Is Functional Outcome Different in Posterior and Anterior Circulation Stroke?

Background and Purpose- Posterior circulation stroke (PCS) account for 20% of all ischemic strokes. There is limited evidence whether functional outcome of PCS is comparable to that of anterior circulation stroke (ACS). We aimed to analyze whether 3-month functional outcome is different in PCS and ACS. Methods- Patients with acute ischemic stroke prospectively enrolled within the Austrian Stroke Unit Registry were stratified by infarct localization according to the Oxfordshire Community Stroke Project Classification. Propensity score matching was used to control for covariate imbalances and to match patients with PCS and ACS. Patients were matched for stroke severity, recombinant tissue-type plasminogen activator treatment, and demographic and vascular risk factors. Main outcomes were the distribution of modified Rankin Scale after 3 months and multiple proportional odds models to estimate the influence of the infarct localization on the functional outcome. Results- From a total of 90 484 patients enrolled within the Austrian Stroke Unit Registry, 9208 (4604 PCS/4604 ACS) were matched, of those 954 (477 in each group) were treated with recombinant tissue-type plasminogen activator. We detected a significant shift towards better 3-month functional outcome in patients with ACS compared with PCS (odds ratio [OR], 1.19; 95% CI, 1.1-1.28; P<0.0001). In particular, functional outcome was worse in PCS with onset-to-door-time >270 minutes (OR, 1.34; 95% CI, 1.17-1.54; P<0.0001) and in PCS with unknown onset-to-door-time (OR, 1.26; 95% CI, 1.13-1.42; P<0.0001); however, we did not detect any difference in functional outcome between ACS and PCS in patients with an onset-to-door-time ≤270 minutes (1-180 minutes: OR, 0.92, 95% CI, 0.78-1.09, P=0.3554; 181-270 minutes: OR, 1.04, 95% CI, 0.79-1.37, P=0.7689). In patients treated with recombinant tissue-type plasminogen activator, functional outcome was not significantly different between PCS and ACS. Conclusions- PCS was associated with worse outcome compared with ACS in patients arriving later than 4.5 hours at hospital or in those with unknown onset of symptoms. Our results urge for implementation of symptoms found in the posterior circulation into preclinical patient-triage tools.