• Participants will then be instructed in the completion of the daily headache diary (this is estimated to take 10 - 20 minutes). This diary will keep track of daily pain scores, activity, headache medication use and visits to the emergency room. Headache severity is recorded four times daily on an 11 point numerical rating scale (NRS) anchored at zero for no pain and 10 for the worst imaginable pain. Participants will be asked to keep this diary for 7 days pre-randomization and for 30 days commencing the day after the treatment / infusion.