Parsonage-Turner Syndrome: Diagnosis and Management
What is Parsonage-Turner Syndrome?
Parsonage-Turner syndrome (PTS), also called neuralgic amyotrophy or acute brachial neuritis, is a rare inflammatory brachial plexopathy characterized by sudden-onset severe shoulder pain followed by progressive weakness and muscle atrophy. 1, 2
The combined incidence of PTS and its hereditary form ranges from 3 to 100 per 100,000 persons per year. 2 The condition is distinct from traumatic brachial plexus injury and typically follows an immune-mediated inflammatory process. 1, 2
Clinical Presentation
Pain Phase (Initial 1-2 Weeks)
- Abrupt onset of severe, neuropathic shoulder and arm pain is the hallmark presenting feature, typically unilateral but can be bilateral. 2, 3
- Pain is described as sharp, burning, or stabbing and often awakens patients from sleep. 2
- Pain intensity peaks within hours to days and is often refractory to standard analgesics. 2, 3
Weakness Phase (Develops as Pain Subsides)
- Progressive motor weakness begins 1-2 weeks after pain onset, affecting muscles innervated by the brachial plexus or individual shoulder girdle nerves. 2, 3
- The suprascapular nerve (innervating supraspinatus and infraspinatus) is most commonly affected, followed by the long thoracic nerve (serratus anterior) and axillary nerve (deltoid). 2, 4
- Early muscle atrophy develops rapidly, often visible within 2-3 weeks of weakness onset. 2, 3
- Sensory symptoms (dysesthesias, numbness) occur but are less prominent than motor deficits. 3
Nerve Distribution Beyond the Plexus
- The phrenic nerve is commonly involved (10-30% of cases), causing diaphragmatic paralysis that may be asymptomatic or present with dyspnea. 2
- Other cranial nerves and lumbosacral plexus can rarely be affected. 2
Diagnostic Approach
Clinical Diagnosis
The diagnosis of PTS is primarily clinical, based on the characteristic sequence of severe pain followed by weakness and atrophy in a brachial plexus or shoulder nerve distribution. 1, 2, 3
Key diagnostic features include:
- Acute onset of severe shoulder/arm pain (hours to days)
- Progressive weakness developing 1-2 weeks after pain onset
- Rapid muscle atrophy (visible within 2-3 weeks)
- Distribution crossing multiple peripheral nerve territories (not single nerve root)
- Absence of trauma or structural compression 2, 3
Electrodiagnostic Studies
- Nerve conduction studies and electromyography (EMG) should be performed 3-4 weeks after symptom onset to confirm denervation and localize the lesion. 2
- Early testing (within 2 weeks) may be normal or show only reduced recruitment; repeat testing at 3-4 weeks improves diagnostic yield. 2
- Findings typically show axonal loss in affected nerves with preserved conduction velocities in unaffected segments. 2
MRI of the Brachial Plexus
- MRI of the brachial plexus with and without IV contrast is the gold standard imaging modality, showing T2 hyperintensity in affected nerves and muscles, with 81% sensitivity and 91% specificity. 1, 5
- Imaging should be delayed until approximately 1 month after symptom onset to allow resolution of acute hemorrhage and edema. 1
- MRI findings include:
Ultrasound
- Ultrasound can identify nerve hourglass constrictions and assess diaphragmatic function when phrenic nerve involvement is suspected. 2
- Diaphragm ultrasound showing paradoxical or absent movement confirms phrenic nerve palsy. 2
Laboratory Testing
- No specific laboratory test confirms PTS. 2
- Exclude alternative diagnoses: complete blood count, glucose, electrolytes, creatine kinase, inflammatory markers (ESR, CRP), and rheumatologic panel if systemic disease is suspected. 1, 5
Differential Diagnosis: Critical Distinctions
PTS vs. Cervical Radiculopathy
- Radiculopathy follows a single nerve root dermatomal distribution; PTS crosses multiple peripheral nerve territories. 1, 5
- Radiculopathy typically has neck pain radiating down the arm; PTS has shoulder girdle pain without neck involvement. 1
PTS vs. Rotator Cuff Tear
- Rotator cuff tears cause mechanical shoulder pain worsened by movement, not severe neuropathic pain at rest. 3
- MRI shows tendon disruption in rotator cuff tears; PTS shows muscle edema without tendon pathology. 6
PTS vs. Guillain-Barré Syndrome (GBS)
- GBS presents with ascending bilateral weakness, areflexia, and sensory loss in a symmetric pattern. 7, 8
- PTS is typically unilateral, affects upper extremity only, and has prominent pain as the initial feature. 2, 3
- Cerebrospinal fluid in GBS shows albumino-cytological dissociation; CSF is normal in PTS. 7, 8
Etiology and Triggers
Immune-Mediated Inflammation
- PTS is believed to result from an aberrant immune response targeting peripheral nerves, triggered by infections, vaccinations, surgery, or childbirth. 2, 3
- Nerve biopsies show inflammatory infiltrates supporting an immune-mediated mechanism. 2
Common Triggers
- Recent viral infection (within 6 weeks) is the most common associated risk factor, including influenza, COVID-19, Epstein-Barr virus, and cytomegalovirus. 2, 6, 9
- Vaccination (influenza, tetanus, COVID-19) is a recognized trigger, with an attributable incidence of 0.5-1 case per 100,000 tetanus toxoid recipients. 7, 4
- Postoperative PTS occurs after shoulder, thoracic, or cardiac surgery. 2, 3
- Childbirth is a trigger in women, particularly in hereditary brachial plexus neuropathy (HBPN). 2
- Bacterial infections (e.g., Staphylococcus aureus spondylodiscitis) have been reported. 9
Hereditary Form (HBPN)
- Hereditary brachial plexus neuropathy is caused by dominant mutations in the SEPT9 gene and presents with recurrent attacks indistinguishable from idiopathic PTS. 2
- Suspect HBPN if there is a family history of similar attacks or recurrent episodes. 2
Management
Acute Pain Control (First 2-4 Weeks)
High-dose pulsed corticosteroids (e.g., methylprednisolone 1 g IV daily for 3-5 days or prednisone 1 mg/kg/day orally for 2 weeks with taper) are recommended for initial pain control during the acute phase. 2, 4
- Corticosteroids reduce pain severity and duration when initiated within the first 1-2 weeks of symptom onset. 2, 4
- Weakness and subsequent chronic pain are not clearly responsive to steroids; the primary benefit is acute pain relief. 2
Non-Narcotic Pain Management
- Gabapentinoids (gabapentin 300-1200 mg three times daily or pregabalin 75-150 mg twice daily) are first-line agents for neuropathic pain. 2
- Tricyclic antidepressants (amitriptyline 25-75 mg at bedtime) or duloxetine (60 mg daily) are alternatives. 2
- Avoid opioids due to limited efficacy for neuropathic pain and risk of dependence. 2
Physical Therapy and Rehabilitation
Physical therapy focusing on restoring functional scapular mechanics, preventing contractures, maintaining range of motion, and energy conservation is critical and should begin as soon as pain allows. 2, 4
- Passive range-of-motion exercises prevent frozen shoulder and contractures. 2, 4
- Progressive strengthening begins once acute pain subsides (typically 4-6 weeks). 2
- Scapular stabilization exercises are essential for functional recovery. 2
Monitoring and Follow-Up
- Serial clinical examinations every 4-6 weeks to assess motor recovery and muscle atrophy. 2
- Repeat EMG at 3-6 months if recovery is not progressing to confirm reinnervation. 2
- Diaphragm ultrasound should be performed if dyspnea or unexplained fatigue develops, as phrenic nerve involvement may be subclinical. 2
Prognosis and Recovery
Expected Recovery Timeline
- Most patients (70-90%) make dramatic functional recovery within 2-3 years, although some residual weakness or pain may persist. 2, 3
- Recovery begins 3-6 months after onset and continues for up to 3 years. 2
- Early muscle atrophy does not predict poor outcome; reinnervation can occur even with severe initial atrophy. 2
Factors Associated with Prolonged Recovery
- Involvement of multiple nerves or bilateral disease. 2
- Delayed diagnosis and rehabilitation. 2
- Recurrent attacks (more common in HBPN). 2
Surgical Intervention
- Tendon transfers should be considered if no recovery occurs after 18 months of conservative management. 2
- Early neurolysis and nerve grafts are controversial and not routinely recommended. 2
Recurrence and Prevention
Recurrence Risk
- Recurrent attacks are common in hereditary brachial plexus neuropathy (HBPN) but rare in idiopathic PTS. 2
- Recurrence in idiopathic PTS is estimated at 5-10% over a lifetime. 2
Prophylaxis in HBPN
- Prophylactic corticosteroids (prednisone 1 mg/kg starting 1 week before and continuing 2 weeks after) or intravenous immunoglobulin (IVIG 2 g/kg) may reduce surgery- or childbirth-induced attacks in patients with known HBPN. 2
Common Pitfalls and Caveats
Diagnostic Pitfalls
- Do not dismiss PTS based on normal early EMG or MRI; repeat testing at 3-4 weeks improves diagnostic yield. 2
- Do not order cervical spine MRI alone when PTS is suspected; a dedicated brachial plexus MRI protocol is required. 1, 5
- Bilateral facial palsy or ascending weakness should prompt consideration of Guillain-Barré syndrome, not PTS. 7, 8
Management Pitfalls
- Do not delay physical therapy waiting for complete pain resolution; early range-of-motion exercises prevent contractures. 2, 4
- Do not rely on corticosteroids alone for long-term management; they are effective only for acute pain, not for weakness or chronic pain. 2
- Do not overlook phrenic nerve involvement; unexplained dyspnea or fatigue warrants diaphragm ultrasound. 2