The most common form of brachial plexus injury is which?

• A. Upper arm paralysis (Erb-Duchenne)
• B. Lower arm paralysis (Klumpke)
• C. Paralysis of the entire arm
• D. Phrenic nerve injury

Answer: (A)

The most frequent brachial plexus injury involves the upper trunk, specifically C5-C6, causing Erb-Duchenne palsy. This traction-type injury commonly happens with shoulder dystocia during birth or with neck trauma and injures the nerves that power the shoulder and elbow flexors (deltoid, supraspinatus, biceps). Clinically, this presents as weakness of shoulder abduction and external rotation with elbow flexion loss, often described as a “waiter’s tip” posture: the arm adducted and internally rotated, the elbow extended, and the forearm pronated. Because lower trunk (C8-T1) injuries affect the intrinsic hand muscles (Klumpke palsy) and injuries involving the entire arm or high lesions causing phrenic involvement are less common, the upper-trunk Erb-Duchenne palsy is the most typical form seen.