1. Headache Clinic, Mediterraneo Hospital, 16675 Athens, Greece
2. Euromedica General Clinic, 54645 Thessaloniki, Greece
3. Department of Neurology, University Hospital of Larissa, University of Thessaly, 41110 Larissa, Greece
4. Department of Neurology, Tzaneio General Hospital of Piraeus, 18536 Athens, Greece
5. Independent Researcher, 24100 Kalamata, Greece
6. Headache Outpatient Clinic, Department of Neurology, Agios Andreas State General Hospital of Patras, 26335 Patras, Greece
7. 404 Military Hospital, 41222 Larisa, Greece