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Posterior femoral cutaneous nerve

The posterior femoral cutaneous nerve is a major sensory nerve of the posterior thigh, perineum, and upper leg. It arises from the sacral plexus and descends through the gluteal region into the thigh, lying beneath the gluteus maximus. The nerve provides cutaneous innervation to the skin of the posterior thigh, gluteal fold, perineum, and scrotum or labia. It has important clinical significance in neuropathic pain syndromes, trauma, pelvic surgery, and regional anesthesia.

Synonyms

  • Posterior cutaneous nerve of thigh

  • Small sciatic nerve (historic term)

  • PFCN (abbreviation in clinical use)

Origin, Course, and Branches

  • Origin: Arises from the sacral plexus (ventral rami of S1–S3), sometimes with contributions from the pudendal nerve

  • Course:

    • Leaves the pelvis via the greater sciatic foramen, usually inferior to the piriformis muscle

    • Travels deep to the gluteus maximus, accompanied by the inferior gluteal artery and vein

    • Descends vertically beneath the fascia lata along the posterior thigh

    • Reaches the popliteal fossa and continues as terminal branches to the posterior leg and calf

  • Branches:

    • Inferior cluneal nerves: supply skin of lower gluteal region

    • Perineal branches: supply perineum and posterior scrotum or labia

    • Cutaneous branches to posterior thigh: supply posterior thigh and upper calf skin

Relations

  • Superiorly: Piriformis and gluteus maximus

  • Anteriorly: Quadratus femoris, hamstring origins

  • Posteriorly: Gluteal fascia and skin of buttock

  • Laterally: Sciatic nerve runs parallel and lateral to it

Function

  • Provides cutaneous sensation to posterior thigh, buttock crease, and proximal leg

  • Supplies inferior gluteal skin via inferior cluneal branches

  • Provides perineal sensation via perineal branches

  • Plays a role in sensory feedback during sitting, standing, and locomotion

Clinical Significance

  • Entrapment or compression: Can cause posterior thigh or perineal neuropathic pain

  • Surgical relevance: At risk during gluteal and pelvic surgeries (hip replacement, pelvic tumor resection)

  • Regional anesthesia: Targeted for analgesia in posterior thigh or perineal procedures

  • Peripheral neuropathy: May mimic sciatica or pudendal neuralgia

MRI Appearance

T1-weighted images:

  • Nerve appears as a small linear or oval low-to-intermediate signal structure

  • Surrounded by bright fat, which enhances its visualization

T2-weighted images:

  • Nerve shows low-to-intermediate baseline signal

  • Pathology (neuritis, compression, trauma) appears as bright hyperintensity

STIR (Short Tau Inversion Recovery):

  • Normal nerve is dark to intermediate signal

  • Pathology (inflammation, edema) appears as bright hyperintensity

T1 Fat-Sat Post-Contrast:

  • Normal nerve shows minimal or no enhancement

  • Pathology (inflammation, tumor infiltration) may show focal or diffuse enhancement

CT Appearance

Non-Contrast CT:

  • Nerve is not clearly visualized due to limited soft tissue resolution

  • Appears as a small soft tissue density line within surrounding fat planes if high resolution used

  • Can be inferred by position in relation to gluteus maximus and sciatic nerve

Post-Contrast CT:

  • Nerve itself shows minimal enhancement

  • Pathology (nerve sheath tumors, inflammatory changes) may show contrast enhancement

  • Adjacent fat stranding suggests inflammation or trauma

MRI image

Posterior femoral cutaneous nerve MRI axial anatomy image-img-00000-00000

MRI image

Posterior femoral cutaneous nerve MRI axial anatomy image-img-00000-00000_00001

MRI image

Posterior femoral cutaneous nerve MRI SAG anatomy image-img-00000-00000

CT image

Posterior femoral cutaneous nerve CT axial anatomy image-img-00000-00000_00001