A randomised controlled trial to determine the optimum frequency of Botulinum Toxin injections to the calf in children with cerebral palsy

INTERVENTION: Intervention group: Botulinum Toxin A calf muscle injections every 4 months over a 2 year period. Dose: 6 U/kg per gastrocnemius in diplegia or per gastrocnemius and soleus in hemiplegia with 6 U/kg available for use elsewhere as clinically indicated. Total upper dose of 18 U/kg. CONDITION: Cerebral palsy in children PRIMARY OUTCOME: Passive length of gastrocnemius in degrees of dorsiflexion SECONDARY OUTCOME: 3D ultrasound of medial gastrocnemius to determine muscle volumes Assessing the amount of dynamic gastrocnemius shortness measured by gait analysis ; Level of Function measured using the Functional Mobility Scale ; Quality of Life measured using the Child Health Questionnaire ; Secondary Unresponsiveness to Botulinum Toxin A measured in two ways: ; Assessing for the presence of neutralising antibodies to Botulinum Toxin A ; INCLUSION CRITERIA: Level I, II, or III on the Gross Motor Function Classification System for cerebral palsyGastrocnemius muscle length greater than 5 degrees with the knee extendedGastrocnemius spasticity (no heel contact during the stance phase of gait)