Quick Facts
Origin: In or just lateral to the intervertebral foramen below the fourth lumbar (L4) vertebra.
Course: Medially through the intervertebral foramen and superiorly towards the posterior surface of the appropriate spinal cord level.
Branches: Unnamed rootlets just prior to entering the spinal cord.
Supply: Sensory innervation from the skin of the lower back and medial leg.
Origin
The posterior root of the fourth lumbar nerve originates in, or just lateral, to the intervertebral foramen, inferior to the fourth lumbar (L4) vertebra. It is at this point that the fourth lumbar nerve splits into anterior and posterior roots.
Course
The posterior root of the fourth lumbar nerve runs medially through the intervertebral foramen. Inside the vertebral canal, it runs superiorly towards its corresponding spinal cord level. The posterior root runs posterior to the denticulate ligament and splits into smaller rootlets before entering the dorsal aspect of the spinal cord.
Branches
The posterior root of the fourth lumbar nerve branches into several smaller rootlets before entering the dorsal aspect of the spinal cord.
Supplied Structures
The posterior root of the fourth lumbar nerve carries sensory information from the skin of the lower back and medial surface of the leg.
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