Posterior circulation ischaemia

Abstract

One fifth of all transient ischaemic attacks (TIAs) and ischaemic strokes affect the posterior circulation. Patients with posterior circulation ischaemia can present with focal neurological symptoms (e.g., hemiparesis or visual field defects), but often also complain about accompanying non-focal neurological symptoms (e.g., non-rotatory dizziness). The prevalence and prognosis of non-focal neurological symptoms in these patients are largely unknown.

In about a quarter of patients with posterior circulation ischaemia an atherosclerotic stenosis of the vertebral or basilar artery is found. The risk of recurrent stroke is much higher in these patients than in patients without a stenosis. Therefore, stenting of a symptomatic vertebrobasilar stenosis is often considered an attractive therapeutic option and this is widely performed despite the lack of evidence on the benefit and safety.

This thesis focusses on the epidemiology of vertebrobasilar stenosis, the clinical presentation of patients with posterior circulation ischaemia, the prevalence and prognosis of non-focal neurological symptoms, and, finally, on the effects of stenting of symptomatic vertebral artery stenosis.

We found a vertebral artery origin stenosis in almost 8% of patients with clinically manifest arterial disease but without recent vertebrobasilar ischaemia. Patients with such an asymptomatic vertebral artery origin stenosis had a low absolute risk of posterior circulation stroke during the following years (annual stroke rate, 0.4%).

Almost three quarters of patients with a TIA or ischaemic stroke in the posterior circulation presented with both focal and non-focal neurological symptoms. Patients with non-focal neurological symptoms had no increased risk of cardiac events or death during long-term follow-up.

The final part of this thesis reports the results of the Vertebral Artery Stenting Trial (VAST), a randomised phase II trial investigating the safety and feasibility of stenting in patients with recently symptomatic vertebral artery stenosis ≥50%. Patients were randomised to stenting and best medical treatment or to best medical treatment alone. The primary outcome, the composite of vascular death, stroke, or myocardial infarction within 30 days, occurred in 3 (5%; 95% CI, 0-11%) patients assigned to stenting and in 1 (2%; 95% CI, 0-5%) patient assigned to medical treatment. In both groups the cumulative incidences of posterior circulation stroke during a median follow-up of three years were low: 12% (95% CI, 6-24%) in the stenting group and 7% (95% CI, 2-17%) in the medical treatment group. We conclude that stenting of symptomatic vertebral artery stenosis is associated with a periprocedural risk of major vascular complications of about 5%. Because of the low risk of recurrent stroke in the medical treatment group during follow-up,stenting should not be considered a first-line treatment in current clinical practice. A phase III trial to assess the efficacy of stenting of symptomatic vertebral artery stenosis seems not feasible due to the low rates of posterior circulation stroke in VAST.

Our findings contribute to the knowledge of symptoms and treatment of patients with posterior circulation ischaemia and vertebral artery stenosis. These findings are important for the development of preventive and treatment strategies for patients with posterior circulation ischaemia.