Birth trauma and brachial plexus injury — formative SAQs

SAQ 1 — The upper-trunk injury and the 3-month threshold (20 marks, ~15 minutes)

A term infant (40 weeks, birthweight 4100 g) is born after a prolonged second stage complicated by shoulder dystocia, requiring the McRoberts manoeuvre and suprapubic pressure. On the routine newborn examination the right arm is adducted and internally rotated at the shoulder, extended at the elbow, and flexed at the wrist. The Moro reflex is absent on the right. The hand and wrist move spontaneously. There is no ptosis, miosis, or anhidrosis. ^[1]

Questions

1. Classify the injury using the Narakas system, state the nerve roots involved, and name the clinical posture. (5 marks) ^[2]
2. Describe your immediate management of this newborn, including the investigations you would perform to exclude coexisting injuries. (5 marks) ^[6]
3. Describe how you will monitor this infant's recovery over the first three months, and state the threshold that triggers microsurgical referral. (6 marks) ^{[2] [4]}
4. Outline the microsurgical nerve reconstruction that would be offered if the threshold is met, including the optimal timing window and the common nerve transfers. (4 marks) ^{[2] [9]}

Model answer (must-hit)

1. This is an upper-trunk (Erb-Duchenne) brachial plexus birth injury involving C5–6 (with possible C7 contribution). The posture is the classic waiter's-tip: shoulder adducted and internally rotated, elbow extended, forearm pronated, wrist and fingers flexed. This is Narakas grade I or II (no Horner syndrome, hand movement preserved), the most common pattern, with the best recovery prognosis. ^[2]
2. Immediate management: gently rest the arm across the chest for 1–2 weeks (no rigid splinting, which causes contracture). Exclude coexisting injuries: palpate the clavicle for fracture (crepitus or angulation), obtain a chest radiograph to exclude clavicular fracture and an elevated hemidiaphragm (phrenic nerve palsy C3–5), and examine the face and eyes (facial nerve palsy, Horner syndrome). After the first week, begin gentle passive range-of-motion exercises taught by a physiotherapist to prevent shoulder adduction and internal rotation contractures. ^[6]
3. Monitor with the Active Movement Scale (AMS), assessing 15 joint movements monthly from the first outpatient visit. The single most important item is elbow flexion (biceps, C5–6). The threshold for microsurgical referral is absent antigravity biceps recovery (AMS below 5) at 3 months, combined with a Toronto Test Score below 3.5. Infants who recover antigravity biceps by 3 months continue conservative management; those who do not are referred for surgery. The presence of Horner syndrome or total-plexus involvement from birth would lower the threshold for earlier referral. ^{[2] [4]}
4. Microsurgical nerve reconstruction is performed optimally between 3 and 9 months of age. It involves nerve grafting (using the sural nerve as a cable graft to bridge a postganglionic rupture) and nerve transfer. The common transfers are the spinal accessory nerve to the suprascapular nerve (for shoulder abduction and external rotation) and the Oberlin transfer (a fascicle of the ulnar nerve to the musculocutaneous nerve for elbow flexion). Preganglionic avulsions cannot be grafted and require extra-plexal nerve transfers. The long-term results of Gilbert and colleagues confirmed that primary repair produces durable functional improvements into adolescence. ^{[2] [9]}