Fig. 2From: The HortONS study. Treatment of chronic cluster headache with transcutaneous electrical nerve stimulation and occipital nerve stimulation: study protocol for a prospective, investigator-initiated, double-blinded, randomized, placebo-controlled trialOutcome parameters in correlation to trial phases and study visits. TENS, transcutaneous electrical nerve stimulation. ONS, occipital nerve stimulation. PGIC, patient's global impression of change. HADS, hospital anxiety and depression scale. EuroQoL-5D, European Quality of Life – 5 DimensionsBack to article page