Birth trauma and brachial plexus injury — structured clinical encounter

Station brief (candidate)

You are the neonatal registrar. A term infant (40 weeks, birthweight 4100 g) born after a prolonged second stage complicated by shoulder dystocia (McRoberts manoeuvre and suprapubic pressure required) is found on the routine newborn examination to have an abnormal right arm posture. The 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; hand and wrist movements are preserved. There is no ptosis, miosis, or anhidrosis. The team asks you to classify the injury, exclude the coexisting injuries, establish the management plan, and outline the 3-month threshold decision. You have 12 minutes with the team and 5 minutes for examiner discussion. [1]

Information available on request

• Term infant (40 weeks), birthweight 4100 g; shoulder dystocia requiring McRoberts and suprapubic pressure; Apgar scores 8 and 9 at 5 and 10 minutes; no resuscitation beyond drying and stimulation. [1]
• Newborn exam: right arm adducted and internally rotated, elbow extended, wrist flexed; Moro absent on right; hand and wrist move spontaneously; no Horner syndrome; face symmetric; suck and cry normal. [2]
• On palpation, there is no crepitus or angulation at the right clavicle; the chest is clear with equal air entry; the chest radiograph is normal (no clavicle fracture, no elevated hemidiaphragm). [6]

Tasks

1. Classify the injury using the Narakas system, state the nerve roots involved, and explain why this grade has the best prognosis. [2]
2. Describe your immediate management, including the coexisting injuries you exclude and why rigid splinting is harmful. [6]
3. Outline the follow-up plan: the Active Movement Scale, the monthly monitoring, the single most important item, and the threshold that triggers microsurgical referral. [2] [4]
4. Describe what microsurgical nerve reconstruction involves if the threshold is met, including the optimal timing window and the common nerve transfers, citing the supporting evidence. [9]

Marking anchors

Must-hit

• Classifies the injury as upper-trunk (Erb-Duchenne) involving C5–6, Narakas grade I or II, with the waiter's-tip posture. States this grade has the best prognosis because the lesion is typically neurapraxia or mixed neurapraxia and axonotmesis (not avulsion), and the majority recover antigravity biceps within 3 months. [2]
• Immediate management: gently rest the arm across the chest for 1–2 weeks; no rigid splinting because it promotes shoulder adduction and internal rotation contractures. Excludes coexisting injuries: palpates the clavicle (no crepitus), obtains a chest radiograph (no clavicle fracture, no elevated hemidiaphragm from phrenic nerve palsy), examines the face (no facial nerve palsy) and eyes (no Horner syndrome). Begins gentle passive range-of-motion exercises after the first week. [6]
• Follow-up: monthly Active Movement Scale (15 joint movements, scored 0–7). The single most important item is biceps (elbow flexion). Antigravity biceps recovery (AMS 5 or above) by 3 months predicts spontaneous recovery — continue conservative management. Absent recovery by 3 months (Toronto Test Score below 3.5) triggers microsurgical referral. [2] [4]
• Microsurgical reconstruction: nerve grafting (sural nerve cable graft for postganglionic rupture) and nerve transfer (spinal accessory to suprascapular for shoulder, Oberlin ulnar-to-musculocutaneous for elbow flexion), optimal window 3–9 months. Cites Waters 1999 (microsurgical repair improves outcome vs natural history) and Gilbert 2006 (durable long-term primary repair results). [4] [9]

Merit

• Explains the physiological basis of the 3-month threshold: axons regenerate at ~1 mm/day; the biceps is the nearest target muscle to the upper trunk, so it receives regenerating axons first; if it has not recovered by 3 months, the lesion is too severe for spontaneous regeneration to reach the target. [4]
• Discusses the epidemiology: shoulder dystocia increases BPBI risk ~100-fold; over half of affected infants have no identifiable risk factor; caesarean delivery is protective but not absolute. [1]
• Describes the secondary musculoskeletal procedures for residual deficits and glenohumeral dysplasia: tendon transfers, derotational humeral osteotomy, and glenohumeral reduction, guided by the Waters classification. [2]

Fail

• Rigidly splints the arm, causing contracture rather than preventing it. [6]
• Fails to establish the 3-month biceps threshold and the Toronto Test Score, deferring the surgical decision indefinitely with watchful waiting. [4]
• Misses a coexisting clavicle fracture or phrenic nerve palsy by fixating on the arm alone. [6]