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The effect of botulinum toxin A on gastrocnemius length: magnitude and duration of response
1The Gait Analysis Laboratory, Musgrave Park Hospital, Belfast, N Ireland.
Insights
Botulinum toxin A injections for spastic cerebral palsy in children effectively reduced spasticity, with hemiplegia cases showing longer-lasting effects. These treatments may help delay the need for surgery by managing muscle shortening.
Area of Science:
- Pediatric Neurology
- Rehabilitation Medicine
- Movement Disorders
Background:
- Spastic cerebral palsy (CP) often involves gastrocnemius muscle spasticity.
- Botulinum toxin A injections are used to manage spasticity in children with CP.
Purpose of the Study:
- To prospectively evaluate the efficacy of botulinum toxin A injections in the gastrocnemius muscle.
- To correlate spasticity components with treatment response and duration.
- To compare outcomes between children with hemiplegia and diplegia.
Main Methods:
- Prospective study of 39 ambulant children with spastic CP (hemiplegia and diplegia).
- Gastrocnemius muscle length measurement to assess spasticity and response to botulinum toxin A.
- Analysis of correlation between dynamic spasticity, response magnitude, and duration.
Main Results:
- Strong correlation found between pre-injection dynamic spasticity and post-injection response magnitude.
- Duration of response strongly correlated with the dynamic component of spasticity.
- Children with hemiplegia experienced twice the duration of response compared to diplegia for the same dose.
- No long-term muscle lengthening observed, but some responses persisted at 12 months.
Conclusions:
- Botulinum toxin A injections are effective in managing dynamic spasticity in children with CP.
- Injections may delay the need for surgical intervention by managing muscle shortening.
- Treatment is well-tolerated with minimal side effects.
Abstract:
Thirty-nine ambulant children (22 with hemiplegia, 17 with diplegia) with spastic cerebral palsy receiving isolated gastrocnemius muscle injection with botulinum toxin A were studied prospectively. The children had a mean age of 6 years (range 3 to 13 years). Measurement of gastrocnemius muscle length was used to estimate the dynamic component of each child's spasticity and to quantify the response. There was a strong correlation between the dynamic component of spasticity before injection and the corresponding magnitude of the response after injection. Children undergoing repeated injections showed similar correlations. A strong correlation was found between the duration of response and the dynamic component. Children with hemiplegia showed twice the duration for a given dynamic component compared with those with diplegia when injected with the same total dose per unit body weight. Long-term lengthening did not occur for the cohort, although some patients showed a response at a 12-month follow-up. By delaying shortening, the injections may have a role in delaying the need for surgery. Injections were well tolerated with few side effects.