The strain used is Clostridium botulinum type A. It works by blocking acetylcholine release at neuromuscular junctions. The injection starts to work after a few days with the maximum effect at about 2 weeks. However the treatment will only last for 3-4 months. After this the effects wear off and the patient is reassessed before being re injected again if required. There are three products licensed in UK – Botox, Dysport and Xeomin.
Using ultrasound to guide injections
It can be difficult to place the dose of toxin in to the muscle in the most effective position. Ultrasound is one way to guide to the area of muscle for treatment. Electrical stimulation and EMG are also common modes of injection guidance.
Site of injections
Ideal site of Botulinum Toxin injection is at the neuromuscular junction or motor end plate. This gives maximal paralysing effect.
Almost all muscles of the legs and arms have a single innervation band, situated in the middle of the muscle. Rarely innervation bands are scattered along the entire length of the muscle. The effect progressively diminishes as the distance between the injection site and the end plate increases.
Royal College of Physicians Guidelines
Royal College of Physicians: Spasticity in adults: management using botulinum toxin 2018
Page last reviewed: 06 May 2020
