How Much Evidence do we have on the Central Effects of Botulinum Toxin in Spasticity and Dystonia?

The brain is continually reorganizing (plasticity). Plastic changes within the sensorimotor system are not only beneficial (adaptive plasticity) but may even worsen function (maladaptive plasticity). Conditions such as dystonia and poststroke spasticity (PSS) that interfere with motor performance could be attributed to maladaptive plasticity. Botulinum toxin (BoNT) has been proven to be safe and effective in treating various hyperfunctional cholinergic states. Beside the well-known neuromuscular junction site of action, BoNT also exerts effects through supraspinal mechanisms and can even affect cortical reorganization. The hypothesis of central reorganization following BoNT treatment has been supported by studies using neurophysiological and imaging methods in patients with focal dystonia and PSS. The growing evidence of BoNT-related central (remote) effects make BoNT injections a promising tool to favorably affect maladaptive changes even at the cortical level