Botulinum toxin type A injections for the treatment of lower limb spasm in cerebral palsy

Cerebral palsy (CP) is a non-progressive lifelong condition resulting from damage to the newborn brain. Most infants have spasms (spasticity) affecting at least one leg that prevents normal movement. It can cause muscle contractures and deformities and the affected muscles do not grow as rapidly as neighbouring bone and soft tissue. Treatment includes physiotherapy, oral anti-spasticity drugs, casts, splints and orthopaedic surgery. Injection of botulinum toxin (BtA) into muscle causes local muscle weakness and so may help counter spasticity. This review found that published, controlled evidence was weak as they identified three controlled trials involving only a small number of children (2 to 11 years). Children receiving a single course of injections of BtA (Botox®, 3 to 8 µg/kg or Dysport®, 15 µg /kg) into the calf muscle tended to have an improved pattern of walking (gait) compared with inactive injections (placebo). Both BtA injections and lightweight walking plaster casts below the knee (for four to six weeks) produced similar significant improvements in gait. Some calf pain was reported among the 26 children injected with BtA and parents reported inconvenience with wearing casts and weakness of legs following removal.
 

Authors' conclusions: 

This systematic review has not revealed strong controlled evidence to support or refute the use of BtA for the treatment of leg spasticity in cerebral palsy.

Ongoing randomised controlled trials are likely to provide useful data on the short term effects of BtA for leg spasticity.

Future research should also assess the longer term use of BtA. Ideally studies should be pragmatic in their approach to dose and distribution of toxin to reflect practise. Outcome measures assessing function and disability would give the most useful information.

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Background: 

Children with cerebral palsy often have spasticity of the legs, a condition in which the legs are stiff because of involuntary muscle overactivity caused by the brain or spinal cord disorder. Spasticity causes poor coordination, spasms, abnormal posture and pain, and contributes greatly to the developmental deformities and disability of cerebral palsy. Conventional treatment with physiotherapy, splinting, oral medications and sometimes plaster casting and surgery may prove inadequate. Open label studies and some RCTs suggest that botulinum toxin injections into the spastic muscles can alleviate the spasticity and help some of these problems. Botulinum toxin blocks the release of acetylcholine from the neuromuscular junction and weakens the muscle. This and other effects may account for the apparent benefit in spasticity, but also highlight the importance of clarifying safety, especially in this group of growing children.

Objectives: 

To determine whether botulinum toxin (BtA) is an effective and safe treatment for lower limb spasticity in children with cerebral palsy. Functional outcomes are of particular interest.

Search strategy: 

Studies for inclusion in the review were identified using the Movement Disorders Review Group trials register, the Cochrane Controlled Trials Register, MEDLINE, pharmaceutical company databases, communication with other researchers in the field and reference lists of papers found using above search strategies.

Selection criteria: 

Studies were considered eligible for inclusion in the review if they evaluated the efficacy of BtA for the treatment of leg spasticity in children with cerebral palsy. They must have been randomised and include a concurrent control group receiving another intervention.

Data collection and analysis: 

A paper pro forma was used to collect data from the included studies using double extraction by two independent reviewers. Each trial was assessed for internal validity by each of the two reviewers.

Meta-analysis was not possible because results were presented in an incompatible form. A Peto odds ratio was calculated where this was appropriate, otherwise a descriptive summary of the results of the individual studies was compiled.

Main results: 

Three eligible studies were found each with small numbers of subjects. They were short term, used single injection sessions with follow-up of between 4 and 26 weeks.

One study (Koman), of twelve ambulant children, compared BtA with injection of a placebo and found non-significant improvements in gait in the BtA group compared to the placebo group.

Two studies (Corry 1998, Flett 1999) compared BtA with the use of casts. Each included 20 ambulant children and found improvements in gait, range of ankle movement and muscle tone in both the BtA and cast groups . However there were no significant differences between the groups in either trial. One of these trials (Flett 1999) also assessed motor function using the gross motor function measure (GMFM) (Russell 1989) and found significant improvements in each group compared to baseline but no significant differences between the groups. The other trial (Corry 1998) performed 3D gait analysis on those children able to co-operate. Maximal plantar flexion and maximal dorsiflexion during walking were both found to be significantly greater in the BtA group compared to the cast group. In all other dimensions there were no significant differences between the groups.

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