Parsonage–Turner syndrome
Summary
Parsonage–Turner syndrome (PTS) = acute brachial neuritis / neuralgic amyotrophy.
Sudden severe shoulder/upper arm pain → days–weeks later patchy weakness + muscle atrophy, due to immune-mediated brachial plexus / peripheral nerve inflammation. MRI: multifocal denervation; not a single focal entrapment.
Terminology
- Parsonage–Turner syndrome (PTS)
- Neuralgic amyotrophy
- Acute brachial neuritis
Pathogenesis
- Thought to be immune-mediated inflammation of:
- Brachial plexus trunks/divisions
- Individual peripheral nerves (e.g. suprascapular, long thoracic, axillary)
- Often follows a trigger (not always present):
- Viral or systemic infection
- Vaccination
- Surgery / anaesthesia
- Pregnancy/post-partum period
- Results in axonal neuropathy with denervation of affected muscles.
Epidemiology
- Typically young to middle-aged adults
- Slight male predominance reported in many series
- Up to one-third have bilateral or recurrent episodes over time.
Clinical features
Classic story
Previously well adult → sudden, brutal shoulder/upper arm pain (often nocturnal, unilateral) → pain gradually settles over days–weeks → weakness and visible wasting in a patchy, non-dermatomal distribution.
Pain phase
- Acute onset, often at night
- Severe, deep, burning or stabbing pain in:
- Shoulder
- Proximal arm
- Periscapular region
- Pain lasts days to weeks, then improves spontaneously.
Weakness / atrophy phase
- Appears as pain settles
- Weakness depends on which nerves/branches are involved:
- Muscle wasting becomes visible over weeks–months.
- Sensory loss: often mild and patchy, not purely dermatomal.
Key clinical contrast to entrapment
- PTS: dramatic pain first, then weakness; pattern is multifocal, not a single nerve root or tunnel.
- Entrapment: usually chronic, load-related pain with progressive symptoms in one nerve/space.
Common patterns of involvement
- Upper trunk / suprascapular nerve predominant
- Supra/infraspinatus denervation → weak abduction/external rotation
- Long thoracic nerve palsy
- Scapular winging (medial border prominence)
- Axillary nerve involvement
- Deltoid ± teres minor denervation
- Often multiple nerves together, giving a “crazy” pattern that does not respect simple root or peripheral nerve maps.
Imaging
MRI shoulder / brachial plexus
MRI hallmark
Multifocal denervation in a distribution that crosses a single peripheral nerve or a single muscle tendon lesion, often involving several shoulder girdle muscles.
Muscle changes
- Acute–subacute
- T2/STIR: hyperintense oedema in involved muscles
- Mild enlargement/bulkiness
- Chronic
- T1: fatty replacement, volume loss (atrophy)
- Pattern:
- Often involves multiple muscles:
- e.g. supra + infraspinatus ± deltoid ± serratus anterior
- Not explained by:
- A single tendon tear
- A single focal nerve entrapment alone
- Often involves multiple muscles:
Plexus / nerve changes (MR neurography)
- Thickening and T2 hyperintensity of:
- Brachial plexus segments
- Individual branches (e.g. suprascapular nerve)
- No discrete compressive mass or bony bottleneck.
Radiograph / CT
- Usually normal, or only background degenerative change
- Important mainly to exclude other structural causes of shoulder pain (fracture, large cuff tear, mass).
Electrophysiology (EMG/NCS)
- Confirms axonal neuropathy of affected nerves:
- Reduced recruitment
- Fibrillation potentials
- Distribution is patchy:
- Multiple nerves and/or plexus segments
- Helps differentiate from single-nerve entrapment or pure root radiculopathy.
Differentials
Don’t miss these
- C5–C6 cervical radiculopathy
- Rotator cuff tear
- Quadrilateral space syndrome
- Motor neurone disease / other neuropathies
- Myopathies (e.g. inflammatory myositis)
Management
Role of imaging
Radiology mainly:
- Support diagnosis (demonstrate denervation pattern + exclude structural causes)
- Help distinguish from surgically correctable pathologies (disc, entrapment, massive cuff tear).
- Acute phase
- Strong analgesia (NSAIDs, neuropathic pain agents, sometimes opioids)
- Some clinicians use corticosteroids early; evidence is mixed.
- Rehabilitation
- Physiotherapy:
- Maintain range of motion
- Prevent capsular contracture/frozen shoulder
- Gradual strengthening of recovering muscles
- Physiotherapy:
- Prognosis
- Recovery over months to years
- Many patients regain good function, but:
- Residual weakness
- Endurance loss
- Persistent scapular dyskinesis are not uncommon.
- Recovery over months to years
