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Superficial fibular nerve

The superficial fibular nerve (also known as the superficial peroneal nerve) is one of the two terminal branches of the common fibular (peroneal) nerve, the other being the deep fibular nerve. It arises in the lateral compartment of the leg and supplies the fibularis longus and brevis muscles, providing motor innervation to evert the foot and sensory supply to the dorsum of the foot and toes, except the first interdigital cleft.

Because of its superficial course in the distal leg and ankle, it is prone to compression, traction injury, and entrapment, especially where it pierces the deep fascia. Clinically, injury results in sensory loss over the dorsum of the foot and weakness of foot eversion.

Synonyms

  • Superficial peroneal nerve

  • Musculocutaneous nerve of the leg

Origin, Course, and Branches

  • Origin: Arises from the common fibular (peroneal) nerve near the neck of the fibula, within the lateral compartment of the leg.

  • Course:

    • Descends between the fibularis longus and fibularis brevis muscles.

    • In the middle third of the leg, it pierces the deep fascia to become subcutaneous.

    • Continues along the anterolateral aspect of the leg to reach the dorsum of the foot.

  • Branches:

    • Muscular branches: Supply the fibularis longus and fibularis brevis muscles.

    • Cutaneous branches:

      • Medial dorsal cutaneous nerve: Supplies the medial part of the dorsum of the foot and medial side of the hallux.

      • Intermediate dorsal cutaneous nerve: Supplies the central dorsum of the foot and adjacent sides of the second to fourth toes.

    • Articular branches: To the ankle and subtalar joints.

Relations

  • Superiorly: Deep fibular nerve and anterior tibial vessels (medial to its origin)

  • Laterally: Fibularis longus muscle

  • Medially: Fibularis brevis muscle and deep fascia

  • Anteriorly: Pierces the deep fascia in the lower third of the leg

  • Distally: Lies superficial to the extensor retinacula and divides into dorsal branches

Nerve Supply

  • Muscular: Fibularis longus and fibularis brevis (for foot eversion)

  • Sensory: Dorsum of foot, excluding first interdigital cleft (deep fibular nerve area) and lateral side of little toe (sural nerve area)

Function

  • Motor:

    • Controls eversion of the foot via fibularis longus and brevis muscles.

    • Assists in maintaining lateral stability during gait.

  • Sensory:

    • Provides cutaneous sensation to most of the dorsum of the foot and lower anterolateral leg.

Clinical Significance

  • Entrapment neuropathy: Occurs where the nerve pierces the deep fascia; results in numbness or tingling on the dorsum of the foot.

  • Trauma: Vulnerable to injury from ankle sprains, tight footwear, or fibular fractures.

  • Surgical relevance: Commonly at risk during lateral leg incisions and fibular surgeries.

  • Compression injuries: Often seen in skiers, runners, and habitual leg crossers.

  • Clinical signs:

    • Sensory loss over dorsum of foot

    • Weakness of foot eversion

    • Pain radiating along the lateral leg and dorsal foot

MRI Appearance

  • T1-weighted images:

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

    • Surrounding subcutaneous fat provides a bright contrast, outlining the nerve.

    • Muscle supplied (fibularis longus/brevis) normally shows intermediate signal.

    • Denervation or neuropathy: muscle may become hyperintense on T1 due to fatty infiltration in chronic stages.

  • T2-weighted images:

    • Normal nerve: intermediate signal, slightly darker than muscle.

    • In neuropathy, nerve becomes hyperintense (bright) due to edema or inflammation.

    • Muscle denervation: increased T2 signal (acute) reflecting edema.

    • Helps delineate entrapment site, especially where the nerve pierces deep fascia.

  • STIR:

    • Normal nerve: dark-to-intermediate signal.

    • Pathologic nerve: bright hyperintensity representing neuritis, edema, or traction injury.

    • Useful for identifying nerve inflammation and muscular edema.

  • Proton Density Fat-Saturated (PD FS):

    • Normal: nerve appears low-to-intermediate signal within surrounding suppressed fat.

    • Pathology: focal or diffuse bright hyperintense signal within nerve.

    • Excellent for mapping nerve continuity and detecting subtle entrapments.

  • T1 Fat-Sat Post-Contrast:

    • Normal nerve: minimal or no enhancement.

    • Pathologic enhancement indicates neuritis, perineural fibrosis, or tumor infiltration.

    • Surrounding inflammatory changes may enhance diffusely.

CT Appearance

Non-Contrast CT:

  • The superficial fibular nerve is not directly visible due to its small size and soft-tissue density.

  • Indirect findings: soft tissue swelling or fat stranding along the anterolateral leg may suggest nerve injury or entrapment.

  • Chronic changes: muscle atrophy or fatty replacement of fibularis longus/brevis may be observed.

Post-Contrast CT (standard):

  • Normal nerve: non-enhancing small soft-tissue structure.

  • Pathology: perineural enhancement or soft tissue thickening indicates inflammation or scarring.

  • Useful to assess post-traumatic changes, masses, or entrapment causes (fibrous bands, scarring, or cysts).

MRI image

Superficial fibular nerve axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

Superficial fibular nerve axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001

MRI image

Superficial fibular nerve axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00002

MRI image

Superficial fibular nerve axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00003

MRI image

Superficial fibular nerve axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00004