Lecture Notes: Nerves of the Lower Limb

Introduction

• Speaker: Dr. Adel Bandek, Professor of Anatomy and Neuroscience
• Topic: Nerves of the lower limb

Overview of Nerve Supply

• The lower limb is supplied by:
  • Lumbar Plexus
    • Femoral Nerve: Supplies anterior compartment of thigh; arises from L2, L3, L4 (posterior divisions)
    • Obturator Nerve: Supplies medial compartment of thigh; arises from L2, L3, L4 (anterior divisions)
  • Sacral Plexus
    • Gluteal Nerves: Superior (gluteus medius, minimus, tensor fasciae latae) and inferior (gluteus maximus)
    • Sciatic Nerve: Arises from L4, L5, S1, S2, S3; main nerve of the lower limb

Detailed Nerve Descriptions

Femoral Nerve

• Origin: Posterior divisions of L2, L3, L4
• Course: Lies between psoas and iliacus muscles, lateral to femoral artery, outside femoral sheath
• Branches:
  • Cutaneous: Medial, intermediate, saphenous nerves
  • Muscular: Quadriceps, iliacus, pectineus
  • Articular: Hip and knee joints

Obturator Nerve

• Origin: Anterior divisions of L2, L3, L4
• Course: Divides into anterior and posterior divisions by adductor brevis
• Branches:
  • Cutaneous: Anterior division to middle third of medial thigh
  • Muscular: Anterior (adductor longus, adductor brevis, gracilis), Posterior (adductor magnus, obturator externus)
  • Articular: Anterior (hip joint), Posterior (knee joint)

Sciatic Nerve

• Origin: L4, L5, S1, S2, S3
• Course: Enters gluteal region below piriformis, covered by gluteus maximus, hamstring muscles
• Termination: Divides into tibial and common peroneal nerves in the middle of the thigh
• Branches:
  • Muscular: Hamstrings, adductor magnus (ischial part)
  • Articular: Hip and knee joints

Sciatic Nerve Injury

• Causes: Incorrect intramuscular injection, compression by piriformis muscle
• Effects: Motor paralysis (hamstrings, muscles of leg and foot), sensory loss below knee (except medial side)
• Deformity: Foot drop

Terminal Branches of the Sciatic Nerve

Tibial Nerve

• Course: Most superficial in popliteal fossa; terminates into medial and lateral plantar nerves
• Branches:
  • Cutaneous: Sural nerve
  • Muscular: Supplies muscles of the back of the leg
  • Articular: Knee and ankle joints

Common Peroneal Nerve

• Course: Lateral side of the neck of the fibula; divides into deep and superficial peroneal nerves
• Branches:
  • Cutaneous: Sural communicating nerve, lateral cutaneous nerve of the calf
  • Muscular: Supplies no muscles directly
  • Articular: Knee joint

Common Peroneal Nerve Injury

• Common Site: Lateral side of the neck of the fibula
• Effect: Paralysis of anterior and lateral leg compartments leading to foot drop

Deep Peroneal Nerve

• Branches: Supplies anterior compartment of the leg
• Effect of Injury: Leads to foot drop due to dorsiflexor paralysis

Superficial Peroneal Nerve

• Branches: Supplies peroneus longus and brevis; cutaneous supply to middle dorsum of the foot
• Effect of Injury: Loss of eversion; no foot drop

Dermatomes of the Lower Limb

• Thigh: L1 (upper), L2 (middle), L3 (lower)
• Leg: L4 (medial), L5 (lateral), S2 (upper back), S1 (lower back)
• Foot: L5 (big toe), S1 (little toe)

Conclusion

• Importance of understanding dermatomes for neurological exams
• Thank you and best wishes