Abstract WP60: Absence of Hyperdense Middle Cerebral Artery Sign, as Measured on the Hounsfield Scale, Predicts Poor Functional Outcome and May Indicate Atherosclerotic Disease in Patients Undergoing Mechanical Thrombectomy for M1 Occlusion

Introduction: The hyper-dense middle cerebral artery sign (HMCAS) on computed tomography (CT) is associated with ischemic stroke involving the middle cerebral artery (MCA) territory. While its presence is indicative of acute thromboembolic disease, the clinical implications of its absence in patients presenting with M1 occlusions have not been widely studied. Methods: We retrospectively analyzed104 consecutive patients presenting with acute M1 occlusions undergoing mechanical thrombectomy. Pertinent clinical/radiological variables were obtained from the electronic medical records and review of angiographic images. Presence of HMCAS was defined as a difference of >5 Hounsfield units (HU) between the occlusion site and the corresponding contralateral MCA segment. Patients were stratified based on the presence (HD group) vs. absence (nHD group) of HMCAS. Primary outcomes included mortality, reperfusion status (TICI), and 3-month Modified Rankin Scale (mRS). Other relevant clinical variables were statistically analyzed and compared. Statistical analyses were two-tailed and considered significant if p Results: Out of the 104 patients with M1 occlusions, 78 had a measurable HMCAS (HD group), while 22 patients did not (nHD group). 4 patients were excluded due to CT artifacts. Age (69.2 ± 16.0), presenting NIHSS (15.8 ± 5.1), and time to groin (347.0 ± 282.6 min) were similar in the two groups. Mortality and 3-month mRS were 50% and 4.4 (±1.9) in the nHD group versus 27% and 3.1 (±2.2) in the HD group, both significant, with p=0.0201. and p=0.0152, respectively. The nHD patients had significantly higher incidence of diabetes (40.9% vs. 19.2%, p=0.0178). TICI score was unfavorable (2A, 1, or 0) in 31.8% of the nHD- and 24.4% of the HD patients, although not statistically significant. Lesions were presumed to be atherosclerotic (based on cerebral angiography) in 40.9% of nHD- and 7.7% of HD cases (p=0.00006). Conclusion: Absent HMCAS - defined as a