Neurological Side Effects of Long-term Botulinum Toxin Use

Abstract

Aims: To analyze and understand the neurological side effects associated with long-term use of botulinum toxin type A (BoNT-A), highlighting its implications on motor and sensory function in patients undergoing prolonged therapeutic application. Study Design:  Qualitative exploratory-descriptive bibliographic review. Place and Duration of Study: The study was conducted using data collected from scientific literature indexed in PubMed, SciELO, and the Virtual Health Library (VHL), covering publications from 2013 to 2023. Methodology: A systematic search was performed using controlled descriptors such as Neurological Side Effects, Botulinum Toxin, Central Nervous System, and Peripheral Nervous System. Boolean operators “AND” and “OR” were applied to refine the search. Inclusion criteria focused on full-text articles in English, Portuguese, and Spanish that directly addressed the neurological impacts of BoNT-A. The review excluded duplicated materials, summaries, debates, and inaccessible content. The selected studies were analyzed through three axes: identification of neurological side effects, impacts on motor and sensory function, and mechanisms of influence on the central nervous system. Results: Findings indicated that BoNT-A is generally effective and safe for motor conditions such as spasticity and facial paralysis, though long-term use may result in mild to moderate adverse effects, including fatigue and muscle weakness. In chronic migraine treatment, BoNT-A showed significant improvement in pain frequency and quality of life. Potential retrograde transport of the toxin suggests central nervous system involvement. Statistical values were not derived as this was a literature-based review, but recurrent patterns across studies support the findings. Conclusion: Botulinum toxin type A remains a valuable therapeutic option; however, prolonged administration requires caution and individualized monitoring. Further research is necessary to fully understand its central mechanisms and to establish safer, optimized protocols for long-term neurological applications.