Treatment and outcome in basilar artery occlusion

Abstract

Background Stroke is the leading cause of disability in developed countries. Posterior circulation stroke accounts for about 20% of all ischemic stroke. The basilar artery is the main vessel of the posterior circulation. Basilar artery occlusion (BAO) is associated with a high mortality and an often poor outcome among survivors. Treatment strategies for acute BAO are based on small case series of selected patients and data that have been extrapolated from stroke intervention trials in other cerebrovascular territories. This thesis consists of a review of existing knowledge on BAO, a report of a multicenter study of patients treated conventionally and a detailed report of outcomes and differences in treatment response in a large multicenter observational registry. Finally, we describe the design of a randomised controlled intervention trial of patients with BAO, based on our findings in the registry. Methods The Basilar Artery International Cooperation Study (BASICS) is a prospective, observational registry of consecutive patients who presented with an acute symptomatic and radiologically confirmed BAO between November 1, 2002, and October 1, 2007. Stroke severity at time of treatment was dichotomised as severe (coma, locked-in state, or tetraplegia) or mild to moderate (any deficit that was less than severe). Outcome was assessed at 1 month. Poor outcome was defined as a modified Rankin scale score of 4 or 5, or death. Patients were divided into three groups according to the treatment they received: antithrombotic treatment only (AT), which comprised antiplatelet drugs or systemic anticoagulation; primary intravenous thrombolysis (IVT), including subsequent intra-arterial thrombolysis; or intra-arterial therapy (IAT), which comprised thrombolysis, mechanical thrombectomy, stenting, or a combination of these approaches. Risk ratios (RR) for treatment effects were adjusted for known predictors of outcome. Findings 619 patients were entered in the registry. 27 patients were excluded from the analyses because they did not receive AT, IVT, or IAT, and all had a poor outcome. Of the 592 patients who were analysed, 183 were treated with only AT, 121 with IVT, and 288 with IAT. Overall, 402 (68%) of the analysed patients had a poor outcome. No statistically significant superiority was found for any treatment strategy. Compared with outcome after AT, patients with a mild-to-moderate deficit (n=245) had about the same risk of poor outcome after IVT (adjusted RR 0·94, 95% CI 0·60–1·45) or after IAT (adjusted RR 1·29, 0·97–1·72) but had a worse outcome after IAT compared with IVT (adjusted RR 1·49, 1·00–2·23). Compared with AT, patients with a severe deficit (n=347) had a lower risk of poor outcome after IVT (adjusted RR 0·88, 0·76–1·01) or IAT (adjusted RR 0·94, 0·86–1·02), whereas outcomes were similar after treatment with IAT or IVT (adjusted RR 1·06, 0·91–1·22). Interpretation Most patients in the BASICS registry received IAT. Our results do not support unequivocal superiority of IAT over IVT, and the efficacy of IAT versus IVT in patients with an acute BAO needs to be assessed in a randomised controlled trial.