A newborn is noted to have the arm adducted and internally rotated at shoulder, forearm pronated, and wrist flexed. Which nerve roots are injured and what is this called?
- A C5, C6 — Erb's palsy (Erb-Duchenne) ✓
- B C8, T1 — Klumpke's palsy
- C C7, C8 — middle trunk palsy
- D C5, C6, C7 — extended Erb's palsy
Correct answer: A. C5, C6 — Erb's palsy (Erb-Duchenne)
Explanation
The 'waiter's tip' position (arm adducted, internally rotated, forearm pronated, wrist flexed) is the classic presentation of Erb-Duchenne palsy affecting the upper trunk of the brachial plexus (C5, C6), typically due to excessive lateral neck flexion during difficult delivery. Muscles paralyzed include deltoid (axillary, C5), biceps (musculocutaneous, C5-C6), brachialis, and supinator. The deltoid and infraspinatus are paralyzed causing adduction and internal rotation. Klumpke's palsy involves C8-T1 causing intrinsic hand muscle weakness with a claw hand.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
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Written and medically reviewed by the StethoPrep medical team.