Objectives: The aim of this study was to assess the changes of the spasticity and gait pattern after botulinum toxin A injection on the gastrocnemius muscle.

Method
Thirty five legs of twenty-six ambulatory cerebral palsy children aged from two to sixteen year old were treated. Botulinum toxin A (Allergan, USA) from 2 to 8 U/Kg bodyweight was injected on the gastrocnemius without sedation and electromyographic guidance. The modified Ashworth scale, the reflex excitability test were used for the assessment of spasticity. The changes of gait pattern were collected using 6 camera VICON system. All assessments were measured before and at two weeks after injection.

Results
1) The modified Ashworth scale of ankle plantar flexor improved significantly. 2) The reflex excitability test result decreased significantly in gain. 3) The kinematic data showed significant improvements in sagittal plane of the ankle at two weeks after injection. The children with the genu recurvatum showed improvement in sagittal plane of the knee and those with the crouch gait didn't show aggravation of gait pattern after the injection.

Conclusion
The intramuscular botulinum toxin A injection reduced the spasticity and improved the gait pattern in the cerebral palsied children with ankle plantar flexor spasticity.