1. Department of Neurology, Leiden University Medical Centre, Leiden
2. Department of Neurology, Rijnland Hospital, Leiderdorp
3. Department of Human and Clinical Genetics, Leiden University Medical Centre, Leiden, The Netherlands
4. Department of Paediatric Neurology, Guy's Hospital, London, UK
5. Department of Neurology, University Hospital Marques de Valdecilla, Santander, Spain