Biological and Procedural Predictors of Outcome in the Stroke Preclinical Assessment Network (SPAN) Trial.

BACKGROUND: The SPAN trial (Stroke Preclinical Assessment Network) is the largest preclinical study testing acute stroke interventions in experimental focal cerebral ischemia using endovascular filament middle cerebral artery occlusion (MCAo). Besides testing interventions against controls, the prospective design captured numerous biological and procedural variables, highlighting the enormous heterogeneity introduced by the multicenter structure that might influence stroke outcomes. Here, we leveraged the unprecedented sample size achieved by the SPAN trial and the prospective design to identify the biological and procedural variables that affect experimental stroke outcomes in transient endovascular filament MCAo. METHODS: The study cohort included all mice enrolled and randomized in the SPAN trial (N=1789). Mice were subjected to 60-minute MCAo and followed for a month. Thirteen biological and procedural independent variables and 4 functional (weight loss and 4-point neuroscore on days 1 and 2, corner test on days 7 and 28, and mortality) and 3 tissue (day 2, magnetic resonance imaging infarct volumes and swelling; day 30, magnetic resonance imaging tissue loss) outcome variables were prospectively captured. Multivariable regression with stepwise elimination was used to identify the predictors and their effect sizes. RESULTS: Older age, active circadian stage at MCAo, and thinner and longer filament silicone tips predicted higher mortality. Older age, larger body weight, longer anesthesia duration, and longer filament tips predicted worse neuroscores, while high-fat diet and blood flow monitoring predicted milder neuroscores. Older age and a high-fat diet predicted worse corner test performance. While shorter filament tips predicted more ipsiversive turning, longer filament tips appeared to predict contraversive turning. Age, sex, and weight interacted when predicting the infarct volume. Older age was associated with smaller infarcts on day 2 magnetic resonance imaging, especially in animals with larger body weights; this association was most conspicuous in females. High-fat diet also predicted smaller infarcts. In contrast, the use of cerebral blood flow monitoring and more severe cerebral blood flow drop during MCAo, longer anesthesia, and longer filament tips all predicted larger infarcts. Bivariate analyses among the dependent variables highlighted a disconnect between tissue and functional outcomes. CONCLUSIONS: Our analyses identified variables affecting endovascular filament MCAo outcome, an experimental stroke model used worldwide. Multiple regression refuted some commonly reported predictors and revealed previously unrecognized associations. Given the multicenter prospective design that represents a sampling of real-world conditions, the degree of heterogeneity mimicking clinical trials, the large number of predictors adjusted for in the multivariable model, and the large sample size, we think this is the most definitive analysis of the predictors of preclinical stroke outcome to date. Future multicenter experimental stroke trials should standardize or at least ensure a balanced representation of the biological and procedural variables identified herein as potential confounders.

Hippocampal infarction and generalized seizures predict early mortality after endovascular middle cerebral artery occlusion in mice.

Endovascular middle cerebral artery occlusion (MCAO) is a widely used experimental ischemic stroke model. However, the model carries high early mortality. Our aim was to investigate the factors that influence early mortality within 48 h of reperfusion after transient MCAO. Using C57BL/6 mice, we induced 1-hour endovascular filament MCAO. To introduce heterogeneity of infarct volumes, a subset of animals had additional tandem common carotid artery occlusion (MCAO+CCAO). Continuous video monitoring was used to gain insight into the cause of death. Mortality within 48 h was 25% in the pooled cohort. All animals with early mortality suffered from infarcts in the hippocampus, sometimes accompanied by infarcts in the thalamus and midbrain, which occurred exclusively in the MCAO+CCAO group. All animals with early mortality developed convulsive seizures captured on video monitoring. None of the animals that did not develop convulsive seizures died. Among the three regions, hippocampal infarction appeared necessary for convulsive seizures and early mortality. Our data highlight seizures as the primary cause of mortality within the first 48 h after endovascular filament MCAO, linked to hippocampal infarction. Since hippocampal blood supply is mainly from the posterior cerebral artery (PCA), avoiding concurrent PCA ischemia can decrease mortality in proximal MCAO models.