FREE SHIPPING over $40
OVER 10000 FIVE-STAR REVIEWS
5% OFF ALL SUBSCRIPTIONS
100% HAPPINESS GUARANTEE
Analyze Diet
0
Veterinary surgery : VS2026; doi: 10.1111/vsu.70083

Functional and histopathologic evidence of laryngeal reinnervation using the spinal accessory nerve in horses.

Abstract: To evaluate functional and histopathologic outcomes of standing selective laryngeal reinnervation using the spinal accessory nerve (SAN) in horses with experimentally induced recurrent laryngeal neuropathy (RLN). Methods: Five Thoroughbred mares. Methods: Prospective cohort study. Methods: The horses underwent left recurrent laryngeal neurectomy followed 8 weeks later by selective laryngeal reinnervation using the SAN. Follow-up evaluations at 4.5, 6, 8, and 12 months included treadmill exercising endoscopy, ultrasonography of intrinsic laryngeal muscles, and percutaneous electrical stimulation of the SAN. Twelve months postoperatively, the horses were euthanized for macroscopic and histopathologic examination of the cricoarytenoideus dorsalis (CAD), cricoarytenoideus lateralis (CAL), sternomandibularis (SM), spinal accessory and recurrent laryngeal nerves. Results: Twelve months following laryngeal reinnervation, mean left-to-right quotient angle ratio (LRQ) recovered to 94% of predenervation values with no difference from the baseline (95% CI [90, 98]; p = .69). One horse exhibited a slower and incomplete recovery. Post-mortem examination confirmed successful spinal accessory nerve implantation in the left CAD muscle in all horses. Histopathologic examination revealed axonal regeneration of the spinal accessory nerve and reinnervation of the left lateral CAD muscle belly with fiber type grouping and a shift toward an increased proportion of type I fibers consistent with functional reinnervation. Conclusions: Selective laryngeal reinnervation using the spinal accessory nerve restored functional arytenoid abduction at exercise in 4/5 horses with experimentally induced RLN. Conclusions: In horses with RLN and mild to moderate CAD muscle atrophy, selective laryngeal reinnervation using the SAN represents a physiological and effective treatment option.
© 2026 American College of Veterinary Surgeons.
Get Full Text
Publication Date: 2026-02-18 PubMed ID: 41705478DOI: 10.1111/vsu.70083Google Scholar: Lookup
The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
LinkedInCopy
  • Journal Article

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.

Overview

  • The study investigated the effectiveness of using the spinal accessory nerve (SAN) to restore function in horses suffering from induced recurrent laryngeal neuropathy (RLN), a nerve condition that impairs breathing by affecting the larynx.
  • The researchers evaluated both functional recovery and tissue-level changes after reinnervation surgery in experimental horses over a one-year period.

Background and Purpose

  • Recurrent laryngeal neuropathy (RLN) in horses causes paralysis of the left arytenoid cartilage, impairing airway function during exercise.
  • The cricoarytenoideus dorsalis (CAD) muscle, responsible for opening the airway, becomes paralyzed due to nerve damage.
  • This study aimed to test if selectively reconnecting the CAD muscle to the spinal accessory nerve (SAN)—a different nerve—can restore muscle function and improve airway performance.

Methods

  • Subjects: Five Thoroughbred mares were used in a controlled, prospective setup.
  • Procedure:
    • First, the left recurrent laryngeal nerve was surgically cut (neurectomy) to induce RLN-like paralysis.
    • Eight weeks later, selective laryngeal reinnervation surgery was performed to connect the SAN to the left CAD muscle.
  • Follow-up assessments were conducted at 4.5, 6, 8, and 12 months including:
    • Treadmill endoscopy during exercise to observe airway function and arytenoid cartilage movement.
    • Ultrasonography to image intrinsic laryngeal muscles.
    • Electrical stimulation of the SAN to test nerve-muscle connectivity.
  • At 12 months post-surgery, horses were euthanized for detailed tissue examination:
    • Macroscopic evaluation of nerve and muscle structures.
    • Histopathology focusing on nerve regeneration and muscle fiber changes.

Results

  • Functional Recovery:
    • Four out of five horses showed near-complete recovery of arytenoid movement during exercise, with the left-to-right arytenoid abduction ratio reaching 94% of original baseline values.
    • One horse had slower and incomplete recovery, indicating some variability in surgical or biological response.
  • Post-Mortem Findings:
    • Successful integration of the SAN into the left CAD muscle was confirmed visually in all horses.
    • Histological analysis showed:
      • Axonal regeneration of the spinal accessory nerve fibers into the CAD muscle.
      • Muscle reinnervation evidenced by fiber type grouping—a sign that nerve fibers had re-established control over muscle fibers.
      • A shift toward more type I muscle fibers, which are associated with endurance and improved muscle function.

Conclusions and Implications

  • Selective laryngeal reinnervation using the spinal accessory nerve effectively restores functional movement of the arytenoid cartilage in horses with RLN, especially when muscle atrophy is mild to moderate.
  • This approach offers a physiological alternative to current treatments, potentially improving respiratory function during exercise.
  • The evidence supports the capacity for nerve regeneration and muscle fiber adaptation following this surgical intervention, demonstrating both functional and structural recovery.

Cite This Article

APA
Campos Schweitzer A, Mespoulhes-Rivière C, Perkins JD, Ducharme NG, Piercy RJ, Lynch N, Rossignol F. (2026). Functional and histopathologic evidence of laryngeal reinnervation using the spinal accessory nerve in horses. Vet Surg. https://doi.org/10.1111/vsu.70083

Publication

Veterinary surgery : VS
ISSN: 1532-950X
NlmUniqueID: 8113214
Country: United States
Language: English

Researcher Affiliations

Campos Schweitzer, Ariane
  • Grosbois Equine Clinic, Boissy-Saint-Léger, France.
Mespoulhes-Rivière, Céline
  • National Veterinary School of Alfort, Equine Referral Hospital, Maisons-Alfort and Goustrainville, France.
  • Royal Veterinary College, Equine Referral Hospital, Hatfield, UK.
Perkins, Justin D
  • Royal Veterinary College, Equine Referral Hospital, Hatfield, UK.
Ducharme, Norm G
  • Equine Referral Hospital, Cornell University, Ithaca, New York, USA.
Piercy, Richard J
  • Royal Veterinary College, Equine Referral Hospital, Hatfield, UK.
Lynch, Nicola
  • Comparative Neuromuscular Diseases Laboratory, Royal Veterinary College, London, UK.
Rossignol, Fabrice
  • Grosbois Equine Clinic, Boissy-Saint-Léger, France.

Grant Funding

  • Sport Horse Research Foundation Inc.
  • European College of Veterinary Surgeons (ECVS)

References

This article includes 46 references
  1. Draper ACE, Piercy RJ. Pathological classification of equine recurrent laryngeal neuropathy. J Vet Intern Med 2018;32(4):1397‐1409.
  2. Duncan ID, Griffiths IR, McQueen A, Baker GJ. The pathology of equine laryngeal hemiplegia. Acta Neuropathol 1974;27:337‐348.
  3. Dixon PM, McGorum BC, Railton DI. Clinical and endoscopic evidence of progression of 152 cases of equine recurrent laryngeal neuropathy (RLN). Equine Vet J 2002;34:29‐34.
  4. Derksen FJ, Stick JA, Scott EA, Robinson NE, Slocombe RF. Effect of laryngeal hemiplegia and laryngoplasty on airway flow mechanics in exercising horses. Am J Vet Res 1986;47:16‐20.
  5. Cramp P, Barakzai SZ. Surgical management of recurrent laryngeal neuropathy. Equine Vet Educ 2012;24:307‐321.
  6. Luedke LK, Cheetham J, Mohammed HO, Ducharme NG. Management of postoperative dysphagia after prosthetic laryngoplasty or arytenoidectomy. Vet Surg 2020;49(3):529‐539.
  7. Speirs VG, Bourke JM, Anderson GA. Assessment of the efficiency of an abductor muscle prosthesis for the treatment of laryngeal hemiplegia in horses. Aust Vet J 1983;60:294‐299.
  8. Dixon PM, McGorum BC, Railton DI. Long‐term survey of laryngoplasty and ventriculocordectomy in an older, mixed‐breed population of 200 horses. Part 1: Maintenance of surgical arytenoid abduction and complications of surgery. Equine Vet J 2003;35:389‐396.
  9. Hawkins JF, Tulleners EP, Ross MW. Laryngoplasty with or without ventriculectomy for treatment of left laryngeal hemiplegia in 230 racehorses. Vet Surg 1997;26:484‐491.
  10. Marie JP. Contribution à l’étude de la réinnervation laryngée expérimentale: intérêt du nerf phrénique. 1999.
  11. Swanson AN, Wolfe SW, Khazzam M, Feinberg J, Ehteshami J, Doty S. Comparison of neurotization versus nerve repair in an animal model of chronically denervated muscle. J Hand Surg Am 2008;33(7):1093‐1099.
    doi: 10.1016/j.jhsa.2008.02.025google scholar: lookup
  12. van Lith‐Bijl JT, Desuter GRR. Laryngeal reinnervation: the history and where we stand now. Adv Otorhinolaryngol 2020;85:98‐111.
  13. Rossignol F, Brandenberger O, Perkins JDM, Marie JP, Mespoulhès‐Rivière C, Ducharme NG. Modified first or second cervical nerve transplantation technique for the treatment of recurrent laryngeal neuropathy in horses. Equine Vet J 2018;50(4):457‐464.
  14. Campos Schweitzer A, Mespoulhès‐Rivière C, Möller D. Laryngeal reinnervation using the spinal accessory nerve: electromyographic study of the sternomandibularis muscle. Equine Vet J 2022;55(3):515‐523.
  15. Satoh M, Higuchi T, Inoue S. External transcutaneous ultrasound technique in the equine cricoarytenoideus dorsalis muscle: assessment of muscle size and echogenicity with resting endoscopy. Equine Vet J 2020;52(4):500‐508.
    doi: 10.1111/evj.13209google scholar: lookup
  16. Barakzai SZ, Wells J, Parkin TDH, Cramp P. Overground endoscopic findings and respiratory sound analysis in horses with recurrent laryngeal neuropathy after unilateral laser ventriculocordectomy. Equine Vet J 2019;51(2):185‐191.
    doi: 10.1111/evj.12993google scholar: lookup
  17. Tulloch LK, Perkins JD, Piercy RJ. Multiple immunofluorescence labelling enables simultaneous identification of all mature fibre types in a single equine skeletal muscle cryosection. Equine Vet J 2011;43(4):500‐503.
    doi: 10.1111/j.2042‐3306.2010.00329.xgoogle scholar: lookup
  18. Cercone M, Hokanson CM, Olsen E. Asymmetric recurrent laryngeal nerve conduction velocities and dorsal cricoarytenoid muscle electromyographic characteristics in clinically normal horses. Sci Rep 2019;9(1):2713.
    doi: 10.1038/s41598‐019‐39189‐zgoogle scholar: lookup
  19. Duncan ID, Reifenrath P, Jackson KF, Clayton M. Preferential denervation of the adductor muscles of the equine larynx. II: nerve pathology. Equine Vet J 1991;23(2):99‐103.
  20. Kumar R, Katoch SS, Sharma S. Beta‐adrenoceptor agonist treatment reverses denervation atrophy with augmentation of collagen proliferation in denervated mice gastrocnemius muscle. Indian J ExpBiol 2006;44(5):371‐376.
  21. Wu P, Chawla A, Spinner RJ. Key changes in denervated muscles and their impact on regeneration and reinnervation. Neural Regen Res 2014;9(20):1796‐1809.
  22. Chalmers HJ, Viel L, Caswell JL, Ducharme N. Ultrasonographic detection of early atrophy of the intrinsic laryngeal muscles of horses. Am J Vet Res 2015;76(5):426‐436.
  23. Chalmers HJ, Caswell J, Perkins J. Ultrasonography detects early laryngeal muscle atrophy in an equine neurectomy model. Muscle Nerve 2016;53(4):583‐592.
    doi: 10.1002/mus.24785google scholar: lookup
  24. Chalmers HJ, Yeager AE, Cheetham J, Ducharme N. Diagnostic sensitivity of subjective and quantitative laryngeal ultrasonography for recurrent laryngeal neuropathy in horses. Vet Radiol Ultrasound 2012;53(6):660‐666.
    doi: 10.1111/j.1740‐8261.2012.01974.xgoogle scholar: lookup
  25. Gutman E, Young JZ. The reinnervation of muscle after various periods of atrophy. J Anat 1944;78(1–2):15‐43.
  26. Kostrominova TY. Skeletal muscle denervation: past, present and future. Int J Mol Sci 2022;23(14):7489.
  27. Chalmers HJ, Cheetham J, Yeager AE, Ducharme NG. Ultrasonography of the equine larynx. Vet Radiol Ultrasound 2006;47(5):476‐481.
  28. Gordon T. Peripheral nerve regeneration and muscle reinnervation. Int J Mol Sci 2020;21(22):8652.
    doi: 10.3390/ijms21228652google scholar: lookup
  29. Carraro U, Boncompagni S, Gobbo V. Persistent muscle fiber regeneration in long term denervation: past, present, future. Eur J Transl Myol 2015;25(2):4832.
  30. Lee J, Talukder M, Karuman Z. Functional recovery and muscle atrophy in pre‐clinical models of peripheral nerve transection and gap‐grafting in mice: effects of 4‐aminopyridine. Neural Regen Res 2023;18(2):439‐444.
  31. Cebasek V, Kubínová L, Janácek J, Ribaric S, Erzen I. Adaptation of muscle fibre types and capillary network to acute denervation and short‐lasting reinnervation. Cell Tissue Res 2007;330(2):279‐289.
    doi: 10.1007/s00441-007-0484-5google scholar: lookup
  32. Lowe AL, Rivera Santana MV, Bopp T. Volume loss during muscle reinnervation surgery is correlated with reduced CMAP amplitude but not reduced force output in a rat hindlimb model. Front Physiol 2024;15:1328520.
    doi: 10.3389/fphys.2024.1328520google scholar: lookup
  33. Gordon T. Reinnervated muscle fiber type‐grouping—inevitable?. Oncotarget 2017;8(11):17410‐17411.
  34. Salem KF, Jeng SF, Rau CS. Profiling muscle‐specific microRNA expression after peripheral denervation and reinnervation in a rat model. J Neurotrauma 2009;26(12):2345‐2353.
    doi: 10.1089/neu.2009.0960google scholar: lookup
  35. Williams AH, Valdez G, Moresi V. MicroRNA‐206 delays ALS progression and promotes regeneration of neuromuscular synapses in mice. Science 2009;326(5959):1549‐1554.
    doi: 10.1126/science.1181046google scholar: lookup
  36. Gordon T, Tyreman N, Raji MA. The Basis for Diminished Functional Recovery after Delayed Peripheral Nerve Repair. J Neurosci 2011;31(14):5325‐5334.
  37. Chung D, Shum A, Caraveo G. GAP‐43 and BASP1 in axon regeneration: Implications for the treatment of neurodegenerative diseases. Front Cell Dev Biol 2020;8:567537.
  38. Rhee HS, Lucas CA, Hoh JFY. Fiber types in rat laryngeal muscles and their transformations after denervation and reinnervation. J Histochem Cytochem 2004;52(5):581‐590.
    doi: 10.1177/002215540405200503google scholar: lookup
  39. Cheetham J, Perkins JD, Jarvis JC. Effects of functional electrical stimulation on denervated laryngeal muscle in a large animal model. Artif Organs 2015;39(10):876‐885.
    doi: 10.1111/aor.12624google scholar: lookup
  40. Hill JL, Turner LC, Jones RD, Jimulia DT, Miller C, Power DM. The stages of rehabilitation following motor nerve transfer surgery. J Musculoskelet Surg Res 2019;3:60‐68.
    doi: 10.4103/jmsr.jmsr_79_18google scholar: lookup
  41. Covault J, Sanes JR. Neural cell adhesion molecule (N‐CAM) accumulates in denervated and paralyzed skeletal muscles. Proc Natl Acad Sci USA 1985;82(13):4544‐4548.
    doi: 10.1073/pnas.82.13.4544google scholar: lookup
  42. Perkins JD, Raffetto J, Thompson C, Weller R, Piercy RJ, Pfau T. Three‐dimensional biomechanics of simulated laryngeal abduction in horses. Am J Vet Res 2010;71(9):1003‐1010.
    doi: 10.2460/ajvr.71.9.1003google scholar: lookup
  43. Cercone M, Olsen E, Perkins JD, Cheetham J, Mitchell LM, Ducharme NG. Investigation into pathophysiology of naturally occurring palatal instability and intermittent dorsal displacement of the soft palate (DDSP) in racehorses: thyro‐hyoid muscles fatigue during exercise. PLoS One 2019;14(10):e0224524.
  44. Plotkin D, Roberts M, Haun C, Schoenfeld B. Muscle fiber type transitions with exercise training: shifting perspectives. Sports (Basel) 2021;9(9):127.
  45. Ju C, Park E, Kim T. Effectiveness of electrical stimulation on nerve regeneration after crush injury: comparison between invasive and noninvasive stimulation. PLoS One 2020;15(5):e0233531.
  46. Stölting M, Arnold A, Haralampieva D, Handschin C, Sulser T, Eberli D. Magnetic stimulation supports muscle and nerve regeneration after trauma in mice. Muscle Nerve 2016;53(4):598‐607.

Citations

This article has been cited 0 times.
Subscribe to our newsletter
Join 99,850 horse owners like you who receive our email updates on horse health and nutrition.