Swelling of the cauda equina in patients who have herniation of a lumbar disc. A possible pathogenesis of sciatica.

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.