šŸ”‘ Key Learning

  • Brachial plexus = C5ā€“T1 ā†’ 5 terminal branches
  • Radial = wrist drop
  • Ulnar = claw hand
  • Median = hand of benediction
  • Axillary = regimental badge numbness
  • Musculocutaneous = loss of elbow flexion

šŸŒ Brachial Plexus Overview

  • Roots: C5ā€“T1
  • Divides into: trunks ā†’ divisions ā†’ cords ā†’ 5 terminal branches
    • Musculocutaneous
    • Axillary
    • Radial
    • Median
    • Ulnar

šŸ”Œ Musculocutaneous Nerve

Roots: C5ā€“C7
Motor: Biceps, brachialis ā†’ elbow flexion, supination
Sensory: Lateral forearm
Injury: Rare; upper arm trauma
Signs: Loss of elbow flexion, ā†“ biceps reflex

šŸ”Œ Axillary Nerve

Roots: C5ā€“C6
Motor: Deltoid, teres minor ā†’ shoulder abduction, ER
Sensory: Regimental badge area (lower deltoid)
Injury:

  • Anterior shoulder dislocation
  • Surgical neck of humerus fracture
  • Signs:
    • Loss of abduction, sensory loss over deltoid (regimental) patch

šŸ”Œ Radial Nerve

Roots: C5ā€“T1
Motor: Triceps (elbow extension), wrist/finger extensors
Sensory: Posterior arm + forearm, lateral dorsum of hand
Injury:

  • Humeral shaft fracture
  • Saturday night palsy
  • Radial head fracture
  • Signs:
    • Wrist drop
    • ā†“ triceps reflex
    • Sensory loss over posterior arm/forearm/hand

šŸ”Œ Median Nerve

Roots: C5ā€“T1
Motor: Anterior forearm (flexion, pronation), LOAF hand muscles
Sensory: Thenar eminence, lateral palm, lateral 3.5 fingers
Injury:

  • Carpal tunnel syndrome
  • Supracondylar humerus fracture
  • Signs:
    • Hand of benediction (on attempted fist)
    • Thenar wasting
    • Sensory loss as above

šŸ”Œ Ulnar Nerve

Roots: C8ā€“T1
Motor: Intrinsics of hand, flexor carpi ulnaris, FDP (medial half)
Sensory: Medial 1/3 hand, hypothenar, medial 1.5 fingers
Injury:

  • Medial epicondyle fracture
  • Cubital tunnel syndrome
  • Supracondylar fracture
  • Signs:
    • Claw hand
    • Weak wrist flexion/adduction
    • Sensory loss in ulnar distribution

šŸ“ Exam Clues & Clinchers

  • Wrist drop = radial nerve
  • Claw hand = ulnar nerve
  • Hand of benediction = median nerve
  • Regimental badge numbness = axillary nerve
  • Loss of elbow flexion = musculocutaneous nerve
  • Thenar wasting + night pain = carpal tunnel (median nerve)
  • Saturday night palsy = radial nerve compression