[1] Natl Hosp Neurol & Neurosurg, NHS Natl Pr Clin, London WC1N 3BG, England
[2] UCL Inst Neurol, Dept Neurodegenerat Dis, MRC Pr Unit, London, England
[3] UCL Inst Neurol, Dept Brain Repair & Rehabil, Acad Neuroradiol Unit, London, England
[4] UCL Ctr Med Image Comp, London, England