1. Biomedical Engineering Group, E.T.S. Ingenieros de Telecomunicación, University of Valladolid, Valladolid, Spain
2. Centro de Investigación Biomédica en Red en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Valladolid, Spain
3. Headache Unit, Neurology Department, University Hospital of Valladolid, Valladolid, Spain
4. Institute for Biomedical Research of Salamanca (IBSAL), Salamanca, Spain
5. Department of Medicine, University of Valladolid, Valladolid, Spain