Children with spastic quadriplegic cerebral palsy often have osteoporosis, or weak bones. This makes them prone to have fractures with very minor injuries. Elderly adults also frequently have osteoporosis, and they are often treated for this problem with medications called bisphosphonates. The purpose of this research study is to assess whether one of these medications, called pamidronate, is safe and effective for the treatment of osteoporosis in children with cerebral palsy. Although doctors have used this medication in children, including children with cerebral palsy, the safety and effectiveness of pamidronate have not been fully evaluated in children. Therefore, this is an investigational use of pamidronate.