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Neurophysiological changes and rehabilitation implications induced by botulinum toxin type A injection in children with cerebral palsy


1. Neurorehabilitation, Children Hospital `Bambino Gesu”, Rome Italy;
2. Physical Medicine and Rehabilitation, `Sapienza’ University of Rome, Rome, Italy

Background/Objectives: Cerebral Palsy (CP) is due to immature brain lesion involving the motor descending pathways and it is characterized by movement and posture disorders. Previous studies of somatosensory evoked potentials (SEPs) have observed that their transmission was significantly abnormal. The SEPs amplitude decreased during muscles activation and it is absent during muscles co-contraction, so we suppose that spasticity may partially contribute to the abnormal response of cortical SEP. The botulinum toxin injection seems interact with intrafusal and extrafusal fibers producing a reduction of hypertone both through synaptic blockade and both for inhibition of stretch reflex loop. And these changes may influence not only the spinal cord but also the central nervous system (CNS). The purpose of our study was to determine the effect of spasticity on cortical SEPs through an evaluation of their amplitude variation in comparison with the amplitude variation of H wave that is the index of excitability of stretch reflex loop, after botulinum toxin type A injection.

Design: This is an intervention study with pre-post treatment outcome comparison.

Participants and Setting: Fifteen children with spastic diplegia CP, aged between 5 and 12 years, were recruited at Children’s Hospital `Bambino Gesu’ of Rome.

Materials/Methods: All children underwent a clinical evaluation with videotaping, Passive Range of Motion (PROM) of ankle joint, Modified Ashworth Scale (MAS) of plantar flexor muscles, Selective Control Scale (SC) of lower limb before and 1 month after the botulinum toxin type A injection. Neurophysiological measurement outcome were performed before and 1 month after the botulinum toxin injection through lower limb SEPs and Soleus H wave recording. In the six month before and during the period of the study children were not treated with antispastic pharmacological or surgical treatment but they continued rehabilitation therapy.

Results: After the injection the results showed a statistically significant improvement of MAS, PROM and SC. The normal response of cortical SEPs and Soleus H wave increased after injection. In particular SEPs showed more frequent amplitude improvement in the limbs with higher grade of spasticity measured with MAS.

Conclusions/Significance: The observed improvement of cortical SEPs with associated reduction of spasticity induced by botulinum toxin type A injection suggests that spasticity itself can be considered as a factor affecting the cortical SEPs. And even though it is not directly related to the synaptic inhibition induced by botulinum toxin type A it could be the expression of the modulation of afferent fibers that, after the treatment, are more sensitive to the rehabilitation training. Hence the period of pharmacological activity of botulinum toxin could be exploited in order to obtain a real no-drug-dependent change of motor pattern.

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