Snapshot A G1P1 woman gives birth to a boy at 41 weeks gestational age via vaginal delivery. Labor was prolonged due to shoulder dystocia which required a forceps delivery. The child's APGAR scores were 8 and 9 at 1 and 5 minutes, respectively. The child's weight at birth is 9 pounds 8 ounces. On exam, the baby's left upper extremity is notable for arm adduction, elbow extension, and forearm pronation. Introduction Clinical definition lesion in the upper trunk (C5-C6) of the brachial plexus leading to the characteristic "waiter's tip" deformity Epidemiology incidence most common neonatal brachial plexus palsy approximately 1 per 1000 live births risk factors obstetric login to view 5 more bullets Etiology excess traction on head away from the ipsilateral shoulder this motion puts tension on the upper trunk of the brachial plexus common clinical scenarios obstetric complication login to view 1 more bullet trauma login to view 1 more bullet Pathoanatomy normal anatomy brachial plexus diagram upper trunk of brachial plexus login to view 12 more bullets injury anatomy lesion in the upper trunk will weaken muscles innervated by the axillary, musculocutaneous, and suprascapular nerves resulting in weak login to view 11 more bullets Associated conditions clavicle fracture humerus fracture shoulder dislocation Prognosis unfavorable concomitant Horner syndrome C7 involvement cord avulsion Presentation Symptoms infant unable to move affected upper extremity Physical exam "waiter's tip" deformity arm is adducted login to view 2 more bullets arm is internally rotated login to view 2 more bullets forearm is pronated login to view 2 more bullets elbow is extended login to view 2 more bullets Imaging Radiographs indication radiographs are not routinely performed unless another diagnosis is being considered login to view 2 more bullets Magnetic resonance imaging (MRI) indication MRI is not routinely performed unless another diagnosis is being considered login to view 2 more bullets Differential Klumpke palsy distinguishing factors lesion in C8-T1 nerve roots (lower trunk) caused by upward traction of arm presents with "claw hand" due to impaired lumbrical muscles login to view 2 more bullets Radial head subluxation distinguishing factors subluxation of the radial head relative to the radiocapitellar joint occurs in children 2-5 years of age due to excess traction on the arm elbow held in slight flexion and pronation Treatment Nonoperative observation and daily passive exercises indications login to view 2 more bullets Complications Joint contracture Hemidiaphragm concomitant injury to the phrenic nerve