A newborn presents with a limp right arm in internal rotation, extension, and pronation. What is the likely pathology?

• A. Klumpke's palsy
• B. Erb-Duchenne palsy
• C. Cervical myelopathy
• D. Capsular tear

Answer: (B)

The presentation of a newborn with a limp right arm that is held in internal rotation, extension, and pronation is indicative of Erb-Duchenne palsy, which is associated with an injury to the upper trunk of the brachial plexus, typically resulting from shoulder dystocia during delivery.

In Erb-Duchenne palsy, the affected arm often assumes a characteristic position known as the "waiter's tip" posture. This position is due to the weakness in the muscles that are typically innervated by the upper trunk, including the deltoid and supraspinatus, leading to loss of shoulder abduction and external rotation, while the muscles that cause elbow flexion may be intact, creating the appearance of the arm hanging down.

The condition arises from traction or excessive pull on the infant's shoulder during birth, resulting in damage to the nerve roots C5 and C6. Recognizing this typical presentation helps in understanding the pathology and distinguishing it from other conditions that may present similarly but are associated with different injury patterns, such as Klumpke's palsy, which primarily affects the lower trunk of the brachial plexus, or cervical myelopathy, which involves spinal cord compression and would present differently in this