1 Penn Center for Brain Injury and Repair and Department of Neurosurgery, University of Pennsylvania, Philadelphia, PA, USA.
2 Penn Center for Brain Injury and Repair and Department of Neurosurgery, University of Pennsylvania, Philadelphia, PA, USA; Department of Neuropathology, Queen Elizabeth University Hospital, Glasgow G51 4TF, UK; Institute of Neuroscience and Psychology, University of Glasgow, Glasgow, UK. Electronic address: William.Stewart@glasgow.ac.uk.