EFFICACY OF BOTULINUM TOXIN TYPE A IN THE TREATMENT OF REFRACTORY CHRONIC MIGRAINE: ANALYSIS OF CLINICAL OUTCOMES

Abstract

Chronic refractory migraine is a highly disabling neurological condition, defined as headache occurring on ≥15 days per month, with migrainous features on at least 8 days, and is associated with a significant reduction in quality of life and increased functional burden (Headache Classification Committee of the International Headache Society, 2018; Lipton et al., 2011). In this context, botulinum toxin type A has emerged as a relevant therapeutic alternative, particularly in patients with inadequate response to conventional prophylactic treatments (Diener et al., 2010; Aurora et al., 2014). The aim of this study was to critically analyze the literature regarding the efficacy of botulinum toxin type A in the treatment of chronic refractory migraine, with emphasis on key clinical outcomes. A systematic literature review was conducted using PubMed, Scopus, and Web of Science databases, including studies published between 2015 and 2025, with the addition of classical studies of fundamental relevance to the topic. Randomized clinical trials, systematic reviews, and observational studies evaluating patients with chronic migraine treated with botulinum toxin type A were included. A total of 25 studies were included in the qualitative analysis. The results indicate that botulinum toxin type A is associated with a significant reduction in the frequency of migraine attacks, with a decrease in the number of headache days per month, as well as reduced pain intensity and improvement in quality-of-life scores, such as HIT-6 and MIDAS (Diener et al., 2010; Dodick et al., 2010). A reduction in the use of abortive medications and a favorable safety profile, with a low incidence of serious adverse events, were also observed (Aurora et al., 2014; Blumenfeld et al., 2018). These benefits were more evident in patients with chronic refractory migraine. Despite these favorable findings, heterogeneity among studies regarding application protocols, patient selection criteria, and outcome assessment methods represents a relevant limitation. Nevertheless, the results support the role of botulinum toxin type A as an effective therapeutic strategy in the management of chronic refractory migraine, particularly in cases of difficult clinical control.