Abstract DP361: Detection of Focal Cortical Injury in Minor Acute Ischemic Stroke Patients Using Serial 3D T1 MRI

Introduction: In some minor acute ischemic stroke (mAIS) patients (admit NIHSS<6), acute cortical lesions seemingly “disappear” on FLAIR MRI over time. Although chronic conspicuity of injury may be minimal in these patients, cortical gray matter (GM) loss has been observed focal to the acute ischemia on 3D T1 MRI. In these instances, FLAIR may be inadequate for detecting long-term GM damage that may impact brain health. We explored imaging markers to identify GM injury using high-resolution 3D T1. Methods: This pilot, retrospective analysis included mAIS patients involving the anterior circulation. Patients were prospectively enrolled in the Focusing on Interesting Neurological Diseases (FIND) Natural History Study. Available FLAIR and 3D T1 at 5-days and 30-days post-stroke were processed with FreeSurfer’s (MGH) automated pipeline and segmented into anatomical parcellations (Destrieux atlas). FLAIR positive lesions at 5-days were segmented. GM volume and changes across time and hemisphere were compared. ADC masks were thresholded (>1.8 x 10 -5 cm 2 /s) to measure change in CSF at 30-days. FLAIR lesion positivity was determined independently at 30-days. Results: This study included 23 mAIS patients (median age 66 years [59-69], 35% female, with admit NIHSS 2 [0-4] and median 5-day GM volume 1.45mL [0.33-3.48]). Sixty-one percent of patients had FLAIR positive lesions at 30-days. These 14 patients had larger GM involvement within the FLAIR lesions at 5-days, 1.54mL vs 0.33mL (p=0.017), compared to the 9 patients with lesions that “disappeared” on FLAIR at 30-days. The amount of GM loss was also larger in these 14 patients from 5-days to 30-days, -0.16mL vs 0.00mL in the 9 patients (p=0.21). Fourteen patients (61%) had some amount of GM loss at 30-days, but 4 (29%) had lesions that disappeared on FLAIR at 30-days. There was no change in GM in the contralateral hemisphere regardless of whether the FLAIR lesion was positive at 30-days. Across all 23 patients, there was a significant increase in CSF volume from 5-days to 30-days (0.15mL, p<0.001) in the area defined by the 5-day FLAIR positive lesion. Conclusion: Focal GM atrophy was shown at 30-days in the majority of mAIS patients without a significant reduction in homologous GM. Some patients with disappearing FLAIR lesions still demonstrated GM loss at 30-days. The increase in CSF reflected expansion of sulcal spaces. Future work will investigate long-term changes in gray and white matter.