Non-invasive Neurostimulation of the Vagus Nerve for the Treatment of Cluster Headache

Phase 1: Prospective, randomized (1:1 active treatment:sham control allocation), double blinded, sham controlled treatment (active or sham) phase Phase 2: Prospective, non-randomized, active treatment phase. Phase 1 - Two Arms: 1. Active Treatment with the GammaCore Device 2. Sham Treatment with a placebo device Phase 2 - One Arm: Active Treatment with the GammaCore Device