Morphological changes in the cauda equina in patients who have
herniation of a lumbar disc have not been previously reported, to our
knowledge. Using computed tomographic myelography, we found swelling of
nerve-root elements in the cauda equina that corresponded to the affected
root in seventeen of twenty-eight patients who had proved herniation of a
lumbar disc. All seventeen patients had severe sciatica. The swelling of
the nerve-root elements gradually returned to normal after surgical
decompression, which was also associated with improvement of the sciatica.
Patients who did not have severe sciatica did not show swollen nerve-root
elements. These findings may be an important clue to the mechanism of
sciatic pain in patients who have herniation of a lumbar disc.