Updated: 3/8/2018

Brachial Neuritis (Parsonage-Turner Syndrome)

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Introduction
  • An uncommon disorder characterized by severe shoulder pain followed by patchy muscle paralysis and sensory loss involving the shoulder girdle and upper extremity. 
    • 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
  • 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)
  • 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
  • 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
Classification
 
Factor
Idiopathic Neuralgic Amyotrophy (INA)
Hereditary Neuralgic Amyotrophy (HNA)
Incidence
1-30/100,000/yr
Rare
Gene - Septin 9 (c'some 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 Diagnosis
  • 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, slow-release
          • 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
 

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