Purpose: The purpose of the present study was to investigate whether electrical stimulation (ES) improves the paralytic effect of botulinum toxin type A (BTX-A) and evaluate the differences between low frequency (LF) and high frequency (HF) ES in children with spastic diplegic cerebral palsy (CP).
Materials and methods: Twenty-three children with spastic diplegia CP who had BTX-A injections into both gastrocnemius muscles were assessed. Following the toxin injection, electrical stimulation was given to 1 side of the injected muscles and a sham-stimulation to the other side for 30 min a day for 7 consecutive days [HFES (25Hz) to 11 children, LFES (4Hz) to 12 children]. The compound motor action potentials (CMAP) from the gastrocnemius muscle were assessed before injection and at 5 time points (days 3, 7, 14, 21, and 30) after injection. The clinical assessments of spasticity were performed before and 30 days after injection.
Results: The CMAP area became significantly lower in both LFES and HFES sides from 3 days after injection compared to baseline values. In other words, the CMAP area of the sham-stimulated side showed a significant decrease at 7 or 14 days after injection. However, there were no significant differences in clinical assessment of spasticity between the stimulated and sham-stimulated sides.
Conclusion: Short-term ES in both LF and HF to the spastic muscles injected with BTX-A might induce earlier denervating action of BTX-A. However, it does not necessarily lead to clinical and electrophysiological benefits in terms of reduction of spasticity.