Anatomy Series: Lower Extremity Nerves

Overview

• Focus on high-yield lower extremity nerves.
• Builds on the upper extremity nerves video.
• Emphasis on:
  • Origin of the nerve
  • Mechanism of injury
  • Sensory and motor functions
  • High-yield findings or branches

Key Concepts

• Mechanism of Injury: Often a key point in clinical questions.
• Mnemonics: Used to remember complex details.

Specific Nerves

Iliohypogastric Nerve

• Origin: T12-L2
• Injury: Abdominal surgery
• Sensory: Suprapubic region
• Motor: Transverse abdominis, internal obliques
• Mnemonic: Abdominal surgery damages the "ill-eo" (iliohypogastric nerve).

Genitofemoral Nerve

• Origin: L1-L2
• Injury: Laparoscopic surgery
• Sensory: Scrotum, labia
• Motor: Cremaster muscle
• Mnemonic: "Genital femoral nerve" for sensory and motor near the genitals.

Lateral Femoral Cutaneous Nerve

• Origin: L2-L3
• Injury: Tight clothing, obesity
• Sensory: Anterior and lateral thigh
• Mnemonic: LFC (Lateral Femoral Cutaneous) nerve associated with tight clothing or obesity.

Obturator Nerve

• Origin: L2-L4
• Injury: Pelvic surgery
• Sensory: Medial thigh
• Motor: Obturator externus, adductors of thigh
• Mnemonic: "Obturator damaged by the operator" during pelvic surgery.

Femoral Nerve

• Origin: L2-L4
• Injury: Pelvic fracture
• Sensory: Anterior thigh (via anterior femoral cutaneous), medial leg (via saphenous nerve)
• Motor: Thigh flexion, leg extension
• Mnemonic: FEM - Flexors (thigh), Extension (leg), Medial leg (sensory - saphenous).

Sciatic Nerve

• Origin: L4-S3
• Injury: Disc herniation, piriformis muscle injury
• Motor: Semimembranosus, semitendinosus, biceps femoris, adductor magnus
• Sensory: Entire leg and foot (except saphenous branch)

Common Peroneal Nerve

• Origin: L4-S2
• Injury: Lateral blow to fibular neck
• Branches: Deep and superficial peroneal nerves
• Motor: Peroneus longus, brevis, tibialis anterior
• Mnemonic: Common peroneal wraps around fibular neck.

Tibial Nerve

• Origin: L4-S3
• Injury: Baker cyst (popliteal fossa), Tarsal tunnel syndrome
• Motor: Popliteus, plantaris, triceps surae, biceps femoris, foot flexors
• Clinical Sequelae: TIP and PED mnemonics for function loss.

Summary

• Nerve Mastery: Understanding origin, injury, and functions critical for exams.
• Mnemonics & Diagrams: Aid memory and application in clinical scenarios.
• Review Chart: Available for studying major nerve origins and injuries.