Absence of the Lumbosacral Trunk.

The lumbosacral trunk, typically comprised of part of the fourth lumbar ventral rami and the entirety of the fifth lumbar ventral rami, serves as a connection between the lumbar and sacral plexuses. Developmental differences underlie the variable relative contributions of L4 and L5 to the lumbosacral trunk. Herein, we report a rare case in which dissection of an adult male cadaver revealed no L4 contribution to the lumbosacral plexus. We discuss the surgical and clinical implications of such an anatomic variation.