Study design: The level of dorsal root ganglia that receives sensory afferent nerves from the anterior portion of the lower lumbar intervertebral disc was investigated in rats using a retrograde transport method.
Objectives: Sometimes patients with lower lumbar disc lesions complain of inguinal pain that does not correspond to the dermatome of the injured nerve roots. To investigate the origin of the pain, the authors studied the sensory innervation to the anterior portion of the lumbar intervertebral disc.
Summary of background data: The innervation to the posterior portion of the lumbar disc has been extensively investigated and has been reported to be segmental. However, little is known about the nerve supply to the anterior portion of the lumbar disc.
Methods: The retrograde transport method was used in rats. As tracers, horseradish peroxidase and choleratoxin B subunit were used. Horseradish peroxidase crystals were placed on the anterior portion of the L5-L6 disc, and choleratoxin B subunit was injected into the L5-L6 disc. The bilateral dorsal root ganglia were histologically examined.
Results: Labeling of L1 and L2 dorsal root ganglia neurons was recognized. No neurons were labeled in dorsal root ganglia of other levels, including the segmentally corresponding L5.
Conclusions: Using the retrograde transport method, the authors demonstrated that the anterior portion of the L5-L6 lumbar intervertebral disc was innervated from L1 or L2 spinal nerves in rats. These results appear to explain the reason why patients with lower lumbar disc lesions sometimes complain of inguinal pain corresponding to the L1-L2 dermatome.