Ultrasound assessment of muscle and fascia properties and the effects of spasticity and botulinum toxin injections on spastic muscles in chronic stroke survivors

Abstract Objective To objectively quantify changes in muscle properties in chronic stroke survivors and the effects of spasticity and botulinum toxin injections (BoNTi) on muscle properties using ultrasonography. Design In this cross-sectional observational study, 24 stroke subjects with history of BoNTi to biceps brachii muscles (BB) but without BoNTi to the triceps (TRI) were included. Results 12 subjects had spastic TRI, the other half did not. 20 subjects had spasticity in wrist flexors, and 11 subjects received BoNTi to the flexor carpii ulnaris (FCU). On average, a significant decrease in muscle thickness (16.5% loss in TRI), a thicker fascia with higher echo intensity were noted on muscles in the paretic limb. Percent muscle loss (PML) was significantly less (11.0%) in spastic TRI than in non-spastic TRI (22.1%). There was no statistically significant difference in muscle and fascia properties in spastic FCU with and without BoNTi. Spasticity did not correlate significantly with muscle loss, fascia thickness or echo intensity. Conclusion Our results provided evidence that muscles on the spastic-paretic side had less muscle mass, thicker fascia and greater echo intensity. Our results showed that spasticity helped maintain muscle mass, but failed to reveal additional muscle loss after botulinum toxin injection.