Events were classified as hardware related when a malfunction or migration of any device component including leads, extensions, IPG's, occurred. Events will classified as biological in cases where there was a biological reaction (hematoma, pain, etc.) to either the device or the surgical procedure to implant the device. Events were classified as stimulation related if the event was known to be caused by stimulation.

Patient reported headache pain relief in percentage for the previous month; patients were asked about their pain relief in percentage in the previous month; patient were asked "in the last month", how much headache relief has the implant provided (0% represents no relief, 100% represents complete relief)

82 patients had available data for pain relief in the previous month at the 3 month follow-up visit

Percentage change in number of Headache days from Baseline to 3 Months. Headache days are the amount of days the subject had an headache in the previous 3 months as captured by the MIDAS questionnaire.

69 patients had available data for headache days in the previous 3 months at the 3 month follow-up visit

Percentage change in Midas score from Baseline to 3 Months. The Midas questionnaire consists out of 5 questions to be answered by the patient. Three questions address the number of missed days due to headache in school or paid work, household work and family, social or leasure activities. The two remaining questions document the number of additional days with significant limitations to activity (defined as at least 50% reduced productivity) in the domains of employment and household work. The total score is the sum of days completed for questions 1-5. Midas score ranges from 0 to 21+ with higher values indicating greater disability.

63 patients had available data for all 5 questions of the Midas questionnaire computing the total score at the 3 month follow-up visit. Excluding the outliers, 59 patients had available data.

Patients very satisfied or satisfied with the headache relief since the implant. Patients were asked about their satisfaction (very satisfied, satisfied, neither satisfied or dissatisfied, unsatisfied, very unsatisfied)

84 subjects had available data for patient satisfaction at the 3 month follow-up visit.

Patients for who the physician is very satisfied or satisfied with the patient headache relief since the implant. Physicians were asked about their satisfaction (very satisfied, satisfied, neither satisfied or dissatisfied, unsatisfied, very unsatisfied)

84 subjects had available data for physician satisfaction at the 3 month follow-up visit.

Patients who reported the change in overall quality of life since the implant with greatly improved or improved. Patients were asked about their change in overall quality of life (Greatly improved, improved, neither improved or deteriorated, deteriorated, greatly deteriorated)

83 subjects had available data for Quality of life at the 3 month follow-up visit.

Patients for who the physician reported the change in overall quality of life of the patient since the implant with greatly improved or improved. Physicians were asked about the change in overall quality of life of the patient(Greatly improved, improved, neither improved or deteriorated, deteriorated, greatly deteriorated)

84 subjects had available data for physician reported overall quality of life