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Spinal nerve L2

The spinal nerve L2 is the second lumbar spinal nerve, formed by the union of dorsal (sensory) and ventral (motor) roots from the L2 spinal segment. Its rootlets arise from the spinal cord (conus region, typically around T12 vertebral level), descend within the cauda equina, and the named L2 nerve exits the vertebral canal through the L2–L3 intervertebral foramen.

L2 contributes substantially to the lumbar plexus, participating in the formation of the femoral, obturator, lateral femoral cutaneous, and genitofemoral nerves. It supplies motor innervation to thigh flexors/adductors and sensory innervation to the anterolateral thigh.

Synonyms

  • Second lumbar spinal nerve

  • L2 nerve root

  • Lumbar segment 2 nerve

Origin, Course, and Branches

  • Origin:

    • Formed by the union of dorsal and ventral rootlets from the L2 spinal segment

  • Course:

    • Rootlets form dorsal and ventral roots, which join as the spinal nerve within the thecal sac

    • Traverses the lateral recess and exits through the L2–L3 intervertebral foramen

    • Enters the psoas major muscle, dividing into branches for the lumbar plexus

  • Branches (via lumbar plexus):

    • Femoral nerve (L2–L4) – motor to quadriceps, iliacus; sensory to anterior thigh

    • Obturator nerve (L2–L4) – motor to adductors; sensory to medial thigh

    • Lateral femoral cutaneous nerve (L2–L3) – sensory to anterolateral thigh

    • Genitofemoral nerve (L1–L2) – motor (cremaster), sensory to scrotum/labia and upper thigh

    • Muscular twigs to psoas and quadratus lumborum

Relations

  • Anterior: Psoas major muscle, lumbar plexus fascicles

  • Posterior: Lamina, ligamentum flavum, and facet joint at L2–L3

  • Superior: L1 spinal nerve

  • Inferior: L3 spinal nerve

Function

  • Motor: Contributes to hip flexion (iliopsoas) and thigh adduction (via obturator nerve)

  • Sensory: L2 dermatome covers anterior and anterolateral thigh

  • Reflex: Part of input for lower limb reflex arcs (with L3, L4 in patellar reflex)

Clinical Significance

  • Compression at L2–L3 (disc herniation, stenosis) may cause pain, numbness, or weakness in anterior thigh

  • Contributes to lumbar radiculopathy syndromes

  • Relevant in surgical exposure (retroperitoneal, spine, hip surgery)

  • Important target in lumbar plexus blocks for anesthesia

MRI Appearance

T1-weighted images:

  • L2 root appears as low-to-intermediate signal linear structure within bright epidural/perineural fat

T2-weighted images:

  • Root shows intermediate to mildly hyperintense signal compared to muscle

  • Inflammation or compression increases hyperintensity

STIR (Short Tau Inversion Recovery):

  • Normal root: low signal

  • Pathological root (radiculitis, edema): bright hyperintensity

T1 Fat-Sat Post-Contrast:

  • Normal root: minimal enhancement

  • Pathology: focal or diffuse enhancement (neuritis, tumor infiltration)

3D T2 SPACE / CISS:

  • Root displays intermediate to mildly hyperintense signal vs muscle

  • Surrounded by bright CSF within the thecal sac, providing high-contrast delineation

  • Excellent for visualizing foraminal course at L2–L3 exit, and detecting subtle compressive lesions

CT Appearance

Non-Contrast CT:

  • Root not directly visible; position inferred within L2–L3 intervertebral foramen

  • Fat planes highlight foraminal passage

  • Bony changes (osteophytes, disc narrowing) may suggest compression

Post-Contrast CT:

  • Nerve does not enhance normally

  • Enhancement or mass along root suggests nerve sheath tumor, infiltration, or inflammation

  • Perineural fat stranding may be seen in infection or tumor spread

MRI image

Spinal nerve L2 MRI coronal image

MRI image

Spinal nerve L2 MRI sagittal anatomy image