Rozen TD - An open label, observational, case series study was carried out to determine the effectiveness of high-volume anesthetic suboccipital nerve blocks (HVSON) for chronic cluster headache (CCH) as well as to illustrate the consistency of response over long-term use. For this investigation, patients with CCH seen at a dedicated headache clinic over a 7-year time period and injected on at least 2 separate occasions were used. Data reported that HVSON from this open label study seems to be effective in the preventive treatment of medicinal refractory CCH and shows consistent response over long-term use with high rates of pain freedom.