Incidence of Neuralgic Amyotrophy (Parsonage Turner Syndrome) in a Primary Care Setting – A Prospective Cohort Study

Abstracts & Literature Review

Incidence of Neuralgic Amyotrophy

(Parsonage Turner Syndrome) in a Primary

Care Setting – A Prospective Cohort Study

Nens van Alfen, Jeroen J. J. van Eijk, Tessa Ennik, Sean O. Flynn, Inge E.

G. Nobacht, Jan T. Groothuis, Sigrid Pillen, Floris A. van de Laar

PLoS ONE. 2015;10(5):

e0128361. doi:10.1371/journal.pone.0128361; May 27. 2015

JACO Editorial Reviewer: Steven G. Yeomans, DC, FACO, DABCC

Published: September 2016

Journal of the Academy of Chiropractic Orthopedists

September 2016, Volume 13, Issue 1

The original article copyright belongs to the original publisher. This review is available from: http://www.dcorthoacademy.com © 2015 Yeomans and the Academy of Chiropractic Orthopedists. This is an Open Access article which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Authors’ Abstract:

Objective: Neuralgic amyotrophy is considered a rare peripheral nervous system disorder but in practice seems grossly under recognized, which negatively affects care for these patients. In this study we prospectively counted the one-year incidence rate of classic neuralgic amyotrophy in a primary care setting.

Methods: In a prospective cohort study during the year 2012 we registered all new cases of neck, shoulder, or arm complaints from two large primary care centers serving a population of

14,118. Prior to study, general practitioners received a short training on how to diagnose classic neuralgic amyotrophy. Neuralgic amyotrophy was defined according to published criteria irrespective of family history. Only patients with a classic phenotype were counted as definite cases. After inclusion, patients with suspected neuralgic amyotrophy who had not yet seen a neurologist were offered neurologic evaluation for diagnostic confirmation.

Results: Of the 492 patients identified with new onset neck, shoulder or arm complaints, 34 were suspected of having neuralgic amyotrophy. After neurologic evaluation the diagnosis was confirmed in 14 patients. This amounts to a one-year incidence rate for classic neuralgic amyotrophy of 1 per 1000.

Conclusions: Our findings suggest that neuralgic amyotrophy is 30-50 times more common than previously thought. Unawareness of the disorder and its clinical presentation seems the most likely explanation for this difference. An incidence rate of 1 per 1000 and the long-term sequelae many patients suffer warrant more vigilance in diagnosing the disorder, to pave the way for timely treatment and prevent complications.

Clinical Relevance

This study suggests that neuralgic amyotrophy is much more common than that previously thought/reported and should be considered when patients present with radiating neck pain to the upper extremity.

JACO Editorial Summary

  • This article was written by authors primarily from the Netherlands (where the study took place) with one author from Ireland.
  • Neuralgic amyotrophy or NA (a.k.a. Parsonage Turner syndrome or brachial plexus neuritis) is a distinct type of peripheral neuropathy, with one or more episodes of acute, severe pain in the upper extremity which is quickly followed by multifocal paresis with a slow 1-2 year recovery time of which a large subset become disabled (estimated at 25% of NA cases in this study).
  • Diagnostic difficulty is common (about 30% of the cases) due to the high variance in clinical presentations such as painless episodes and lower brachial plexus, or other peripheral nerve involvement.
  • In about 70%, the “classic presentation” is: acute shoulder region pain followed by scapular winging, weakness in shoulder abduction, external rotation, grip/pinch strength, and forearm pronation.
  • The cause is thought to be autoimmune but difficulty proving this has occurred most commonly due to delay in diagnosis (median time: 11 weeks) and hence, difficulty randomizing subjects to corticosteroids or IV gammaglobuline groups.
  • This study changes the prior incidence rate estimate from 1-3/100,000 per year to 1 in 1000 (30-50 times more frequent for the “classic presentation.”
  • History criteria: 1) New / subacute onset of uni- or bilateral shoulder pain; 2) NRS pain score of ≥7/10; 3) History of weakness with abnormal shoulder ROM (abduction, ER, FFL); 4) When ≥3 weeks post-onset: Paresis of the long thoracic, suprascapular, and anterior interosseous nerves; 5) Slow recovery.
  • Physical exam criteria: 1) Scapular winging/dyskinesia; 2) Signs of muscle atrophy; 3) Weakness of shoulder abduction, external rotation, serratus anterior, forearm pronation and/or pinch strength.
  • Probable reasons for “missing” this diagnosis: 1) Diagnostic unfamiliarity (many physicians simply do not know about it); 2) Given it’s rarity, it’s simply not considered as a differential diagnosis; 3) Many physicians don’t look at scapular stability, don’t perform a detailed neurological exam of all the upper extremity muscles, and/or don’t “tie” the findings of NA together.
  • The ratio of classic NA to that of other disorders in this study was 3% or, 1 in every 33 patients with a new onset of neck, shoulder, or arm complaints in a primary care setting will have NA (this compares to 47% or 1 in 2 patients that were diagnosed with shoulder pathology; 15x more common).
  • An incidence rate of 1 per 1000 per year suggests NA is NOT “rare” which is defined as 1 per 2000 per year. This equates to 17,000 new cases per year in the Netherlands.
  • Table 4: Points that lead to a correct diagnosis
    • Any patient with 1) acute onset, 2) severe pain (≥7/10), 3) Analgesic resistant shoulder &/or upper arm pain
    • Pain worse at night and still severe at rest
    • Multifocal motor/sensory losses that can be bilateral but asymmetrical
    • PE: Remove clothing – inspect/palpate shoulder/arms for scapular asymmetry and muscle atrophy
    • Look for scapular motion dyskinesia during slow abduction, FFL (video clips available)
    • Test/compare bilaterally the strength of the serratus anterior, shoulder external rotation, long thumb and index finger flexors (pinch), forearm pronation: Any weakness found in combination is suspect for NA and rare in other disorders with similar presentations
  • Periscapular weakness and a pain score of ≥7/10 are needed as “minimums.”
  • Training of primary care physicians (PCP’s) in two, 1-hour teaching sessions followed by a simple diagnostic protocol led to a 3-fold increase of identifying NA (confirmed by an experienced neurologist).
  • Limitations in the study include: 1) All PCP’s involved were aware of the study goal (which can lead to bias); 2) They did not systematically refer every patient with suspected NA for neurological examination &/or ancillary tests (EMG, cervical MRI)
    • There is no “gold standard” test to confirm NA; the diagnosis is made by adhering to clinical criteria (history/examination).
  • Recommendation: Every PCP be given a short educational program on NA, confirm suspected cases with a neurologist, in order to pave the way for acute phase immunomodulating therapy trials to prevent long-term complications

Summary

The results of this investigation should raise awareness of all health care providers that treat neuromusculoskeletal disorders that: 1) NA is not rare; 2) Diagnosis is clinical, NOT reliant on expensive diagnostic tests; 3) A prompt diagnosis can help to avoid the common (25% incidence) long-term disability associated with NA, i.e., to improve clinical outcomes.

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