Fig. 1

Participant disposition. For analysis of reliability and validity, chronic and active episodic CH patients, named ‘active CH patients’ (n = 196), were evaluated. In this figure, this group is highlighted by the broken fringe. After 14 days, patients were invited to take part in a second survey to evaluate test-retest reliability. Only participants with active CH at both surveys and a change in attack frequency ≤ 2 attacks per week (from first to follow-up survey) were included in the analysis of test-retest reliability (n = 41). cCH, chronic cluster headache; eCH, episodic cluster headache