Treatment of Chronic Cluster Headache with TENS and ONS

The study is an investigator-initiated, prospective, randomized, placebo-controlled, double blind clinical trial that aims to investigate the effect of transcutaneous electrical nerve stimulation (TENS) and occipital nerve stimulation (ONS) on attack frequency and severity in patients with chronic cluster headache (CH). Study outline Month 1: Baseline. Establishment of a baseline profile of the participants CH attacks (severity, duration, medicine utilization etc), health-related quality of life (QoL) and symptoms of anxiety and depression. No active treatment. Follow-up visit after 30 days. Months 2-4: TENS period. All participants will receive TENS-treatment. Clinical follow-up visit by the end of month four. Months 5-7: Double-blinded, randomized experimental period. All participants will have an ONS-system (lead, impulse generator) implanted and will be randomized 1:1 to receive either 1) burst (paresthesia-free) ONS or 2) placebo (deactivated ONS system). Clinical follow-up visit by the end of month seven. Months 8-10: Open label period. All participants will receive tonic (conventional, paresthesia-inducing) ONS. Clinical follow-up visit by the end of month ten. During every study phase each participant will fill out a weekly electronic headache registration as well as answering questionnaires regarding health-related quality of life and symptoms of anxiety and depression before every follow-up visit.