1. Department of Neurology Oslo University Hospital PO Box 4956 Nydalen Oslo N‐0424 Norway
2. Department of Neurology Faculty of Medicine University of Oslo PO Box 1078 Blindern Oslo N‐0316 Norway
3. Department of Neurology Molde Hospital HF Parkveien 84 Molde N‐6407 Norway
4. Laboratory Genetic Metabolic Diseases Department of Clinical Chemistry Academic Medical Centre Meibergdreef 9 Amsterdam 1105 AZ The Netherlands
5. Department of Neurology University Hospital of Northern Norway Tromsø N‐9038 Norway
6. Department of Clinical Medicine UiT the Arctic University of Norway PO Box 6050 Langnes N‐9037 Tromsø Norway
7. Department of Medical Genetics Oslo University Hospital N‐0424 Oslo Norway