Onabotulinumtoxin type A (BoNTA) is manufactured as powder that requires reconstitution with normal saline prior to injection. Previous literature has suggested that preserved saline (PS) exerts a local anesthetic effect, and reduces the procedure discomfort when used in reconstitution in lieu of preservative-free saline (PFS). However, this was mainly studied in the aesthetics indications of BoNTA, and never in its use for the treatment of chronic migraine. The distinction is important as the population of patients with chronic migraine suffers high incidence of scalp allodynia which makes it more prone to injection site pain. In addition, the pain of the procedure itself may be related to the spike of migraine frequency in the immediate post- procedural period which can occur in up to 5% of patients receiving the treatment. Our trial aimed to study the difference in procedural pain scale, and post-procedural headache rating with the use of PS vs PFS in constitution of BoNTA when used as a treatment for chronic migraine.