Objective: The objective of this analysis is to identify an optimal muscle selection pattern for onabotulinumtoxinA injection for the treatment of post-stroke lower-limb spasticity (PSLLS).

Background: OnabotulinumtoxinA injection has been shown to decrease muscle tone in PSLLS; however, optimal muscle selection patterns for injection have not been previously identified.

Methods: Adults with PSLLS (Modified Ashworth Scale [MAS] ≥3 in the ankle) were enrolled in a multicenter, phase 3, placebo-controlled study. The 12-week double-blind phase randomized patients to onabotulinumtoxinA (300U, mandatory muscles [gastrocnemius, soleus, tibialis posterior] and ≤100U, optional lower limb muscles [flexor digitorum longus (FDL), flexor digitorum brevis, flexor hallucis longus (FHL), extensor hallucis, rectus femoris]) or placebo. The primary endpoint, MAS change from baseline, and a secondary endpoint, physician-assessed Clinical Global Impression of Change (CGI), were each reported as the average score of weeks 4 and 6.

Results: In the intent-to-treat group (n=468), onabotulinumtoxinA significantly improved ankle MAS (–0.81 vs –0.61; P=0.01) and CGI (0.86 vs 0.65; P=0.012) versus placebo. 211 patients received treatment in the mandatory muscles only; 119 received treatment in the mandatory muscles plus FHL and FDL muscles. Injection of the mandatory muscles alone did not improve ankle MAS (P=0.255) or CGI (P=0.576) in all patients; however, it was adequate among those ≤2 years post-stroke (MAS, –1.13 vs –0.62, P=0.019; CGI, 1.24 vs. 0.68, P=0.006). Additional injections into FDL and FHL muscles significantly improved ankle MAS (–0.98 vs –0.52; P=0.002) and CGI (0.80 vs 0.38; P=0.023) versus placebo regardless of their time since stroke. OnabotulinumtoxinA 300-400 U was well tolerated with no new safety findings.

Conclusions: Additional injections of onabotulinumtoxinA into the toe flexors (FDL, FHL) significantly improved ankle MAS and CGI scores compared with injections into the mandatory muscles alone, particularly when treatment was initiated >2 years post-stroke.

1. American Academy of Neurology (AAN) 2016 Annual Meeting, Vancouver, BC, Canada, April 15–21, 2016. 2. World Congress for NeuroRehabilitation (WCNR) 2016, Philadelphia, PA, May 10-13, 2016.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/muscle-selection-patterns-for-injection-of-onabotulinumtoxina-in-adult-patients-with-post-stroke-lower-limb-spasticity-influence-outcome-results-from-a-double-blind-placebo-controlled-phase-3-clinic/