Organization of intrathecal nerve roots at the level of the conus medullaris
Wall, E.J.; Cohen, M.S.; Abitbol, J.J.; Garfin, S.R.
Journal of Bone and Joint Surgery. American Volume 72(10): 1495-1499
1990
ISSN/ISBN: 0021-9355 PMID: 2254357 Document Number: 365624
The three-dimensional organization of the spinal nerve roots at the level of the conus medullaris has not been described previously, to our knowledge. In this study, we used a newly developed technique of in situ fixation and embedding to define the cross-sectional anatomy at the level of the conus medullaris in ten fresh human cadavera. A highly organized overlapping pattern of nerve roots was demonstrated in all specimens. The nerve roots form a peripheral rim around the spinal cord at the level of the tenth and eleventh and the eleventh and twelfth thoracic intervertebral discs. More caudally, the cord diminishes in size and the nerve roots predominate. The most cephalad roots lie laterally, with the motor roots ventral to their sensory counterparts. The more caudad roots overlap toward the midline, and the motor and sensory portions of each root are separated by spinal cord tissue. An intricate web of arachnoid membrane holds the nerve roots in a fixed relationship to each other. This previously undescribed three-dimensional anatomy at the level of the conus medullaris may aid in the understanding of neurological deficits secondary to trauma to the thoracolumbar junction, high lumbar-disc herniations (such as those at the first and second lumbar intervertebral disc), and tumors in this region.