OnabotulinumtoxinA for Painful Foot Dystonia in Parkinson Disease: A Randomized, Double-Blind, Placebo-Controlled Trial.
OnabotulinumtoxinA for Painful Foot Dystonia in Parkinson Disease: A Randomized, Double-Blind, Placebo-Controlled Trial.
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Original abstract
BACKGROUND AND OBJECTIVES: Pain associated with foot dystonia is a common and disabling symptom of Parkinson disease (PD), often occurring during OFF periods, yet frequently refractory to medication optimization. Evidence supporting treatments for dystonia-related pain in PD remains limited. This study evaluated the efficacy and safety of onabotulinumtoxinA (BTXA) for pain associated with foot dystonia in patients with PD. METHODS: This single-center, randomized, double-blind, placebo-controlled trial assessed outcomes at 6 and 12 weeks, followed by a 12-week open-label extension. Adults with unilateral PD and painful foot dystonia refractory to medication optimization were randomized 1:1 to receive BTXA (100 units) or placebo using a guided injection protocol targeting the tibialis posterior, extensor hallucis longus, and flexor digitorum brevis. The primary outcome was change from baseline in dystonia-related pain assessed using Item 5 of the King's Parkinson's Disease Pain Scale (KPPS). Secondary outcomes included responder rates (≥30% pain reduction), KPPS Domain 3 total score, KPPS Item 5 pain severity and frequency subitems, Visual Analogue Scale (VAS) pain, Clinical Global Impression, motor outcomes (Movement Disorder Society-Unified Parkinson's Disease Rating Scale III and IV), quality of life, and safety. RESULTS: Thirty-three participants were randomized (BTXA, n = 16; placebo, n = 17). BTXA resulted in significantly greater reduction in dystonia-related pain assessed by KPPS Item 5 total score compared with placebo at 6 weeks (mean difference -3.60), with effects sustained at 12 weeks (p < 0.001). The between-group effect size for the primary outcome was large (Hedges' g -1.33; 95% CI -2.13 to -0.53). Improvements were observed in KPPS Item 5 pain severity and frequency and in KPPS Domain 3 total scores at 6 and 12 weeks. VAS pain was reduced at 6 weeks, with no significant between-group difference at 12 weeks. Responder rates (≥30% pain reduction) were higher with BTXA at both 6 and 12 weeks (75.0% vs ≤ 11.8 and 5.6%, respectively; p < 0.001). No differences were observed in motor outcomes, quality of life, or adverse events, which were mild. DISCUSSION: BTXA reduced pain associated with foot dystonia in PD without adversely affecting motor outcomes and was well tolerated, supporting its use as a targeted treatment for this disabling symptom. TRIAL REGISTRATION INFORMATION: NCT04277247.