The Effects of Botulinum Toxin Injections on Plantar Flexor Spasticity in Different Phases After Stroke: A Secondary Analysis From a Double-Blind, Randomized Trial

Background: There are no guidelines on the ideal time to inject botulinum toxin type A (BT-A) for lower leg spasticity in stroke patients. An early injection may produce unwanted weakness, interfering with gait recovery. Objective: To evaluate whether the outcomes after BT-A injection for plantarflexion spasticity can be different according to stroke chronicity. Design: A secondary analysis study from a double-blinded, randomized trial with group reclassification according to stroke chronicity. Setting: Two rehabilitation centers. Participants: Stroke participants (n = 40) with plantar flexor spasticity, treated with BT-A (200 units) into the gastrocnemius muscle. Methods: Outcome parameters were reanalyzed serially using 2-way repeated measures of analysis of variance (ANOVA), at baseline and 2, 4, and 8 weeks postinjection. Subjects were reclassified into 3 groups: early, within 6 months (n = 12); middle, between 6 months and 1 year (n = 14); and late, between 1 and 2 years from stroke onset (n = 12). Main Outcome Measures: The Modified Ashworth Scale, clonus scale, 10-m walking test, ABILOCO, and the Functional Ambulation Category. Results: The 2-way repeated measures of ANOVA showed improvement in gait and spasticity after injection in the 3 groups. Significant improvement in the Modified Ashworth Scale (P < .001) was observed, starting from the post-2 week injection period. Improvement of gait as assessed by the functional measurement ABILOCO and the Functional Ambulation Category (P < .001) were observed in all 3 groups, mostly at the post-8 week injection period. Conclusions: Our serial measurements of the outcome parameters indicated that BT-A could be expected to lead to consistent improvement in both the muscle tone and gait quality in those with plantar flexor spasticity regardless of stroke chronicity, including those injected as early as within the first 6 months.