1. Hellenic Headache Society, Athens, Greece
2. Attikon University Hospital, Chaidari, Greece
3. Neurology Department, 401 Army General Hospital of Athens, Athens, Greece
4. Department of Neurology, Papageorgiou General Hospital, Thessaloniki, Greece
5. Neurology Department, 251 Air Forces General Hospital of Athens, Athens, Greece
6. Department of Neurology, Athens Medical Center, Athens, Greece
7. First Neurology Department, Aeginition Hospital, School of Medicine, National & Kapodistrian University of Athens, Athens, Greece