**6. Conclusion**

OnabotulinumtoxinA injection is an effective strategy to treat chronic migraine. At 56 weeks, the percentage of patients in the PREEMPT trials that received at least 50% reduction in headache days was 68%, significantly better than the reduction seen in patients who received placebo [48]. In addition to being effective, BTX-A has also been shown to cause very minimal adverse effects. Some commonly seen complications include neck pain/weakness, eyelid ptosis, and injection site pain. There have been no reported deaths among migraine BTX-A studies, and only 1.4–3.8% of patients discontinued treatment due to adverse effects [9, 10, 16, 17, 24].

BTX-A injection is an effective and well-tolerated treatment option for chronic migraine patients who have previously failed a number of traditional medications. It is most effective in patients who suffer from a higher frequency of headache days, such as those seen in chronic migraines. Additionally, it is well known that chronic migraine patients often suffer from medication overuse. In a subanalysis of PREEMPT trial results, BTX-A demonstrated significant effectiveness in reducing frequency of headache days even in patients who are designated with medication overuse [49]. Sometimes, patients may not respond from the first injection interval. It has been shown even among patients that fail to respond initially, a meaningful proportion of patients responded in the second and third treatment cycles [50]. ART injection on the other hand is a newer, expanded, and more refined version of the targeted injection based on recent neurology data and theories suggesting that BTX-A is more effective if deposited closer to nerves. Although available studies are less robust, preliminary clinical results show less complications than PREEMPT.

While onabotulinumtoxinA injection has been shown to be both safe and effective among a broad group of patients, demonstrating versatile and robust efficacy, research is ongoing to develop the best and most efficient ways to deliver this treatment. Knowledge of potential culprit nerves and the accurate understanding of surrounding tissue anatomy are essential to maximize efficacy and efficiency in chronic migraine pain management.
