What are the causes and management of medial cord (medial cord of the brachial plexus) plexopathy?

Causes and Management of Medial Cord Plexopathy

Medial cord plexopathy is most commonly caused by trauma, malignancy, radiation therapy, infection, and inflammatory processes, with MRI of the brachial plexus being the gold standard for diagnosis and treatment varying based on etiology. 1

Causes of Medial Cord Plexopathy

Traumatic Causes

• Blunt trauma: Motor vehicle accidents (particularly motorcycle accidents), falls, and sports injuries 1
• Penetrating injuries: Gunshot wounds and other penetrating trauma 1
• Iatrogenic causes:
  • Surgical procedures involving the thoracic region or shoulder 2
  • Improper arm positioning during surgery (especially shoulder arthroplasty) 2
  • Specific risk positions: shoulder abduction >70°, combined external rotation >60° with extension >50° 2

Non-Traumatic Causes

• Neoplastic:

  • Primary tumors: Schwannomas, neurofibromas, malignant peripheral nerve sheath tumors 1
  • Metastatic disease: Lung cancer (Pancoast tumors), breast cancer 1
  • Lymphoma (through local encasement or direct infiltration) 1

• Radiation-induced:

  • Radiation therapy for breast cancer affecting the brachial plexus 3
  • Higher risk with radiation doses exceeding 50 Gy and larger fraction sizes 3

• Inflammatory/Immune-mediated:

  • Parsonage-Turner syndrome (neuralgic amyotrophy) 1
  • Chronic inflammatory demyelinating polyradiculoneuropathy 1
  • Multifocal motor neuropathy 1
  • Lewis-Sumner syndrome 1

• Infectious:

  • Post-herpetic plexopathy (rare but documented) 4
  • Other viral or bacterial infections 1

• Other causes:

  • Hereditary neuropathies (e.g., Charcot-Marie-Tooth syndrome) 1
  • Sarcoidosis 1
  • Compression from adjacent hematoma or mass 1

Diagnostic Approach

Imaging

• MRI of the brachial plexus: Gold standard for evaluation 1

  • High sensitivity (84%) and specificity (91%) for traumatic plexopathy 1
  • Should include T1-weighted, T2-weighted, fat-saturated T2-weighted or STIR sequences 1
  • IV contrast helps differentiate vascular structures from nerves and detect inflammatory changes 1
  • For traumatic cases, imaging should be delayed until approximately 1 month after injury 1

• CT with IV contrast: Alternative when MRI is contraindicated 1

  • Offers the next best anatomic visualization after MRI 1
  • Useful for detecting soft-tissue masses and tumors 1

• FDG-PET/CT: Beneficial for differentiating radiation plexitis from tumor recurrence 3

Electrodiagnostic Testing

• Essential for confirming plexopathy and defining localization, pathophysiology, chronicity, and severity 5
• Multiple nerve conduction studies and extensive needle examination are often required 5

Management Based on Etiology

Traumatic Plexopathy

• Acute management:

  • Surgical exploration for penetrating and open injuries 1
  • Conservative management initially for closed injuries 1
  • Surgical intervention if nerve is completely ruptured 1

• Chronic pain management:

  • Neuromodulation techniques:
    • Spinal cord stimulation (SCS) 6, 7
    • Peripheral nerve stimulation (PNS) 6
    • Combined SCS and PNS for refractory cases 6
  • Dorsal root entry zone lesioning for cases with failed SCS 7

Radiation-Induced Plexopathy

• Prevention:

  • Modern radiation techniques with precise targeting 3
  • Fractions of 2 Gy or less 3
  • Reduction in radiation dose to supraclavicular region 3
  • Exclusion of axillary region from treatment when possible 3

• Treatment:

  • Surgical interventions like omentoplasty for pain control in refractory cases 3
  • Emerging treatments targeting radiation-induced fibrosis, ischemia, and inflammation 3
  • PENTOCLO (pentoxifylline, tocopherol, and clodronate) for radiation-induced neuropathies 3

Inflammatory/Infectious Plexopathy

• Targeted treatment based on underlying etiology 5
• Symptomatic management for pain and functional deficits 5

Neoplastic Plexopathy

• Treatment directed at the underlying malignancy 1
• Palliative measures for symptom control 1

Prevention of Iatrogenic Medial Cord Plexopathy

• During shoulder surgery:
  • Support the arm from under the elbow 2
  • Avoid excessive abduction (>70°) 2
  • Avoid combined external rotation >60° with extension >50° 2
  • Minimize downward forces on the humeral shaft 2
  • Use caution during retractor placement, sounder insertion, humeral prosthesis impaction, and arthroplasty reduction 2

Key Clinical Pearls

• Medial cord plexopathy specifically affects the hand intrinsic muscles and ulnar-innervated structures, causing weakness in pinch grip and the "O" sign 4
• Traumatic injuries to the brachial plexus should be classified as preganglionic or postganglionic as they have different prognoses and reconstruction approaches 1
• MRI can detect pseudomeningocele, a key finding in nerve root avulsion injuries 1
• For post-herpetic plexopathy, MRI may show T2 signal hyperintensity and nerve hypertrophy, but contrast enhancement is rare 4