Redundant nerve roots in patients with degenerative lumbar spinal stenosis.

Extensive fundamental and clinical investigations have been performed concerning redundant nerve roots (RNR) and the pathogenesis of cauda equina claudication (CEC) in degenerative lumbar canal stenosis (DLCS). These investigations consisted of (1) anatomic observations on RNR in 117 fixed cadaveric specimens, (2) myelographic study in 117 patients with or without DLCS, (3) operative observation on neural elements with special reference to the cauda equina in 56 DLCS patients (including a postoperative follow-up), and (4) electrophysiologic tests using spinal cord action potential recording under walking load preoperatively and intraoperative measurement of nerve conduction velocity of RNR. The RNR have neuronal losses resulting from a longer duration stenosis that suggests a sort of friction neuritis. Complicated factors contribute to the pathogenesis of CEC and the development of root gripping, such as the magnitude of RNR, the extent of the stenosis, a narrowed sac, age-dependent axial shortening of the spinal canal, and dynamic or postural factors. In cases with severe RNR, satisfactory operative results can be obtained only after thorough decompression with dural incision.