Objective: To evaluate efficacy of botulinum toxin for shoulder spasticity using a post-hoc analysis.

Background: Botulinum toxin has been shown to be effective for treating upper-limb spasticity, but there are few studies on the efficacy of botulinum toxin for use in the shoulder. Using botulinum toxin to treat the shoulder is challenging because of proximity to respiratory muscles. However, successful treatment of this area may be important for patients with respect to quality of life (QoL). The TOWER study examined the efficacy and safety of escalating doses of incobotulinumtoxinA for upper- and lower-limb spasticity. Seven upper limb clinical patterns were treated and evaluated, including the shoulder.

Methods: 155 subjects were treated in 3 treatment cycles with escalating fixed doses of incobotulinumtoxinA (400U, 600U and 600–800U). Study assessments included muscle tone (Ashworth Scale; AS) for all clinical patterns, quality of life (QoL; EQ-5D instrument) and adverse events. Using a post-hoc analysis, subjects who received treatment in the shoulder were compared with those who did not. The individual AS scores for shoulder adductors, extensors, and internal rotators were combined to calculate an AS shoulder sumscore (AS-SSS).

Results: Eighty-four subjects received incobotulinumtoxinA treatment in the shoulder in cycle 3 (mean [standard deviation; SD] shoulder dose 118.4 [60.2]U), and 57 subjects did not. The mean [SD] AS-SSS improvement among treated subjects during cycle 3 was -1.7 [1.8], compared with -0.9 [1.4] for untreated subjects. A significant dose dependence for effect of incobotulinumtoxinA on AS-SSS (P=0.0081) was revealed using multiple regression analysis (adjusting for AS-SSS baseline). Improvements in shoulder muscle tone were similar to AS score improvements for other upper limb clinical patterns. All dimensions of the EQ-5D improved across injection cycles. There were no treatment-related AEs indicating toxin spread from the shoulder to the lung (eg, respiratory depression).

Conclusions: This post-hoc analysis demonstrates that incobotulinumtoxinA is safe and effective for the treatment of shoulder spasticity and supports further clinical evaluation.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/efficacy-of-incobotulinumtoxina-for-the-treatment-of-shoulder-spasticity/