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Background: Chronic migraine represents a profound global source of neurological disability. Since the landmark trials establishing the efficacy of onabotulinumtoxinA, the therapeutic landscape has evolved rapidly, particularly with the advent of calcitonin gene-related peptide (CGRP) monoclonal antibodies. The role of botulinum toxin type A (BoNT-A) continues to be reassessed in terms of real-world durability, safety in special populations such as pregnant women and adolescents, and comparative effectiveness against newer pharmacological prophylactic agents. An updated synthesis of the literature is required to delineate the current evidence base, mechanistics, and practical positioning of BoNT-A in refractory headache management. Methods: A comprehensive literature review was conducted covering publications from year 2024 to 2026. The source framework was based on MEDLINE, PubMed, and Ovid database retrieval. Studies included systematic reviews, meta-analyses, randomized controlled trials, retrospective cohort analyses, case reports, mechanistic investigations, and narrative reviews. Emphasis was placed on efficacy, tolerability, biomarkers, pediatric applications, and treatment resistance. All included studies were critically analyzed and classified according to the Oxford Centre for Evidence-Based Medicine 2009 Levels of Evidence to provide a structured hierarchy of the current therapeutic evidence. Results: Recent evidence strongly reaffirms the long-term efficacy and safety of BoNT-A in chronic migraine prophylaxis. Extensive real-world data and systematic reviews demonstrate sustained reductions in headache days and acute medication reliance. While CGRP-targeted therapies offer formidable alternatives, large-scale comparative and umbrella reviews indicate BoNT-A remains highly competitive, often serving as a reliable rescue or combination therapy. Emerging literature highlights BoNT-A’s expanding utility in medically refractory pediatric cohorts and presents reassuring, albeit preliminary, safety profiles in pregnant populations. Mechanistic studies increasingly point toward complex central and peripheral neuromodulation, supported by measurable shifts in neurochemical biomarkers. However, the literature reveals uneven methodological quality, with a reliance on retrospective registries and narrative updates highlighting the need for rigorously controlled head-to-head trials. Conclusions: Botulinum toxin type A remains a cornerstone intervention for chronic migraine. Its established safety profile, sustained real-world effectiveness, and utility as an adjunctive or rescue treatment solidify its therapeutic relevance even in the CGRP era. Current practice should continue to emphasize individualized patient selection, recognizing the robust evidence for long-term burden reduction while navigating emerging off-label applications with critical caution.

Keywords: migraine disorders; chronic disease; botulinum toxins; type A; headache disorders; primary; calcitonin gene-related peptide; adolescent; pregnancy