Brachial Plexus and Its Injuries

Anatomy of the Brachial Plexus

Anatomical diagram (Gray's Anatomy for Students)

Schematic: Roots → Trunks → Divisions → Cords

Full plexus with named branches (Miller's Orthopaedics)

Components

Pre-terminal branches (from roots/trunks)

• Dorsal scapular nerve (C5) - rhomboids
• Long thoracic nerve (C5-7) - serratus anterior
• Nerve to subclavius (C5-6)
• Suprascapular nerve (C5-6, from superior trunk) - supraspinatus + infraspinatus

Classification of Nerve Injuries

Seddon's Classification (1943) - 3 types

Sunderland's Classification (5 degrees)

Types of Brachial Plexus Injuries

By Level

1. Upper Trunk Injury - Erb's Palsy (C5-C6)

• Mechanism: Forced depression of the shoulder (traction away from neck); most common in neonates with shoulder dystocia; also motorcycle accidents
• Clinical features:
  • Arm hangs at side, internally rotated, elbow extended, forearm pronated - the classic "waiter's tip" or "bellhop's tip" posture
  • Deltoid, biceps, brachialis, brachioradialis paralyzed
  • Loss of shoulder abduction/external rotation, elbow flexion, forearm supination
  • Absent biceps reflex
  • Hand movements preserved
• Most common brachial plexus injury (~20x more frequent than Klumpke's)

2. Lower Trunk Injury - Klumpke's Palsy (C8-T1)

• Mechanism: Forced extension/abduction of the arm over the head
• Clinical features:
  • Claw hand deformity - intrinsic hand muscle paralysis (interossei + lumbricals)
  • Absent grasp reflex
  • If T1 sympathetic fibers involved: Horner syndrome (ptosis, miosis, anhidrosis, enophthalmos)
  • Weakness similar to ulnar nerve injury
• Rare in clinical practice

3. Complete Plexus Injury (C5-T1)

• Flail, anesthetic arm
• Rarest pattern; most severe
• Often associated with root avulsions

By Injury Type

Special Patterns

• Obstetric brachial plexus palsy: Large newborns with shoulder dystocia; upper plexus (Erb) most common; may be associated with diaphragmatic paralysis (C3-5), Horner syndrome, fractured clavicle/humerus
• Radiation plexopathy: Progressive painless weakness post-radiotherapy; myokymia on EMG; must differentiate from neoplastic infiltration (which is painful)
• Thoracic outlet syndrome: Lower trunk compression; weakness of intrinsic hand muscles; mainly ulnar sensory loss; cervical rib possible
• Pancoast tumor: Apical lung tumor compressing lower trunk (C8-T1) + sympathetics = arm pain + Horner syndrome

Assessment

Clinical

• Document sensory + motor deficits precisely
• Test biceps reflex (C5-6), triceps reflex (C7), finger reflexes
• Moro reflex asymmetry in neonates
• Progressive deficits suggest expanding hematoma - consider early exploration

Investigations

• EMG/NCS: Do at 3-6 weeks post-injury (Wallerian degeneration needs time; before 3 weeks results are uninformative)
• Myokymia on EMG suggests radiation plexopathy
• MRI/CT: Rule out disc herniation, spondylosis, subluxation, tumor infiltration; identify root avulsion
• Plain X-ray: Exclude skeletal injury (clavicle fracture, etc.)
• In neonates: electrodiagnostic tests technically difficult; serial examinations more practical

Prognosis

• Neonatal Erb's palsy: Evidence of recovery within 2-4 weeks = good prognosis for full recovery; ~75% recover fully; biceps function is the key prognostic indicator
• ~25% of birth palsies have persistent deficits
• Rate of nerve regeneration: ~1 mm/day (3 mm/month)
• Root avulsions have the worst prognosis

Management

Conservative

• All injury types: Occupational and physiotherapy at a multidisciplinary center by 1 month of age (neonates)
• Early range-of-motion exercises
• Splinting to prevent contractures
• Serial examinations to track recovery

Surgical Indications

• Adults: No functional improvement after 3 months of conservative management
• Neonates: No evidence of spontaneous recovery at 3 months
• Progressive deficit (expanding hematoma) - early surgical exploration
• Clean, sharp injuries - may benefit from early primary repair

Surgical Options

Summary Table: Clinical Syndromes at a Glance