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Anterior lateral femoral cutaneous nerve

The anterior branch of the lateral femoral cutaneous nerve (LFCN) is a purely sensory nerve arising from the L2–L3 roots of the lumbar plexus. It is a terminal branch of the LFCN after the nerve passes beneath or through the inguinal ligament near the anterior superior iliac spine (ASIS). The anterior branch supplies sensation to the anterolateral thigh, extending toward the knee.

This nerve is clinically important because it is commonly involved in meralgia paresthetica, a neuropathy caused by entrapment of the LFCN near the inguinal ligament or ASIS.

Synonyms

  • Anterior branch of the LFCN

  • Anterior cutaneous branch of lateral femoral cutaneous nerve

  • Sensory branch to the anterolateral thigh

Origin, Course, and Branches

  • Origin: Arises as the anterior division of the lateral femoral cutaneous nerve (L2–L3, lumbar plexus)

  • Course:

    • After the LFCN crosses under or through the inguinal ligament near the ASIS, it divides into anterior and posterior branches

    • The anterior branch passes inferiorly over the anterolateral thigh within the subcutaneous tissue

    • It accompanies small cutaneous vessels and remains superficial, lying within the fat and dermis of the thigh

  • Branches:

    • Small cutaneous filaments that supply the skin of the anterolateral thigh down to the level of the knee

Relations

  • Superiorly: Inguinal ligament and ASIS

  • Inferiorly: Skin and subcutaneous tissue of the thigh

  • Anteriorly: Dermis and superficial fascia

  • Posteriorly: Quadriceps fascia and thigh muscles (rectus femoris, vastus lateralis)

Function

  • Provides pure sensory innervation to the anterolateral thigh from hip to knee

  • No motor contribution

  • Involved in the sensation of touch, pain, and temperature in its cutaneous distribution

Clinical Significance

  • Most commonly implicated in meralgia paresthetica (pain, numbness, tingling in anterolateral thigh) due to compression under the inguinal ligament or trauma near ASIS

  • May be injured in pelvic or hip surgeries or during laparoscopic port placement

  • Important to recognize in imaging and nerve conduction studies

MRI Appearance

T1-weighted images:

  • Nerve appears as a thin linear low-to-intermediate signal structure within bright subcutaneous fat planes

T2-weighted images:

  • Nerve appears with intermediate to mildly hyperintense signal compared to muscle

  • Pathological nerve shows increased hyperintensity

STIR (Short Tau Inversion Recovery):

  • Normal nerve is low signal

  • Inflamed or compressed nerve shows bright hyperintensity

T1 Fat-Sat Post-Contrast:

  • Normal nerve shows little or no enhancement

  • Pathological nerve (neuritis, entrapment) shows focal or diffuse enhancement

3D T2 SPACE / CISS:

  • Nerve demonstrates intermediate to mildly hyperintense signal relative to muscle

  • Surrounded by bright fat planes, allowing excellent visualization of its superficial course

  • Useful for identifying entrapment or trauma near the inguinal ligament

CT Appearance

Non-Contrast CT:

  • Nerve itself is not directly visualized

  • Course inferred from fat planes of the anterolateral thigh near ASIS and inguinal ligament

Post-Contrast CT:

  • Normal nerve does not enhance significantly

  • Pathology appears as soft tissue thickening, fat stranding, or enhancing nodules in its expected course

MRI image

Anterior branch lateral femoral cutaneous nerve