Significant reduction of muscle diameter after Botulinum Toxin injection in gastrocnemius muscle in children with cerebral palsy

Introduction: Within the last years Botulinum Toxin injection has been established as a new treatment strategy for patients with central movement disorders.

This study should answer the question whether a therapeutic denervation in the gastrocnemius muscle results in muscular atrophy which can be detected by myosonography. Goal is to establish an objective parameter to prove local therapeutic effect.

Patients/Methods: Until now we investigated n=69 children (healthy n=5;children with CP according to SCPE-classificationsystem n=64). The average age was 4 6/12 years (range: 23–179 months). We measured the diameter of the medial and lateral gastrocnemius muscle of both sides at the proximal 1/5 of the distance between fibula head and lateral malleolus of the distal lower limb. Analysis was performed with Ultrasound system Sonos 5500 from Philips using a linear 12MHz transducer. Patients lay in a prone position with plantarflexion of the talocalcanean joint. At least to two pictures of each muscle belly were stored and analysed by a third person off-line using the ImageJ®Software, NIH, USA.

Results: Myosonography proved to be a simple quick and reliable technique with high compliance through the patiens during examination. Our preliminary data shows 6 weeks after injection a significant reduction of 16,8%±12,4% in muscle diameter (average value, standard deviation, p 0,03). With ongoing data collection further analysis concerning variables like age, classification, and severity of muscle alteration within children with CP will be possible.

Conclusion: Treatment of medial and lateral gastrocnemius muscle with Botulinum Toxin leads to a statistically significant reduction of muscle diameter compared to non-treated muscles. This can be used as an objective parameter to measure the effect of Botulinum Toxin.