Brachial Plexus Injuries: Erb's vs Klumpke's Palsy Clinical Rationale
High-Yield Clinical Pearls & Exam Keys
Erb's Point is the confluence of 6 nerve tracts at C5-C6 junction (Nerve to subclavius, Suprascapular nerve, Anterior & Posterior divisions of Upper Trunk, C5 root, C6 root).
Erb's palsy results in the classic 'Policeman's / Waiter's Tip Hand' deformity (adducted, medially rotated, extended, and pronated).
Klumpke's palsy (C8-T1) leads to 'True Claw Hand' involving all intrinsic muscles of the hand (interossei, lumbricals) and is frequently accompanied by Horner's Syndrome due to sympathetic T1 involvement.
Erb's Palsy Clinical Presentation Triad
Arm hangs by the side (Loss of Abductors: Deltoid, Supraspinatus)
Arm medially rotated (Loss of Lateral Rotators: Infraspinatus, Teres Minor)
Forearm extended & pronated (Loss of Biceps Brachii, Brachialis, Supinator)
High-Yield Comparison: Erb's Palsy vs Klumpke's Palsy
| Clinical Parameter | Erb's Palsy | Klumpke's Palsy |
|---|---|---|
| Root Level Involved | Upper Trunk (C5, C6) | Lower Trunk (C8, T1) |
| Mechanism of Injury | Undue separation of head from shoulder (Breech delivery, Fall on shoulder) | Undue upward pull of arm (Catching branch while falling, Difficult delivery) |
| Main Muscles Paralyzed | Deltoid, Biceps, Brachialis, Brachioradialis, Supraspinatus, Infraspinatus | Intrinsic hand muscles (Interossei, Lumbricals), Flexors of wrist/fingers |
| Characteristic Deformity | Policeman's tip / Waiter's tip / Porter's tip hand | True Claw Hand (Main en griffe) |
| Horner's Syndrome | Absent | Present (Ptosis, Miosis, Anhidrosis, Enophthalmos if T1 white rami communicantes involved) |
Viva Examiner Traps & Model Answers
Oral Exam PrepBiceps brachii (musculocutaneous nerve C5-C6) is both a powerful flexor and the primary supinator of the flexed forearm. Paralyzing Biceps and Supinator leaves the Pronator Teres (C6-C7) and Pronator Quadratus unopposed, causing persistent pronation.
Interactive Clinical Vignette Practice
Rule-Out EngineA neonate delivered after a prolonged and difficult breech labor presents with an inability to abduct and laterally rotate the right shoulder. The right forearm is extended and pronated with the palm facing backward. Which spinal root levels are injured?
A 22-year-old worker falls from a scaffolding and catches a beam with his left hand to break his fall. He presents with severe wasting of the left thenar and hypothenar eminences, hyperextension of MCP joints, flexion of IP joints, and left-sided ptosis. The most probable injury is:
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