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Plastic changes in spinal synaptic transmission following botulinum toxin A in patients with post stroke spasticity

Abstract : Objective: The therapeutic effects of intramuscular injections of botulinum toxin-type A on spasticity can largely be explained by its blocking action at the neuromuscular junction. Botulinum toxin-type A is also thought to have a central action on the functional organization of the central nervous system. This study assessed the action of botulinum toxin-type A on spinal motor networks by investigating post-activation depression of the soleus H-reflex in post-stroke patients. Post-activation depression, a presynaptic mechanism controlling the synaptic efficacy of Ia-motoneuron transmission , is involved in the pathophysiology of spasticity. Patients: Eight patients with chronic hemiplegia post-stroke presenting with lower limb spasticity and requiring botuli-num toxin-type A injection in the ankle extensor muscle. Methods: Post-activation depression of soleus H-reflex assessed as frequency-related depression of H-reflex was investigated before and 3, 6 and 12 weeks after botulinum toxin-type A injections in the triceps surae. Post-activation depression was quantified as the ratio between H-reflex amplitude at 0.5 and 0.1 Hz. Results: Post-activation depression of soleus H-reflex, which is reduced on the paretic leg, was affected 3 weeks after botulinum toxin-type A injection. Depending on the residual motor capacity of the post-stroke patients, post-activation depression was either restored in patients with preserved voluntary motor control or further reduced in patients with no residual voluntary control. Conclusion: Botulinum toxin treatment induces synaptic plasticity at the Ia-motoneuron synapse in post-stroke pa-retic patients, which suggests that the effectiveness of bot-ulinum toxin-type A in post-stroke rehabilitation might be partly due to its central effects.
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Marjorie Kerzoncuf, Laurent Bensoussan, Alain Delarque, Jacques Durand, Jean Michel Viton, et al.. Plastic changes in spinal synaptic transmission following botulinum toxin A in patients with post stroke spasticity. Journal of Rehabilitation Medicine, Foundation for Rehabilitation Information, 2015, 47, pp.910-916. ⟨10.2340/16501977-2014⟩. ⟨hal-01463696⟩

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