How does botulinum toxin help children with cerebral palsy?

What is spasticity?

Spasticity is a common feature of cerebral palsy in which muscles are stiff and overactive because of changes in the brain's control of movement. It can make walking, sitting, dressing and hand use difficult, cause pain and, over time, contribute to muscle shortening and joint deformities.

Common patterns include tight calf muscles causing toe walking, tight hamstrings and hip adductors affecting walking and sitting, and a tight elbow, wrist or thumb affecting hand use.

How does botulinum toxin work?

Botulinum toxin type A is injected into specific muscles, where it blocks the signals from nerves that make the muscle contract. This reduces overactivity in the injected muscle for a period of weeks to months, after which nerve connections recover and the effect wears off.

Injections are often guided by ultrasound or muscle stimulation to reach the correct muscles. Children may have numbing cream, sedation or anaesthesia depending on age and the number of muscles injected.

What does the evidence show?

A Cochrane review of 31 randomised trials with 1,508 children found that, compared with placebo or sham, botulinum toxin improved overall gait scores in the short term (risk ratio 1.66) and medium term (risk ratio 1.90), based on moderate-quality evidence 1. It was not more effective than placebo for improving function in the short term 1.

Compared with usual care or physiotherapy, botulinum toxin may improve function, ankle range of motion and spasticity, although the evidence was of very low quality 1. A systematic overview of cerebral palsy interventions rates botulinum toxin, and its combination with casting or occupational therapy, as effective 2.

Who is botulinum toxin suitable for?

UK guidance on spasticity in children and young people suggests considering botulinum toxin when focal spasticity impedes motor function, causes pain, disturbs sleep, makes care and hygiene difficult or limits tolerance of other treatments such as orthoses 3.

Clear, individual goals are agreed before treatment, such as improving walking pattern, fitting into an ankle-foot orthosis or making nappy changes easier. Botulinum toxin is less helpful when muscles are already fixed and shortened.

Why is therapy needed after injections?

Botulinum toxin creates a window of opportunity in which the muscle is more relaxed. Stretching, strengthening, task practice, serial casting or orthoses during this period help children make the most of the reduced spasticity.

Without therapy, the effect on function may be limited. Treatment plans are reviewed after each cycle to decide whether further injections are useful.

What are the side effects?

Side effects are usually mild and temporary and can include pain at the injection site, bruising, temporary weakness, tiredness and flu-like symptoms. In the Cochrane review, adverse events were reported in children receiving botulinum toxin, with very low-quality evidence on their frequency 1.

Rarely, the effect can spread beyond the injected muscle, causing difficulty swallowing, speaking or breathing. Seek urgent medical help if these symptoms occur.

How can families prepare a child for injections?

Explaining the procedure in simple, honest language suited to the child's age, bringing a comfort toy and planning a favourite activity afterwards can reduce anxiety. Numbing cream, distraction techniques and sedation or anaesthesia are options depending on the child and the number of muscles injected.

After injections, families usually receive a plan for therapy, casting or orthoses and a date for review. Keeping notes about changes in walking, comfort, sleep and daily care helps the team assess how well the treatment has worked.

How often can injections be repeated?

Injections are generally not repeated more often than every three months, and the interval depends on the response and goals 3. Many children have repeated cycles over several years as part of a long-term plan.

Other spasticity treatments, such as oral medicines, intrathecal baclofen or selective dorsal rhizotomy, may be considered when spasticity is widespread or botulinum toxin is not effective enough.

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