What is Parsonage-Turner syndrome?

Parsonage-Turner Syndrome

Parsonage-Turner syndrome (PTS), also known as neuralgic amyotrophy or brachial plexitis, is an inflammatory disorder of the brachial plexus characterized by acute onset of severe shoulder pain followed by progressive neurologic deficits including motor weakness, dysesthesias, and numbness. 1

Clinical Presentation

• Initial phase: Abrupt onset of severe shoulder pain, typically unilateral
• Secondary phase: Pain subsides and is followed by:
  • Progressive muscle weakness
  • Muscle atrophy
  • Possible sensory abnormalities (dysesthesias, numbness)
  • Motor deficits in the distribution of brachial plexus nerves

Etiology and Associations

PTS has been reported in various clinical scenarios:

• Post-infectious: Most common associated risk factor 2
  • Various viral, bacterial, and fungal infections
  • Recent reports of association with SARS-CoV-2 (COVID-19) infection 2
• Post-surgical: Surgery is the most commonly recognized antecedent event 3
  • Can occur after surgery at remote sites (definite PTS)
  • Can occur after surgery of ipsilateral upper extremity or cervical spine (probable PTS)
• Post-traumatic
• Post-vaccination
• Idiopathic: Many cases have no identifiable trigger 4

Pathophysiology

The exact cause and pathophysiology remain incompletely understood, but several mechanisms have been implicated:

• Autoimmune processes
• Genetic factors
• Infectious triggers
• Mechanical processes 5

Diagnosis

Diagnosis is primarily clinical, as there is no gold standard diagnostic test. Key diagnostic elements include:

1. Clinical history:

   • Acute onset severe shoulder/scapular pain
   • Progressive weakness following pain
   • Possible history of preceding infection, surgery, trauma, or vaccination

2. Physical examination:

   • Motor weakness in specific nerve distributions
   • Muscle atrophy
   • Possible sensory deficits

3. Imaging:

   • MRI brachial plexus: Superior soft-tissue contrast and spatial resolution
     • Can show increased T2 signal in affected muscles 2
     • Helps exclude other causes of brachial plexopathy 1
   • MRI at 1.5T may be beneficial to reduce artifact if metal is present 1

4. Electrodiagnostic studies:

   • Denervation localized to branches of the brachial plexus
   • Helps confirm diagnosis and map affected nerves 3

Commonly Affected Nerves

The most frequently affected nerves in PTS include:

1. Anterior interosseous nerve (AIN)
2. Posterior interosseous nerve (PIN)
3. Suprascapular nerve 3

Differential Diagnosis

• Cervical radiculopathy
• Rotator cuff pathology
• Thoracic outlet syndrome
• Compressive neuropathies
• Neoplastic brachial plexopathy
• Post-radiation plexopathy
• Inflammatory conditions affecting the shoulder

Treatment

No specific treatments have been proven to reduce neurologic impairment or improve prognosis 5. Management is supportive:

1. Pain management:

   • NSAIDs
   • Short course of corticosteroids (in acute phase)
   • Neuropathic pain medications (gabapentin, pregabalin)

2. Physical therapy:

   • Maintain range of motion
   • Prevent contractures
   • Strengthen affected muscles
   • Compensatory techniques

3. Multidisciplinary approach:

   • Neurologist
   • Physical medicine and rehabilitation specialist
   • Pain management specialist

Prognosis

• Recovery is variable and can take months to years
• Some patients may have residual weakness or sensory deficits
• Complete recovery occurs in approximately 80-90% of patients
• Recurrence is possible in up to 25% of cases

Clinical Pearls

• PTS can be easily misdiagnosed in postoperative patients, as symptoms may be attributed to surgical positioning, postoperative recovery, or post-anesthetic block pain 4
• Early diagnosis allows for appropriate patient education, expectations management, and targeted therapy
• Consider PTS in patients who develop severe shoulder pain and weakness after surgery, even if the surgery was not performed on the affected extremity 3
• The condition can present with varying patterns of nerve involvement, making clinical presentation highly variable