A Randomized Multicentre Study for the Acute Relief of Episodic and Chronic Cluster Headache.

Inclusion Criteria: * Is 18 years or older * Has been diagnosed with episodic or chronic cluster headache in accordance with the ICHD-2 Classification criteria (2ndEd) * Is capable of completing the 5-point pain scale, disability scale and other self-assessments * Agrees to refrain from starting new medication aimed to control the cluster headache for the duration of the run-in and randomized phase * Is able to provide written Informed Consent Exclusion Criteria:1. * Episodic cluster headache sufferers who are not in a cluster headache bout at the time of screening and enrollment * 2\. Need to commence treatment with oral or injectable steroids for eventual concomitant medical conditions * 3\. Has a lesion (including lymphadenopathy), dysaesthesia, previous surgery or abnormal anatomy at the GammaCore® treatment site * 4\. Is currently taking medication for indications other than CH that in the opinion of the clinician may interfere with the study * 5\. Has a history of any cranial aneurysm, intracranial haemorrhage, brain tumours or significant head trauma * 6\. Diagnosed or suspected secondary headache * 7\. Has other significant pain problem that might confound the study assessments in the opinion of the investigator * 8\. Has known or suspected severe atherosclerotic cardiovascular disease, severe carotid artery disease (e.g. bruits or history of transient ischemic attack (TIA) or cerebral vascular accident CVA), congestive heart failure (CHF), known severe coronary artery disease or recent (5 years) myocardial infarction * 9\. Has an abnormal baseline ECG (e.g. second and third degree heart block, atrial fibrillation, atrial flutter, recent history of ventricular tachycardia or ventricular fibrillation, or clinically significant premature ventricular contraction) * 10\. Has had a previous, cervical vagotomy * 11\. Has uncontrolled high blood pressure * 12\. Is currently implanted with an electrical and/or neurostimulator device, including but not limited to cardiac pacemaker or defibrillator, vagal neurostimulator, deep brain stimulator, spinal stimulator, bone growth stimulator, or cochlear implant * 13\. Has a history of carotid endarterectomy or vascular neck surgery * 14\. Has been implanted with metal cervical spine hardware or has a metallic implant near the GammaCore stimulation site * 15\. Has a recent (12 months) or repeated history of syncope * 16\. Has a recent (12 months) or repeated history of seizure * 17\. Has a known history or suspicion of substance abuse or addiction, or overuse of acute headache medication * 18\. Has psychiatric or cognitive disorder and/or behavioural problems which in the opinion of the clinician may interfere with the study * 19\. Is pregnant, nursing, thinking of becoming pregnant in the next 6 weeks 20. Is participating in any other therapeutic clinical investigation or has participated in a clinical trial in the preceding 30 days * 21\. Is a relative of or an employee of the investigator or the clinical study site