- Painful weakness of shoulder muscles (with atrophy). Beware radiculopathy or cord pathology.
- Brachial neuritis (BN) is a rare syndrome affecting LMN of brachial plexus.
- Acute onset of excruciating unilateral shoulder pain, followed by flaccid paralysis of shoulder and parascapular muscles several days later.
- 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)
- Pain max at onset. No specific exacerbating factors. (? recent drugs / bugs as trigger)
- Weakness, maximal at onset, several days after onset pain. Typically involves rotator cuff muscles and deltoid.
- Muscle wasting early
- Sometimes vague numbness of proximal area
- Phrenic nerve or cranial nerve involvement very rare
- Consider shoulder views to exclude calcific tendonitis
- CXR to exclude sarcoidosis or mitotic disease
- Consider MRI to exclude cervical radiculopathy
- Consider referral to neurophysiologist for EMG studies (looking for denervation and proximal block)
Treatment and management
- NSAIDS (± opiates in acute setting)
80% recover functionally by 2 years; 90% by 3 years.
Red flags and pitfalls
- Acute Poliomyelitis, Amyotrophic Lateral Sclerosis
- Frozen shoulder
- Biceps tendonitis or Rotator Cuff Disease
- Cervical Disc Disease or Mononeuritis Multiplex
- Human immunodeficiency virus (HIV)
- Pack palsy
- Polymyalgia rheumatica
- Sarcoidosis and other granulomatous infiltration