A study on thoracic splanchnic nerves: Anatomo-surgical appraisal

Introduction: The thoracic splanchnic nerves greater, lesser, and least are derived from medial branches of the lower seven thoracic sympathetic ganglia; they carry preganglionic fibers, pierce the diaphragmatic crura, and supply the abdominal viscera through coeliac and aorticorenal plexus. These splanchnic nerves carry pain conducting visceral afferent fibers from the upper abdominal organs, including the pancreas. The origin of the splanchnic nerves from different roots may have a significant role in clinical presentation of patients than the normal or absence of consecutive nerve roots. Material and Methods: The study was done on 26 formalin-fixed cadavers (52 sides) from the Chettinad Hospital and Research Institute, Chennai, and University College of Medical Sciences, Delhi. The endothoracic tissue and the parietal pleura in the paravertebral region were carefully removed from the 1st rib to 12th rib (costodiaphragmatic recess). The thoracic sympathetic chain and its medial branches were traced from its origin to medial arcuate ligament. Any variations in the origin, formation, and communication of the splanchnic nerves were noted and photographed. Results: The origins of splanchnic nerves were bilaterally asymmetrical in most of the cases. The greater splanchnic nerve (GSN) was always present, whereas lesser splanchnic nerve and least splanchnic nerve were found to be absent in 40% and 80% cases, respectively. The GSN showed great variability both in the level of its origin and in the pattern of its formation. In the present study, four different patterns of GSN origin were observed in addition to normal. Discussion and Conclusion: Significant differences were noted in the formation and communication between the thoracic splanchnic nerves. The patterns in the formation were not only different from cadaver to cadaver but also were bilaterally asymmetrical.