[1] Oslo Univ Hosp, Dept Neurol, Unit Inborn & Hereditary Neuromuscular Disorders, Oslo, Norway
[2] Univ Hosp North Norway, Natl Neuromuscular Ctr Norway, Tromso, Norway
[3] Vikersund Rehabil Ctr, Vikersund, Norway
[4] Frambu Resource Ctr Rare Disorders, Siggerud, Norway
[5] Univ Amsterdam, Locat Univ Amsterdam, Med Ctr, Dept Neurol, Amsterdam, Netherlands