1. Department of Neurology, University Hospital Schleswig-Holstein, Lübeck, Germany
2. Kiel Migraine and Headache Centre, Kiel, Germany
3. College of Medicine, University of Sharjah, Sharjah, United Arab Emirates
4. College of Medicine, King Saud University, Riyadh, Kingdom of Saudi Arabia
5. Institute of Transfusion Medicine, University Hospital Schleswig-Holstein, Lübeck, Germany