Data Collection on the ATI Neurostimulation System: SPG Stimulation for Cluster Headache

Inclusion Criteria: * Subject meets CE marked labeling for cluster headache. * Subject's typical cluster headache bouts last a minimum of 16 weeks, in the opinion of the Investigator. * Subject agrees to maintain current preventive headache medication regimens (no change in type, frequency or dose except to manage tolerability) from Study Enrollment through the completion of the Therapy Evaluation Period. * Subject has the ability to read, comprehend and to reliably record information as required by the Protocol. * Subject is able to provide written informed consent prior to participation in the study. Exclusion Criteria: * Subject has had a change in type, dosage or frequency of taking preventive headache medications \< one (1) month prior to Study Enrollment. * Per the CE marked labeling: In the opinion of the Investigator, subject has bony facial deformities, inappropriate surgical anatomy or has had facial surgery in the surgical area on the same side as the planned surgery that would prevent the proper placement of the ATI Neurostimulator. * Subject has other significant pain problem that might confound the study assessments in the opinion of the Investigator.