Dramatic changes in muscle contractile and structural properties after 2 botulinum toxin injections |
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| Authors: | Viviane B. Minamoto PT PhD Kentaro P. Suzuki MD Shannon N. Bremner BS Richard L. Lieber PhD Samuel R. Ward PT PhD |
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| Affiliation: | 1. Department of Orthopaedic Surgery, University of California San Diego, La Jolla, California, USA;2. Department of Bioengineering, University of California, San Diego, La Jolla, California, USA;3. Veterans Affairs San Diego Healthcare System, La Jolla, California, USA;4. Department of Radiology, University of California San Diego, La Jolla, California, USA |
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| Abstract: | Introduction: Botulinum toxin is frequently administered serially to maintain therapeutic muscle paralysis, but the effect of repeated doses on muscle function are largely unknown. This study characterized the muscle response to 2 onabotulinum toxin (BoNT) injections separated by 3 months. Methods: Animal subjects received a single toxin injection (n = 8), 2 BoNT injections separated by 3 months (n = 14), or 1 BoNT and 1 saline injection separated by 3 months (n = 8). Results: The functional effect of 2 serial injections was exponentially greater than the effect of a single injection. While both groups treated with a single BoNT injection had decreased torque in the injected leg by approximately 50% relative to contralateral legs, the double BoNT injected group had decreased torque by over 95% relative to the preinjection level. Both single and double BoNT injections produced clear signs of fiber‐type grouping. Conclusions: These experiments demonstrate a disproportionately greater effect of repeated BoNT injections. Muscle Nerve 52: 649–657, 2015 |
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| Keywords: | Botox® denervation fiber type muscle physiology neurotoxin |
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