The most common form of brachial plexus injury is:

• A. Klumpke
• B. Upper arm paralysis (Erb-Duchenne)
• C. Paralysis of entire arm
• D. None

Answer: (B)

The most common brachial plexus injury in newborns is an upper trunk (C5–C6) injury known as Erb-Duchenne palsy. This happens when the neck is tractioned during a difficult birth, stretching the nerves that supply the shoulder and elbow. Because the C5–C6 nerves are most often affected, this pattern appears most frequently, leading to weakness of shoulder abduction and elbow flexion. The typical “waiter’s tip” posture—shoulder adducted and internally rotated, elbow extended, forearm pronated—reflects this pattern of muscle paralysis.

Klumpke’s palsy involves the lower trunk (C8–T1) and primarily affects hand and finger movements, which is less common than the upper-trunk injury in newborns. Paralysis of the entire arm would require injury to all trunks and is not the usual presentation. Many infants with Erb-Duchenne palsy recover with time and physical therapy as nerves heal.