Optimal Muscle Selection for OnabotulinumtoxinA Injections in Poststroke Lower-Limb Spasticity: A Randomized Trial

The aim of the study was to identify optimal muscle selection patterns for onabotulinumtoxinA treatment of poststroke lower-limb spasticity.

Adults with poststroke lower-limb spasticity (ankle Modified Ashworth Scale ≥3) were randomized to onabotulinumtoxinA (300 U, mandatory ankle plantar flexors; ≤100 U, optional lower-limb muscles) or placebo. Post hoc analysis assessed the impact of muscle selection patterns on ankle Modified Ashworth Scale and physician-assessed Clinical Global Impression of Change based on change from baseline to average of weeks 4/6 versus placebo.

Among 468 patients randomized, onabotulinumtoxinA improved ankle Modified Ashworth Scale (-0.81 vs -0.61, P = 0.01) and Clinical Global Impression of Change (0.86 vs 0.65, P = 0.012) versus placebo. Injection of mandatory muscles alone was not sufficient in improving ankle Modified Ashworth Scale (P = 0.255) or Clinical Global Impression of Change (P = 0.576) versus placebo but was adequate 24 mos or less after stroke (Modified Ashworth Scale, -1.13 vs -0.62, P = 0.019; Clinical Global Impression of Change, 1.24 vs 0.68, P = 0.006). Additional injections into toe muscles (flexor digitorum longus, flexor hallucis longus) improved ankle Modified Ashworth Scale (-0.98 vs -0.52, P = 0.002) and Clinical Global Impression of Change (0.80 vs 0.38, P = 0.023) versus placebo regardless of time since stroke. OnabotulinumtoxinA was well tolerated, with no new safety findings.

Post hoc analyses suggested additional injections of onabotulinumtoxinA into toe flexors improved ankle Modified Ashworth Scale and Clinical Global Impression of Change scores versus mandatory muscles alone overall and with treatment initiation more than 24 mos after stroke.