Effectiveness of multiple botulinum toxin sessions and the duration of effects in spasticity therapy in children with cerebral palsy

PURPOSE: The aim of this study was to assess the effectiveness of long-term therapy with multiply botulinum neurotoxin (BoNT) injections. METHODS: In 2004–2010, 60 children with spastic cerebral palsy aged 2–16 were treated multiple botulinum toxin sessions (injections in gastrocnemius muscle and soleus muscles). In each patient, we rated muscle tone by Modified Ashworth Scale, passive range of motion in ankle joint with extended, and flexed knee joint and gait using the Physician Rating Scale. Assessment was done before and after injection, up to eight BoNT sessions. RESULTS: The generalized additive models showed that a single treatment effect was visible for 3 months. The number of injections did not impact the effectiveness. Improvement in muscle tone was greater in children with hemiplegia than diplegia (β = − 0.294; p = 0.014). Improvement in range of motion with extended knee joint was greater in hemiplegic than diplegic types (β = 0.414; p =0.002), and improvement in range of motion with flexed knee was greater in children with more severe impairment (Gross Motor Function Classification System III vs. I, β = 0.0603, p = 0.025; V vs. I, β = 0.691, p = 0.023). The gait improvement rate decreased with patient age (p = 0.007). CONCLUSIONS: BoNT therapy is effective regardless of the number of injection sessions and duration of treatment. However, it is affected by the patient’s age, type of cerebral palsy, and degree of impairment.