Differential Diagnosis in Neurology

7.2. Differential Diagnosis by Plexus Component

Supraclavicular Lesions

• General Features:
  • Supraclavicular lesions present in myotomal and dermatomal distribution

Infraclavicular Lesions

• Infraclavicular Lesions are in Peripheral Nerve Distributions:
  • Obstetric palsy ( Erb-Duchenne ) C5–C6; C8–T1
  • Brachial plexus traction injury (flexion–extension) neck injury); neurogenic thoracic outlet syndrome (neuropraxic lesions)
  • Neuralgic amyotrophy (parsonage Turner); C5–C6 roots most severely affected
  • Pack palsy (poorly packed knapsack)
  • Burner or Stingers (face mask injuries; sudden neck torsion)
  • Direct lateral neck trauma; open traction injuries
  • Cervical rib anomalies (C8–T1 roots)
  • Trauma from TOS surgery, C8–T1 > C5–C6
  • Infraclavicular lesions:
    • Trauma
    • Neurovascular causes
    • X-RT
    • Fractures of the humerus

Upper Trunk Lesions by Location

• Involvement of serratus anterior, spinate, rhomboids, brachialis, brachioradialis
• Abduction, external rotation of the shoulder; forearm flexion and supination are primarily involved
• Sensory loss has two patterns:
  • Lateral deltoid and lateral forearm
  • Trapezius ridge and medial scapular border (most common) in neuropraxic injuries (C4–C7 roots are involved)
• Lesions at the level of formation of the trunks:
  • Serratus anterior and rhomboids are normal
• Lesions at mid or distal upper trunk level:
  • The supra and infraspinatus muscles are normal

Middle Trunk Lesions by Location

• Rarely occur alone (concomitant with upper and lower trunk lesions)
• Weakness of forearm and wrist and some components of finger extension; weakness of forearm pronation, radial hand flexion
• Sensory loss:
  • Tinel's sign at the Arcade of Frohse (medial to the lateral epicondyle)
  • Dorsal portion of thumb, index and long finger
  • Decreased triceps reflex (if proximal)

Clinical Signs and Symptoms of Middle Trunk Lesions

• Muscle involvement from lower trunk lesions:
  • Ulnar innervated muscles of the hand and forearm (C8–T1 roots)
  • Median innervated hand intrinsic muscles; muscles innervated by the anterior interosseous nerve
  • Extensor indicis proprius; extensor pollicis brevis; innervated by the radial nerve
  • Wasted medial forearm and hand (Klumpke's paralysis from obstetric injury)
  • Sensory loss:
    • Medial forearm to medial humerus in the axilla
    • Entire 4th and 5th fingers; ulnar nerve territory ends slightly above the wrist
    • Often Tinel's sign at the cubital tunnel
    • T1 damage causes Horner's syndrome
    • T2 damage, sympathetic symptoms noted in the upper extremity (abnormal sweating, pain, swelling, autonomic dysregulation)

Lower Trunk Lesions (C8/T1 root)

• Most frequently involved with moderate to severe brachial plexus traction injury (neuropraxic)
• Metastatic plexopathy
• Pancoast tumor (apical lung)
• Medial sternotomy
• Breast surgery (arm hyperabducted during anesthesia)
  • Intercostobrachial nerve damaged
• Thoracic outlet surgery
• Klumpke's paralysis (rare now; birth injury)

Differential Diagnosis of Subclavicular Lesions

• At the level of the anterior and posterior divisions
• Clavicular trauma (fractures):
  • Immediate onset with direct neurological injury
  • Delayed: inadequate bony fixation; compression by excess callus formation
• Compression between clavicle and first rib during surgical procedure for repair of Sprengel's deformity
• Component of neurogenic brachial plexus traction injury

Differential Diagnosis of Infraclavicular Plexus Lesions

• Cords and terminal nerves affected:
  • Deficits in distribution of two or more peripheral nerves or portions of their territories
  • Differential diagnosis:
    • X-RT
    • Trauma
    • Neuropraxic injury (flexion–extension and torsional neck injury)
• Lateral cord lesion
  • Clinical symptoms and signs:
  • Weakness of elbow flexion, forearm pronation, radial hand flexion (musculotendinous; lateral portion of median nerve)
  • Sensory loss:
    • Lateral forearm
    • Thumb (particularly the base) index and radial side of the third finger)
• Medial Cord Lesions:
  • Weakness of finger flexion; extension and abduction; ulnar wrist flexion and abduction
  • Medial half of the median nerve and the ulnar nerve are involved
  • Sensory loss:
    • Medial forearm and arm
    • Ulnar side of the 3rd finger; complete 4th and 5th finger
• Posterior cord lesions:
  • Injury to the subscapular, thoracodorsal, axillary and radial nerves (proximal lesion)
  • Weakness of the abduction, forward elevation and extension of the shoulder; internal and external arm rotation; diminished forearm, hand and finger extension
  • Sensory loss is often partial:
    • Posterior deltoid
    • Triceps
    • Dorsal base of the thumb
    • Dorsal forearm

Differential Diagnosis of Infraclavicular Brachial Plexus Injury

• Brachial Plexus traction injury (BPTI) of mild to moderate severity:
  • MVA (flexion–extension or torsional neck injury)
  • Falls
  • Repetitive overhand arm movements
  • Rotator cuff injuries
• Severe infraclavicular plexus injuries:
  • Motor cycle and car injuries
  • Falls
  • Gun shot
  • Knife wounds
  • X-RT plexopathy
• Associated injuries in which infraclavicular plexus is involved:
  • Long crutch injury (improperly used)
  • Humeral head dislocation
  • Clavicular, scapular, humeral fracture
  • Axillary artery or vein rupture (surgical procedures)