Minimal tethered cord syndrome: what's necessary to justify a new surgical indication?

Traditionally, surgical division of the terminal filum (filum terminale) has been reserved for patients with imaging-apparent spinal cord tethering. The occurrence of medically refractory voiding dysfunction of neurogenic origin, without magnetic resonance (MR) imaging documentation of abnormality in the spine, has been termed "minimal" tethered cord syndrome (TCS). The rationale for and utility of using surgical division of the terminal filum in the treatment of minimal TCS are unproven. Six studies that involved surgical division of the terminal filum for minimal TCS were identified and reviewed. A seventh study conducted prior to the MR imaging era, in which authors used myelography, was also included. In addition, two investigations of the clinicopathological findings in such cases were analyzed. A tripartite criterion for justifying the introduction of a new surgical indication is proposed and analyzed in light of this evidence. In children with minimal TCS there are definite pathological changes in the terminal filum that are not visible on routine spinal MR imaging. These changes suggest that the pathophysiology of minimal TCS, like TCS that is demonstrated on neuroimaging, may involve abnormal traction on the distal spinal cord. Additional data are needed regarding the sensitivity and specificity of various clinical studies intended to identify children with minimal TCS. All existing data supporting the efficacy of surgery for minimal TCS have been generated by Class III studies. Clinical equipoise exists for this surgical indication, and, therefore, a prospective randomized trial should be completed.