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Muscle & nerve2019; 60(6); 762-768; doi: 10.1002/mus.26699

Assessing pathological changes within the nucleus ambiguus of horses with recurrent laryngeal neuropathy: An extreme, length-dependent axonopathy.

Abstract: Equine recurrent laryngeal neuropathy (RLN) is a naturally occurring model of length-dependent axonopathy characterized by asymmetrical degeneration of recurrent laryngeal nerve axons (RLn). Distal RLn degeneration is marked, but it is unclear whether degeneration extends to include cell bodies (consistent with a neuronopathy). With examiners blinded to RLN severity, brainstem location, and side, we examined correlations between RLN severity (assessed using left distal RLn myelinated axon count) and histopathological features (including chromatolysis and glial responses) in the nucleus ambiguus cell bodies, and myelinated axon count of the right distal RLn of 16 horses. RLN severity was not associated with RLn cell body number (P > .05), or degeneration. A positive correlation between the left and right distal RLn myelinated axon counts was identified (R = 0.57, P < .05). We confirm that RLN, a length-dependent distal axonopathy, occurs in the absence of detectable neuronopathy.
© 2019 Wiley Periodicals, Inc.
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Publication Date: 2019-10-09 PubMed ID: 31498901DOI: 10.1002/mus.26699Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research examined the pathological changes in a specific area of the brainstem (nucleus ambiguus) in horses with a nerve disease called Equine recurrent laryngeal neuropathy (RLN) – a disorder where certain nerves of the larynx degrade. The study found that the severity of this condition was not related to nerve cell numbers or their degeneration, but there was a significant association between the counts of degraded nerve fibers in the left and right laryngeal nerves.

Understanding the Research Context

  • The researchers are studying a condition known as Equine recurrent laryngeal neuropathy (RLN), a nerve disorder typically observed in horses, characterized by asymmetrical degeneration of recurrent laryngeal nerve axons. The condition is considered a naturally occurring model of a class of diseases called ‘length-dependent axonopathies’ which primarily affect the longest nerve fibers.
  • Previous studies established that the distal (or end) parts of the RLn nerve fiber are markedly degenerated in horses with RLN. However, it wasn’t clear whether this condition also involves the degeneration of nerve cell bodies, which would then classify it as a neuronopathy. In the current study, the researchers addressed this question.

Methodology of the Study

  • They focused on the nucleus ambiguus, a region in the brainstem, and examined the pathological changes (histopathological features) in the cell bodies residing in that area as well as the axon counts in the right distal RLn.
  • The study involved 16 horses and examiners were blinded to RLN severity, brainstem location, and the side of the horse that was examined to reduce biases.
  • The severity of RLN was measured based on the count of myelinated axons (nerve fibers wrapped with an insulating layer) in the left distal RLn.

Key Findings of the Study

  • Contrary to what might be suspected, the study shows that the severity of RLN in horses is not associated with the number of nerve cells in the affected region or their degeneration, meaning that RLN does not appear to be a form of neuronopathy.
  • The researchers did find, however, a positive correlation between the count of affected nerve fibers in the left and right distal RLns, supporting the notion that RLN is a length-dependent distal axonopathy, a disease that primarily affects the lengthiest segments of the nerve fibers.

Cite This Article

APA
Draper ACE, Cahalan SD, Goodwin D, Perkins J, Piercy RJ. (2019). Assessing pathological changes within the nucleus ambiguus of horses with recurrent laryngeal neuropathy: An extreme, length-dependent axonopathy. Muscle Nerve, 60(6), 762-768. https://doi.org/10.1002/mus.26699

Publication

Muscle & nerve
ISSN: 1097-4598
NlmUniqueID: 7803146
Country: United States
Language: English
Volume: 60
Issue: 6
Pages: 762-768

Researcher Affiliations

Draper, Alexandra C E
  • Comparative Neuromuscular Disease Laboratory, Department of Clinical Sciences and Services, Royal Veterinary College, University of London, London, UK.
Cahalan, Stephen D
  • Comparative Neuromuscular Disease Laboratory, Department of Clinical Sciences and Services, Royal Veterinary College, University of London, London, UK.
Goodwin, David
  • Comparative Neuromuscular Disease Laboratory, Department of Clinical Sciences and Services, Royal Veterinary College, University of London, London, UK.
Perkins, Justin
  • Comparative Neuromuscular Disease Laboratory, Department of Clinical Sciences and Services, Royal Veterinary College, University of London, London, UK.
Piercy, Richard J
  • Comparative Neuromuscular Disease Laboratory, Department of Clinical Sciences and Services, Royal Veterinary College, University of London, London, UK.

MeSH Terms

  • Animals
  • Atrophy
  • Cell Body / pathology
  • Cell Count
  • Horses
  • Medulla Oblongata / pathology
  • Nerve Fibers, Myelinated / pathology
  • Neurons / pathology
  • Recurrent Laryngeal Nerve / pathology
  • Recurrent Laryngeal Nerve / physiopathology
  • Vocal Cord Paralysis / pathology
  • Vocal Cord Paralysis / physiopathology

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Citations

This article has been cited 1 times.
  1. Al Shehab G, Naji R, Alali F, Alali A, Allowaim A, Almohammed A, Aljasim D, Alkhalifah A, Alhammad YMA, Marzok M, Mohamad ZA, Almuhanna AH. Laryngoscopic evaluation of arytenoid movements in pure Arabian horses. Open Vet J 2025 Jun;15(6):2875-2881.
    doi: 10.5455/OVJ.2025.v15.i6.56pubmed: 41069487google scholar: lookup
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