Pathoanatomical correlation of bladder sparing in cauda equina syndrome due to posteriorly sequestered lumbar disc herniation.

The pathoanatomical explanation of lumbar disc herniation causing the rare cauda equina syndrome with sacral 2- sacral 4 roots sparing is not well described. A case report of bladder sparing cauda equina syndrome due to a large posteriorly sequestered lumbar disc fragment is presented. Magnetic resonance imaging of the lumbosacral spine showed herniation of a large disc fragment at lumbar 3-lumbar 4 deforming the thecal sac posteriorly, with the left side more affected than the right. Bladder sparing cauda equina syndrome can be explained by the anatomical organization of the nerve roots within the thecal sac. The medial sacral roots are not as stretched and strained by the herniating disc as the laterally placed lumbar roots. Early laminectomy and decompression of the thecal sac may relieve this stretch and strain on the nerve roots and therefore preserve bladder function.