[1] Hosp Univ Princesa, Headache Unit, Madrid, Spain
[2] Inst Invest St Princesa IIS Princesa, Madrid, Spain
[3] Hosp Univ Fdn Alcorcon, Headache Unit, Alcorcon, Spain
[4] Hosp Fuenlabrada, Headache Unit, Madrid, Spain
[5] Hosp Clin Univ Valladolid, Headache Unit, Valladolid, Spain
[6] Hosp Clin San Carlos, Headache Unit, Madrid, Spain
[7] Hosp Clin Univ Valladolid, Headache Unit, Valladolid, Spain
[8] Univ Valladolid, Dept Med, Valladolid, Spain
[9] Hosp Univ Gregorio Maranon, Headache Unit, Madrid, Spain
[10] Hosp Severo Ochoa, Headache Unit, Madrid, Spain
[11] Hosp Clin Univ La Paz, Headache Unit, Madrid, Spain