Thirty-two children with spinal dysraphism have been studied with phase MRI to assess longitudinal cord motion. Seventeen children who were asymptomatic and who had normal or slightly decreased motion were not operated. Fifteen had signs and symptoms of spinal cord tethering as well as decreased cord motion and underwent surgery. None of the nonsurgical patients have become symptomatic. The children with markedly decreased cord motion did not improve after surgery. A trend was seen toward a better outcome in younger patients with slight or moderate decrease in cord motion. All children with worse outcome were previously operated meningomyeloceles who had markedly decreased cord motion and who were greater than 10 years old.