1Radiology, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States, 2Radiology, University of Miami, Miami, FL, United States, 3Neurosurgery, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, United States, 4Neurology, Duke University Medical Center, Durham, NC, United States, 5Department of Cellular and Molecular Physiology, University of Liverpool, Liverpool, United Kingdom