to carotid territory events, for which research has been stimulated by the development of carotid endarterectomy and stenting, there has, until recently, been little systematic research into the prognosis of patients with posterior circulation TIA. Nevertheless, there has been a widely held opinion that vertebrobasilar TIAs have a more benign prognosis than carotid events,47, 48 mainly on the basis of findings from early cohort studies.48, 49 Patients with vertebrobasilar events are

Asymptomatic vertebral artery stenosis

The prevalence of asymptomatic vertebral artery stenosis in the general population is unknown. In a hospital-based series of 339 patients with peripheral arterial disease, reported in the 1980s, 7% had either a stenosis or retrograde flow in an extracranial vertebral artery.58 In a more recent hospital-based study59 of 3717 patients with clinically manifest atherosclerotic arterial disease, 7·6% of patients (95% CI 6·8–8·5) had an asymptomatic vertebral artery origin stenosis of at least 50% or

Secondary prevention of posterior circulation ischaemia

Much of the management of a patient with posterior circulation stroke or TIA is similar to that for ischaemic stroke in general, and this Review will only cover specific issues relating to secondary prevention of posterior circulation ischaemia.

Medical treatment and risk factor management is similar for anterior and posterior circulation stroke. Recommended treatment is covered in recent guidelines.60, 61 Clopidogrel alone (or aspirin and dipyridamole) is recommended for long-term secondary

Interventional treatment of vertebral artery disease

For symptomatic carotid stenosis, carotid endarterectomy is beneficial. Owing to the high early risk of recurrent stroke, for maximum effectiveness surgery needs to be done soon after TIA or minor stroke.57 Recent data showing a high risk of recurrent stroke in patients with symptomatic vertebral artery stenosis56 suggest that the atherosclerotic vertebral plaque acts in a similar fashion to the symptomatic carotid plaque, and raises the possibility that surgical or neuroradiological

Future directions

In this Review, we have highlighted several areas in which further research is needed to improve diagnosis of posterior circulation stroke and TIA, and for secondary prevention in patients with these disorders. Early and accurate diagnosis remains a challenge in a substantial minority of cases, and diagnostic and risk prediction instruments have lower sensitivity than for anterior circulation stroke and TIA; better diagnostic aids are therefore needed. Finding factors that differentiate

Search strategy and selection criteria

References for this Review were identified through searches of PubMed with the search terms “posterior circulation” AND “stroke” OR “TIA” and “vertebrobasilar” AND “stroke” OR “TIA”, from 1990 until March, 2013. Articles were also identified through searches of the authors' own files. Only papers published in English were reviewed. The final reference list was generated on the basis of originality and relevance to the broad scope of this Review.

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