[Mechanism of action, clinical indication and results of treatment of botulinum toxin].

Botulinum toxin, the most potent of the neurotoxins, produces paralysis by blocking presynaptic release of the neurotransmitter (acetylcholine) at the neuromuscular junction, with reversible chemical denervation of the muscle fibre, thereby inducing partial paralysis and atrophy. Because chemical denervation is reversible, botulinum toxin has temporary effects, the muscle being progressively reinnervated by nerve sproutings. Type A botulinum toxin (Bix-A) is available under two dosage forms: Botox and Dysport. Although the initial clinical indication was strabismus, subsequent studies have demonstrated the efficacy of Btx-A, mainly in dystonia, hemifacial spasm and spasticity. However, botulinum toxin has been successfully used in various other clinical indications. In regard to spasticity associated with cerebral palsy, Btx-A is a promising treatment requiring a multidisciplinary approach. Btx-A injections lead to effective reduction of muscle hyperactivity with minor side-effects. They are painless, even though electromyographic guidance may be required for the injection of deep muscles. However, the production of antibodies to Btx-A may compromise the effect of long-term treatment.