[1] Univ Helsinki, Folkhalsan Inst Genet, FI-00014 Helsinki, Finland
[2] Univ Helsinki, Ctr Neurosci, FI-00014 Helsinki, Finland
[3] Univ Helsinki, Dept Med Genet, FI-00014 Helsinki, Finland
[4] Pietarsaari Hosp, Dept Neurol, FI-68601 Pietarsaari, Finland
[5] Univ Oulu, Dept Neurol, Oulu, Finland
[6] Univ Strasbourg 1, CNRS, INSERM, Inst Genet Biol Mol & Cellulaire, FR-67404 Illkirch Graffenstaden, France
[7] Univ Helsinki, Ctr Neurosci, FI-00014 Helsinki, Finland
[8] Univ Helsinki, Biomedicum Helsinki, Program Dev & Reprod Biol, FI-00014 Helsinki, Finland
[9] Univ Helsinki, Childrens Hosp, FI-00014 Helsinki, Finland
[10] Univ Helsinki, Dept Pathol, FI-00014 Helsinki, Finland
[11] Univ Helsinki, Cent Hosp, FI-00014 Helsinki, Finland
[12] Univ Tromso Hosp, Dept Med Genet, N-9012 Tromso, Norway
[13] Bispebjerg Hosp, Dept Audiol, DK-2200 Copenhagen, Denmark
[14] Univ Copenhagen, Panum Inst, Inst Med Biochem & Genet IMBG, Wilhelm Johannsen Ctr Funct Genom, DK-2200 Copenhagen, Denmark
[15] Clin St Odile, FR-67100 Strasbourg, France
[16] Uppsala Univ, Dept Womens & Childrens Hlth Pediat, SE-75186 Uppsala, Sweden
[17] Vaasa Cent Hosp, Dept Neurol, Vaasa, Finland
[18] Tampere Univ Hosp, Dept Neurol, Tampere, Finland
[19] Family Federat Finland, FI-00101 Helsinki, Finland
[20] Univ Helsinki, Dept Neurol, FI-00014 Helsinki, Finland