How does botulinum toxin treatment for spasticity work?

Spasticity-reducing medications (spasmolytics) taken as tablets (oral medication) affect the entire musculature. For patients who experience severe spasticity in specific parts of the body, such as the hand or foot (focal spasticity), oral medications usually do not provide adequate treatment.

In this situation, treatment with botulinum toxins is a suitable option—medications that are injected directly into the muscles and cause a localized reduction in muscle tension. This class of medications was derived more than 20 years ago from a neurotoxin (hence the term “toxin”) and is now produced synthetically. This substance blocks the transmission of nerve impulses at the junction between motor neurons and the muscles (motor end plate), thereby reducing muscle tone. The block lasts two to four months, during which time the muscles into which the botulinum toxin was injected remain relaxed. During this period, the body breaks down the medication and muscle tone returns, so the medication must be re-administered to prevent further spasticity.

Botulinum toxin therapy involves a specialized physician (usually a neurologist with experience in botulinum toxin therapy) using a fine needle to inject small amounts of the medication into the spastic muscles at several sites. The injection is usually performed under ultrasound guidance. At least two to three injections are required for each muscle. Depending on the extent of the treatment needed, the procedure can take 20–40 minutes. As the effects of the botulinum toxin wear off, a repeat injection is necessary every three to four months.