Time course of surface electromyography during walking of children with spastic cerebral palsy treated with botulinum toxin type A and its rehabilitation implications

Background: The timing of the effects of botulinum toxin A on spastic muscles is not yet fully clarified. The goal of this study was to follow the temporal changes of surface electromyographic activity of lower limb muscles during walking, after a therapeutic dose of botulinum toxin A injected into the calf muscles of children with spastic cerebral palsy.Methods: A group of children with spastic equinus foot was administered botulinum toxin A into the gastroc-nemius medialis and lateralis muscles. Surface electromyographic activity of the tibialis anterior, gastrocnemius medialis, rectus femoris and medial hamstrings, was recorded before botulinum toxin A injections and after 4, 8, and 16 weeks. Children walked on ground and on a treadmill at an incline of 0% and 12%. The area of elec-tromyographic activity and the index of muscle co-contraction were calculated for specific segments of gait cycle.Findings: Botulinum toxin A did not modify the speed of gait on ground. ANOVA showed significant differences in electromyography during the stance phase segments with a maximum decrease between 4 and 8 weeks' post botulinum toxin A and a full recovery at 16 weeks. A significant co-contraction of rectus femoris/gastrocnemius medialis, between 0 and 20% and 35-50% of the gait cycle, was observed from the 4th to the 8th week post-botulinum toxin A for both treadmill settings.Interpretation: The temporal identification of deterioration/recovery of electromyographic activity as well as of muscle co-contractions, could be key elements in a rehabilitation program planning combined with botulinum toxin A.