Nerves of Upper Limb

Brachial Plexus - Nerve Network Central

📌 RTDCB: Roots (C5-T1) → Trunks (Upper, Middle, Lower) → Divisions (Ant/Post) → Cords (Lat, Post, Med) → Branches.

• Roots Nerves: Dorsal Scapular (C5), Long Thoracic (C5-C7).
• Trunk Nerve: Suprascapular (Upper Trunk C5-C6).
• Cords: Lateral, Posterior, Medial. (📌 LML: Love My Life).
  • Lateral: Lat. Pectoral. Terminal: Musculocutaneous, Lat. root Median.
  • Posterior: Upper/Lower Subscapular, Thoracodorsal. Terminal: Axillary, Radial.
  • Medial: Med. Pectoral, Med. Cut. N. of Arm/Forearm. Terminal: Ulnar, Med. root Median.
• Injuries:
  • Erb's Palsy (C5-C6): "Waiter's tip" hand.
  • Klumpke's Palsy (C8-T1): Claw hand.

⭐ Injury to Long Thoracic nerve (C5, C6, C7) causes "winging of scapula".

Axillary & Musculocutaneous Nerves - Shoulder & Arm Allies

• Axillary N. (C5, C6): From posterior cord. Through quadrangular space (w/ post. circumflex humeral artery).
  • Motor: Deltoid, Teres minor.
  • Sensory: Skin over deltoid ("Regimental badge" area).
  • Injury: Surgical neck of humerus fracture, shoulder dislocation → impaired abduction (15-90°).
• Musculocutaneous N. (C5, C6, C7): From lateral cord. Pierces coracobrachialis.
  • Motor: BBC muscles (Biceps brachii, Brachialis, Coracobrachialis). 📌
  • Sensory: Lateral forearm (via lateral cutaneous nerve of forearm).

⭐ Axillary nerve injury is commonly tested with fractures of the surgical neck of the humerus.

Radial Nerve - The Extension Expert

• Roots: C5, C6, C7, C8, T1 (Posterior cord).
• Course: Passes via spiral groove of humerus with profunda brachii artery.
• Motor: Triceps, Anconeus, Brachioradialis, Supinator, Extensors of wrist & fingers. (📌 Mnemonic: BEST - Brachioradialis, Extensors, Supinator, Triceps).
• Sensory: Posterior arm, forearm; dorsal lateral 3.5 digits (not nail beds).
• Clinical:
  • Humerus shaft fracture (spiral groove) → Wrist drop.
  • Crutch palsy / Saturday night palsy → Wrist drop.

⭐ Injury at the spiral groove (e.g., mid-shaft humerus fracture) classically causes wrist drop. oka

Median Nerve - Hand's Main Mover

• Roots: C5-T1 (Lat, Med cords).
• Course: Axilla → Arm → Cubital fossa → Forearm → Carpal tunnel.
• Motor:
  • Forearm: Pronators, most flexors (excl. FCU, med ½ FDP).
  • Hand: Thenar (LOAF), lat 2 lumbricals. 📌 LOAF: Lumbricals 1&2, Opponens, Abductor P.B., Flexor P.B.
• Sensory: Palmar lat 3.5 digits & dorsal tips.
• Lesions:
  • Elbow: Pointing Index/Hand of Benediction (fist attempt).
  • Wrist (CTS): Ape hand, weak thumb opposition, night paresthesia.

  ⭐ Hand of Benediction (median nerve injury at elbow/proximal forearm) is seen when patient attempts to make a fist, while Ulnar Claw (ulnar nerve injury) is present at rest.

Ulnar Nerve - Inner Hand Hero

• Roots: C8, T1 (Medial cord).
• Key Course: Posterior to medial epicondyle ("funny bone"); through Guyon's canal.
• Motor:
  • Forearm: FCU, FDP (medial half).
  • Hand: Most intrinsics (hypothenar, interossei, medial 2 lumbricals, adductor pollicis). 📌 Ulnar For Fine Functions.
• Sensory: Medial 1.5 digits (palmar & dorsal).
• Lesion Signs:
  • Ulnar Claw Hand (4th, 5th digits).
  • Froment's sign (adductor pollicis weak).

  ⭐ Ulnar Paradox: Proximal lesion → less claw deformity than distal, due to FDP paralysis.

High‑Yield Points - ⚡ Biggest Takeaways

• Brachial Plexus (C5-T1): Erb's palsy (C5-C6) → Waiter's tip. Klumpke's (C8-T1) → Total claw hand.
• Axillary Nerve: Injury → Deltoid paralysis, regimental badge anesthesia.
• Radial Nerve: Wrist drop classic; vulnerable at spiral groove/humerus fracture.
• Median Nerve: Ape thumb, carpal tunnel syndrome, Sign of Benediction (proximal).
• Ulnar Nerve: Claw hand (4th-5th), Froment's sign; injured at medial epicondyle.
• Long Thoracic Nerve: Winging of scapula (Serratus Anterior paralysis).