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]

SAQ 2 — The total-plexus injury with Horner syndrome (20 marks, ~15 minutes)

A term infant (38 weeks, birthweight 3500 g) born by emergency caesarean for failure to progress has a flail left arm at the newborn examination — no movement from shoulder to fingers. The left eyelid droops, the left pupil is constricted, and the left forehead is dry compared with the right. The chest radiograph shows a normal hemidiaphragm and no clavicle fracture. [2]

Questions

1. Grade this injury using the Narakas system, state the root involvement, and explain the significance of the eye findings. (5 marks) [2]
2. Explain why this infant should be referred for specialist assessment earlier than the standard 3-month threshold, and what pathway differs from the standard approach. (5 marks) [9]
3. State the investigations that would be performed in surgical planning, and what each contributes. (5 marks) [2]
4. Describe the prognosis for this injury grade compared with an upper-trunk injury, and the comorbidities that should be screened for in follow-up. (5 marks) [1] [3]

Model answer (must-hit)

1. This is a total-plexus injury with Horner syndrome — Narakas grade IV, the most severe grade. The roots involved are C5 through T1. The eye findings (ptosis, miosis, anhidrosis) are Horner syndrome, caused by disruption of the sympathetic chain at T1. This signals a T1 preganglionic avulsion — the root has been torn from the spinal cord — which is the lesion with the poorest prognosis and the least potential for spontaneous recovery. [2]
2. Standard watchful waiting until the 3-month threshold is inappropriate for this infant because the probability of useful spontaneous recovery is very low (under 30 percent for grade IV). The Horner syndrome signals preganglionic avulsion, which cannot regenerate — the motor neurons in the anterior horn are disconnected from the peripheral nerve, and only surgical re-implantation or extra-plexal nerve transfers can restore any function. This infant is referred early, before the 3-month threshold, for specialist brachial plexus assessment and surgical planning. The surgical pathway uses extra-plexal nerve transfers (such as intercostal nerves to the musculocutaneous nerve for elbow flexion) rather than standard grafting, because avulsed roots cannot be grafted. [9]
3. Investigations for surgical planning include MRI of the brachial plexus with MR neurography (to define the lesion anatomy and identify pseudomeningocoeles that signal root avulsion), CT myelography in some centres (the gold standard for detecting nerve root avulsion via pseudomeningocoele), and electrodiagnostic studies (nerve conduction and electromyography to distinguish preganglionic avulsion from postganglionic rupture and to assess the integrity of the remaining roots). Shoulder ultrasound and MRI in follow-up assess glenohumeral dysplasia for planning secondary musculoskeletal procedures. [2]
4. The prognosis for grade IV is poor — spontaneous recovery is under 30 percent, and even with surgery, residual deficits of the hand and wrist are expected. This contrasts sharply with the upper-trunk grade I–II injury, which recovers in 80 to 90 percent of cases. The comorbidities to screen for in follow-up include torticollis, developmental concerns, sensory deficits, and glenohumeral dysplasia — the scoping review by Lewis and Sweeney documented elevated rates of multisystem comorbidities in children with NBPP, supporting structured multisystem screening rather than an arm-only focus. Every child with a grade IV injury enters long-term specialist surveillance for residual deficits and secondary procedures. [1] [3]