[1] Univ Sherbrooke, Serv Neuropediat, Sherbrooke, PQ J1K 2R1, Canada
[2] Catholic Univ Louvain, Clin Univ St Luc, Serv Neuropediat, B-1200 Brussels, Belgium
[3] Catholic Univ Louvain, Clin Univ St Luc, Serv Radiopediat, B-1200 Brussels, Belgium
[4] Great Ormond St Hosp Sick Children, Dept Radiol, London, England
[5] Great Ormond St Hosp Sick Children, Dept Haematol, London, England
[6] Great Ormond St Hosp Sick Children, Dept Neurol, London, England
[7] Birmingham Childrens Hosp NHS Trust, Dept Paediat Neurol, Birmingham, W Midlands, England
[8] UCL, Inst Child Hlth, Ctr Paediat Epidemiol & Biostat, London, England
[9] UCL, Inst Child Hlth, Neurosci Unit, London, England
[10] Southampton Gen Hosp, Dept Child Hlth, Southampton SO9 4XY, Hants, England
[11] Univ Paris Sud, Hop Bicetre, Serv Radiopediat, F-94275 Le Kremlin Bicetre, France