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PubMed This is a summary of 14 peer-reviewed journal articles Updated
Neurology

The Attack on Your Nerves: Understanding Symptoms and Biology

At a Glance

Neuralgic Amyotrophy (NA) is an immune-mediated condition characterized by a unique two-phase timeline. It begins with an acute phase of severe, relentless pain caused by nerve inflammation, which subsequently transitions into profound muscle weakness and atrophy as the pain subsides.

Neuralgic Amyotrophy (NA) can feel like two different conditions happening one after the other. Understanding the biology of this “attack” and the timeline it follows can help you navigate the transition from intense pain to muscle weakness.

The Biphasic Timeline: From Pain to Weakness

The hallmark of NA is its biphasic (two-phase) nature. It is crucial to understand that the appearance of weakness is part of the original injury, not a new problem [1][2].

  1. Phase 1: The Acute Pain Phase: This phase usually starts with an explosion of severe, relentless pain, often at night [2]. This pain typically lasts for an average of 3 weeks [2]. It is the result of active inflammation where your immune system is attacking the nerve fibers [1][3].
  2. Phase 2: The Weakness and Atrophy Phase: As the intense pain begins to fade, it is replaced by neurological “deficits”—specifically weakness and atrophy (muscle wasting) [1][4]. Many patients find this phase just as scary as the pain, but it is the natural consequence of the nerve damage that occurred during the first phase [1][3].

The Biology: An Immune System Mistake

The underlying cause of NA is an immune-mediated inflammatory response [1][3]. Essentially, your immune system—often triggered by a virus, surgery, or vaccination—mistakenly identifies your nerves as a threat and attacks them [5][6]. This attack causes:

  • Axonal Damage: The “axons” are the long wires inside your nerves that carry electrical signals. When they are damaged, the signals to your muscles are cut off [1].
  • Hourglass Constrictions: In some cases, the inflammation is so localized that the nerve develops a tight, narrow spot that looks like an hourglass on an ultrasound or specialized MRI [7][8]. These constrictions can physically block the nerve from healing on its own [9].

Common Nerve Targets and What They Look Like

While NA can affect any nerve in the arm or shoulder, certain nerves are targeted more often than others:

Affected Nerve Common Symptoms Physical Sign Diagnostic Notes
Long Thoracic Nerve Difficulty stabilizing the shoulder Scapular Winging: The shoulder blade sticks out like a wing [1]. Often noticeable when pushing against a wall.
Suprascapular Nerve Deep ache and weakness when lifting the arm out to the side Visible hollow or “dent” in the muscle above the shoulder blade [1]. Can mimic a rotator cuff tear.
Anterior Interosseous Nerve Difficulty with fine motor tasks in the hand Inability to make a perfect “OK” sign with the thumb and index finger [10]. Purely a motor nerve; causes no numbness.
Phrenic Nerve Shortness of breath, especially when lying flat (orthopnea) Difficulty breathing or getting a full breath [11][8]. Actionable Step: Ask your doctor for a “sniff test” on fluoroscopy or a diaphragm ultrasound.

The Slow Road to Recovery

Recovery from NA is a marathon, not a sprint. Because the nerves must literally regrow from the site of the injury down to the muscle, progress is measured in months and years rather than days or weeks [12][13]. While the pain subsiding is a good sign that the “attack” is over, the real work of nerve regeneration and muscle rebuilding is just beginning [1][14].

Common questions in this guide

Why does Neuralgic Amyotrophy cause both severe pain and weakness?
Neuralgic Amyotrophy follows a two-phase timeline. The initial intense pain is caused by your immune system actively attacking and inflaming your nerves. As the pain eventually fades, it is replaced by muscle weakness and atrophy, which are the physical results of the nerve damage that occurred during the first phase.
What is an hourglass constriction in a nerve?
An hourglass constriction happens when localized nerve inflammation is so severe that it creates a tight, narrow spot in the nerve. This physical pinch looks like an hourglass on medical imaging and can block electrical signals, sometimes preventing the nerve from healing on its own.
Why does my shoulder blade stick out like a wing?
This condition is known as scapular winging. It occurs when Neuralgic Amyotrophy attacks the long thoracic nerve, which is responsible for controlling the muscles that keep your shoulder blade stabilized against your back.
Can Neuralgic Amyotrophy cause shortness of breath?
Yes, if the inflammation targets the phrenic nerve, it can weaken your diaphragm. This often leads to shortness of breath, particularly when you are trying to lie flat in bed. You should ask your doctor about a diaphragm ultrasound to check your breathing muscles if you experience this.
Why does it take so long to recover from muscle weakness?
Nerve healing is a very slow process because the nerve fibers must literally regrow from the site of the injury all the way down to the affected muscles. Because of this, progress is typically measured in months or even years rather than days.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Which specific nerves in my brachial plexus appear to be most affected by the inflammation?
  2. 2.Since the pain is subsiding and the weakness is starting, is this the expected 'biphasic' transition for this condition?
  3. 3.Are there any concerns about my phrenic nerve, and should we order a diaphragm ultrasound or fluoroscopy to check my breathing muscles?

Questions For You

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References

References (14)
  1. 1

    Parsonage-Turner syndrome after COVID-19 infection.

    Voss TG, Stewart CM

    JSES reviews, reports, and techniques 2022; (2(2)):182-185 doi:10.1016/j.xrrt.2021.12.004.

    PMID: 35039808
  2. 2

    [Parsonage-Turner syndrome: Unknown but not infrequent. Apropos of 6 cases].

    Martínez Bermúdez CM, Fernández de Gea I, Yusá Cubes B, Valera Martínez H

    Rehabilitacion 2019; (53(1)):56-59 doi:10.1016/j.rh.2018.05.001.

    PMID: 30929832
  3. 3

    Clinico-diagnostic features of neuralgic amyotrophy in childhood.

    Rotondo E, Pellegrino N, Di Battista C, et al.

    Neurological sciences : official journal of the Italian Neurological Society and of the Italian Society of Clinical Neurophysiology 2020; (41(7)):1735-1740 doi:10.1007/s10072-020-04314-8.

    PMID: 32140911
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    Bilateral Brachial Neuritis after COVID-19: Case Report.

    Abdouni YA, Viamont-Guerra MR

    Revista brasileira de ortopedia 2024; (59(Suppl 2)):e173-e175 doi:10.1055/s-0042-1750756.

    PMID: 39735454
  5. 5

    Peripheral neuropathy following monkeypox infection: an unexpected diagnosis of Parsonage-Turner syndrome.

    Gerber F, Zenkhri S, Farron A, Traverso A

    BMJ case reports 2024; (17(10)) doi:10.1136/bcr-2023-258334.

    PMID: 39419600
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    A Parsonage-Turner Syndrome secondary to Parvovirus B19 infection.

    Mozzani F, Marino NG, Becciolini A, et al.

    Acta bio-medica : Atenei Parmensis 2021; (92(S1)):e2021129 doi:10.23750/abm.v92iS1.10702.

    PMID: 33944819
  7. 7

    Imaging of neuralgic amyotrophy in the acute phase.

    Ripellino P, Arányi Z, van Alfen N, et al.

    Muscle & nerve 2022; (66(6)):709-714 doi:10.1002/mus.27732.

    PMID: 36214185
  8. 8

    Imaging and treatment of phrenic nerve hourglass-like constrictions in neuralgic amyotrophy.

    Krishnan KR, Wolfe SW, Feinberg JH, et al.

    Muscle & nerve 2020; (62(5)):E81-E82 doi:10.1002/mus.27049.

    PMID: 32841403
  9. 9

    Anterior interosseous nerve and posterior interosseous nerve involvement in neuralgic amyotrophy.

    Akane M, Iwatsuki K, Tatebe M, et al.

    Clinical neurology and neurosurgery 2016; (151()):108-112 doi:10.1016/j.clineuro.2016.11.001.

    PMID: 27821298
  10. 10

    Anterior Interosseous Nerve Syndrome Reconsidered: A Critical Analysis Review.

    Krishnan KR, Sneag DB, Feinberg JH, Wolfe SW

    JBJS reviews 2020; (8(9)):e2000011 doi:10.2106/JBJS.RVW.20.00011.

    PMID: 32890049
  11. 11

    Hepatitis E: A breathtaking virus.

    van de Wardt J, Verrips A, van Griensven CHS, van Eijk JJJ

    Neurology. Clinical practice 2019; (9(5)):e39-e41 doi:10.1212/CPJ.0000000000000600.

    PMID: 31750032
  12. 12

    The electrodiagnostic natural history of parsonage-turner syndrome.

    Feinberg JH, Nguyen ET, Boachie-Adjei K, et al.

    Muscle & nerve 2017; (56(4)):737-743 doi:10.1002/mus.25558.

    PMID: 28044362
  13. 13

    Phrenic neuropathy and diaphragm dysfunction in neuralgic amyotrophy.

    van Alfen N, Doorduin J, van Rosmalen MHJ, et al.

    Neurology 2018; (91(9)):e843-e849 doi:10.1212/WNL.0000000000006076.

    PMID: 30054437
  14. 14

    Modeling of Lung Function Recovery in Neuralgic Amyotrophy With Diaphragm Impairment.

    Rice BL, Ashton RW, Wang XF, et al.

    Respiratory care 2017; (62(10)):1269-1276 doi:10.4187/respcare.05568.

    PMID: 28698264

This page explains the symptoms and biology of Neuralgic Amyotrophy for educational purposes. Always consult your neurologist or physician for an accurate diagnosis and personalized recovery plan.

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