Endovascular Therapy for Acute Basilar Artery Occlusion
Endovascular Therapy for Acute Basilar Artery Occlusion
Basilar artery occlusion is an infrequent form of acute stroke; clinical outcomes are heterogeneous, but the condition can be fatal. There is a lack of randomized controlled trial data in this field. Case series suggest that patients who are recanalized have much better outcomes than those who are not, and it is generally accepted that intra-arterial techniques achieve high rates of recanalization. Controversially, several studies, including a meta-analysis and registry-based investigation, that have compared intravenous thrombolysis (IVT) and intra-arterial treatment suggest similar outcomes. However, there are many potential sources of bias in each of these studies, precluding a firm conclusion. Indeed, there are many confounding factors that can influence the outcome including severity of presentation, site of occlusion, clot load, degree of collateral flow, timing of therapy, agent used for recanalization and dose of thrombolytic agent. Additionally, pretreatment infarct core imaging using diffusion-weighted imaging and the posterior circulation Acute Stroke Prognosis Early CT Score (pc-ASPECTS) scoring systems have been shown to predict outcome and therefore may be useful in selecting patients for aggressive therapy. Protocols combining intravenous agents such as glycoprotein IIb/IIIa receptor antagonists or thombolytics agents with intra-arterial techniques ('bridging' therapy) have shown encouraging improvements in neurological outcome and survival. Furthermore, initial case series describing the use of mechanical clot extraction devices or aspiration catheters suggest high rates of recanalization. What would be useful is a randomized trial comparing IVT, endovascular approaches and a combined IVT/endovascular approach. However, the small numbers of patients and multiple confounding factors are barriers to the development of such a trial.
Basilar artery occlusion is an uncommon cause of stroke, accounting for only 6–10% of large vessel strokes. The most common underlying mechanism is atherosclerosis, but the basilar artery is also affected by embolism from both cardiac and proximal arterial sources, dissections, migraine and inflammatory conditions. The condition presents with a variety of clinical signs and symptoms. Most patients suffer prodromal symptoms in the preceding 2 weeks including headache, vertigo or both. In the acute presentation, altered levels of consciousness, dysarthria, paresis, hemiplegia or tetraplegia, ataxia, cranial nerve deficits and supranuclear occulomotor disturbances are the commonest presenting signs. Although prognosis is variable, basilar occlusion has traditionally been thought to be associated with a poor outcome. More recently there has been an emphasis on acute therapeutic recanalization to re-establish perfusion, with several case series suggesting a reduction in mortality and improved functional outcomes following thrombolytic treatment. There is controversy as to the best mode of treatment; both intravenous thrombolysis (IVT) and/or endovascular techniques including intra-arterial thrombolysis (IAT) and mechanical clot extraction are advocated, though each mode of treatment has its proponents. In this study we explore the literature comparing IVT and IAT and examine the evidence pertaining to the use of endovascular techniques such as mechanical thrombectomy and thromboaspiration used to assist recanalization.
Abstract and Introduction
Abstract
Basilar artery occlusion is an infrequent form of acute stroke; clinical outcomes are heterogeneous, but the condition can be fatal. There is a lack of randomized controlled trial data in this field. Case series suggest that patients who are recanalized have much better outcomes than those who are not, and it is generally accepted that intra-arterial techniques achieve high rates of recanalization. Controversially, several studies, including a meta-analysis and registry-based investigation, that have compared intravenous thrombolysis (IVT) and intra-arterial treatment suggest similar outcomes. However, there are many potential sources of bias in each of these studies, precluding a firm conclusion. Indeed, there are many confounding factors that can influence the outcome including severity of presentation, site of occlusion, clot load, degree of collateral flow, timing of therapy, agent used for recanalization and dose of thrombolytic agent. Additionally, pretreatment infarct core imaging using diffusion-weighted imaging and the posterior circulation Acute Stroke Prognosis Early CT Score (pc-ASPECTS) scoring systems have been shown to predict outcome and therefore may be useful in selecting patients for aggressive therapy. Protocols combining intravenous agents such as glycoprotein IIb/IIIa receptor antagonists or thombolytics agents with intra-arterial techniques ('bridging' therapy) have shown encouraging improvements in neurological outcome and survival. Furthermore, initial case series describing the use of mechanical clot extraction devices or aspiration catheters suggest high rates of recanalization. What would be useful is a randomized trial comparing IVT, endovascular approaches and a combined IVT/endovascular approach. However, the small numbers of patients and multiple confounding factors are barriers to the development of such a trial.
Introduction
Basilar artery occlusion is an uncommon cause of stroke, accounting for only 6–10% of large vessel strokes. The most common underlying mechanism is atherosclerosis, but the basilar artery is also affected by embolism from both cardiac and proximal arterial sources, dissections, migraine and inflammatory conditions. The condition presents with a variety of clinical signs and symptoms. Most patients suffer prodromal symptoms in the preceding 2 weeks including headache, vertigo or both. In the acute presentation, altered levels of consciousness, dysarthria, paresis, hemiplegia or tetraplegia, ataxia, cranial nerve deficits and supranuclear occulomotor disturbances are the commonest presenting signs. Although prognosis is variable, basilar occlusion has traditionally been thought to be associated with a poor outcome. More recently there has been an emphasis on acute therapeutic recanalization to re-establish perfusion, with several case series suggesting a reduction in mortality and improved functional outcomes following thrombolytic treatment. There is controversy as to the best mode of treatment; both intravenous thrombolysis (IVT) and/or endovascular techniques including intra-arterial thrombolysis (IAT) and mechanical clot extraction are advocated, though each mode of treatment has its proponents. In this study we explore the literature comparing IVT and IAT and examine the evidence pertaining to the use of endovascular techniques such as mechanical thrombectomy and thromboaspiration used to assist recanalization.
