Common Peroneal

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COMMON PERONEAL NERVE ¹

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%: Muscles supplied by Superficial peroneal nerve
Branches
- Common peroneal in popliteal fossa: Sensory
- Superficial (fibular) peroneal nerve
  - 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 (fibular) nerve
  - Motor branches in leg
    - Tibialis anterior
    - Extensor hallucis & Extensor digitorum longus
    - Peroneus tertius: May be absent
  - 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: General

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
- External: Blunt; Traction; Fractures
- Ankle movement: Acute plantar flexion & inversion
  - Injury caused by: Nerve stretch
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
Intraneural ganglion cyst
- Frequency: 18%
- Location: Fibular head
- Course: Progressive
- Detectable on ultrasound
- Treatment: Surgery
Mononeuropathy in systemic disorder
Deep peroneal (fibular) nerve
- Innervation
  - Muscles for foot & toe dorsiflection
  - Sensory: Web space of great toe
  - Tinel sign: Fibular neck
- Lesion causes
  - 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
- Lesion at ankle
  - Trauma & External compression
  - Weak: Extensor digitorum brevis
- Anterior tarsal tunnel syndrome
  - Injury
    - Deep fibular (peroneal) nerve in ankle
    - After exit of motor branches to TA & EHL
  - Clinical
    - Sensory loss: 1st web space
    - Motor: Normal
Superficial peroneal (fibular) nerve
- Causes of damage
  - Peroneal compartment syndrome
  - Local trauma
- Clinical features of lesion
  - Weakness: Ankle eversion
  - Sensory loss: Dorsum of foot
- Variant: Compression of sensory branch when traversing deep fascia of lower leg
- Variant structure: Accessory peroneal nerve
  - Branch from: Distal superficial peroneal nerve
  - Course: Posterior to lateral malleolus
  - Supplies: Lateral extensor digitorum brevis muscle

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
- Leg, Posterior compartment: 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 plantar sole & 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
    - Inferior calcaneal nerve (Baxter's nerve)
      - Anatomy: 1st branch of lateral plantar nerve
      - Motor: Abductor digiti minimi pedis
      - Sensory: None
      - Causative Lesions
        
        Entrapment: Between Quadratus plantae & hypertrophied Abductor hallucis in athletes
        
        Other: Accessory muscle, Tumor, Varices of veins travelling with nerve, Calcaneal spur
      - Diagnosis, Late: MRI signal in Abductor digiti minimi

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

Tibial nerve: Other

Holstein dairy cows ⁶
- Tibial neuropathy common
- May be unilateral or bilateral
- Related to: Pregnancy or Birth; Cauda equina syndrome
- Clinical: Pain; Locomotor impairmant
- Laboratory: Serum CK high

External link: Wheeless

LATERAL FEMORAL CUTANEOUS NERVE

Anatomy
- Extensions from L2 & L3 ± L1 roots: Via Lumbar plexus
- Sensory distribution: Anterior & Lateral thigh
- May anatomose with: Superior perforator & Median perforator nerves
- Anatomic variants medial to sartorius origin (46%): Less susceptible to mechanical trauma
  - More anterior thigh sensory field
Lateral Femoral Cutaneous Neuropathy: Meralgia paresthetica ³
- Nosology: Bernhardt-Roth syndrome
- Entrapment site: Inguinal ligament as nerve exits pelvis
- 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
  - Frequency: 33–43 per 100,000 patient-years
  - Predisposing factors
    - Obesity (BMI > 30)
    - Tight garments: Pants or belt; Armor; Police uniforms
    - Diabetes: 7-fold increased risk; Often after neuropathy onset
    - Pregnancy
    - Abdominal pressure: Increased
    - Surgery: Spine; Pelvic osotomy; Hip resurfacing, especially anterior approach
    - Sports associations: Gymnastics, Baseball, Soccer, Body building, Strenuous exercise
    - Iliacus hematoma
- Clinical
  - Pain
    - Burning, Tingling, Aching
    - Sitting, or Pelvic compression, may reduce symptoms
    - Symptom duration: 2 weeks to 20 years
  - Sensory loss
    - Sharply defined region
    - Lateral (73%), Antero-lateral (26%) or Anterior thigh
    - Never involves: Patella; Knee; Lateral iliac crest
  - Tendon reflexers: Normal
  - Strength: Normal
  - Bilateral: 10%; Usually asymmetric
  - Course: Chronic or Resolves over months
  - Management
    - Conservative in most cases
    - Weight loss
    - Eliminate tight fitting clothes
    - Neurectomy
- NCV
  - Side to side variation of orthodromic amplitude >2.3 fold
  - SNAP amplitude < 3 μV
- Nerve pathology
  - Axon loss: Large, Multifocal
  - Axon regeneration
  - Perineurium: Thick
  - Subperineurial edema
  - Inflammation: Epineurial & Intraneural
External link: Lateral femoral cutaneous nerve of the thigh

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
    - Sensory: Medial & Intermediate cutaneous nerves of thigh
    - Motor: Sartorius & Pectineus muscles
  - Posterior
    - Motor: Quadriceps femoris (Vasti & Rectus femoris)
    - Sensory: Saphenous nerve
Neuropathy
- General anatomy
  - Weakness: Hip flexion; Knee extension
  - Sensory loss: Anterior & Medial thigh; Medial leg to medial malleolus
  - Tendon reflex: Knee reduced or absent
  - Pain: Anterior thigh
- Lesions
  - Compression
    - Surgical positioning (Lithotomy)
    - Retraction
  - Ischemia: Renal transplantation; Diabetes
  - Retroperitoneal hemorrhage: Lumbar plexopathy with prominent femoral involvement
    - Anticoagulation
    - Hemophilia
  - Pelvic mass
  - Renal transplant
    - Especially with: Internal iliac ligation with external iliac anastomosis
    - Recovery: Common
  - Aneurysm: Aorta; Iliac
  - Hyperextension stretch
    - Dancing: Nerve stretch (Neurapraxia) or Hip dislocation
    - "Hanging leg"
      - May be associated with sciatic lesion
      - Unilateral or Blateral
  - Ischemia
  - Saphenous nerve: Axon loss with increasing age; Surfing
- Similar syndrome: Often related to
  - L2-L4 radiculopathy
  - Lumbar plexus lesions

SCIATIC NERVE

Roots: L4 - S2
Lumbosacral plexus
Vascular supply
- Inferior gluteal artery
- Popliteal artery: At knee
Causes of compression & damage
- Surgery
  - Hip
  - Arthroplasty: Especially peroneal division
- Myositis ossificans
- Spasm
- Edema
- Contractures
- Gluteal disorders: Compartment; Injection
- Vascular
- Fractures
  - Posterior acetabular
  - Femur
- Mass: Lymphoma; Endometriosis; Aneurysm
- Piriformis syndrome ⁴
  - Piriformis muscle: Features
    - Innervation: S1 & S2 roots
    - Functions
      - External: Thigh rotation
      - Hip flexed: Thigh abduction
  - Causes
    - Athletics: Walkers; Soccer; Gymnastics; Swimming
    - Post-traumatic
    - Anatomic abnormalities
    - Myositis
    - Dystonia
    - Fibrosis after deep injections
    - Radiation
  - Clinical
    - Onset age: 2nd to 7th decade
    - Pain
      - Location: Buttock
      - May be referred to: Thigh & Leg ("Sciatica")
      - Sciatica maneuvers
        
        In sitting position: Homolateral leg is crossed over unaffected side
        
        Intolerance to sitting: On involved side with body inclined over thigh
        
        Exacerbated: Internal rotation & maximal adduction of hip
      - No pain: Lower back or Sacroiliac joint
    - Tenderness: Digital pressure of sciatic notch
    - Sensory: Dysesthesias
    - Muscle: Gluteal atrophy (10%)
    - Treatment
      - Physical therapy: Stretching
      - Muscle corticosteroid injection
      - Surgery
  - Laboratory
    - MRI
      - Piriformis hypertrophy: On affected side
      - Sciatic venous plexus congestion
    - H-reflex (Peroneal or Posterior tibial)
      - Disappears, reduced or prolonged with: Hip flexion, adduction & internal rotation (FAIR position)

SURAL NERVE ⁵

Pathology: Normal structure
Anatomy
- Gross
  - Origins
    - Roots: L5, S1, S2
    - Lumbosacral plexus
    - Nerves
      - Tibial nerve in popliteal fossa (100%): Medial sural cutaneous branch
      - Peroneal nerve (80%): Lateral sural cutaneous branch
      - Location of origin: 11–20 cm proximal to lateral malleolus
  - Nerve configurations
    - Passes between 2 heads of gastrocnemius
    - Pierces deep fascia half-way down leg
    - Posterior to lateral malleolus
    - Branches: At acute angles
    - Connects to
      - Sural communicating nerve (88%): Below bellies of gastrocnemius
      - Superficial fibular nerve (superficial peroneal nerve): On dorsum of foot
      - Posterior cutaneous nerve of thigh: In leg
  - Small saphenous vein
    - Along medial side of nerve
    - Branches: At right angles
- Innervation patterns
  - Posterolateral lower third of leg to lateral malleolus
  - Lateral dorsum of foot to little toe
  - Lateral side of little toe alone (46%)
    - 2nd to 5th toes supplied by: Superficial fibular nerve
  - Lateral 2½ toes (29%) alone
  - Lateral 2½ toes + 2 toes also with Superficial fibular nerve (20%)
Function: Pure sensory
Disorders
- General features
  - Symptoms
    - Discomfort (98%): Pain, Numbness, Burning
    - Localization: Posterolateral lower calf or lateral foot
  - Sensory exam: Loss (60%); Normal (30%); Hyperesthesia (7%)
  - Sural SNAP abnormal in 94%
  - Course
    - Resolution: Common
    - Long term sensory symptoms: Some patients
- Etiologies
  - Trauma or Surgery (50%)
    - Vein stripping
    - Achilles tendon surgery
  - Benign compression (8%): Boots; Stockings
  - Immune (20%): Sjögren; Vasculitis
  - Neoplasm
    - Ganglion cyst
    - Neurofibromatosis 1 (5%)
  - Cellulitis
Common uses
- Diagnostic biopsy
- Nerve transplantation
- Electrodiagnostic

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, Neurology 2014;82: Online March, Int J Sports Phys Ther 2013;8:883-893
4. J Orthop Surg Res 2010;5:3, Can J Neurol Sci 2012;39:577-583
5. Clinical Anatomy 2011;24:237–245, Muscle Nerve 2014;49:443–445
6. Tierarztl Prax Ausg G Grosstiere Nutztiere 2021;49:79-90

4/27/2021