In patients with degenerative disease of the lumbar spine, stenosis not only in the entrance zone but also in the mid- and exit zones of the nerve root pathway can occur. With the development of magnetic resonance imaging (MRI), it has become easier to assess stenosis of the root pathway, especially in the mid- and exit zones. T1-weighted sagittal images in the lateral facet plane show the state of the exit zone. I studied the incidence of severe exit-zone stenosis of L3-5 roots in 45 patients aged over 50 years 15 in their fifties, 15 in their sixties, and 15 in their seventies) by MRI and assessed the results on the basis of age, intervertebral disc degeneration, and disc height. I also studied the relationship between clinical symptoms and severe stenosis in both entrance and exit zones of the L4 and L5 roots. The incidence of severe exit-zone stenosis at the L3 root was 20% at all ages. On the other hand, L4 and L5 nerve root stenosis increased with age and severe stenosis affected 70% of L4 roots and 80% of L5 roots in patients in their seventics. The incidence of deformation or disappearance of the dorsal root ganglion (DRG) was 10% or less at L3 and L5 roots, while it was 10% at L4 root. The incidence of severe stenosis both in entrance and exit zones in a single root was 20% at L4 root in all age groups, while it was 19% of patients in their fifties and increased to 29% of patients in their sixties and then 46% of patients in their seveties at L5 root. This study showed the high frequency of root pathway stenosis at L4 and L5 in the degenerative lumbar spine. However, not all patients with exit stenosis suffered from radicular symptoms. Stenosis in the mid- and exit zones of the root pathway has been an important factor in failed back surgery. It seems to be important to determine whether entrance, mid- and exit zone stenosis exist or not in order to clarify the pathological conditions of patients, especially in disorders affecting L4 and L5 nerve roots. T1-weighted MRI images can provide useful information concerning lesions in the mid- and exit zones in the degenerative lumbar spine.
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Sasaki, K. Magnetic resonance imaging findings of the lumbar root pathway in patients over 50 years old. Eur Spine J 4, 71–76 (1995). https://doi.org/10.1007/BF00278915
- Lumbar spine
- Root pathway
- Magnetic resonance imaging
- Dorsal root ganglia
- Failed back surgery