Laryngeal Dysfunction: What the Research Says
Evidence from 32 peer-reviewed studies
13 Cohort Study
5 Case Report
14 Expert Opinion
What Professionals Should Know
- •Selective laryngeal reinnervation using the spinal accessory nerve is a viable surgical option for horses with RLN and mild-to-moderate CAD muscle atrophy, with an 80% functional success rate.
- •Recovery timeline extends to 12 months post-operatively; practitioners should counsel clients on realistic expectations for gradual return of exercise tolerance.
- •This physiological approach may be considered before or alongside other RLN management strategies, particularly in horses with mild-to-moderate rather than severe laryngeal collapse.
- •Yearling sale videoendoscopic assessments showing grade II.2 or worse laryngeal dysfunction are at significantly increased risk of requiring surgery later; this should inform purchasing decisions and expected outcomes
- •Many horses requiring prosthetic laryngoplasty had relatively mild yearling findings (≤grade II.2), suggesting laryngeal disease often deteriorates after sale—continued monitoring of horses with early-grade dysfunction is warranted
- •Laryngeal grading at yearling sales has meaningful predictive value for future surgery risk and should be considered alongside other pre-purchase evaluation findings
- •Yearlings with mild-to-moderate laryngeal dysfunction (grades II.2 and below) should not be penalized at sales or excluded from racing, as they perform similarly to normal horses throughout early careers
- •Only the most severe laryngeal grades (III.1–III.2) warrant concern for reduced future earnings, particularly as horses mature beyond 4 years old
- •Consider age-related performance when counseling clients about laryngeal grades: early career performance may be normal, but problems emerge in older horses with severe dysfunction
- •Horses with grade III.2/III.3 laryngeal function are more likely to return to racing after LPVC than grade IV horses, though both groups can race postoperatively
- •Grade IV horses should be counseled to expect a longer recovery time before first race, but financial returns per start are comparable across all preoperative grades
- •Preoperative racing status is a stronger predictor of postoperative performance than laryngeal grade alone
- •External transcutaneous ultrasound is a practical, noninvasive alternative to transoesophageal ultrasound for diagnosing recurrent laryngeal neuropathy in horses—no need for expensive endoscope equipment or invasive techniques
- •Measuring left-to-right muscle thickness and cross-sectional area ratios provides objective criteria to help decide whether a horse needs laryngoplasty or nerve graft procedures
- •Asymmetric atrophy and hyperechogenicity of the left cricoarytenoideus dorsalis muscle on ultrasound can be used as a screening tool to identify RLN suspects before or alongside endoscopic examination
- •LTF with soft palate cautery is an effective treatment option for NH racehorses with palatal dysfunction; aryepiglottic fold resection is not necessary for most cases and adds operative complexity without clear performance benefit
- •Consider this surgical combination for horses with confirmed palatal displacement showing exercise intolerance or poor race performance, particularly in jumping disciplines
- •Racing return rates and performance metrics should be tracked post-operatively to assess individual horse recovery and readiness for competition
- •Resting endoscopy alone is insufficient for pre-purchase or pre-racing evaluation of yearlings; dynamic endoscopy should be considered standard protocol
- •Functional respiratory pathology may only manifest during exercise, making resting examination miss clinically significant conditions
- •Incorporate exercise endoscopy into yearling vetting protocols to improve accuracy of fitness assessments for racing suitability
- •Laryngoplasty successfully returns most National Hunt horses to racing with short-term performance comparable to unaffected peers, making it a viable treatment option for RLN
- •Expect roughly half of operated horses to improve performance, but plan for potentially shorter racing careers than non-affected horses
- •The procedure appears to restore immediate function effectively, but monitor these horses for earlier-than-normal retirement from racing
- •Endoscopic findings of moderate pharyngeal lymphoid hyperplasia warrant attention as they correlate with reduced racing performance, particularly in younger horses
- •Common post-race findings like laryngeal and tracheal debris should not be assumed to impair performance; severe laryngeal dysfunction is rare and not performance-limiting in this population
- •Tracheal cartilaginous nodules, though more prevalent in males, do not indicate poor prognosis and may even be associated with competitive success
- •Partial arytenoidectomy with primary mucosal closure is an effective procedure for returning racehorses with arytenoid chondropathy or failed laryngoplasty to racing, with 4 in 5 horses returning to competition
- •Plan for a 6-month recovery period before expecting the horse to return to racing after this procedure
- •Anticipate that approximately 1 in 6 horses may require a second procedure for granulation tissue management, but this does not appear to affect long-term racing performance
- •Draft horse owners and trainers should be aware that laryngeal disease prevalence varies by age, breed, and type of work—screening may be warranted for high-risk categories
- •Understanding which draft horse populations are predisposed to ILH and EIPH can inform preventive management and performance expectations
- •Tracheal mucus observation during endoscopic evaluation may serve as a practical indicator of concurrent laryngeal dysfunction affecting performance
- •Electrolaryngeography reflex latency testing provides a sensitive, objective measurement that may help clinicians differentiate between grades of RLN severity in resting horses
- •This diagnostic technique is reliable and not affected by sedation, making it practical for clinical use without altering results
- •Reflex latency measurements could improve clinical assessment and potentially help identify subtle disease progression in Thoroughbreds with RLN
- •RLN is not always static—15% of cases progress over time, so repeat endoscopic examination may be warranted in horses with worsening clinical signs months or years after initial diagnosis
- •Sudden onset of respiratory noise or performance decline in a previously diagnosed RLN horse should prompt re-evaluation, as significant endoscopic deterioration may not always match clinical presentation
- •Pre-purchase evaluations showing normal laryngeal function do not exclude future RLN development or progression, which is relevant for liability and warranty disputes
- •Laryngeal prosthesis effectiveness for treating RLN is not compromised by patient age, allowing treatment consideration across all age groups
- •Prosthesis location choice can be based on surgical accessibility and anatomical factors rather than age-related concerns about tissue response
- •Standardized tensioning protocols enable consistent prosthesis placement and predictable airway outcomes regardless of horse age
- •Understanding individual cricoid cartilage conformation may help predict which horses are at higher risk for recurrent laryngeal nerve dysfunction and suture slippage after laryngoplasty
- •Pre-operative CT assessment of cricoid anatomy could guide surgical technique selection and suture placement strategy to optimize post-operative outcomes
- •Recognition of normal anatomical variation in cricoid structure is essential for surgeons performing laryngoplasty to anticipate and mitigate complications
- •Using 2 prosthetic sutures in laryngoplasty produces a larger airway opening than single-suture techniques, potentially improving breathing outcomes in horses with laryngeal paralysis
- •The specific placement matters: dorsal suture at the cricoid caudal rim plus lateral suture 1.5cm lateral and more distal/caudal provides additive benefit rather than redundant tension
- •This study provides a biomechanical rationale for adopting dual-suture laryngoplasty techniques in clinical practice
- •Always position the horse's head in extension (115°) when taking radiographs to assess laryngeal tie-forward surgery — this is the only reliable position for detecting whether the procedure has successfully repositioned the larynx
- •Avoid flexed head positions for postoperative assessment as they may falsely suggest the surgery failed or succeeded due to positioning artifact rather than actual surgical effect
- •Standardize your radiographic technique using extended head position to enable meaningful comparison between pre- and postoperative films and between cases
- •This condition may be clinically silent at rest but could contribute to poor performance or respiratory noise during exercise; high-speed treadmill endoscopy may be needed to detect it during work
- •Prevalence in Clydesdales (5.2%) suggests breed predisposition; consider laryngeal pathology in draft horses with unexplained poor performance
- •Clinical significance remains unclear from this case series; further investigation needed to determine whether intervention is warranted
- •When evaluating laryngeal endoscopy videos, use frame-by-frame playback at known frame rates and apply this decision tree to achieve more consistent, objective grading of laryngeal function across cases.
- •The critical distinction between grades III.1 and II.2 depends on whether arytenoid abduction is maintained for at least 0.2 seconds—use this as your timing benchmark during video review.
- •This standardized approach reduces subjective interpretation and improves communication with referring veterinarians by providing consistent, evidence-based laryngeal grades.
- •3D-printed laryngeal clamps show promise for improving prosthesis stability in laryngoplasty, potentially reducing recurrent prosthesis failure rates in clinical cases
- •The mechanism shifts failure from cartilage tearing (typical failure mode) to whole-cartilage fracture, suggesting better load distribution and longer functional lifespan
- •In vivo clinical trials are needed before adoption; this technology may become a valuable option for horses with recurrent laryngeal neuropathy that fail standard laryngoplasty
- •While two-prosthesis techniques with single-loop arytenoid fixation dominate practice, evidence suggests alternative biomechanical approaches may offer advantages—consider exploring these if outcomes warrant it
- •Standing sedation is increasingly used for laryngoplasty (36% of respondents), offering potential advantages in recovery and cost—evaluate feasibility in your facility
- •Antimicrobial protocols vary widely with no consensus on duration or local vs. systemic use—audit your current practice against evidence-based guidelines to optimize outcomes
- •CFD modeling offers a non-destructive method to predict outcomes of upper airway procedures before performing them clinically, potentially improving surgical planning
- •This technology could help identify which procedural combinations work best for individual horses with airway obstruction, reducing trial-and-error approaches
- •Cadaveric validation supports future clinical application of computational modeling to optimize laryngeal surgeries and improve post-operative breathing outcomes
- •Partial arytenoidectomy under standing sedation and local anesthesia is a viable alternative to general anesthesia for RLN cases, particularly those with failed laryngoplasty
- •Success rate is high (64-75% return to work without noise), but monitor for postoperative granuloma formation which may require tracheostomy in some cases
- •This technique eliminates anesthetic risk for horses that may be poor candidates for general anesthesia due to age, fitness level, or comorbidities
- •ZipFix implants show biomechanical advantages over traditional suture but carry unacceptable risk of iatrogenic cartilage damage during placement—clinicians should not use this implant for equine laryngoplasty
- •Traditional TiCron suture remains safer for prosthetic laryngoplasty despite lower load-bearing capacity, as it does not fracture cartilage during implant insertion
- •Further implant design modifications are needed before ZipFix or similar devices can be safely used in equine laryngeal surgery
- •Ethibond™ appears mechanically superior for laryngoplasty as it resists pull-through of the arytenoid cartilage better than Lycra®, which may translate to improved long-term surgical outcomes
- •The greater displacement properties of Lycra® could result in prosthesis loosening and recurrence of clinical signs despite theoretical advantages in suture loop strength
- •Material selection for laryngoplasty should prioritize resistance to pull-through forces through cartilage rather than isolated suture strength, based on these biomechanical findings
- •Understanding cricothyroid muscle anatomy and innervation is essential for veterinarians considering functional electrical stimulation as treatment for recurrent laryngeal neuropathy
- •Proper electrode placement requires detailed knowledge of muscle neuroanatomy to effectively recruit muscle fibers and improve laryngeal patency
- •This anatomic foundation supports development of therapeutic interventions for horses with upper airway obstruction secondary to laryngeal nerve damage
- •The relatively straight geometry and high stiffness of equine cricoid cartilage means the larynx is mechanically robust; understanding these properties helps explain why soft tissue collapse causes obstruction rather than cartilage deformation
- •Age-related increases in cartilage stiffness may influence laryngeal function and response to surgical interventions in older horses
- •These biomechanical baseline values provide reference data for assessing laryngeal disease and optimizing surgical techniques like prosthetic laryngoplasty
- •Laryngeal tie-forward surgery is an effective treatment for persistent DDSP in racehorses, with 87% successfully returning to racing; some cases benefit from additional laser staphylectomy
- •Radiographic evaluation of laryngohyoid position can help differentiate persistent from intermittent DDSP and may guide treatment selection
- •The anatomical differences in laryngeal position between persistent and intermittent DDSP suggest different underlying pathophysiology and support the caudal laryngeal descent hypothesis
- •When performing arytenoid prosthesis placement, prioritise double suture patterns over single patterns for improved construct stability and resistance to failure
- •Ensure sutures engage the spine of the muscular process, as this anatomical engagement provides superior biomechanical strength compared to alternative positioning
- •Design surgical approach to minimise muscular process failure, which is the most common failure mode in poorly configured single suture patterns
- •This in vitro model enables systematic testing and optimization of laryngoplasty implants and suture techniques before clinical application, reducing need for trial-and-error in surgery
- •The validated pressure and flow data provide objective benchmarks for evaluating whether new prosthetic designs actually improve airway function during maximal exercise conditions
- •Surgeons can use findings to understand which suture materials and abduction angles best maintain upper airway patency under the high-demand conditions horses experience at speed
- •When performing endoscopic examination of the larynx for diagnostic purposes, be aware that sedation with detomidine and acepromazine can alter findings and may not reflect the horse's resting laryngeal function
- •Consider performing unsedated endoscopy when possible, or interpret sedated findings cautiously, particularly for purchase examinations where accurate laryngeal assessment is critical
- •Document whether sedation was used during endoscopy as it significantly impacts the reliability and comparability of findings between examinations
- •Both suture placement techniques achieve similar mechanical strength in vitro, so choice may depend on surgeon preference and equipment availability
- •Bone trocar pre-drilling appears to produce more predictable failure patterns with reduced fissure formation, potentially lowering long-term complications from suture pullout
- •Results suggest bone trocar technique may be preferable for laryngoplasty in clinical practice to minimize cartilage damage, though clinical validation is needed
Key Research Findings
Selective laryngeal reinnervation using the spinal accessory nerve restored arytenoid abduction at exercise in 4 of 5 horses (80% success rate) at 12 months post-operatively.
Mean left-to-right quotient angle ratio recovered to 94% of predenervation values with no statistically significant difference from baseline (p = 0.69).
Histopathologic examination confirmed successful axonal regeneration of the spinal accessory nerve and functional reinnervation of the lateral CAD muscle with increased type I fiber proportion.
One horse exhibited slower and incomplete recovery, demonstrating variable individual responses to the reinnervation procedure.
Yearling laryngeal function ≥grade II.2 had 4.61 times higher odds of requiring prosthetic laryngoplasty compared to <grade II.2
Yearling laryngeal function ≥grade III.1 had 10.7 times higher odds of requiring prosthetic laryngoplasty compared to <grade III.1
Three-quarters of the prosthetic laryngoplasty group had ≤grade II.2 yearling laryngeal function, indicating post-sale deterioration in laryngeal function was common
Risk of requiring prosthetic laryngoplasty increased progressively from grade II.2 onwards, with grades III.2 and above showing dramatically elevated odds ratios
95% of yearlings had YLF grades I, II.1, or II.2 with minimal performance differences between them
YLF grades II.2 and III.1 showed no significant difference in career earnings compared to grades I/II.1
Grade III.2 horses earned significantly less overall ($46,015 less; p=0.04) compared to grades I/II.1
Grade III.1 and III.2 horses had substantially reduced earnings at ≥4 years old compared to normal grades
Grade III.2/III.3 horses had 1.88 times higher odds of racing after laryngoplasty and ventriculocordectomy (LPVC) compared to grade IV horses (P = 0.04)
Grade IV horses took significantly longer to return to racing compared with grade III.1 and III.2/III.3 horses on Kaplan-Meier survival analysis
Preoperative laryngeal function grade did not influence mean earnings per start postoperatively
Evidence Base
Functional and histopathologic evidence of laryngeal reinnervation using the spinal accessory nerve in horses.
Campos Schweitzer Ariane, Mespoulhes-Rivière Céline, Perkins Justin D et al. (2026) — Veterinary surgery : VS
Cohort Study
Yearling laryngeal function in Thoroughbreds that underwent a laryngoplasty differs from controls.
Hardwick Josephine L, Ahern Benjamin J, Crawford Kylie L et al. (2025) — Equine veterinary journal
Cohort Study
Yearling laryngeal function grades II.2 and below are not associated with reduced performance.
Hardwick Josephine L, Ahern Benjamin J, Crawford Kylie L et al. (2025) — Equine veterinary journal
Cohort Study
The impact of grade of laryngeal function immediately prior to laryngoplasty and ipsilateral ventriculocordectomy on postoperative performance: 623 Thoroughbred racehorses (1998-2013).
Broyles Ali H, Embertson Rolf M, Brett Woodie J et al. (2022) — Equine veterinary journal
Cohort Study
External transcutaneous ultrasound technique in the equine cricoarytenoideus dorsalis muscle: Assessment of muscle size and echogenicity with resting endoscopy.
Satoh Masato, Higuchi Tohru, Inoue Satoshi et al. (2020) — Equine veterinary journal
Cohort Study
Racing performance of National Hunt thoroughbred racehorses after treatment of palatal dysfunction with a laryngeal tie-forward procedure and thermocautery of the soft palate with or without aryepiglottic folds resection.
Koskinen Milja J, Virtala Anna-Maija K, McNally Turlough (2020) — Veterinary surgery : VS
Cohort Study
Comparison of dynamic and resting endoscopy of the upper portion of the respiratory tract in 57 Thoroughbred yearlings.
Kelly P G, Reardon R J M, Johnston M S et al. (2013) — Equine veterinary journal
Cohort Study
Race performance after laryngoplasty and ventriculocordectomy in National Hunt racehorses.
Barakzai Safia Z, Boden Lisa A, Dixon Padraic M (2009) — Veterinary surgery : VS
Cohort Study
Prevalence of pharyngeal, laryngeal and tracheal disorders in thoroughbred racehorses, and effect on performance.
Saulez M N, Gummow B (2009) — The Veterinary record
Cohort Study
Long-term study of partial arytenoidectomy with primary mucosal closure in 76 Thoroughbred racehorses (1992-2006).
Parente E J, Tulleners E P, Southwood L L (2008) — Equine veterinary journal
Cohort Study
The prevalence of laryngeal disease in a large population of competition draft horses.
Brakenhoff Jeffrey E, Holcombe Susan J, Hauptman Joe G et al. (2006) — Veterinary surgery : VS
Cohort Study
Thoracolaryngeal reflex latencies in Thoroughbred horses with recurrent laryngeal neuropathy.
Curtis R A, Hahn C N, Evans D L et al. (2005) — Veterinary journal (London, England : 1997)
Cohort Study
Clinical and endoscopic evidence of progression in 152 cases of equine recurrent laryngeal neuropathy (RLN).
Dixon P M, McGorum B C, Railton D I et al. (2002) — Equine veterinary journal
Cohort Study
Effect of age and prostheses location on rima glottidis area in equine cadaveric larynges.
Bischofberger Andrea S, Hadidane Ines, Wereszka Marta M et al. (2013) — Veterinary surgery : VS
Case Report
Analysis of conformational variations of the cricoid cartilages in Thoroughbred horses using computed tomography.
Dahlberg J A, Valdes-Martinez A, Boston R C et al. (2011) — Equine veterinary journal
Case Report
Effect of prosthesis number and position on rima glottidis area in equine laryngeal specimens.
Dart Andrew, Tee Elizabeth, Brennan Moses et al. (2009) — Veterinary surgery : VS
Case Report
Effect of head position on radiographic assessment of laryngeal tie-forward procedure in horses.
McCluskie Laura K, Franklin Samantha H, Lane J Geoffrey et al. (2008) — Veterinary surgery : VS
Case Report
Ventroaxial luxation of the apex of the corniculate process of the arytenoid cartilage in resting horses during induced swallowing or nasal occlusion.
Barakzai S Z, Es Cert, Milne E M et al. (2007) — Veterinary surgery : VS
Case Report
A first step towards objective grading of equine laryngeal function.
Hardwick Josephine, Ahern Benjamin, Franklin Samantha (2024) — Veterinary journal (London, England : 1997)
Expert Opinion
Enhancing prosthesis stability at the cricoid cartilage in equine laryngoplasty using 3-D-printed laryngeal clamps: An ex vivo model study.
Grzeskowiak Remigiusz, Schumacher Jim, Omidi Omid et al. (2024) — Veterinary surgery : VS
Expert Opinion
Show 12 more references
Variations in the application of equine prosthetic laryngoplasty: A survey of 128 equine surgeons.
Byrne Christian A, Hotchkiss Joel W, Barakzai Safia Z (2023) — Veterinary surgery : VS
Expert Opinion
Computational fluid dynamic analysis of upper airway procedures in equine larynges.
Tucker Michelle L, Wilson David G, Bergstrom Donald J et al. (2023) — Frontiers in veterinary science
Expert Opinion
Partial arytenoidectomy in 14 standing horses (2013-2017).
Gray Sarah M, Gutierrez-Nibeyro Santiago D, Secor Erica J (2019) — Veterinary surgery : VS
Expert Opinion
Ex Vivo Mechanical Evaluation of a Sternal ZipFix(®) Implant for Prosthetic Laryngoplasty in Horses.
Markwell Harry J, Mueller P O Eric (2016) — Veterinary surgery : VS
Expert Opinion
In vitro mechanical testing of braided polyurethane elastic fiber and braided polyester for equine laryngoplasty.
Willsallen Hadley, Heller Jane, Kark Lauren et al. (2015) — Veterinary surgery : VS
Expert Opinion
Anatomic and neuromuscular characterisation of the equine cricothyroid muscle.
Reesink H L, Hermanson J W, Cheetham J et al. (2013) — Equine veterinary journal
Expert Opinion
Biomechanical characterisation of equine laryngeal cartilage.
Passman S N, Cheetham J, Bonassar L J et al. (2011) — Equine veterinary journal
Expert Opinion
Successful treatment of persistent dorsal displacement of the soft palate and evaluation of laryngohyoid position in 15 racehorses.
Ortved K F, Cheetham J, Mitchell L M et al. (2010) — Equine veterinary journal
Expert Opinion
Biomechanical comparison of six suture configurations using a large diameter polyester prosthesis in the muscular process of the equine arytenoid cartilage.
Kelly Jenny R, Carmalt James, Hendrick Steven et al. (2008) — Veterinary surgery : VS
Expert Opinion
In vitro model for testing novel implants for equine laryngoplasty.
Cheetham Jon, Witte Thomas H, Soderholm Leo V et al. (2008) — Veterinary surgery : VS
Expert Opinion
Sedation with detomidine and acepromazine influences the endoscopic evaluation of laryngeal function in horses.
Lindegaard C, Husted L, Ullum H et al. (2007) — Equine veterinary journal
Expert Opinion
In vitro comparison of two techniques for suture prosthesis placement in the muscular process of the equine arytenoid cartilage.
Rossignol Fabrice, Perrin Roland, Desbrosse Francis et al. (2006) — Veterinary surgery : VS
Expert Opinion