Non-contrast computer tomography detects the presence of hyperdense middle cerebral artery sign (HMCAS). Studies on the prognostic value of HMCAS among patients undergoing mechanical thrombectomy (MT) are conflicting. A retrospective analysis of consecutive patients with acute ischemic stroke due to middle cerebral artery occlusion, presenting with or without HMCAS, who underwent MT, was performed. We enrolled 191 patients (HMCAS +, n = 140; HMCAS –, n = 51). Prevalence of successful recanalization was significantly higher in patients with HMCAS than in those without HMCAS (92.1% versus 74.5%, p = 0.001). Patients with HMCAS had a better clinical outcome than those HMCAS – (54.3% versus 37.3%, p = 0.037, for three-month favorable outcome; 62.9% versus 39.3%, p = 0.004, for major neurological improvement at discharge; 8.6% versus 19.6%, p = 0.035, for in-hospital mortality; 14.3% versus 27.5%, p = 0.035, for intracranial hemorrhage; 2.9% versus 17.6%, p = 0.001, for symptomatic intracranial hemorrhage). Multivariate analyses confirmed that HMCAS represents an independent predictor of three-month favorable outcome (OR 2.48, 95% CI 1.10–5.58, p = 0.028), major neurological improvement at discharge (OR 2.40, 95% CI 1.09–5.20, p = 0.030), in-hospital mortality (OR 0.29, 95% CI 0.010–0.81, p = 0.018), presence of ICH (OR 0.49, 95% CI 0.25–0.97, p = 0.042) and presence of SICH (OR 0.16, 95% CI 0.04–0.63, p = 0.009). HMCAS presence predicts favorable outcome in patients undergoing MT. This result may indicate that hyperdense clots are more likely to respond to MT than isodense ones. This effect is mediated by reduction in hemorrhagic transformation.
