Intramuscular Botulinum Toxin for Complex Regional Pain Syndrome: A Narrative Review of Published Cases.

[BACKGROUND] Since the 1980s, numerous case reports have explored the use of intramuscular botulinum toxin (BoNT) for Complex Regional Pain Syndrome (CRPS), with significant variation in rationale, dosing, guidance techniques, and outcome measures. This narrative review aims to summarize published evidence on the use of intramuscular BoNT in patients with CRPS, including studies using earlier terminology such as reflex sympathetic dystrophy (RSD). Given the heterogeneous and largely anecdotal nature of the literature, this review is intended to map the existing landscape rather than conduct a formal analysis.

[METHODS] The PubMed and EMBASE databases were searched in August 2024 using terms related to CRPS and botulinum toxin. Following abstract and full-text screening, 25 publications were included.

[RESULTS] The included studies span single case reports, case series, and small cohorts, encompassing at least 96 individual CRPS patients treated with intramuscular BoNT. Reported outcomes were heterogeneous, and key treatment parameters-such as toxin type, target muscles, guidance technique, and dosing-were inconsistently reported.

[CONCLUSION] The evidence for intramuscular BoNT in CRPS remains limited and heterogeneous, preventing firm conclusions on its efficacy or safety. Its use may be considered in select cases, particularly those with disabling or painful focal dystonia or myofascial pain, but standardized prospective studies are needed to clarify its clinical role.