Abstract

Ten California sea lion (Zalophus californianus) and four northern elephant seal (Mirounga angustirostris) specimens were dissected in order to determine the origin and ending of nerves of the lumbosacral plexus. The goal of this study was to investigate the exact nerve constituents of the lumbosacral plexus in pinnipeds from anatomical and topographical standpoint and to determine the appropriate injection site for the administration of a local anesthetic. Fresh or formalin fixed caudal portions of the previously necropsied animals were dissected, the course of the nerves were described and documented, and the appropriate injection sites were determined (in vitro). General anesthesia in pinnipeds is considered to carry a prolonged recovery and is associated with certain risks of the dive reflex that occurs during anesthesia (apnea, vasoconstriction, and bradycardia). Ventral branches of lumbosacral nerves are involved in innervation of the lateral abdomen, pelvic musculature, and caudal extremities. Although not previously investigated or considered in practical pinniped medicine, anatomy of these nerves can provide useful guideline for the potential application of local anesthesia for surgical procedures involving the hind limbs, as an alternative to general anesthesia.

Acknowledgments

This work was approved by NOAA and supported by a grant from Western University of Health Sciences. The authors wish to thank Dr. Pamela Govett for her contribution.