Effect of Botulinum Toxin on Muscles of Children With Cerebral Palsy

A biopsy (specifically done for the study) of a muscle that has already been injected with botulinum toxin before inclusion of the patient in the study will be performed, taken during a planned surgery (for tendon transfer or muscle lengthening). A biopsy of a muscle that has never been injected with botulinum toxin may be performed during surgery. No biopsy will be made on a member that would not require surgery. Thus sampling will be conducted on a muscle requiring a surgery: 2 to 3 millimeters will be taken on 10 mm muscle before transfer or lengthening.