Ischemic stroke due to acute basilar artery occlusion: Proportion and outcomes

Background: Multiple case series, mostly highly selected, have demonstrated a very high mortality following acute basilar artery occlusion. The more widespread availability and use of non-invasive vascular imaging over recent years has increased the rate of ABAO diagnosis. Objectives: To estimate the proportion of diagnosed ABAO among all-cause ischemic stroke in an era of increasing use of non-invasive vascular imaging and to compare the characteristics and outcomes between these two groups. Methods: We compared 27 consecutive cases of ABAO identified in a university hospital between 2003 and 2007 with 311 unselected cases of ischemic stroke from two 4 month surveys. Results: ABAO diagnosis increased from 0.3% of all-cause ischemic stroke (2003-2004) to 1.1% (2007), reflecting the increased use of non-invasive vascular imaging. In comparison to all-cause ischemic stroke, ABAO patients were younger (mean age 60 vs. 71 years), were more likely to be male (89% vs. 60%), had less atrial fibrillation (7% vs. 26%), more severe strokes (baseline NIHSS over 20: 52% vs. 12%), higher admission white cell count (12,000 vs. 9000 cells/ mm³), lower admission systolic blood pressure (140 ± 24 vs. 153 ± 27 mmHg), higher in-hospital mortality rates (30% vs. 8%) and worse functional outcome (modified Rankin scale ≤ 3, 22% vs. 56%) (P < 0.05 for all). Rates of reperfusion therapy for ABAO increased from 0 in 2003-2004 to 60% in 2007. Conclusions: In this study, ABAO patients represented approximately 1% of all-cause ischemic stroke and were about a decade younger than patients with allcause ischemic stroke. We report a lower ABAO mortality compared to previous more selected case series; however, most survivors had a poor functional outcome. Given the marked clinical heterogeneity of ABAO, a low threshold for non-invasive vascular imaging with a view to definitive reperfusion treatment is needed.