Introduction: Stroke is a leading cause of disability worldwide. Mechanisms of post-stroke recovery are complex, and conventional outcome prediction models are limited. “Brain reserve” (BR) has been proposed as a construct to model the brain’s capacity to withstand insults. BR has been shown to co-vary with white matter hyperintensity volume (WMHv) using structural equation modeling (SEM), a technique to test models with latent variables.
Hypothesis: We hypothesize that BR is a protective mechanism that improves functional outcome after acute ischemic stroke (AIS).
Methods: We define an effective brain reserve (eBR), the remaining brain reserve after other influences have been accounted for. Using SEM, we characterize eBR through intra-cranial volume (ICV), age and systolic blood pressure (SBP). Our model incorporates known relationships between age, SBP, WMHv, acute infarct volume on diffusion-weighted imaging (DWIv) and 90-day functional post-stroke outcome (modified Rankin Scale; mRS), as shown in Figure 1. Path analysis was performed (R; package lavaan) to estimate the relations within the model in a dataset of 451 AIS patients. No priors were used for the path coefficients.
Results: The estimated model coefficients (Figure 1) show that eBR is negatively associated with age and SBP, but positively with ICV, while association between age, SBP and WMHv are positive. Outcome is positively associated with WMHv and DWIv and negatively with eBR, suggesting that eBR acts as a protective mechanism. All path coefficients are statistically significant, except for WMHv and mRS.
Conclusion: Our analysis shows that eBR is negatively associated with post-stroke outcome (the higher eBR, the lower mRS), suggesting that eBR acts as a protective mechanism. Additionally we reproduced known relationships between WMHv, SBP, age, DWIv and mRS.