1. Department of Neurology, The Ural State Medical University, 620028 Yekaterinburg, Russia
2. International Headache Centre “Europe-Asia”, 620144 Yekaterinburg, Russia
3. Medical Union “New Hospital”, 620028 Yekaterinburg, Russia
4. Danish Headache Centre, Department of Neurology, Rigshospitalet-Glostrup, University of Copenhagen, 1172 Copenhagen, Denmark