Management of Neonatal Brachial Plexus Injury
Immobilization of the affected arm with supportive care is the most appropriate initial management for this macrosomic infant with a weak Moro reflex on the right side, which indicates brachial plexus injury (Erb's palsy).
Clinical Presentation and Diagnosis
This clinical scenario describes a classic birth injury complication:
- Macrosomic infant (birth weight ≥4,000g) born to a mother with uncontrolled diabetes mellitus 1, 2
- Weak/absent Moro reflex on one side indicates unilateral brachial plexus injury, most commonly Erb's palsy affecting C5-C6 nerve roots
- Risk factors present: maternal diabetes with poor glycemic control, macrosomia, and vaginal delivery 1, 2
The incidence of Erb's palsy in macrosomic infants (≥4,500g) delivered vaginally can be as high as 5%, compared to 0.7% in infants weighing <4,500g 1.
Initial Management Approach
Primary Treatment: Conservative Management
Immobilization and supportive positioning is the cornerstone of initial management:
- Position the affected arm across the abdomen in a "waiter's tip" position or neutral position
- Gentle passive range-of-motion exercises should begin after the first week to prevent contractures
- Most brachial plexus injuries (80-90%) resolve spontaneously within 3-12 months with conservative management
Why NOT Surgery Initially?
- Surgery is not indicated in the acute neonatal period
- Surgical intervention is only considered if there is no recovery by 3-6 months of age
- Early surgery does not improve outcomes and may cause additional harm
Why NOT IV Dextrose as Primary Treatment?
While neonatal hypoglycemia is a concern in infants of diabetic mothers 1, IV dextrose addresses a different complication:
- Check blood glucose levels in all macrosomic infants of diabetic mothers
- Treat hypoglycemia if present (glucose <40-45 mg/dL), but this is separate from the brachial plexus injury management
- The weak Moro reflex is due to mechanical nerve injury, not metabolic derangement
Associated Complications to Monitor
Macrosomic infants of mothers with uncontrolled diabetes are at increased risk for multiple complications 1, 2:
- Hypoglycemia: Monitor blood glucose in the first 24-48 hours
- Shoulder dystocia: Often the mechanism causing brachial plexus injury
- Clavicle fractures: May coexist with brachial plexus injury
- Birth asphyxia: Risk is 2-3 times higher than normal 1
- Transient tachypnea: Risk is 2-3 times higher 1
Follow-up and Prognosis
- Weekly assessment of motor function and range of motion in the first month
- Referral to pediatric neurology or orthopedics if no improvement by 3 months
- Physical therapy should be initiated early to maintain joint mobility
- Most cases show significant improvement within the first 3 months, with complete recovery in the majority
Key Clinical Pitfall
Do not confuse the need to treat potential hypoglycemia with the management of brachial plexus injury. While both conditions may coexist in this infant, they require separate assessment and treatment. The weak Moro reflex specifically indicates nerve injury requiring immobilization and supportive care, not metabolic intervention.