Chronic Cluster Headache

• Policlinico Umberto I — Rome, Italy

• Headache Research Unit. University Department of Neurology, Citadelle Hospital — Liège, Belgium
• Danish Headache Center & Department of Neurology, Glostrup Hospital, University of Copenhagen — Glostrup, Copenhagen, Denmark
• Servicio de Neurologia, Hospital Clinico Universitario — Valencia, Spain

• CHR Citadelle — Liège, Liege, Belgium

• University Department of Neurology CHR — Liège, Belgium
• Krankenhaus Lindenbrunn, Department of Neurology — Coppenbrügge, Germany
• Westdeutsches Kopfschmerzzentrum — Hufelandstr. 26, Hesse, Germany
• Migräne- und Kopfschmerzklinik Königstein — Königstein im Taunus, Königstein Im Taunus, Germany

• Citadelle Hospital — Liège, Belgium
• Danish Headache Center, Dept. of Neurology, Glostrup Hospital — Glostrup Municipality, Denmark
• Headache Center, Dept. of Neurology, University Duisburg-Essen — Essen, Germany
• Institut fur systemische Neurowissenschaften, Universitastsklinikum Hamburg-Eppendorf (UKE) — Hamburg, Germany

Not specified

• Resolve Pain — Buderim, Queensland, Australia