Common Peroneal

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COMMON PERONEAL NERVE¹

Anatomy

Formed by: Axons from L4, L5, S1 & S2 roots
Course of axons
- Through popliteal fossa: Separates from sciatic nerve in upper fossa
- Behind head & along fibula: Covered only by skin & subcutaneous tissue
- Behind peroneus longus muscle (fibular tunnel): In anterior compartment of leg
- Emerge from fibular tunnel: Nerve divides into superficial & deep branches
- Deep peroneal nerve passes through: Anterior tarsal tunnel
  - Divides into lateral and medial terminal branches
  - Lateral terminal branch: Supplies Extensor digitorum brevis & Extensor hallucis brevis
  - Medial terminal branch
    - Supplies adjacent sides of great & 2nd toes (92%)
    - Absent in 8%: Muslces supplied by Superficial peroneal nerve
Branches
- Common peroneal in popliteal fossa: Sensory
- Superficial peroneal
  - Motor
    - Peroneus brevis
    - Peroneus longus
    - Accessory deep peroneal branch: Innervates Extensor digitorum brevis
  - Cutaneous sensory
    - Lower leg: Anterolateral
    - Foot: Dorsum, except between 1st 2 toes
    - Medial & Intermediate dorsal cutaneous nerves of foot
- Deep peroneal
  - Motor branches in leg
    - Tibialis anterior
    - Extensor hallucis & Extensor digitorum longus
    - Peroneus tertius
  - Lateral terminal branch in foot
    - Extensor digitorum brevis
      - May also be innervated by accessory deep peroneal from superficial peroneal (28%)
    - Cutaneous: Skin between 1st & 2nd toes

Clinical syndrome

Weakness
- Foot: Dorsiflexion & Eversion of foot
- Toes: Extension
- Gait: Steppage
Sensory loss
- Lower leg: Anterolateral
- Foot & Toes: Dorsum
Tendon reflexes: Normal
Pain & Tinel's sign: Over lateral fibular neck

Differential diagnosis

L5 root: EHL may be weaker than Anterior tibial
Lumbosacral trunk or plexus
Sciatic nerve: Lateral trunk

Causes

External compression
- Fibular head lesion
  - Etiologies
    - Especially with weight loss
    - Altered consciousness: Coma, Anesthesia, Sleep & Bed rest
    - Crossed legs
    - Leg braces
  - Partial lesion: More involvement of deep peroneal than superficial peroneal axons
- Distal: Superficial peroneal nerve (Sensory branches)
  - Branches: Medial & Intermediate Dorsal cutaneous branches
  - Clinical
    - Sensory loss: Medial dorsal foot up to ankle
Trauma: Blunt; Traction; Fractures
- Ankle: Acute plantar flexion & inversion
Entrapment
- Squatting (Gardners & Farmers): Lesion locations
  - Compression between biceps tendon & lateral head of gastrocnemius + Head of the fibula
  - Fibular tunnel
  - Anterior tarsal tunnel: Deep peroneal nerve
- Masses
  - Ganglia: From the superior tibiofibular joint
  - Baker's cyst
  - Schwannoma & Neurofibromas: Especially in popliteal fossa
- Fibular tunnel: Crescentic band at origin of peroneus longus
Mononeuropathy in systemic disorder
Deep peroneal
- Anterior compartment syndrome
  - Raised pressure in fascial compartment
  - Causes: Excessive exercise, Soft tissue trauma, fractures, haemorrhage, occlusion of anterior tibial artery
  - Clinical associations: Leg swelling
- Compression: Ganglia, Osteochondroma, Aneurysm
- At ankle
  - Trauma & External compression
  - Weak: Extensor digitorum brevis
Superficial peroneal
- Peroneal compartment syndrome
- Local trauma
- Compression of sensory branch when traversing deep fascia of lower leg

External link: Wheeless

POSTERIOR TIBIAL NERVE

Anatomy

Formed by: Axons from L4, L5, S1 & S2 roots
Anatomy
- Anterior component: Muscles of posterior thigh (except short head of biceps)
- Popliteal space: Branches to popliteus; Gastrocnemius; Soleus; Plantaris
- Posterior compartment of leg: Tibialis posterior, Flexor hallucis longus; Flexor digitorum brevis
- Behind medial malleolus to plantar side of foot
- Tarsal Tunnel
  - Anatomy: Behind mdial malleolus; Covered by flexor retinaculum
  - Contents: Tibial nerve; Tibial artery; Tendons FHL, FDL, Tibialis posterior
- Distal tibial nerve branches
  - Medial & Lateral Calcaneal: Sensory supply to heel of sole
  - Medial Plantar nerve
    - Sensory: Medial 3 1/2 toes
    - Motor: Abductor hallucis brevis; Flexor hallucis brevis; Flexor digitorum brevis; Lumbricales
  - Lateral Plantar nerve
    - Sensory: Little toe & Lateral 4th toe
    - Motor: Abductor digiti quinti brevis; FDB; Quadratus plantae

Tarsal Tunnel Syndrome

Anatomy: Entrapment of tibial nerve in tarsal tunnel
Clinical
- Pain
  - Peri-malleolar
  - Ankle & Sole: Burning; Worse with weight bearing & at night
  - Tinel sign: Over tarsal tunnel
  - Ankle dorsiflexion
- Paresthesias & Sensory loss
  - Sole of foot
- Intrinsic foot muscles: Weak & Wasted
- Tendon reflexes: Normal
Causes
- Mass in tunnel: Lipoma, Ganglia, Neoplasms
- Exostosis within the tarsal tunnel
- Accessory flexor digitorum longus muscle: 4% to 8% of legs
- Hindfoot valgus deformity
- Athletics: Heavy stress on ankle joint; Sprinting, Jumping
Differential diagnosis
- Sensory polyneuropathy
- Orthopedic: Fasciitis; Tendonitis

External link: Wheeless

LATERAL FEMORAL CUTANEOUS NERVE

Anatomy
- Direct extensions from L2 & L3 roots
- Passes under inguinal ligament
- Sensory distribution: Anterior lateral thigh
- May anatomose with: Superior perforator & Median perforator nerves
  - More anterior thigh sensory field
Lateral Femoral Cutaneous Neuropathy: Meralgia paresthetica ³
- Entrapment site: Inguinal ligament
- General
  - Male > Female at older ages
  - Age: Mean 51 years; Range 15 to 81 years; Most frequent 4th to 6th deacde
  - Symptom duration: 0.5 months to 20 years; Mean 3 years
- Clinical
  - Pain: Burning, tingling, Aching
  - Sensory loss
    - Sharply defined region
    - Anterior or Lateral thigh or Both
    - Never involves: Patella; Knee; Lateral iliac crest
  - Tendon reflexers: Normal
  - Strength: Normal
  - Bilateral: 10%; Usually asymmetric
- Predisposing factors
  - Obesity
  - Tight pants or belt
  - Diabetes: 7-fold risk; Often after neuropathy onset
  - Pregnancy
  - Abdominal pressure: Increased
  - Surgery: Spine; Pelvic osotomy
- NCV
  - Side to side variation of orthodromic amplitude >2.3 fold
  - SNAP amplitude < 3 μV
- Management
  - Conservative in most cases
  - Weight loss
  - Eliminate tight fitting clothes

FEMORAL NERVE

Anatomy
- Roots: L2, L3, L4
- Derived from: Lumbar plexus
- Branches above inguinal ligament: Psoas; Iliacus
- Below inguinal ligament: Divides into anterior & posterior divisions
  - Anterior: Medial & intermediate cutaneous nerves of thigh; Sartorius & Pectineus muscle
  - Posterior: Quadriceps femoris (Vasti & Rectus femoris); Saphenous nerve
Neuropathy
- General
  - Weakness: Hip flexion; Knee extension
  - Sensory loss: Anterior & Medial thigh; Medial leg to medial malleolus
  - Tendon reflex: Knee reduced or absent
- Lesions
  - Compression: Surgical positioning (Lithotomy) & retraction
  - Ischemia: Renal transplantation; Diabetes
  - Retroperitoneal hemorrhage: Lumbar plexopathy with prominent femoral involvement
  - Saphenous nerve: Axonal loss with increasing age

Return to Nerve, Differential Diagnosis
Nerves of leg

References
1. Pract Neurol 2008;8:158-169
2. Muscle Nerve 2006;33:650-654
3. Neurology 2011 Oct 5

10/10/2011

COMMON PERONEAL NERVE1

POSTERIOR TIBIAL NERVE

LATERAL FEMORAL CUTANEOUS NERVE

FEMORAL NERVE

COMMON PERONEAL NERVE¹