[1] Natl Publ Hlth Inst, Dept Human Mol Genet, FIN-00300 Helsinki, Finland
[2] Univ Helsinki, Cent Hosp, Dept Radiol, Helsinki, Finland
[3] Univ Helsinki, Hosp Children & Adolescents, Dept Pediat Neurol, Helsinki, Finland
[4] Queen Siliva Childrens Hosp, Gothenburg, Sweden
[5] Ctr Multiply Handicapped Children & Adults, Doorn, Netherlands
[6] Univ Calif Los Angeles, Sch Med, Dept Human Genet, Los Angeles, CA USA