The US Food and Drug Administration (FDA) has approved Botox (onabotulinumtoxin A) to treat spasticity in the flexor muscles of the elbow, wrist and fingers brought on by a stroke, traumatic brain injury or the progression of multiple sclerosis.

The FDA Centre for Drug Evaluation and Research’s director of neurology Russell Katz said that treatment with Botox was found to be beneficial during clinical trials.

“Muscles affected by spasticity have increased stiffness and tightness, which may lead to pain, difficulties with hygiene and may affect how a patient looks,” Katz said.

Botox, which is manufactured by Allergan, works by temporarily blocking the connections between nerves and muscles, resulting in a temporary paralysis of the spastic muscle.

Botox comes with a boxed warning that says the effects of the botulinum toxin may spread from the area of injection to other areas of the body, causing symptoms similar to those of botulism. Those symptoms include swallowing and breathing difficulties that can be life-threatening.

Botox has not been shown to be safe and effective treatment for other upper limb muscles, spasticity in the legs, or for treatment of fixed contracture – a condition that affects range of motion.