# Equine Larynx Anatomy and Function in Respiration


## Key Takeaways

- The equine larynx is a critical cartilaginous and muscular valve with dual functions: maintaining airway patency during high-flow respiration and preventing aspiration during deglutition. Its structure is adapted to withstand significant collapsing pressures during exercise due to the horse's obligate nasal breathing.
- Key cartilaginous components include the epiglottis, thyroid, cricoid, and paired arytenoids, with the arytenoids being pivotal for airway dynamics via their muscular and corniculate processes. Mineralization patterns of these cartilages, particularly the arytenoids, are diagnostically relevant for conditions like arytenoid chondropathy.
- The intrinsic laryngeal musculature, primarily the cricoarytenoideus dorsalis (CAD), is essential for arytenoid abduction and airway dilation. Dysfunction of the CAD, often due to left recurrent laryngeal neuropathy, leads to dynamic obstruction and performance-limiting disorders.
- The recurrent laryngeal nerve innervates most intrinsic laryngeal muscles, with the left nerve's longer intrathoracic course predisposing it to injury and subsequent left-sided neuropathy, the most common cause of laryngeal dysfunction in performance horses.
- Diagnostic assessment relies heavily on resting and dynamic (exercise) endoscopy, with specific maneuvers like nasal occlusion used to evaluate arytenoid abduction. Advanced imaging modalities such as CT and MRI are employed for detailed structural assessment, particularly for chondropathy and masses.
- Recurrent laryngeal neuropathy is graded based on the degree of arytenoid abduction, with grades 3 and 4 typically indicating the need for surgical intervention in athletic horses, with prosthetic laryngoplasty and ventriculocordectomy being common procedures.

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The equine larynx is a cartilaginous and muscular valve positioned at the junction of the nasopharynx and trachea. It serves two non-negotiable functions: maintaining a patent airway during high-flow respiration and protecting the lower airway from aspiration during deglutition. This article provides a detailed anatomical reference for veterinary students, covering the laryngeal cartilages, intrinsic and extrinsic musculature, innervation, and the biomechanical principles that govern airflow and airway protection. The clinical relevance of each structural component is emphasized, particularly where dysfunction produces the performance-limiting disorders described in the contemporary literature on equine upper airway disease.

The horse is an obligate nasal breather, and the larynx sits within a bony and soft-tissue framework that subjects it to substantial collapsing pressures during exercise. Understanding the larynx therefore requires familiarity with its static anatomy and its dynamic behavior under negative intraluminal pressure. The material presented here draws on established anatomical reviews, magnetic resonance imaging studies of the normal equine larynx, and comparative analyzes of exercise-induced laryngeal obstruction in horses and humans.

## At a Glance

| Parameter | Detail |
|---|---|
| Primary functions | Airway patency during respiration, airway protection during swallowing |
| Major cartilages | Epiglottis, thyroid, cricoid, paired arytenoids |
| Intrinsic muscles | Cricoarytenoideus dorsalis (CAD), cricoarytenoideus lateralis, thyroarytenoideus, arytenoideus transversus, vocalis |
| Primary abductor | Cricoarytenoideus dorsalis, the sole arytenoid abductor |
| Motor innervation | Recurrent laryngeal nerve (all intrinsic muscles except cricothyroideus) |
| Sensory innervation | Cranial laryngeal nerve (rostral glottis), recurrent laryngeal nerve (caudal glottis) |
| Clinically critical structure | Left recurrent laryngeal nerve, long intrathoracic course predisposes to neuropathy |
| Imaging modalities | Endoscopy (rest and exercise), radiography, CT, MRI, xeroradiography |

## Cartilaginous Framework

The laryngeal skeleton comprises five principal cartilages: the epiglottis, thyroid, cricoid, and paired arytenoids. The epiglottis is a flexible, leaf-shaped cartilage that projects rostrally beneath the soft palate. Its lingual surface is covered by mucosa that is continuous with the pharynx, and its dorsal surface forms the rostral boundary of the aditus laryngis. The epiglottis does not mineralise appreciably in the normal horse, which aids radiographic identification of the structure.

The thyroid cartilage is the largest laryngeal cartilage. It consists of two lateral laminae that meet ventrally to form the body, with rostral and caudal cornua projecting from each lamina. The thyroid cartilage articulates caudally with the cricoid cartilage via the cricothyroid articulation. The cricoid cartilage is a complete ring, shaped like a signet ring with a broad dorsal lamina and a narrower ventral arch. The dorsal lamina provides attachment for the cricoarytenoideus dorsalis muscles and articulates with the arytenoid cartilages at the cricoarytenoid articulations.

The paired arytenoid cartilages are irregular, pyramidal structures that articulate with the cricoid cartilage. Each arytenoid has a muscular process, a vocal process, and a corniculate process. The corniculate processes project dorsomedially and form the dorsal portion of the rima glottidis. The muscular process receives the insertions of the cricoarytenoideus dorsalis and lateralis muscles, making it the pivotal point for arytenoid abduction and adduction. Mineralisation of the thyroid and arytenoid cartilages increases with age, a finding documented in xeroradiographic studies of clinically normal horses, and abnormal patterns of arytenoid mineralisation are associated with arytenoid chondropathy.

## Intrinsic Musculature

The intrinsic laryngeal muscles adjust the position and tension of the arytenoid cartilages and vocal folds. The cricoarytenoideus dorsalis is the sole abductor of the arytenoid cartilage. It originates on the dorsal lamina of the cricoid and inserts on the muscular process of the arytenoid. Contraction rotates the muscular process dorsolaterally, swinging the corniculate process laterally and widening the rima glottidis. This muscle is the primary dilator of the airway and is the muscle affected in recurrent laryngeal neuropathy.

The cricoarytenoideus lateralis adducts the arytenoid cartilage, opposing the CAD. The thyroarytenoideus and vocalis muscles lie within the arytenoid and thyroid cartilages and adjust tension of the vocal fold. The arytenoideus transversus is an unpaired muscle spanning the dorsal surfaces of both arytenoid cartilages, it assists in adduction and stabilizes the arytenoids during swallowing. The cricothyroideus muscle, innervated by the cranial laryngeal nerve, tenses the vocal folds by rotating the thyroid cartilage relative to the cricoid.

## Innervation

The motor supply to all intrinsic laryngeal muscles except the cricothyroideus is provided by the recurrent laryngeal nerve, a branch of the vagus. The right recurrent laryngeal nerve arises in the cranial thorax and loops around the right subclavian artery. The left recurrent laryngeal nerve arises more caudally and loops around the aortic arch, giving it a longer intrathoracic course. This longer course renders the left nerve more vulnerable to axonal injury, which explains the left-sided predominance of recurrent laryngeal neuropathy.

Sensory innervation is divided between two nerves. The cranial laryngeal nerve, also a vagal branch, supplies sensation to the mucosa of the rostral larynx, including the epiglottis and the rostral aspect of the rima glottidis. The recurrent laryngeal nerve supplies sensation to the mucosa caudal to the vocal folds. The internal branch of the cranial laryngeal nerve carries afferent fibers from the laryngeal mucosa that initiate the cough reflex and protective glottic closure.

## Functional Anatomy in Respiration

During quiet breathing, the rima glottidis remains partially open, with the arytenoid cartilages held in a neutral position by tonic activity of the intrinsic muscles. During exercise, the CAD contracts forcefully and synchronously with inspiration, abducting the arytenoids to their maximal extent. This abduction reduces inspiratory resistance, which is critical because the equine upper airway is the primary site of flow limitation during high-intensity exercise.

The biomechanics of equine upper airway flow differ substantially from human models. Computational fluid dynamic simulations based on computed tomography reconstructions of a racehorse airway demonstrate that airflow in the equine larynx is highly turbulent, with Reynolds numbers far exceeding those seen in the human airway. Velocity magnitudes during inhalation are higher than during exhalation, and the nasopharynx changes geometry between the two phases of respiration. These findings have direct clinical implications: small reductions in laryngeal cross-sectional area produce disproportionately large increases in resistance because of the turbulent flow regime.

The arytenoid cartilages and vocal folds are subjected to collapsing transmural pressures during inspiration. The laryngeal muscles must generate sufficient force to resist this collapse. When the CAD is weakened, as in recurrent laryngeal neuropathy, the affected arytenoid fails to abduct fully and may be drawn medially during inspiration, producing dynamic obstruction. Exercise-induced laryngeal obstruction in horses shares pathophysiological features with analogous conditions in humans, where dynamic collapse of laryngeal structures occurs only during increased ventilatory demand and resolves at rest.

## Endoscopic Assessment of the Equine Larynx

Resting endoscopic examination remains the first-line diagnostic procedure for laryngeal disorders in the horse. The examination should be performed with the horse standing, preferably in a quiet environment with minimal restraint. A 1 m flexible video endoscope is standard, though shorter instruments may suffice for foals. The endoscope is passed through the ventral nasal meatus to avoid trauma to the ethmoid region, and the larynx is assessed as the instrument tip reaches the caudal nasopharynx.

The arytenoid cartilages are evaluated for symmetry of abduction and adduction. The left arytenoid is compared with the right during quiet breathing, during swallowing, and after nasal occlusion. Nasal occlusion for 30 to 60 seconds increases respiratory drive and typically produces full arytenoid abduction in normal horses. A horse that fails to abduct the left arytenoid fully during this maneuve may have recurrent laryngeal neuropathy. The laryngeal lumen should be examined for the presence of the epiglottis dorsal to the soft palate, the appearance of the corniculate processes, and the openings of the lateral ventricles. [Luedke's review of equine laryngeal disorders](https://pubmed.ncbi.nlm.nih.gov/41654449/) describes the resting endoscopic findings that distinguish the major conditions affecting this region.

Dynamic collapse of the arytenoid cartilages or other laryngeal structures may not be apparent at rest. Horses with exercise intolerance and normal resting endoscopic findings require examination during exercise. High-speed treadmill endoscopy allows continuous visualization of the larynx from rest through peak exertion. The endoscopic findings are recorded on video for frame-by-frame analysis, and the point of onset of any collapse is noted. [The comparative review of exercise induced laryngeal obstruction](https://pubmed.ncbi.nlm.nih.gov/31736771/) emphasizes that abnormalities may only appear when ventilatory demands increase, and that examination should progress from rest to peak effort to characterize the pattern of collapse.

### Grading Systems for Recurrent Laryngeal Neuropathy

Several grading schemes exist for recurrent laryngeal neuropathy. The most widely used system assigns grades from 1 to 4 based on the degree of arytenoid abduction at rest. Grade 1 represents full synchronous abduction, grade 2 shows asynchronous movement with full abduction achievable, grade 3 shows asynchronous movement with incomplete abduction, and grade 4 represents complete immobility of the affected arytenoid. The clinical significance of each grade depends on the intended use of the horse. A grade 3 or 4 in a racehorse carries different implications than the same grade in a pasture companion.

| Grade | Resting Abduction | Exercise Findings | Typical Management |
|-------|-------------------|-------------------|---------------------|
| 1 | Full, synchronous | Normal | No treatment |
| 2 | Asynchronous, full achievable | May be normal | Monitor, consider if performance declines |
| 3 | Incomplete abduction | Dynamic collapse | Surgical intervention for athletic use |
| 4 | No abduction | Marked collapse, exercise intolerance | Surgical intervention for athletic use |

The decision to pursue surgical treatment depends on the grade, the horse's athletic discipline, and the owner's expectations. Horses used for low-intensity work may tolerate grade 3 without intervention. [The Massey University studies on laryngeal hemiplegia](https://pubmed.ncbi.nlm.nih.gov/21838638/) established the clinical framework for grading and the recognition that this condition is the most important laryngeal disease affecting performance.

## Imaging of the Equine Larynx

Radiography of the laryngeal region is useful for assessing mineralisation of the laryngeal cartilages and for identifying space-occupying lesions. The normal pattern of mineralisation in the thyroid, arytenoid, and cricoid cartilages has been documented, and the degree of mineralisation increases with age. [Xeroradiographic evaluation of the equine larynx](https://pubmed.ncbi.nlm.nih.gov/2764338/) demonstrated that arytenoid chondropathy produces characteriztic changes including enlargement of the arytenoid region, abnormal mineralisation patterns, and irregular contours of the corniculate processes. Standard laterolateral projections of the pharyngeal and laryngeal region are obtained with the horse standing and the head positioned in a neutral extended posture.

Computed tomography provides cross-sectional imaging of the larynx with superior soft tissue detail compared with radiography. CT is particularly valuable for assessing arytenoid chondropathy, laryngeal masses, and fractures of the laryngeal cartilages. The examination is performed under standing sedation or general anesthesia depending on the equipment available. [The magnetic resonance imaging study of the normal equine larynx](https://pubmed.ncbi.nlm.nih.gov/19697604/) demonstrated that MR imaging clearly identifies the laryngeal cartilages, hyoid apparatus, and associated muscle groups, though individual muscles may not be separable in every plane. MR imaging is reserved for cases where soft tissue characterization is required, such as suspected neoplasia or abscessation.

### Ultrasound Examination

Transcutaneous ultrasonography of the larynx is performed with a linear or microconvex transducer placed on the ventral and lateral aspects of the throat. The examination allows assessment of the cricoarytenoideus dorsalis muscle, which may show atrophy in chronic recurrent laryngeal neuropathy. The muscular process of the arytenoid cartilage serves as a landmark for identifying the insertion of this muscle. Ultrasound is also useful for guiding aspiration or biopsy of laryngeal masses. The technique requires a cooperative horse and is best performed with the head slightly elevated and the neck extended.

## Functional Assessment of Laryngeal Airflow

Pressure measurement during exercise provides quantitative data on upper airway obstruction. A catheter is placed in the pharynx or trachea and connected to a pressure transducer, allowing measurement of the pressure gradient across the larynx during breathing. This technique has been used in research settings to characterize the severity of obstruction and to monitor the response to treatment. [The computational model of equine upper airway airflow](https://pubmed.ncbi.nlm.nih.gov/18532860/) demonstrated that airflow through the equine larynx is highly turbulent, with velocity magnitudes during inhalation exceeding those during exhalation. This turbulence contributes to the pressure changes that drive dynamic collapse of compliant laryngeal structures.

The clinical application of pressure measurement is limited by the need for specialised equipment and expertise. Most clinical decisions are made on the basis of endoscopic findings alone. However, pressure measurement may be useful when endoscopic findings are equivocal or when multiple sites of obstruction are suspected.

## Documentation of Laryngeal Findings

Accurate documentation of laryngeal examination findings is essential for monitoring disease progression and for communicating with referring veterinarians and owners. The endoscopic examination should be recorded as video, with still images captured at key points: resting position, maximal abduction after nasal occlusion, and during swallowing. The grade of arytenoid abduction is recorded using the chosen grading system, and any asymmetry or abnormal movement is described in detail.

A standardized reporting format includes the following elements:

- Signalment and presenting complaint
- Resting arytenoid position and symmetry
- Response to nasal occlusion
- Appearance of the epiglottis, corniculate processes, and ventricular openings
- Presence of discharge, erythema, or masses
- Dynamic findings if exercise endoscopy is performed
- Imaging findings if applicable
- Assessment and recommendations

The report should distinguish between findings that are incidental and those that explain the presenting complaint. A grade 2 left arytenoid in a horse presenting for poor performance may be an incidental finding, whereas the same grade in a horse with respiratory noise at exercise requires further investigation.

## Decision Framework for Laryngeal Surgery

The decision to recommend surgical intervention for recurrent laryngeal neuropathy is based on the grade of the condition, the horse's intended use, and the owner's expectations. The two most common procedures are prosthetic laryngoplasty and ventriculocordectomy. Laryngoplasty involves placing a suture through the muscular process of the left arytenoid cartilage and the caudodorsal border of the cricoid cartilage to maintain abduction. Ventriculocordectomy removes the left vocal cord and laryngeal ventricle to reduce airway obstruction and noise.

Selection between procedures depends on the severity of the condition and the desired outcome. [The review of equine laryngeal disorders](https://pubmed.ncbi.nlm.nih.gov/41654449/) outlines the indications for each procedure and the expected outcomes for different athletic disciplines. Horses undergoing laryngoplasty require a period of stall rest followed by a gradual return to work, and the prognosis for return to previous levels of performance varies with the discipline and the degree of preoperative arytenoid function.

The decision to operate should also consider the horse's age, the chronicity of the condition, and the presence of concurrent upper airway abnormalities. Horses with dynamic collapse of multiple structures may require a combination of procedures, and the surgical plan should be tailored to the individual case.

## Recognized Complications and Early Detection

The principal failure modes of the equine larynx are dynamic obstructions that appear only during high ventilatory demand and structural diseases that are visible at rest. Recurrent laryngeal neuropathy (RLN) is the most important clinical disease affecting the larynx, and its progression from mild asynchronous arytenoid motion to complete hemiplegia is well documented in the landmark studies from Massey University summarized in [The equine larynx](https://pubmed.ncbi.nlm.nih.gov/21838638/). Early detection relies on resting endoscopic examination with a standardized grading system, but the examiner must recognize that a normal resting examination does not exclude dynamic collapse during exercise. Dynamic laryngeal collapse, aryepiglottic fold collapse, and epiglottic retroversion are only reliably identified with exercise endoscopy, as emphasized in the comparative review of [exercise induced laryngeal obstruction in humans and equines](https://pubmed.ncbi.nlm.nih.gov/31736771/).

Arytenoid chondropathy presents a different diagnostic challenge. The affected cartilage enlarges, develops abnormal patterns of mineralisation, and may obliterate the lateral laryngeal ventricle, findings that were characterized using xeroradiography and confirmed at dissection in [xeroradiographic evaluation of the equine larynx](https://pubmed.ncbi.nlm.nih.gov/2764338/). Early detection requires careful comparison of the two arytenoid cartilages for symmetry of the corniculate processes and muscular processes, because unilateral enlargement may be subtle in the early stages. Serial endoscopic examinations are more informative than a single resting study when chondropathy is suspected.

Postoperative complications after laryngeal surgery include persistent coughing, dysphagia, and aspiration pneumonia after prosthetic laryngoplasty, and loss of abduction if the prosthesis fails. Early detection of prosthesis failure relies on repeat endoscopy to compare arytenoid abduction against the immediate postoperative appearance, and on the owner reporting return of abnormal respiratory noise during exercise.

## Common Errors in Assessment

The most frequent error made by students and less experienced clinicians is grading RLN from a single endoscopic view without standardizing head position, swallowing activity, and exercise status. The larynx must be observed continuously through several respiratory cycles, and the horse should be allowed to swallow before the final grade is assigned, because swallowing transiently abducts the arytenoid cartilages and can mask mild paresis.

A second error is interpreting the normal asymmetry of the arytenoid cartilages as pathologic. Mild asymmetry at rest is common in normal horses, and the diagnosis of RLN requires either consistent asynchronous motion during inspiration or a demonstrable reduction in maximal abduction. The examiner should also distinguish true arytenoid paresis from arytenoid fixation caused by chondropathy, since the management and prognosis differ substantially.

A third error is relying on resting endoscopy alone when the history strongly suggests dynamic collapse. The comparative evidence from human and equine exercise laryngoscopy shows that abnormalities are only revealed during exercise and resolve quickly after cessation, so a normal resting examination has limited negative predictive value in a horse with poor performance and abnormal respiratory noise.

## Limitations of Current Evidence

The evidence base for equine laryngeal function rests heavily on endoscopic observation and on computational and imaging studies that carry inherent limitations. The computational model of turbulent airflow through the equine upper airway, developed from CT reconstructions of a racehorse, demonstrates that flow characteriztics differ substantially between inhalation and exhalation and that the nasopharynx changes geometry between phases, but the model represents a single individual and cannot capture the full range of normal variation. Magnetic resonance imaging provides excellent soft tissue differentiation of the laryngeal cartilages, hyoid apparatus, and muscle groups, yet individual muscles cannot always be delineated in every plane, and the technique requires general anesthesia, which limits its use in clinical assessment of dynamic function.

Expert opinion still differs on the clinical significance of mild resting arytenoid asymmetry, on the optimal timing of exercise endoscopy relative to peak exertion, and on the value of quantitative airway pressure measurement versus visual grading. The comparative review notes that quantitative grading techniques proven effective in veterinary research are only now being piloted in human studies, indicating that the field is still developing objective standards.

## Referral and Escalation Criteria

Referral for specialist evaluation is warranted when resting endoscopy reveals arytenoid chondropathy, when dynamic collapse is suspected but cannot be confirmed with available equipment, when the horse fails to improve after surgical treatment, or when performance limitation persists despite a normal resting laryngeal examination. Specialist centers offer high-speed treadmill endoscopy, which allows continuous observation from rest to peak exertion and is the definitive method for characterizing dynamic obstructions. Advanced imaging such as CT or MRI may be indicated when chondropathy, neoplasia, or traumatic injury is suspected, since these modalities define the extent of cartilage involvement better than endoscopy alone.

Laboratory involvement is rarely required for primary laryngeal disease, but histopathology of excised arytenoid cartilage or laryngeal muscle is indicated when the gross appearance is atypical or when the response to treatment is unexpectedly poor. Regulatory reporting is not a routine component of laryngeal disease management in most jurisdictions, but clinicians should be aware that conditions causing persistent respiratory noise or exercise intolerance may be relevant to pre-purchase examinations and to insurance or warranty claims, and the findings should be documented according to the standards expected by the examining body.

## Troubleshooting Guide

| Observation | Likely cause | Discriminating check |
|---|---|---|
| Asynchronous arytenoid motion at rest | Mild RLN versus normal variation | Repeat endoscopy after swallowing, observe through multiple cycles, grade with standardized system |
| Complete arytenoid paralysis | Advanced RLN | Confirm absent abduction on deep inspiration, exclude arytenoid fixation by palpation or imaging |
| Enlarged arytenoid with irregular surface | Arytenoid chondropathy | Compare symmetry of corniculate processes, consider CT or MRI to define cartilage involvement |
| Normal resting endoscopy with exercise intolerance and noise | Dynamic collapse (DLC, aryepiglottic fold collapse, epiglottic retroversion) | Exercise endoscopy from rest to peak exertion |
| Postoperative loss of abduction | Prosthesis failure or suture pull-through | Repeat endoscopy, compare abduction to immediate postoperative appearance |
| Persistent coughing or dysphagia after laryngoplasty | Laryngeal dysfunction or aspiration | Observe swallowing, thoracic auscultation, consider bronchoscopy if aspiration suspected |

## Frequently Asked Questions

### How Should I Adapt My Laryngeal Examination When High-Definition Videoendoscopy Is Unavailable?

A standard 1 m flexible endoscope with a light source remains adequate for resting laryngeal evaluation in most horses. Position the horse in a quiet, dimly lit stall with the head held in a neutral position. Sedation with alpha-2 agonists can reduce swallowing and facilitate a complete examination, but be aware that profound sedation may alter arytenoid abduction symmetry. If dynamic collapse is suspected and treadmill endoscopy is unavailable, consider high-speed treadmill evaluation at a referral center, or perform overground endoscopy if that equipment exists locally. The comparative review of exercise-induced laryngeal obstruction in humans and horses emphasizes that abnormalities may only appear at peak exertion, so a resting examination that appears normal does not exclude dynamic disease.

### What Are the Practical Limitations of CT and MRI for Laryngeal Imaging in Clinical Cases?

Computed tomography and magnetic resonance imaging require general anesthesia, which introduces risk and cost, and the equipment is not universally available. The published MRI protocol for the normal equine larynx used a 0.3 T unit with transverse T2-weighted and T1-weighted sequences as the most useful planes, and contrast administration helped identify vessels. Individual intrinsic muscles were not always separable in every plane. CT provides superior bone and mineralised cartilage detail, which is valuable when arytenoid chondropathy is suspected, because abnormal patterns of mineralisation and contour changes are visible radiographically and tomographically. For most dynamic obstructions, however, resting imaging adds little beyond endoscopy, and functional assessment during exercise remains the diagnostic standard.

### How Do I Distinguish Laryngeal Obstruction From Lower Airway Disease as a Cause of Exercise Intolerance?

Both conditions produce poor performance, abnormal respiratory noise, and increased respiratory effort during exertion. The comparative review of exercise-induced laryngeal obstruction notes that lower airway disease, cardiac disease, and poor fitness are the major differential diagnoses in both horses and humans. Auscultation during exercise, either with a rebreathing bag at rest or during treadmill work, helps identify wheezes originating from the lower airways. Endoscopy during exercise is the definitive method: laryngeal collapse is visible directly, whereas lower airway disease typically shows no dynamic laryngeal abnormality. A resting endoscopic examination cannot reliably differentiate the two, because many horses with recurrent laryngeal neuropathy appear normal at rest. If dynamic endoscopy is unavailable, a therapeutic trial for asthma, such as environmental management and bronchodilator therapy, may be diagnostically useful before pursuing surgical options.

### What Should I Document in the Medical Record for a Horse With Suspected Laryngeal Dysfunction?

Record the examination conditions, including sedation protocol, head position, and whether the horse was exercised before evaluation. Document the resting arytenoid abduction grade using a recognized grading system, noting any asymmetry, and describe the appearance of the corniculate processes, aryepiglottic folds, epiglottis, and soft palate. Include still images or video clips if capture is possible. For dynamic examinations, record the exercise intensity at which any abnormality first appeared and how it progressed. Note the presence or absence of respiratory noise and its timing in the respiratory cycle. The institutional review of laryngeal disorders describes the major conditions and their clinical signs, so use that framework to guide your description. This record supports serial comparisons and provides the referral clinician with the information needed to plan surgery.

### How Should I Explain a Laryngeal Grade to an Owner Who Is Not Familiar With Equine Airway Disease?

Use a simple analogy that preserves the functional message. Explain that the arytenoid cartilages act as a pair of doors that must open fully during exercise to let air pass. In recurrent laryngeal neuropathy, the nerve supply to one door is damaged, so that side does not open as widely, which narrows the airway and increases breathing effort. Describe the grade as a measure of how much the door opens at rest, and clarify that a normal resting grade does not guarantee normal function at high exercise intensity. The owner should understand that surgical options exist, but the choice depends on the intended use of the horse, the severity of the grade, and the findings of dynamic endoscopy. Refer them to the attending surgeon for procedure-specific risks and prognosis.

### What Is the Role of Airway Pressure Measurement in Clinical Laryngeal Assessment?

Airway pressure measurement is primarily a research tool, but it has clinical value in quantifying obstruction severity and in monitoring response to treatment. The comparative review notes that quantitative grading techniques such as airway pressure measurement have proven effective in veterinary research and are being piloted in human studies. In practice, a pressure catheter placed in the pharynx or trachea during exercise can document the pressure swing associated with each breath, and a fixed obstruction produces a characteriztic pressure profile. This technique is most useful when endoscopic findings are equivocal or when a horse has persistent exercise intolerance despite a normal dynamic endoscopic examination. Availability is limited to referral centers with the appropriate equipment and expertise, so its role in first-opinion practice is minimal.

## Related Clinical & Scientific Guides

* [Canine Respiratory System: Anatomy and Physiology](/knowledge/veterinary-medicine/veterinary-anatomy-physiology/canine-respiratory-system-anatomy-physiology)
* [Comparative Anatomy of the Mammalian Kidney](/knowledge/veterinary-medicine/veterinary-anatomy-physiology/comparative-anatomy-mammalian-kidney)
* [Feline Cardiopulmonary Physiology: Heart-Lung Interactions](/knowledge/veterinary-medicine/veterinary-anatomy-physiology/feline-cardiopulmonary-physiology-heart-lung-interactions)


## References and Further Reading

- [Disorders of the Equine Head and Neck: Larynx and Pharynx.](https://pubmed.ncbi.nlm.nih.gov/41654449/). 2026.
- [Magnetic resonance imaging anatomy of the normal equine larynx and pharynx.](https://pubmed.ncbi.nlm.nih.gov/19697604/). 2009.
- [Simulation of turbulent airflow using a CT based upper airway model of a racehorse.](https://pubmed.ncbi.nlm.nih.gov/18532860/). 2008.
- [Exercise Induced Laryngeal Obstruction in Humans and Equines. A Comparative Review.](https://pubmed.ncbi.nlm.nih.gov/31736771/). 2019.
- [The equine larynx.](https://pubmed.ncbi.nlm.nih.gov/21838638/). 2002.
- [Xeroradiographic evaluation of the equine larynx.](https://pubmed.ncbi.nlm.nih.gov/2764338/). 1989.
- [NCBI Bookshelf: Veterinary and Comparative Biomedical Sciences](https://www.ncbi.nlm.nih.gov/books/). NCBI Bookshelf.
- [MSD Veterinary Manual, Professional Edition](https://www.msdvetmanual.com/). MSD Veterinary Manual.
- [American Veterinary Medical Association Practice Resources](https://www.avma.org/resources-tools). American Veterinary Medical Association.

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> This article is educational professional reference material for veterinary audiences. It is not a substitute for veterinary diagnosis, individual clinical judgment, current product labeling, or applicable regulatory requirements.