Equine Pharyngeal and Laryngeal Disorders

Question 1

What is the most common presenting complaint for horses w/ disorders of the nasopharynx and larynx?

Answer 1

Presence of abnormal respiratory noise during exercise. Noise audible when stood near the horse whilst it is exercising, not w/ a stethoscope.
Can also cause poor athletic performance and exercise intolerance dept. on severity.

Question 2

Why does the horse experience upper airway collapse?

Answer 2

Dynamic obstructions so only occurring during exercise.
- dramatic increases in air flows and airway pressure changes.
– structures unable to withstand pressures and collapse into airway.
–> structures held open by muscle activity as opposed to cartilage like other structures like nasal passages and trachea, so larynx and pharynx become the weak point.
Horses are obligate nasal breathers so more prevalence in horse compared to other spp.

Question 3

How to investigate a horse that presents w/ abnormal respiratory noise.

Answer 3

Listen to the horse exercise.
CE - typically not as rewarding.
Resting endoscopy.
Exercising endoscopy.

Question 4

1. What happens to the horse’s breathing at walk, trot and canter.
2. How is this helpful when listening to the horse’s breathing during exercise?

Answer 4

1. Have control over own breathing at walk and trot.
   At canter, have locomotor respiratory coupling, so one breath every one stride.
   Expiration occurs when the front legs hit the floor. Inspiration when front legs off the ground.
2. Can identify if the obstruction is inspiratory or expiratory based on when the respiratory noise is heard (FLs on ground or FLs off ground).

Question 5

1. Normal when listening to horse breathing during exercise?
2. Abnormal when listening to horse breathing during exercise?

Answer 5

1. Can hear expiration, inspiratory sounds should be quiet.
   High blowing - fluttering of false nostril.
   Geldings/stallions - noise from sheath.
2. Inspiratory noise often described as roaring / whistling.
   Expiratory noise often described as gurgling.

Question 6

CE?

Answer 6

Laryngeal palpation.
- Palpate laryngeal cartilages.
– all normal and in place.
- Palpate intrinsic musculature.
– cricoarytenoideus dorsalis muscle to compare L to R.
–> atrophy of L side indicates recurrent laryngeal neuropathy.

Question 7

Resting endoscopy.

Answer 7

Look for any structural abnormalities.
Assess movement and symmetry of arytenoid cartilages.
Assess position of soft palate.

Question 8

Endoscopy during exercise.

Answer 8

For definitive Dx.
Treadmill - high-speed - less common now.
Overground - telemetric system mounted on horse while horse ridden under normal conditions (most applicable to that horse).

Question 9

Naming of most obstructions.

Answer 9

Named simply by which structure is collapsing into the airway.

Question 10

TEST YOURSELF ON LECTURE RECORDING FROM 16 MINS TO 26 MINS.

Question 11

1. What is pharyngeal lymphoid hyperplasia?
2. In what horses is it common?
3. Cause?
4. Dx?
5. Tx?

Answer 11

1. Follicles of lymphoid hyperplasia on the walls of the nasopharynx.
2. Young horses.
3. Exposure to novel antigens (a normal response).
4. Resting endoscopy.
5. Resolution occurs as horse ages and unusual in horses >5yo.
   Most cases do not warrant Tx.
   Severe cases occasionally require anti-inflammatories/ABX.

Question 12

1. What is the most commonly diagnosed dynamic obstruction of URT?
2. Forms of this obstruction.

Answer 12

1. Palatal dysfunction.
2. Dorsal displacement of the soft palate (ddsp).
   Palatal instability.

Question 13

1. What happens in DDSP?
2. In what group of horses is this most common?
3. What signs is DDSP associated with?

Answer 13

1. Caudal border of the soft palate becomes displaced dorsal to the epiglottis.
2. Racehorses - during strenuous exercise.
   Can be seen in sport or pleasure horses.
3. Poor performance and abnormal expiratory noise (“gurgle”).

Question 14

Palatal instability.

Answer 14

Billowing movements of the caudal portion of the soft palate w/ flattening of the ventral surface of the epiglottis against the dorsal surface of the soft palate.
Some cases progress to DDSP but not all.
Causes inspiratory noise.

Question 15

Causes of DDSP.

Answer 15

• Unfitness.
• Neuromuscular dysfunction of soft palate muscles. Innervation from pharyngeal branch of vagus which passes through guttural poch and may be damaged by infection.
• Position of larynx and hyoid - caudal retraction of larynx may predispose to DDSP.
• Oropalatal seal - ventral soft palate should contact base of tongue and factors such as mouth opening because of bit may lead to air disrupting seal.
• Abnormalities w/ epiglottis (small or flaccid).

Question 16

DDSP on resting endoscopy.

Answer 16

Most horses w/ DDSP during exercise are normal during resting endoscopy.
Horses which do displace during resting exam are statistically more likely to displace during exercise.
But exercising endoscopy needed to confirm.

Question 17

Conservative management of DDSP.

Answer 17

Improve fitness.
Rest.
Tongue tie - to mandible (ethically challenging).
Nosebands.
Bit attachments.
Medical treatment - corticosteroids.

Question 18

Surgical treatment of DDSP.

Answer 18

Only moderate efficacy for most treatments.
UK - thermal cautery and/or laryngeal tie forward performed most commonly.

Question 19

Aim of thermal cautery to the palate.

Answer 19

Burn ventral surface of soft palate.
Increase tension or stiffness by creating scar tissue.
Required to be declared to British Horseracing Authority.
Ethically concerning.

Question 20

Aim of laryngeal tie forward.

Answer 20

To position larynx in a more rostral position by placing a suture between the thyroid cartilage and the basihyoid bone.

Question 21

1. Pharyngeal wall collapse types.
2. Associated w/ sign…
3. Pharyngeal wall collapse cause?

Answer 21

1. Dorsal, lateral or circumferential.
2. Abnormal inspiratory noise.
3. Unknown - probably neuromuscular dysfunction of pharyngeal musculature.

Question 22

1. Why is pharyngeal wall collapse more common in sports horses than racehorses?
2. Tx of pharyngeal wall collapse?
3. Px for successful racing career if moderate to severe pharyngeal wall collapse.

Answer 22

1. Due to head flexion.
2. Empirical 4-5mths rest and course of corticosteroids.
3. Poor.

Question 23

1. Arytenoid cartilage collapse AKA?
2. Nerve affected?
3. Muscle therefore affected?
   - action?
4. Side affected mostly?

Answer 23

1. Recurrent laryngeal neuropathy, laryngeal hemiplegia/laryngeal paralysis.
2. Recurrent laryngeal nerve.
3. Cricoarytenoideus dorsalis. - abduction of arytenoid cartilages (opens larynx).
4. Left.

Question 24

What happens to cause the nerve pathology in arytenoid cartilage collapse?

Answer 24

Distal axonopathy whereby the larger myelinated nerve fibres degenerate from the motor end-plate proximally towards the cell body. This causes permanent dysfunction of the muscles innervated by this nerve. Effect on cricoarytenoideus dorsalis leads to failure to achieve arytenoid abduction during exercise.

Question 25

Arytenoid cartilage collapse clinical signs.

Answer 25

Inspiratory noise (whistle/roar), exercise intolerance.
Clinical significance dept. on degree of obstruction of the rima glottidis and the type of work horse expected to perform.

Question 26

Dx of arytenoid cartilage collapse.

Answer 26

Palpate for cricoarytenoideus dorsalis atrophy.
Resting endoscopy.
Exercising endoscopy.

Question 27

Treatment options for arytenoid cartilage collapse.

Answer 27

Prosthetic laryngoplasty.
Implants a ligature between caudal border of cricoid cartilage and muscular process of arytenoid to mimic action of cricoarytenoideus dorsalis in semi-contracted state.
Usually combined w/ ventriculocordectomy (“hobday”).

Laryngeal reinnervation (cervical nerve transplantation.

Question 28

Problems w/ prosthetic laryngoplasty.

Answer 28

Chronic cough due to tracheal contamination of food.
Loss of abduction.

Question 29

1. Affected horses present w/?
2. Severity compared to ACC?
3. Dx of vocal cord collapse?
4. Tx of vocal cord collapse.

Answer 29

1. Inspiratory noise (more high pitched) but are normal on a resting endoscopic exam.
2. Less airway obstruction than ACC.
3. Exercising endoscopy required.
4. Ventriculocordectomy (hobday).
   - surgically, under GA or standing, or by laser.

Question 30

1. What does a horse w/ medial deviation of the aryepiglottic folds present w/?
2. On resting endoscopy?
3. What other conditions does this occur alongside?
4. Tx of medial deviation of the aryepiglottic folds?
5. What does the disorder look like on exercising endoscopy?

Answer 30

1. Abnormal inspiratory noise.
2. Normal.
3. DDSP or ACC.
4. Laser or wedge resection of the aryepiglottic folds.
5. Hourglass shape on collapse.