Botulinum toxin type A for upper limb spasticity after stroke.

Spasticity is involuntary overactivity of muscles that occurs following upper motor neuron damage to the brain or spinal cord. Upper limb spasticity is common after stroke and can cause deformity, pain and reduced function. Botulinum toxin type A is a neurotoxin produced by the bacterium Clostridium botulinum that blocks the release of acetylcholine from cholinergic neurons. When given by intramuscular injection it causes temporary local paresis and has become an important component of focal spasticity treatment. Randomized controlled trials have shown that botulinum toxin type A can decrease upper limb spasticity and improve the ease of performing basic upper limb functional activities, such as cleaning the hand or dressing a sleeve. This article will review the pharmacology of botulinum toxin type A and its clinical efficacy when used to treat upper limb spasticity after stroke.