Fig. 1

Flow-chart. During a first phase, called adaptation period, we used a follow-the-pain approach in order to determine the optimal injection scheme for each individual. Once the best procedure was determined for each patient, it was reproduced at each subsequent injection session. This adaptation phase could necessitate up to three sessions. The observation period started 8 weeks before the first efficacious injection and ended 2 months after the second consecutive efficacious injection, or in case of inefficacy. Throughout the adaptation and the observation phases, patients kept a headache diary where they were asked to note the days with headache and the use of rescue medication. The extension period included all treatment cycles after the observation phase. During this period, the injector was allowed to modify the dosage and sites of injections