Abstract A126: Cerebrovascular underpinnings of aphasia severity changes during subacute stroke recovery with standard care

Introduction: Understanding the physiology of cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) related to changes in aphasia severity during subacute stroke recovery is a crucial and underexplored research area. Methods: In this pilot trial, we recruited 6 male veterans (age = 64 ±6 yrs) from the Atlanta VA and Emory Hospital. The ‘early’ subacute phase was defined as 2-10 weeks post-stroke, followed by 6 weeks of recovery involving standard care. Participants returned for measurements in the ‘late’ subacute phase (<16weeks post-stroke). We conducted language assessments using the Western Aphasia Battery (WAB) and measured CBF with 3D pseudo-continuous arterial spin labeling (pCASL) MRI. CBF included post-labeling delays of 2200ms and 2800ms to analyze blood arrival times. CVR was assessed using a 5% CO2 challenge during rapid fMRI. CVR data was analyzed using novel transfer functional analysis (TFA) to quantify the gain and phase. Finger-prick hemoglobin measurements were also collected to study the impact of blood properties on vascular changes during recovery. We used repeated-measure mixed modeling to estimate associations between physiology, hematocrit (Hct), and WAB-based aphasia severity (WAB-AQ). Results: The CBF and CVR maps from a representative participant ( Figure 1 ) show that CVR gain and phase quantified using novel TFA are more sensitive than traditional CVR amplitude to describe cerebrovascular changes within and around the lesion. We observed that increased Hct resulted in increased collateral CBF (t=2.73, p<0.01) and was sensitive to regional CBF differences in lesion and perilesional areas (p<0.01). We observed greater blood arrival to collateral-supported perilesional brain areas that were supported by less effortful vascular response to CO2 challenge (i.e., decreased CVR gain, Figure 2 ). Finally, we observe marginal improvements (p=0.06) in aphasia severity following standard care, and the CVR phase showed a significant inverse relationship with WAB-AQ (F=11.86, p=0.04, Figure 3 ). Conclusion: Our research establishes a novel framework for understanding the cerebrovascular changes that contribute to changes in aphasia severity during subacute recovery with standard care. Recovery improves the vascular system's efficiency (CVR gain) in blood supply, and effective language recovery is influenced by the speed of the vascular response to CO2 stimuli (CVR phase), especially in the perilesional brain areas with collateral perfusion.