Definition
- Acute painful brachial plexopathy with severe shoulder girdle pain followed by patchy weakness and wasting
- Also called Parsonage Turner syndrome
- Idiopathic and hereditary forms
Aetiology
- Believed to be due to a viral infection of the cervical nerve roots as there is often a history of antecedent viral infection
Epidemiology
- Men affected about twice as often as women
- Most present between 20 and 60 years
- Bilateral asymmetric involvement in up to one third
- Hereditary form autosomal dominant, linked to SEPT9 mutations
Anatomy
- Upper trunk most often involved
- Long thoracic, suprascapular and axillary nerves frequently affected
- Anterior interosseous nerve may be involved in isolation
- Nerves outside the brachial plexus can be involved, including the phrenic nerve and lumbosacral plexus
Pathology
- Immune mediated inflammation of peripheral nerves
- Mononuclear inflammatory infiltrates on nerve biopsy
- Axonal degeneration predominates
- Hourglass constrictions of nerve fascicles seen at surgery or on high resolution imaging
Classification
- Idiopathic neuralgic amyotrophy
- Hereditary neuralgic amyotrophy, autosomal dominant with recurrent attacks
History
- Pain in the shoulder & arm
- intense
- sudden onset
- may extent into the neck & down into the hand
- Usually lasts several days but may continue for several weeks
- Associated with
- paraesthesia of the arm & hand
- weakness of the muscles of the shoulder, forearm & hand
Examination
- Wasting of the shoulder & small muscles of the hand
- may be evident after only a few days
- winging of the scapula is common
- Decreased Shoulder movement
- limited by pain
- sensory loss in one or more of the cervical dermatomes is not uncommon
Investigations
- NCS and EMG after 3 to 4 weeks show patchy denervation
- MRI shoulder shows denervation oedema then fatty atrophy of affected muscles
- MRI or US of the brachial plexus may show nerve swelling and hourglass constrictions
- MRI cervical spine to exclude radiculopathy
- Blood tests to exclude other causes, normal in most
- Chest X-ray or fluoroscopy for suspected phrenic nerve palsy
Differential Diagnosis
- Differentiated from an acute disc herniation as it involves multiple root levels
Treatment
- No specific treatment & pain controlled by analgesics
Complications
- Persistent pain and fatigue
- Scapular winging and dyskinesis
- Secondary adhesive capsulitis
- Residual weakness
- Recurrence, more frequent in the hereditary form
- Diaphragm paralysis with dyspnoea
Prognosis
- Usually good but full neurological recovery may take several months or even years
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.