Subjects enrolled into this 10 week study will for the first two weeks document the number of cluster headaches and the means of treating (medication) of these attacks. Subjects will then be randomized to into either two groups. The first group is continuing with standard of care and the second group is treatment with the investigational device (GammaCore) for a period of 4 weeks. After this 4 week period, all subjects will treat with the GammaCore for another 4 week period. It is hypothesized the the treatment group will have a reduction in mean cluster headaches per week by 50% compared to the standard of care group.