1. Institutes of Neurology and Paediatrics, University Hospital Nijmegen, 6525 GC Nijmegen, The Netherlands
2. University Marburg, Department of Neuropediatrics and Metabolic Diseases, D-35037 Marburg, Germany
3. University Paediatric Hospital Utrecht, Laboratory of Metabolic Diseases, NL-3512 LK Utrecht, The Netherlands
4. Laboratory for Genetic Metabolic Disease, Academic Medical Centre, NL-1105 A2 Amsterdam, The Netherlands