A 28-year-old motorcyclist is thrown from his bike, landing on the left side with violent lateral flexion of the head away from the shoulder. He presents with inability to abduct the arm, inability to flex the elbow, and the affected arm hangs limp in adduction and internal rotation ('porter's tip' posture). The lesion localises to:
- A C8–T1 nerve roots (Klumpke's palsy)
- B Posterior cord of the brachial plexus
- C C5–C6 nerve roots (Erb's palsy) ✓
- D Lateral cord of the brachial plexus
Correct answer: C. C5–C6 nerve roots (Erb's palsy)
Explanation
The classic 'porter's tip' or 'waiter's tip' deformity results from Erb's palsy, involving C5–C6 roots (or the upper trunk). Loss of C5 and C6 denervates the deltoid (abduction), biceps (elbow flexion), and infraspinatus (external rotation), leaving the arm held by the dominant adductors and internal rotators. The mechanism of violent separation between head and ipsilateral shoulder stretches the upper brachial plexus. Klumpke's palsy (C8–T1) produces an intrinsic hand muscle deficit and claw hand.
Reference: BD Chaurasia's Human Anatomy, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.