Cluster headaches occur as attacks of severe, one-sided headaches. Typically, a number of attacks occur over several weeks - about (cluster) of attacks. The headaches then usually go for weeks, months or years until a next cluster of headaches develops. Treatment options for cluster headache (CH) include acute, transitional and prophylactic strategies. A study was conducted to assess the efficacy and safety of a single occipital nerve block (ONB) in patients with episodic (eCH) and chronic CH (cCH).