Fascial Remodeling After Botulinum Toxin Injection in Post-Stroke Spasticity: A Retrospective Ultrasonographic Study

Post-stroke spasticity involves both neural and non-neural mechanisms, including structural alterations of muscles and surrounding fascia. Although botulinum toxin type A (BoNT-A) is widely used to treat focal spasticity, its effects on fascial tissue remain unclear. This retrospective observational study investigated longitudinal changes in fascial thickness after BoNT-A injection using ultrasonography. Thirty-seven patients with post-stroke spasticity were included. Fascial thickness was measured at baseline, 3 weeks, and 3 months after treatment in the injected muscle regions. Clinical outcomes were assessed using the Modified Ashworth Scale (MAS), Fugl–Meyer Assessment (FMA), and Brunnstrom stages. Repeated-measures analysis demonstrated significant reductions in fascial thickness across all evaluated regions. Pairwise comparisons showed significant decreases from baseline to week 3 and month 3, whereas continued reductions between week 3 and month 3 were observed only in the flexor digitorum superficialis fascia, the flexor digitorum superficialis–flexor digitorum profundus interfascial layer, and the deep brachialis fascia. MAS scores and upper extremity Fugl–Meyer scores improved significantly, whereas Brunnstrom stages remained unchanged. These findings suggest that the therapeutic effects of BoNT-A may extend beyond neural inhibition to include fascial remodeling. Ultrasonographic assessment of fascial thickness may represent a potential imaging biomarker for monitoring structural treatment responses in post-stroke spasticity.