Brachial Neuritis (Parsonage Turner Syndrome)

Background

• Painful weakness of shoulder muscles (with atrophy). Beware radiculopathy or cord pathology.
• Brachial neuritis (BN) is a rare syndrome affecting LMN of brachial plexus or mononeuritis
• The syndrome can vary greatly in presentation and nerve involvement
• Aetiology is unknown but probably immune-mediated inflammatory reaction against nerve fibres of the brachial plexus
• Wallerian degeneration and proximal conduction block are seen

Incidence / Prevalence

• In the US is over 1 case per 100,000 person-years
• M: F = 3:1, any age (young adults especially)

Key Clinical Features

• Sudden onset unremitting constant shoulder pain (right > left, occasionally bilateral)
• Acute onset of excruciating unilateral (R>L, 10% bilateral) shoulder pain, followed by flaccid paralysis and wasting of shoulder and parascapular muscles several days later
• Check for scapular winging (early sign of muscle weakness), long thoracic nerve of Bell
• Pain maximal at onset, atypical in nature, but often exacerbated (initially) by shoulder movement.Generally not pleuritic
• Numbness (sometimes myotome and dermatome differ) not very prominent
• Possible rtecent drugs / trauma / bugs as trigger
• Weakness, maximal at onset, several days after onset pain. Typically involves rotator cuff muscles and deltoid
• Phrenic nerve or cranial nerve involvement very rare

Investigations

• Consider shoulder views to exclude calcific tendonitis
• CXR to exclude sarcoidosis or mitotic disease
• FBC, ESR, inflam. markers & autoantibodies (connective tissue disease)?
• HIV if at risk history
• Consider MRI to exclude cervical radiculopathy
• Consider EMG studies (looking for denervation and proximal block and exclude amyotrophic lateral sclerosis)

Treatment and management

• NSAIDs (± opiates in acute setting)
• Consider neuropathic pain medications (e.g. TCADs)
• Physiotherapy (important to m,aintain shoulder ROM)

Prognosis

80% recover functionally by 2 years; 90% by 3 years.

Red flags and pitfalls