1. Department of Neuroscience; Norwegian University of Science and Technology; Trondheim Norway
2. Department of Neurology and Clinical Neurophysiology; St. Olavs Hospital; Trondheim Norway
3. Norwegian National Headache Centre; St. Olavs Hospital; Trondheim Norway
4. Department of Neurology; Haukeland University Hospital; Bergen Norway
5. Department of Clinical Medicine; University of Bergen; Bergen Norway