How does botulinum toxin really work?

Over the past 30 years, Botulinum toxin (BoNT) has emerged as an effective and safe therapeutic tool for a number of neurological conditions, including dystonia. To date, the exact mechanism of action of BoNT in dystonia is not fully understood. Although it is well known that BoNT mainly acts on the neuromuscular junction, a growing body of evidence suggests that the therapeutic effect of BoNT in dystonia may also depend on its ability to modulate peripheral sensory feedback from muscle spindles. Animal models also suggest a retrograde and anterograde BoNT transportation from the site of injection to central nervous system structures. In humans, however, BoNT central effects seem to depend on the modulation of afferent input rather than on BoNT transportation. In this chapter, we aimed to report and discuss research evidence providing information on the possible mechanisms of action of BoNT in relation to treatment of dystonia.