Nerve injuries in the upper body

• Erb palsy

• Klumpke palsy

• Injury to the upper trunk of the brachial plexus (C5–C6)

• Etiology

  • Excessive lateral flexion of the neck

    • Trauma (e.g., falling on the head and shoulder in a motorcycle accident)

    • Birth injury: excessive lateral traction on the neck during delivery and shoulder dystocia

• Clinical features

  • Weakness of muscles in the C5 and C6 myotomes → flexed wrist with an extended forearm and internally rotated and adducted arm (waiter's tip posture)

    • Weak biceps brachii, brachialis, and brachioradialis

      • Impaired flexion and supination of the forearm

      • Absent biceps reflex

    • Weak infraspinatus and supraspinatus → impaired external rotation of the arm

    • Weak deltoid and supraspinatus → impaired arm abduction

    • Weak wrist extensors → impaired wrist extension

  • Asymmetric Moro reflex in infants (absent or impaired on the affected side)

  • Sensory loss in the C5 and C6 dermatomes (thumb and lateral surface of the forearm and arm)

• Treatment

  • Immobilization in flexion and external rotation with an abduction brace

  • Physiotherapy

  • Surgery for severe nerve damage or prolonged cases

For weakened muscles in Erb's palsy, imagine BIRDS eating hERBS served by a waiter: Biceps brachii, Infraspinatus, wRist extensors, Deltoid, Supraspinatus, waiter's tip posture.

• Injury to the lower trunk of the brachial plexus (C8–T1)

• Etiology

  • Hyperabduction of the arm

    • Trauma (e.g., breaking a fall by grabbing a branch)

    • Birth injury: excessive upward traction on the arm during delivery

  • Compression of the lower trunk of brachial plexus (subacute to chronic onset)

    • Pancoast tumor

    • Cervical rib

• Clinical features

  • Weakness of intrinsic hand muscles (thenar, hypothenar, lumbricals, interossei) → total claw hand (persistent flexion of the interphalangeal joints and extension of the metacarpophalangeal joints in the hand)

  • Preganglionic Horner syndrome if injury occurs proximal to the white ramus communicans

  • Decreased peripheral pulses if subclavian vessels are compressed by a Pancoast tumor or cervical rib

  • Absent grasp reflex in infants

  • Sensory loss in the C8 and T1 dermatomes (little finger and medial surface of the forearm and arm)

• Treatment

  • Splinting the hand to correct the claw hand

  • Physiotherapy

  • Surgery for severe nerve damage

• Distal nerve lesions are more likely to cause claw deformities (e.g., ulnar claw or median claw) because they result in a loss of lumbrical function with intact extrinsic flexors

• In proximal nerve lesions, hand distortions (e.g., pope's blessing) are only visible when the patient tries to flex the fingers or make a fist.