Additional Study Information: The purpose of this research study is to check whether an injectable medication called Dysport canrelax the stiffness (spasticity) of the arm muscles and allow your child to improve their ability to use their arm in day to day activities. In addition, this study will check whether treatment with Dysport can lessen the pain caused by spasticity and improve your childs well being. In order to assess whether Dysport will help with your childs spasticity, two doses of Dysport (8U/kg and 16U/kg) will be compared with a low dose of Dysport (2U/kg). Participants in the study attend study visits with the doctor and his researchstaff including either physical or occupational therapists. There are approximately 25 visits that will occurin a maximum time-frame of 1 year and 9 months. You will be required to keep a study diary that will be reviewed at your study visits. All participants will receive individual plan of care, assessments and continuation of care from the doctor and his/her staff at no cost to you. There is a possibility that a minimum stipend will be offered to assist with travel related costs to the study visits.