Differences between Anterior and Posterior Circulation Stroke in TOAST

BACKGROUND AND PURPOSE: Clinicians have tended to view anterior circulation (AC) and posterior circulation (PC) strokes as separate entities, with different underlying pathogenesis, natural histories, and potential responsiveness to interventions such as anticoagulation. We sought to explore differences between AC and PC stroke in the Trial of ORG 10172 in Acute Stroke Treatment (TOAST). METHODS: For patients enrolled in TOAST, prospective clinical information was collected including outcome at 3 months. Data on vascular distribution were obtained from the clinical impression of the investigators. Group comparisons for categorical data were performed using Fisher's exact test. Independent sample t tests and analysis of covariance were used for all continuous data. RESULTS: The analysis included 1,039 patients with AC stroke and 180 patients with PC stroke. There were fewer women in the PC than in the AC groups, but otherwise there were no differences in demographics, risk factors or stroke subtypes between the two groups. Headache (AC 8.7%, PC 15%, p = 0.013) and vomiting (AC 3.5%, PC 17.8%, p < 0.001) were more common among PC patients. Mean baseline National Institutes of Health Stroke Scale (NIHSS) score was lower (less severe) among PC (6.1) than AC patients (9.5; p < 0.001). On univariate analysis, favorable outcome at 3 months was more common for PC patients in both the placebo group (PC 82%, AC 71%, p = 0.04) and heparinoid group (PC 87%, AC 73%, p = 0.005). However, multivariate analysis, controlling for gender, history of previous stroke and baseline NIHSS score, showed no difference in outcome between PC and AC stroke. For favorable outcome, there was no interaction between vascular distribution and treatment category, suggesting that the effect of heparinoid did not differ between PC and AC strokes. CONCLUSION: Patients with PC stroke seem to have a better long-term outcome than do AC patients, but this difference is no longer apparent when controlling for important prognostic variables. PC patients did not show any particular benefit from anticoagulation, and the efficacy of heparinoid did not vary between AC and PC stroke. While AC and PC patients do differ in some respects, it may be inappropriate to single out PC patients for anticoagulant treatment.