Updated: 6/4/2021

Brachial Neuritis (Parsonage-Turner Syndrome)

Review Topic
  • summary
    • Brachial neuritis (Parsonage-Turner syndrome) is an uncommon disorder characterized by severe shoulder pain followed by patchy muscle paralysis and sensory loss involving the shoulder girdle and upper extremity.
    • Diagnosis is made clinically with a through neurological exam that may vary from moderate motorsensory changes to flaccid paralysis of the upper extremity and can be confirmed by EMG/NCS.
    • Treatment is observation and pain control with recovery taking up to 3 years. Operative nerve exploration, neurolysis, nerve transfer or tendon transfer be be indicated if there is no evidence of EMG recovery by 9-12 months.
  • Epidemiology
    • Incidence
      • 1.6-3 cases per 100,000 persons reported per year
        • likely at least 30 cases per year (underdiagnosed)
    • Demographics
      • males > females (range 1.5:1 to 11.5:1)
      • middle-age (4th decade)
        • ages 20-60 most common (average age 41), though any age can be affected (range 3-81 years old)
      • unilateral involvement
        • bilateral in 10-30% of patients (16% simultaneously)
  • Etiology
    • Two clinical types
      • idiopathic neuralgic amyotrophy (INA) (this topic)
      • hereditary neuralgic amyotrophy (HNA) (see associated conditions)
    • Various eponyms for this syndrome include:
      • scapular winging (when long thoracic nerve involved)
      • neuralgic amyotrophy (NA) or idiopathic neuralgic amyotrophy (INA)
      • Parsonage-Turner syndrome (PTS)
      • acute brachial neuropathy / neuritis / plexopathy / plexitis
      • idiopathic brachial plexus neuropathy / neuritis
    • Pathophysiology
      • pathoanatomy
        • any nerve or branch within the brachial plexus can be involved
          • nerves outside the brachial plexus are affected in 17% of cases
        • nerves most commonly affected
          • long thoracic nerve - can cause scapular winging
          • suprascapular nerve
          • axillary nerve
          • musculocutaneous nerve
          • radial nerve
          • other: cervical roots, anterior interosseous nerve (AIN), posterior interosseous nerve (PIN), lateral antebrachial cutaneous nerve (LABC)
      • pathophysiology
        • unclear etiology for idiopathic type, likely multifactorial with autoimmune, genetic, infectious, environmental and biomechanial processes all playing a role
          • autoimmune
            • increased blastogenic activity of lymphocytes
              • transform to larger more active lymphocytes when in contact with brachial plexus tissue
            • increased complement-fixing antibodies to peripheral nerve myelin
          • biomechanical
            • mobility of the upper trunk predisposes to wear-and-tear on the blood-nerve barrier in this region
            • repetitive mobilization of the upper extremity (strenuous exercise, heavy manual labor) may disrupt the blood-nerve barrier that normally prevents immune factors from contacting the peripheral nerve system
        • ultimately, a constellation of processes results in an inflammatory response involving the brachial plexus and its branches
      • risk factors
        • infection
          • viral infections (25-55%)
            • Ebstein-Barr (EBV), varicella-zoster, Coxsackie B, parvovirus B19, cytomegalovirus (CMV), mumps, smallpox, HIV
          • bacterial infections
            • Leptospira, TB, Yersinia, Salmonella, Borrelia burgdorferi
        • immunizations (15%)
          • Tetanus, hepatitis B
        • stress
          • perioperative and peripartum (14%)
          • strenuous exercise (8%)
          • burns
        • drugs
          • abacavir, streptokinase, heroin, infliximab, interferon
        • iatrogenic
          • interscalene block, surgery, lumbar punctures, irradiation
    • Associated conditions
      • hereditary neuralgic amyotrophy (HNA)
        • very rare
          • ~200 families worldwide
        • autosomal dominant
        • mutations in the gene septin 9 on chromosome 17q24
          • cytoskeleton protein highly expressed in glial cells in neuronal tissue
        • differs from idiopathic form by
          • dysmorphic features
            • short stature, hypotelorism, cleft palate, facial asymmetry, unusual skin folds
          • higher incidence of recurrent episodes
            • precipitated similarly to those with INA
          • younger age of onset
            • childhood and adolescent (average age 28)
          • frequent involvement of nerves outside the brachial plexus (56%)
            • most commonly lower cranial nerves (CN VII, IX, X, XI and XII)
            • other: lumbosacral plexus, phrenic and recurrent laryngeal nerves
          • more severe paresis
          • worse functional outcome
  • Classification
      •  Idiopathic Neuralgic Amyotrophy (INA) vs. Hereditary Neuralgic Amyotrophy (HNA)
      • Factor
      • INA
      • HNA
      • Incidence
      • 1-30/100,000/yr
      • Rare
      • Gene
      • Septin 9 (chromosome 17)
      • Age at Onset
      • Middle-age (20-60 y/o)
      • Young (20s)
      • Recurrence
      • Uncommon (~1.5 episodes)
      • More frequent (3.5 episodes)
      • Appearance
      • Normal features
      • Dysmorphic
      • Involvement of Nerves outside Brachial Plexus
      • Uncommon (17%)
      • Common (56%)
  • Presentation
    • History
      • phase I: sudden onset of severe, unrelenting shoulder pain
        • primary symptom in 90% of cases
        • radiates to the proximal arm and/or neck
        • awakens people from sleep
        • lasts days to weeks
          • persists longer in males (45 days vs. 23 days in females)
      • phase II: painless flaccid paralysis
        • after the onset of pain, a period of weakness begins within 24 hours (33%) to 4 weeks (80%)
        • most commonly involves the upper brachial plexus and usually more than one nerve branch
          • deltoid, supraspinatus, infraspinatus, serratus anterior and the biceps brachii
          • often will see differential involvement of muscles innervated by the same nerve (patchy paresis)
            • highly characteristic finding
      • phase III: slow recovery
        • slow and steady return of motor function over 6-18 months
        • duration over the recovery phase is often directly proportional to duration of pain phase at onset
    • Physical examination
      • fasciculations and atrophy may be seen
        • signs of dennervation
      • during the painful phase, the pain is not particularly affected by motion or palpation
      • severe weakness of shoulder external rotation and abduction
        • supraspinatus, infraspinatus and deltoid dysfunction
        • hypotonia and areflexia
          • signs of lower motor neuron involvement
      • medial scapular winging
        • serratus anterior (long thoracic nerve) involvement
      • sensory changes occur in 78% of patients
        • paresthesias and hypoesthesias most common
        • over deltoid, lateral arm and radial forearm
        • may go unnoticed by patient due to overlying pain and weakness
      • autonomic dysregulation occur in 15% of patients
        • trophic skin changes
        • temperature dysregulation
        • increased sweating
        • altered nail/hair growth
  • Evaluation
    • Diagnostic tests can help rule out other conditions and thus support the diagnosis of INA
    • Laboratory
      • CBC and ESR are usually normal
      • labs are largely inconclusive, but may show
        • elevated liver enzymes
        • positive antiganglioside antibodies
        • positive antinuclear antibody (ANA) test
    • Imaging
      • plain radiographs
        • often normal
        • evaluate for calcific tendinitis of the rotator cuff
          • can also present with severe, incapacitating shoulder pain
      • magnetic resonance imaging (MRI)
        • early findings
          • T2: diffuse signal hyperintensity (edema) within muscles innervated by the brachial plexus
            • supraspinatus, infraspinatus, deltoid and teres minor muscles most commonly exhibit MRI abnormalities
        • late findings
          • T1: focal intramuscular signal intensity (fatty infiltration) and atrophy of the involved muscles
    • Other studies
      • electromyography (EMG)
        • helpful to confirm the diagnosis
          • show findings compatible with INA in 96% of patients
        • findings
          • early (3-4 weeks after symptom onset)
            • acute dennervation with positive sharp waves and fibrillation potentials in both peripheral nerve and nerve root distributions
          • late (3-4 months after symptom onset)
            • chronic dennervation and early reinnervation with polyphasic motor unit potentials
      • sensory nerve conduction studies (NCS)
        • less useful than EMG
        • findings
          • reduced amplitude, preserved conduction velocity and distal latency
          • may be normal
            • normal NCS does not preclude diagnosis of INA
      • cerebrospinal fluid (CSF) analysis
        • findings
          • usually normal
          • mildly elevate protein levels, slight pleocytosis and oligoclonal bands have been reported
  • Differential
    • Cervical spine radiculopathy
      • pain and weakness follows a specific nerve root distribution
        • INA involves multiple nerve roots and peripheral nerve distributions
      • starts in the neck and radiates down the arm
        • INA involves the shoulder and occasionally radiates to the neck and proximal arm
      • pain is aggravated by movement
        • in the acute pain phase, motion does not tend to worsen pain
    • Rotator cuff pathology
      • shoulder pain persists despite development of shoulder weakness
        • in INA, shoulder weakness tends to develop after acute pain phase and is often painless
      • impingement signs are often present
      • pain usually resolves or improves with subacromial lidocaine injection
        • subacromial lidocaine injection does not affect INA pain, as the pain is neuropathic and not related to impingement
    • Entrapment neuropathy
      • shoulder pain with progressive weakness in a specific peripheral nerve distribution (ex. supraspinatus and infraspinatus weakness with suprascapular nerve entrapment)
        • INA usually involves the upper brachial plexus, affecting muscles from multiple peripheral nerve distributions (ex. supraspinatus, infraspinatus, deltoid and biceps weakness)
      • EMG shows involvement of an isolated peripheral nerve
        • EMG in INA shows involvement of nerve roots and peripheral nerves
    • Idiopathic hypertrophic brachial neuritis (IHBN)
      • rare disorder characterized by weakness in upper limb muscles and hypertrophy of the brachial plexus
        • brachial plexus hypertrophy can be seen on MRI
      • typically painless
        • INA begins with acute painful phase, followed by painless weakness
      • EMG and NCS exhibit demyelination (slowed velocity, prolonged distal sensory latencies)
        • NCS in INA shows reduced amplitude related to axonal loss, but preserved conduction velocity and distal sensory latencies (no demyelination)
  • Treatment
    • Nonoperative
      • observation and pain control
        • indications
          • mainstay of treatment
        • technique
          • during the early pain phase, pain control is paramount
            • NSAIDs
            • judicious use of narcotic medications
            • immobilization
            • oral corticosteroids (see below)
          • follow patients monthly for improvement
            • can use both physical exam and serial EMGs to follow neurologic recovery
        • outcomes
          • at 1 year, observation alone results in similar functional outcomes compared to observation with physical therapy
          • prognosis is good with most patients making a complete recovery, but progress is slow
            • at 1 year, only 35% of patients have recovered
            • at 3 years, 90% of patients have recovered full muscle strength and function with no residual pain or deficits
      • physical therapy
        • indications
          • once severe pain has abated and weakness is the primary issue
        • technique
          • shoulder girdle strengthening and range of motion
          • pain relief strategies to alleviate traction on the involved nerves
        • outcomes
          • reverses atrophy and improves muscle bulk comparable to contralateral unaffected side
      • oral corticosteroids
        • indications
          • severe pain during early pain phase
        • technique
          • two week course of 1mg/kg/day of prednisone followed by a two week taper
        • outcomes
          • some evidence that this regimen may lead to a more rapid resolution of the pain phase, but does not affect the progression or prognosis
    • Operative
      • nerve exploration, neurolysis, neurorrhaphy, nerve grafting, nerve transfer or muscle/tendon transfers
        • indications
          • no evidence of regeneration or early recovery in a nerve distribution by 6-9 months on physical examination and EMG studies
        • technique
          • neurolysis
            • long thoracic nerve microneurolysis
            • ulnar nerve transposition, Guyon canal release
            • radial tunnel release
            • carpal tunnel release
          • neurorrhaphy and nerve grafting
            • excision of diseased nerve segment and either direct repair (neurorrhaphy) or nerve grafting
          • nerve transfers
          • muscle / tendon transfers
            • split pectoralis major transfer for serratus anterior paralysis
        • outcomes
          • surgical exploration of patients with INA without neurologic recovery revealed hourglass-like constrictions in the peripheral nerves with no external compression
            • neurolysis alone was superior to neurorrhaphy and nerve grafting
  • Prognosis
    • Recurrence is rare in non-hereditary cases
    • Factors associated with poor prognosis
      • female gender
      • lower trunk involvement
        • upper trunk has best prognosis
      • persistent pain and no motor function recovery by 3 months
      • hereditary cases
    • Age has no effect on prognosis
    • Timing of recovery
      • 66% have recovery of motor function within 1 month
      • recovery rated "excellent" in 36% at 1 year, 75% at 2 years and 89% at 3 years
      • may take up to 8 years for full recovery of strength
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Questions (5)

(OBQ19.92) A 43 year-old male presents to your clinic with 3 months of pain and weakness to his right shoulder. One month ago his primary care physician performed multiple injections to his shoulder which did not help him. Before his shoulder problems began he had a minor upper respiratory illness but he is otherwise healthy. He has a normal cervical spine examination. His shoulder has the clinical appearance shown in Figure A. He has marked atrophy about the shoulder musculature and demonstrates flaccidity with any attempted range of motion. What is his diagnosis?

QID: 213994

Amyotrophic lateral sclerosis



Frozen shoulder



Long thoracic nerve palsy



Rotator cuff tear



Upper trunk neuralgic amyotrophy



L 3 A

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