Botulinum Toxin A (BTA)
Updated April 2008
What is Botulinum Toxin A?
Botulinum Toxin A (BTA) is a muscle relaxant derived from the bacterium Clostridium Botulinum. This bacterium has associations with botulism, a rare form of food poisoning, but can, like many toxic substances when used in small, controlled doses, provide safe, effective relief from a number of conditions. Currently BTA, under the brand name BotoxTM, is perhaps more commonly associated with face-lifts.
What Botulinum Toxin A is not
BTA is not a cure for cerebral palsy, nor is it a suitable treatment for all forms of cerebral palsy.
Origins of the treatment
This is not a new treatment. BTA has been used therapeutically for over 20 years, mainly with adults, to treat a variety of conditions characterised by muscle hyperactivity. In 2000, two BTA products, BotoxTM and DysportTM, were licensed for use in the treatment of children with cerebral palsy in the UK.
Treatment aims
BTA is licensed in the UK to treat pes equinus in children with cerebral palsy but its effective uses extend more widely. Pes equinus, often referred to as tip-toe walking, is very common in children with cerebral palsy, and results from spasticity in surrounding muscles which makes it difficult, or impossible, to place the foot flat on the floor. When injected into the calf muscle(s) (gastrocnemius and/or tibialis posterior), BTA can relax these muscles, making walking easier and more comfortable, as well as generally improving balance and reducing the frequency of falls.
Tightness in the muscles at the back of the thigh (hamstrings) makes it difficult to straighten the leg/s, resulting in crouch or squat gait. Injection with BTA can help straighten the legs, resulting in improvements in walking, sitting and/or transferring. BTA is also used to good effect on the adductor muscles in the hip, again a common problem area for children with spastic cerebral palsy. Too much muscle tone in this area impacts on the individual's mobility by making it difficult to keep the legs apart (also known as scissoring). For those with upper limb spasticity, BTA can reduce muscle tone around the elbow, wrist and thumb areas enabling straightening of the arm (helping with personal care and hygiene) and improving pinching, grasping and releasing movements.
In addition to these functional gains, BTA also has the potential to reduce the development of secondary problems. Spasticity can create an imbalance in muscle tone across a joint that not only interferes with motor function but can also lead to fixed contractures (permanent shortening of the muscle and tendon), bony abnormalities and joint instability, such as hip dislocation.
Sometimes surgery will be required, but the earlier this is carried out, the more likely it will need to be repeated as the child grows and matures. Lowering the tone of the more active muscle(s) by using BTA can restore balance across the joint, increase the stretch of the muscle and promote growth, thereby possibly avoiding or minimising potential damage to that joint and the need for surgical intervention.
As the use of BTA has become more widespread treating adults and children with cerebral palsy, goals have expanded to include pain relief, improved positioning, tremor and spasm control, drooling management and facilitation of personal care. Treatment prior to adductor release surgery can significantly reduce post-operative pain, pain management requirements and the length of stay in hospital. Many surgeons use BTA during operations to reduce painful post-operative spasms and to protect soft tissue from involuntary movement until the healing process is complete.
Many teenagers and adults with cerebral palsy report a high level of satisfaction with the cosmetic improvement that BTA can bring about to their appearance as well as the comfort from reduction of tone and spasm, even where there has been no significant change in function or movement.
Tiredness can often be a problem for people with cerebral palsy, due to the increased effort required in moving around. As movement becomes more fluid following BTA treatment, there is often a consequent reduction in energy consumption.
How does it work?
Skeletal muscles tighten or contract in response to the release from nerve endings of the neurotransmitter acetylcholine.
When BTA is injected into the muscle(s), the release of acetylcholine is blocked, resulting in a relaxation of overactive muscles. The injection(s) generally take effect within a few days and last until new nerve endings grow back and the affected muscle(s) recover, which usually takes around 12-16 weeks. Functional benefits, however, usually last longer than this.
Suitability for treatment
Usually a full assessment will be carried out by a hospital medical team, comprising a consultant (either a paediatrician or orthopaedic surgeon) and a physiotherapist. An orthotist or occupational therapist may also be present. This assessment will involve a detailed movement study, which is often videoed, probably lasting around an hour. A decision will then be made as to whether the treatment is appropriate and which muscle or range of muscles will be injected. A clear indication should also be given as to what the result is likely to be.
What does the treatment involve?
BTA is diluted in a saline solution and injected directly into the muscle(s). An anaesthetic cream may be applied to the skin to reduce any discomfort from the injection. Oral sedation is frequently used, or sometimes a local or general anaesthetic, especially if the individual is very young and/or anxious, or where the area to be injected is difficult to access. The muscles to be injected are identified by manual palpation, ultrasound, EMG (electromyography) or stimulation of the nerve.
The amount of BTA used is determined by the size and number of muscle(s) to be treated, the degree of spasticity and the weight of the patient, up to a maximum recommended dose. Multi-level injections, where a number of sites are injected during the one treatment, are now becoming commonplace.
Following the injection(s), advice and direction should be given as to how to maximise the effects of BTA. This may involve more intensive physiotherapy, increased use of walking aids or splinting or some specific changes to the daily routine to incorporate greater involvement of the treated muscles. Sometimes BTA may be used in conjunction with casting to maximise muscle stretch.
A follow-up appointment will be made to assess how successful the injection(s) have been and the treatment repeated as necessary. On average the interval between injections varies from between six to nine months: re-injection will usually be recommended when muscle tone begins to interfere with function rather than when it returns to pre-injection levels. There is currently no absolute limit to the number of re-injections.
Side-effects
In the main, reported side-effects are mild and short-lived. These include:
- Post-injection pain requiring simple analgesia
- Increased frequency of falls within first two weeks of injection
- Mild cold- or flu-like symptoms
- Temporary incontinence
- Positive effect on constipation
- Difficulty with swallowing, especially where upper limb or neck injected
- Mood swings/irritability
- Fatigue
- Anaphylaxis (severe allergic reaction), but this is rare
No cases of generalised botulism have been recorded. A reduced response is occasionally reported to follow-on injections, sometimes due to antibody formation. Adverse long-term side-effects from this treatment cannot be entirely excluded and research is ongoing.
Access to BTA treatment
Although this treatment is now becoming more common, not all NHS Trusts will fund BTA. As with all medical treatments, referral should be made via your GP or consultant.
Conclusion
BTA injections are not suitable for all people with cerebral palsy and patient selection is very important. For this reason, Scope recommends that prospective patients ensure that the medical team involved has considerable experience, both in the management of cerebral palsy and in the administering of BTA. It is also important to have clear, realistic expectations as to what the results of the treatment are likely to be. Any follow-on or associated interventions, such as physiotherapy, splinting or casting, should be discussed fully with the medical team involved.
As with any other therapy or treatment, we advise people with cerebral palsy, their carers or parents to consult their GP, consultant or health professional before starting or paying for any treatment.
Due to the individual nature of cerebral palsy, some children will benefit from specific treatments and therapies; others will not. Assessment of your child's individual needs is very important.
This document is for information purposes only.
For more information about cerebral palsy and Scope services
Contact Scope Response for information, advice and support. Copies of all Scope's information sheets can be downloaded from the website or obtained from Scope Response.
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