Morphological analysis of normal human lumbar dorsal root ganglion

The dorsal root ganglion (DRG) contains the somata of primary sensory neurons. The structure of the DRG is important for understanding the mechanisms of several diseases (e.g., low back pain or sciatica) and the variability in the distribution of regional anesthesia. DRG is also highly sensitive to mechanical compression in radiculopathy. Neuromonitoring and neurostimulation technologies require appropriate electrode placement, which depends on the ganglion's structure. According to certain reports, biganglia occur relatively frequently in the lumbar nerves. This study aimed to investigate the normal morphological features and variations of the human lumbar DRG.

Microanatomic dissections of the lumbar nerves were performed in 10 human cadavers fixed in 10% formalin (6 males and 4 females, aged 69-97 years). A total of 100 DRGs were analyzed morphologically.

Bilateral dissection of the DRG (L1-L5) revealed three types of structures: single ganglion, biganglion, and triganglion. Monoganglion was found most often at the levels of L1 and L2, while polyganglia, such as biganglion or triganglion, may be found at L2, L3, L4, or L5. Distinct layers of connective tissue separate independent ganglion components. In cases of transitional morphology, the division of ganglion components was partial.

The presence of biganglion or triganglion might affect the quality of electrical stimulation of the DRG. The connective tissue between the ganglion components of a polyganglion might influence the spread of impulses. A classification of DRG morphology is proposed. Further research should clarify the distribution of dermatomal innervation of the ganglion components.