1. Department of Hygiene, Epidemiology and Medical Statistics, Medical School, National and Kapodistrian University of Athens, Athens, Greece
2. Second Department of Neurology, “Attikon” University Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece
3. Department of Neurology, University of Tennessee Health Science Center, Memphis, TN, USA
4. Department of Paediatric Hematology and Oncology, Panagiotis and Aglaia Kyriakou Children’s Hospital, Athens, Greece
5. Unit of Clinical Epidemiology, Karolinska Institute, Stockholm, Sweden