1. Hellenic Headache Society, Athens, Greece
2. Second Neurology Department, Attikon Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece
3. Neurology Department, 401 Army General Hospital of Athens, Athens, Greece
4. Department of Neurology, Papageorgiou General Hospital, Thessaloniki, Greece
5. 251 Air Forces General Hospital of Athens, Neurology Department, Leof. Pan. Kannelopoulou, Athens, Greece
6. Department of Neurology, Athens Medical Center, 5–7 Distomou, Marousi, Athens, Greece
7. First Neurology Department, Aeginition Hospital, School of Medicine, National and Kapodistrian University of Athens, Athens, Greece