Effect of short-term electrical stimulation before and after botulinum toxin injection

Objective To compare the effect of electrical stimulation applied before and after botulinum toxin injection. Subjects Eight healthy subjects. Methods Both extensor digitorum brevis muscles were injected with low fixed doses of botulinum toxin. Subjects received a 20-min session of electrical stimulation before botulinum toxin injection for the right foot and after the injection for the left foot. Percentage changes in compound muscle action potential amplitude were calculated at different intervals over a 60-day period. Results A reduction in compound muscle action potential percentage was measured at every time-point, both for the muscles stimulated before injection of botulinum toxin and for those stimulated after injection. The compound muscle action potential percentage was always lower on the side stimulated after injection of botulinum toxin. A reduction in compound muscle action potential percentage was measured on the 7th and 15th days in all extensor digitorum brevis muscles examined. On the 15th day the compound muscle action potential percentage was 38.8 (right foot) vs 24.1 (left foot) (p=0.0117). A slow recovery was observed after this period. Conclusion Electrical nerve stimulation enhances the effect of botulinum toxin to a greater extent if applied after injection rather than before. The short stimulation time used in our study gave similar results to those seen in previous research using longer application times.