Abstract Number: Esoc2026a1813 Oxygen Extraction Raction for the Diagnosis of Stroke Mimics: A Single-Center Observational Study

Background and aims Stroke mimics account for 30% of all stroke codes; their correct identification may avoid inappropriate treatments and reduce treatment times. Perfusion imaging and derived metabolic parameters may improve differential diagnosis in the emergency setting. We aimed to test the ability of Oxygen Extraction Fraction(OEF) and time to maximum(Tmax), to distinguish ischemic stroke (IS) from stroke mimics. Methods We conducted a 5-month prospective observational study including all consecutive stroke codes admitted within 24 hours of symptom onset, excluding intracranial hemorrhage. All patients underwent CT perfusion analyzed with automated software to generate Tmax and OEF maps. Maps were visually assessed on the symptomatic hemisphere and compared with the contralateral side, then quantitatively confirmed with two symmetrically placed ROIs. OEF was classified as normal or increased (≥2-level rise on the colorimetric scale vs the contralateral area). Tmax maps were categorized as hypoperfusion (Tmax>6s), hyperperfusion (Tmax≤3s), or normoperfusion (Tmax>3s and <6 s). Statistical analysis included Pearson’s χ2 test, Student’s t test, and multivariate logistic regression. Results Among 143 patients, 58% had IS and 42% stroke mimic. Both increased OEF (85.7% vs 14.3%; p<0.001) and Tmax>6s were associated with IS. Logistic regression confirmed increased OEF (aOR 0.21[95%CI 0.07–0.64], p=0.006), but not Tmax (aOR 0.78[95%CI 0.29-2.11], p=0.631), as an independent predictor for ruling out stroke mimic, including after adjustment for NIHSS categories (aOR 0.25[95%CI 0.08–0.84], p=0.025). Conclusions OEF is an independent marker distinguidhing IS from stroke mimics and may improve diagnostic accurancy an management in emergency. Conflict of interest E.N. is member of the medical and scientific advisory board of Cercare Medical and declares speaker's honoraria from Boehringer Ingelheim; A.C. has nothing to disclose; M.A. has nothing to disclose; C.A.F. has nothing to disclose; G.S. has nothing to disclose; A.N. has nothing to disclose; A.F. has nothing to disclose; S.L. has nothing to disclose; M.D. has nothing to disclose; D.T. declares consulting or advisory board fees or speaker’s honoraria from Alexion, ASTRA Zeneca, Boehringer, Medtronic and Pfizer.