All consecutive acute ischemic stroke patients with large-vessel occlusion treated by mechanical thrombectomy at a single academic institution between August 2002 and October 2012 were identified from a prospectively maintained database. Patients treated with thrombectomy were either ineligible for IV tPA or refractory to thrombolysis after receiving IV tPA within 4.5 h of stroke onset.3 (link),19 (link) The mechanical clot retrieval devices included Merci Retriever (Stryker neurovascular, Mountain View, CA), Penumbra System (Penumbra, Inc., Alameda, CA), stent retriever with Solitaire FR device (Covidien/eV3, Dublin, Ireland), or Trevo Retriever (Stryker neurovascular).
Magnetic resonance imaging (MRI) before thrombectomy was routinely performed in all patients without selection biases unless contraindicated. Patients also typically underwent follow-up magnetic resonance (MR) within 48 h after thrombectomy. The multimodal MRI protocol included diffusion-weighted imaging, perfusion-weighted imaging, T2∗ gradient-recall echo (GRE), and fluid-attenuated inversion recovery (FLAIR) sequences. We included patients who had serial T2∗ GRE before and 48 h after thrombectomy. The local institutional review board of University of California at Los Angeles approved the study. Informed consent was obtained from the patient or their representative.