A 25-year-old motorcyclist is involved in a high-speed accident with forced depression of the right shoulder. He presents with inability to abduct the shoulder, flex the elbow, and supinate the forearm. Sensory loss is noted over the lateral arm and forearm. Which roots are most likely injured?
- A C8, T1
- B C7, C8
- C C5, C6 ✓
- D C6, C7
Correct answer: C. C5, C6
Explanation
This is Erb's palsy (upper brachial plexus injury, C5-C6). The mechanism is excessive angle between head and shoulder (shoulder depression with head tilting away). Injured muscles include deltoid (axillary nerve), biceps brachii (musculocutaneous nerve), and supinator/brachioradialis. The characteristic posture is the 'waiter's tip' position with the arm adducted, medially rotated, elbow extended, and forearm pronated. Sensory loss is in the C5-C6 dermatome (lateral arm and forearm).
Reference: BD Chaurasia's Human Anatomy, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.