Erb's palsy results from injury to which nerve roots?

Erb's palsy results from injury to which nerve roots?

• A. C5-C6
• B. C8-T1
• C. L2-L4
• D. T12-L1

Answer: (A)

Erb's palsy comes from injury to the upper portion of the brachial plexus, most often the C5 and C6 nerve roots. Those roots feed the nerves that power the shoulder and upper arm muscles, including the deltoid and supraspinatus (for shoulder abduction and external rotation) and the biceps/brachialis via the musculocutaneous nerve (for elbow flexion). When C5-C6 are damaged, you lose these proximal functions, leading to the classic presentation where the arm hangs by the side, adducted and internally rotated, with the elbow extended and forearm pronated—the “waiter’s tip” posture characteristic of Erb's palsy. Injuries to lower roots like C8-T1 affect the hand, while involvement of L2-L4 or T12-L1 involves the lower extremities, not the upper limb.

Erb's palsy comes from injury to the upper portion of the brachial plexus, most often the C5 and C6 nerve roots. Those roots feed the nerves that power the shoulder and upper arm muscles, including the deltoid and supraspinatus (for shoulder abduction and external rotation) and the biceps/brachialis via the musculocutaneous nerve (for elbow flexion). When C5-C6 are damaged, you lose these proximal functions, leading to the classic presentation where the arm hangs by the side, adducted and internally rotated, with the elbow extended and forearm pronated—the “waiter’s tip” posture characteristic of Erb's palsy. Injuries to lower roots like C8-T1 affect the hand, while involvement of L2-L4 or T12-L1 involves the lower extremities, not the upper limb.