Parsonage-Turner Syndrome Overview
Parsonage-Turner syndrome (also called neuralgic amyotrophy or idiopathic brachial plexitis) is an inflammatory immune-mediated condition characterized by sudden-onset severe shoulder/arm pain followed within days by rapid weakness, muscle atrophy, and patchy sensory deficits affecting the brachial plexus and surrounding nerves. 1
Clinical Presentation
The syndrome follows a distinctive temporal pattern:
Pain Phase (Days 1-5):
- Acute, severe neuropathic shoulder and upper arm pain of sudden onset
- Pain typically lasts 1-5 days in most cases, though can persist up to 15 days
- Unilateral involvement in majority (right side affected in 70%, dominant side in 80%)
- Pain severity often described as debilitating 1, 2
Weakness Phase (Following Pain):
- Rapid-onset disabling weakness appearing as pain subsides
- Early muscle atrophy (a hallmark feature distinguishing this from other plexopathies)
- Patchy, multifocal distribution not following typical nerve root patterns
- Most commonly affects suprascapular and axillary nerves, causing deltoid, supraspinatus, and infraspinatus atrophy
- Long thoracic nerve involvement produces winged scapula
- Phrenic nerve affected in some cases causing diaphragm dysfunction 1, 3, 2
Sensory Findings:
- Multifocal, patchy sensory disturbances
- Does not follow dermatomal patterns 4
Etiology and Triggers
The underlying pathophysiology involves inflammatory immune-mediated mechanisms, suggested by nerve biopsy findings. Common triggers include:
- Recent viral infections or upper respiratory illness
- Vaccinations
- Surgery (postoperative complication)
- Childbirth
- Trauma or tissue manipulation
- Staphylococcus aureus and other systemic infections 1, 5, 6
Hereditary form (HBPN): Caused by dominant SEPT9 mutations with clinically indistinguishable attacks but higher recurrence rate (75% vs 26% in idiopathic form) 1, 6
Combined incidence: 3-100 per 100,000 persons per year, with peak incidence in third and seventh decades, affecting men more than women 1, 7
Diagnostic Approach
Clinical diagnosis is primary, as electrodiagnostic and imaging studies may be nondiagnostic early in the disease course 4.
Key diagnostic features to identify:
- Temporal sequence: severe pain → weakness → atrophy over days
- Multifocal, patchy distribution not matching radiculopathy patterns
- Rapid muscle atrophy (within weeks)
- Absence of cervical spine pathology
Electrodiagnostic Testing (performed 3-6 weeks after onset):
- Confirms nerve involvement and localization
- May show involvement of specific nerves (axillary, suprascapular, long thoracic)
- Can be normal or nondiagnostic early, requiring clinical diagnosis 2, 4
MRI of Brachial Plexus:
- Shows multifocal T2 nerve and muscle hyperintensities
- Identifies characteristic "hourglass" nerve swellings and constrictions
- Requires dedicated plexus sequences (not routine neck/spine MRI): orthogonal views through oblique plexus planes with T1, T2, fat-saturated T2 or STIR sequences 8, 1
High-Resolution Ultrasound:
- Rapidly detects nerve twisting and "hourglass-like" constriction sign
- Differentiates PTS from infectious brachial plexitis (neuroborreliosis)
- Can identify diaphragm dysfunction when phrenic nerve involved 1, 9
Management
Acute Pain Control: High-dose pulsed corticosteroids assist initial pain control 1. One case report demonstrated remission with dexamethasone 100 mg IV once 7. However, weakness and subsequent pain are not clearly responsive to steroids 1.
Pain Management:
- Non-narcotic pain medications preferred
- Pregabalin and gabapentin provide variable relief 4
- NSAIDs as needed 7
Rehabilitation (Critical Component):
- Physical and occupational therapy focusing on:
- Restoring functional scapular mechanics
- Energy conservation techniques
- Contracture prevention
- Pain management strategies
- Early initiation prevents muscular atrophy and improves functional outcomes 1, 2, 4
Prophylaxis for Hereditary Form:
- Prophylactic steroids or IVIG may reduce surgical- or childbirth-induced attacks in HBPN patients 1
Surgical Intervention:
- Tendon transfers considered when no recovery after 18 months
- Early neurolysis and nerve grafts remain controversial 1
Prognosis and Recovery
Most patients achieve dramatic functional recovery with time:
- 65% recovery rate at 10 months 6
- Near-complete recovery possible at 6 months with appropriate therapy 4
- Mean Constant-Murley score of 96 after conservative treatment 2
- Lifetime residual pain and weakness are rare 1
Important caveats:
- Symptoms can persist for more than one year 3
- Muscle strength may not completely restore in some patients 2
- Recurrence risk: 26% in idiopathic form, 75% in hereditary form 6
The key pitfall is delayed diagnosis due to lack of clinical suspicion, as the condition often remains underdiagnosed when physicians focus on more common shoulder pathology or cervical radiculopathy rather than recognizing the characteristic pain-to-weakness temporal pattern 7, 6.