Botulinum toxin has been used for almost 30 years to treat spasticity. Out of these experiences it shows that botulinum does not cause long-term side effects. Microscopic examinations showed that no permanent changes have occurred in the nerves or muscles after absorbing Botulinum. After the effect ends, neither the active substance nor its effects on the nerves can be detected. As a calm muscle is usually weaker (think of a leg in a cast), with time a smaller dose of Botulinum toxin is going to be needed, to get the same muscle relaxing effect than before.
Spasticity is one of several clinical features/motor behaviors that may result following damage to the part of the brain or spinal cord involved in controlling voluntary movement. Collectively, these features are known as the upper motor neuron syndrome. Spasticity is associated with a pathologically increased muscle tone. This creates stiffness and resistance to passive movement. This change in muscle tone may increase the disability related to the disease at the origin of spasticity.
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