Brachial Plexus Birth Injury

Brachial plexus birth injury is stretch, rupture or avulsion of the nerve roots of the brachial plexus during delivery, causing flaccid weakness of the arm. It is classified by the roots involved: upper (C5 and C6, Erb palsy), extended upper (C5 to C7), lower (C8 and T1, Klumpke palsy) and total (C5 to T1).

Incidence is about 1 to 2 in 1000 live births. About 70 to 80% recover fully, most within 3 to 6 months.

Risk factors are shoulder dystocia, macrosomia, maternal diabetes, instrumental delivery, breech delivery and previous affected child. About half of cases occur without shoulder dystocia.

Pathophysiology.

Excess lateral traction on the neck during delivery of the shoulder stretches the plexus. Injury ranges from neurapraxia (recovery in weeks), to axonotmesis, to rupture or root avulsion (no recovery).

C5 and C6 injury produces loss of shoulder abduction, external rotation and elbow flexion. Lower root injury affects the hand, and T1 injury can disrupt sympathetic fibres, producing Horner syndrome.

• Arm held limp at the side, with absent or reduced movement from birth and an asymmetric Moro response.
• Upper palsy: adducted, internally rotated shoulder with elbow extended and forearm pronated (waiter's tip posture), with a preserved grasp.
• Total palsy: flail arm, absent grasp and sensation, often with Horner syndrome.
• Associated injuries: clavicle fracture, humeral fracture, phrenic nerve palsy with diaphragmatic elevation, facial palsy and cervical spine injury.

Red flags.

• Horner syndrome (ptosis, miosis, anhidrosis), indicating T1 root avulsion and poor prognosis.
• Total palsy or bilateral palsy.
• Respiratory distress or tachypnoea, suggesting phrenic nerve involvement.
• Painful, immobile limb with fever, suggesting septic arthritis or osteomyelitis.

• Clinical examination of shoulder, elbow, wrist and finger movement against gravity at birth, then at 1 month and 3 months, with documented muscle strength.
• Chest X-ray for clavicle, humerus and diaphragm. Ultrasound or MRI of the shoulder at 3 to 6 months for posterior subluxation.
• MRI myelography and electromyography are used in infants who may need surgery, to show root avulsion.
• Assess for other injuries, and exclude infection and osteomyelitis.

Differential diagnosis. Clavicle or humeral fracture (pseudoparalysis), septic arthritis or osteomyelitis of the shoulder, cervical spinal cord injury, cerebral injury and congenital arthrogryposis.

Early care.

• Gentle positioning and avoidance of forceful movement for 7 to 10 days, then passive range of movement exercises taught by a physiotherapist and repeated with each nappy change.
• Review at 1 month and 3 months. Splints to prevent wrist or elbow contracture.

Surgical indications.

• Referral to a specialist brachial plexus service by 4 to 6 weeks for any total palsy or Horner syndrome.
• Nerve reconstruction (grafting or transfer) at 3 to 6 months of age when elbow flexion against gravity has not returned by 3 months, or earlier for avulsion injuries.
• Botulinum toxin injections for internal rotation contracture, and secondary surgery (tendon transfer, osteotomy, or capsular release) for fixed deformity or shoulder dislocation.

Monitoring. Muscle strength, shoulder joint position, growth of the limb and function at least until age 5 years and often to adolescence.

Referral and escalation. Refer by 1 month to a multidisciplinary brachial plexus clinic, and urgently for total palsy, Horner syndrome or respiratory signs.