A term neonate delivered after shoulder dystocia holds his right arm adducted and internally rotated with the elbow extended, forearm pronated, and wrist flexed. The Moro reflex is asymmetric, absent on the right side, but the right palmar grasp is intact. Which nerve roots are involved?
- A C8 and T1
- B C5 and C6 ✓
- C C7 and C8
- D T1 and T2
Correct answer: B. C5 and C6
Explanation
The classic waiter's tip posture with an asymmetric Moro reflex after shoulder dystocia defines Erb-Duchenne palsy, involving the upper trunk of the brachial plexus at C5 and C6. The intact grasp reflex excludes Klumpke paralysis, which involves C8 and T1 and produces a claw hand with possible Horner syndrome. Preservation of hand function is the single finding that most reliably separates Erb palsy from total plexus injury.
Reference: Nelson Textbook of Pediatrics, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.