The Lumbar Sympathetic Trunk and Its Branching Variability: Relevance for Clinical and Interventional Strategies

Precision medicine relies on a thorough understanding of lumbar sympathetic anatomy and its branches to elucidate related pathophysiology and improve treatment of conditions such as low back pain, lumbopelvic pain, and vascular autonomic disorders affecting the lower limbs. This study aims to expand knowledge of fetal lumbar sympathetic anatomy by providing a detailed description and systematic classification of the communicating branches, their specific distribution to each lumbar spinal nerve, and the origin of lumbar splanchnic nerves. The lumbar and retroperitoneal regions of 25 human fetuses (50 sides) were subjected to detailed sub-macroscopic dissections. The lumbar sympathetic trunk generally comprises three ganglia. The L2 and L3 ganglia are consistently present, but accessory ganglia along certain communicating branches are rare. The 466 communicating branches examined (229 on the right, 237 on the left) comprised 144 superficial, 251 deep transverse, and 71 deep discal branches. Deep transverse branches appeared consistently across all levels, whereas superficial branches originated only from the L1, L2, and occasionally L3 ganglia. Discal branches were inconsistent across ganglionic levels. All lumbar spinal nerves received at least one communicating branch, though the distribution varied by branch type. Most lumbar splanchnic nerves originated from a single root, those having two roots or accessory splanchnic nerves being less common. The origins of splanchnic nerves were frequent at L1 and L2, less common at L3, and inconsistent at L4 and L5. There were no differences between the left and right sides regarding ganglia, origin, or distribution of sympathetic branches. In conclusion, the fetal autonomic branching patterns and connections of the lumbar sympathetic trunk are significantly variable, though they are more consistent than those in the cervical region. Detailed anatomical knowledge of this area is essential for improving the precision and effectiveness of lumbar sympathetic trunk interventions and minimizing complications in lumbar and retroperitoneal surgeries.