Chronic cluster headache (CCH) is a rare primary headache disorder, defined by episodic attacks that occur for more than one year with no remission period or with remission periods lasting \< 3 months (ICHD-3 criteria). In certain cases, CCH patients become drug-resistant and continue to suffer almost daily attacks. Ketamine appears to be effective in a variety of chronic pain conditions, such as refractory headache, and can show an enhanced analgesic effect when combined with magnesium. A single infusion of ketamine-magnesium combination has been described to reduce attacks in 17 patients with rCCH. The main outcome was a comparison of the number of daily attacks two weeks prior to the infusion and one week after (days 7-8). The number of daily attacks decreased from 4.3±2.4 before treatment to 1.3±1.0 after treatment (p\<0.001). 13/17 had at least 50% response. Thus, the goal of this placebo-controlled study is to try to confirm these findings.