Abstract Body: Introduction: Long term (>36 months) recovery after endovascular treatment (EVT) remains largely understudied in acute ischemic stroke (AIS) patients. Previously, we have shown that long-term white matter microstructure damage, iron deposition and atrophy within/remote to the 24-hour stroke lesion could influence long term quality of life. However, the role of baseline and 24-hour lesion characteristics on long term lesion characteristics and the influence of lesion status on recovery to perform daily activities is unknown.

Methods: We executed a quantitative 3T MRI protocol (FLAIR, diffusion MRI, R1, R2*, Quantitative Susceptibility Mapping, Arterial Spin Labeling) after 37 (IQR: 28-38) months in patients from the MR CLEAN No-IV trial who received a 24-hour post-EVT MRI (DWI, FLAIR, SWI). Lateral ventricular volume difference was computed at both time-points to quantify atrophy. Long term MRI was also used to quantify iron deposition (R2*) and volume difference in subcortical nuclei relative to the contralateral nuclei. Long term recovery was defined using daily activity scores from EQ5D5 questionnaire. A Bayesian paired T-test of ventricular lateral atrophy between 24-hour and long term MRI was performed, and a Bayesian correlation of baseline clinical and 24-hour lesion characteristics with long term MRI outcomes (Bayes Factor (BF)<3: no/weak; BF>3: moderate; BF>20: strong evidence).

Results: We included 24 patients with a 24-hour and long-term MRI protocol. Median age was 64 (51-75) years, 11 (46%) patients were randomized to receive intravenous thrombolysis (IVT) prior to EVT, and 19 (79%) patients had an MCA occlusion. Functional independence (mRS 0-2) at 90 days (21 (88%) patients) and long term (20 (83%) patients) was comparable. Ventricular lateral atrophy was observed (BF=4.10⁵), and higher baseline blood pressure and poorer collaterals were associated with larger long term lateral ventricular atrophy (BF: 11, 11, 4.3 respectively). Lower ASPECTS and poorer collaterals were associated with higher thalamic volume difference (BF=111, 11 respectively). Lastly, lower hippocampal volume and iron deposition were associated with reduced long term daily activity (BF=26, BF=4).

Conclusion: While functional independence in our cohort remains comparable over time, baseline, clinical, and treatment characteristics point to long-term brain degradation, which in turn impacts the ability of patients to perform daily activities.