1 Stroke Research Centre, UCL Institute of Neurology, University College London, Russell Square House, 10-12 Russell Square, London, WC1B 5EH, UK.
2 Department of Statistical Science, UCL, London, WC1E 6BT, UK.
3 Neuroradiological Academic Unit, Department of Brain Repair and Rehabilitation, Institute of Neurology, University College London, London, UK.
4 Stroke Research Centre, UCL Institute of Neurology, University College London, Russell Square House, 10-12 Russell Square, London, WC1B 5EH, UK. [email protected].