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Posterior lateral femoral cutaneous nerve

The posterior lateral femoral cutaneous nerve is a sensory branch of the lateral femoral cutaneous nerve, which itself arises from the lumbar plexus. This branch specifically supplies sensation to the posterolateral aspect of the thigh, contributing to cutaneous innervation of the upper leg. Although relatively small, it is clinically relevant in cases of nerve entrapment, trauma, or neuropathy, and can be evaluated on advanced neuroimaging.

Synonyms

  • Cutaneous branch of the lateral femoral cutaneous nerve (posterior division)

  • Posterolateral thigh cutaneous nerve branch

Origin, Course, and Branches

  • Origin: Derived from the lateral femoral cutaneous nerve (L2–L3 roots of the lumbar plexus)

  • Course:

    • The parent nerve emerges from the lumbar plexus, passes under or through the inguinal ligament near the ASIS

    • The posterior lateral branch separates as the nerve enters the thigh

    • Courses posteriorly and laterally through the fascia lata

  • Branches:

    • Provides small cutaneous branches that supply the skin of the posterolateral thigh

Relations

  • Anteriorly: Fascia lata of the thigh

  • Posteriorly: Gluteal fascia and subcutaneous tissue

  • Superiorly: Near ASIS and origin of gluteal muscles

  • Inferiorly: Continues along the posterolateral thigh skin

Function

  • Purely sensory

  • Provides cutaneous innervation to the skin of the posterolateral thigh

Clinical Significance

  • Can be affected in meralgia paresthetica variants (compression or entrapment of lateral femoral cutaneous nerve or branches)

  • Susceptible to injury in pelvic surgery, hip surgery, or trauma

  • Involved in chronic thigh pain syndromes

  • Important to recognize in nerve conduction studies and MRI neurography

MRI Appearance

T1-weighted images:

  • Nerve appears as a fine low-to-intermediate signal intensity line within bright fat planes

T2-weighted images:

  • Nerve shows intermediate to mildly hyperintense signal relative to muscle

  • Pathologic nerves appear more hyperintense

STIR (Short Tau Inversion Recovery):

  • Normal nerve is low signal

  • Entrapped or inflamed nerve appears bright hyperintense

T1 Fat-Sat Post-Contrast:

  • Normal nerve shows minimal or no enhancement

  • Pathological nerve shows linear or focal enhancement (neuritis, entrapment, tumor spread)

3D T2 SPACE / CISS:

  • Nerve appears as a thin intermediate-to-mildly hyperintense structure compared to muscle

  • Surrounded by bright fat, providing excellent contrast

  • Useful for delineating nerve trajectory and identifying entrapment sites near the inguinal ligament or fascia

CT Appearance

Non-Contrast CT:

  • Nerve is not directly visible; course inferred within fat planes of the lateral and posterior thigh

  • Appears as soft tissue strand if thickened by pathology

  • Fat around nerve provides contrast

Post-Contrast CT:

  • Normal nerve does not enhance

  • Pathologic nerve may appear as subtle soft tissue thickening or enhancing strand

  • Surrounding fat stranding may indicate inflammation

MRI image

Posterior Lateral Femoral Cutaneous Nerve MRI coronal image