Spontaneous Migration of a Redundant Nerve Root Accompanied by Absorption of Lumbar Disk Herniation

Abstract

A redundant nerve root is defined as a large, elongated and tortuous nerve root commonly associated with severe lumbar spinal canal stenosis. Elongation of nerve roots as a result of mechanical trapping at stenotic level is assumed to be a possible mechanism. Here we present a case in a patient who showed a redundant nerve root above the level of a lumbar canal stenosis caused by disk herniation and redundancy spontaneously migrating to a lower lumbar stenosis level accompanied by absorption of the herniated disk as shown by magnetic resonance imaging (MRI). A 67-year-old Japanese woman presented with bilateral thigh/leg pain and intermittent claudication. A midsagittal T2-weighted MR image of the lumbar spine revealed severe spinal canal stenosis at the L3–4 and L4–5 levels. At the L3–4 level, central disk herniation compressed the dural tube. An MR image revealed redundant nerve roots just cranial to the severely compressed L3–4 level. A follow-up MRI study revealed regression of disk herniation at the L3–4 level. In contrast, there was no significant change of the stenosis at the L4–5 level. Sagittal T2-weighted MR imaging at follow-up revealed redundant nerve roots just cranial to the L4–5 level, whereas the redundant nerve roots cranial to the L3–4 level had disappeared. The MRI findings of the present case support the “squeeze” hypothesis as causative of redundant nerve roots.