1. Department of Pediatrics, Akershus University Hospital HF, Lørenskog, Norway
2. Department of Pediatrics, Østfold County Hospital HF, Fredrikstad, Norway
3. Women and Children's Division, Section of Child Neurology, Oslo University Hospital HF Rikshospitalet, Oslo, Norway
4. Women and Children's Division, Section of Child Neurology and Division of Surgery and Clinical Neuroscience, Department of Neurology, Resource Centre for Inborn Muscular Diseases, Oslo University Hospital Rikshospitalet, Oslo, Norway