Abstract TP84: Ring-like Pattern On Post-EVT MRI Is A Marker Of Perihematomal Edema

Introduction: Perihematomal edema is a consequence of primary intracerebral hemorrhage. On diffusion MRI, a corresponding heterogenous pattern of hypo- and hyper-intensity is visible on apparent diffusion coefficient (ADC), suggesting both cytotoxic and vasogenic edema. Analogously, endovascular therapy (EVT) for ischemic stroke can result in hemorrhagic transformation (HT) and a concomitant ring-like pattern, or “Rings” of mixed intensity on ADC. The objective of this study is to describe this pattern of secondary injury early after EVT. Methods: Patients were included if they consented to the prospective Natural History of Stroke GUARDS study from April 2018 to February 2022, were treated with EVT for anterior circulation LVO, achieved TICI 2b/3 reperfusion, and had early MRI, ~2h post-EVT. Two independent readers measured early and 24h DWI lesion volumes and 5d FLAIR lesion volumes using a semi-automated validated approach. Presence of any HT on GRE and Rings on ADC (Figure) on early, 24h, and 5d MRI were read independently by multiple readers who then reached consensus. The relationship of Rings with HT and lesion volume was explored. Results: Eighty-nine patients were included with median age 64y, 55% female, median admit NIHSS 18, 64% M1 LVO, and 47% IV tPA. On early MRI, 14 (16%) patients had Rings, 12 (86%) of whom also had HT (p<0.001). At 24h, 42 (50%) patients had Rings with 33 (79%) also having HT (p<0.001). There was a strong association between presence of Rings at 24h and 5d-FLAIR lesion volume, 56mL vs. 24mL in patients with vs. without Rings (p=0.002). Conclusions: Rings on ADC was seen in half of patients 24h post-EVT and appears to reflect peri-lesion edema associated with hemorrhagic transformation. This imaging marker was associated with larger lesion volumes at 5 days and may be able to serve as a target for adjunctive therapy post-EVT to mitigate edema formation.