Sx conditions of the equine larynx

Question 1

Describe 95% of laryngeal hemiplegia cases

Answer 1

Unilateral, left-sided, and idiopathic

Question 2

What is left sided laryngeal hemiplegia?

Answer 2

Progressive neuropathy of the left recurrent laryngeal nerve

Question 3

What innervates the majority of the laryngeal musculature?

Answer 3

The left recurrent laryngeal nerve

Question 4

What is the main abductor muscle of the larynx in the horse?

Answer 4

The cricoarytenoideus dorsalis muscle

Question 5

What breeds are predisposed to laryngeal hemiplegia?

Answer 5

TB, draughts, warmbloods

Question 6

What are the most common causes of right laryngeal hemiplegia?

Answer 6

(1) 4-BAD

(2) Right arytenoid chondritis

Question 7

What can cause laryngeal hemiplegia in horses?

Answer 7

(1) nerve damage
(2) organophosphate or lead toxicity
(3) CNS diseases/hepatic encephalopathy

Question 8

What is the pathophysiology of laryngeal hemiplegia?

Answer 8

Unable to achieve max abduction -> reduced size of the rim glottides -> hypoxemia, hypercapnia, acidosis -> fatigue

Question 9

You are called out to see a horse where the owner is complaining of exercise intolerance and poor performance. On exam, you hear “roaring,” which is abnormal inspiratory noise. What is your top differential?

Answer 9

laryngeal hemiplegia

Question 10

How can you diagnose laryngeal hemiplegia?

Answer 10

Endoscopy, palpation and US

Question 11

What is the gold standard of endoscopy and laryngeal hemiplegia?

Answer 11

Dynamic endoscopy, either overground or treadmill

Question 12

What can you palpate on a horse with laryngeal hemiplegia?

Answer 12

Prominence of the muscular process of the arytenoid cartilage and the dorsal aspect of the cricoid cartilage

Question 13

What is the name of the grading scale for standing endoscopy with laryngeal hemiplegia?

Answer 13

Havermeyer

Question 14

Define a grade 1 havermeyer laryngeal hemiplegia

Answer 14

Movement of arytenoid cartilage is synchronous and symmetrical, full abduction is achieved

Question 15

Define a grade 2 havermeyer laryngeal hemiplegia

Answer 15

Movement of arytenoid cartilage is asynchronous and/or larynx asymmetric at times but full abduction is achieved and maintained

Question 16

Define a grade 3 havermeyer laryngeal hemiplegia

Answer 16

Movement of arytenoid cartilage is asynchronous and or asymmetric. Full abduction cannot be achieved and maintained

Question 17

Define a grade 4 havermeyer laryngeal hemiplegia

Answer 17

Complete immobility of the arytenoid cartilage and vocal fold

Question 18

When is sx indicated for laryngeal hemiplegia and why?

Answer 18

Only if it is necessary for the horse to perform because complications are frequent and often severe

Question 19

What are the surgical options for laryngeal hemiplegia?

Answer 19

(1) prosthetic laryngoplasty
(2) Ventriculocordectomy
(3) Re-innervation of CAD muscle
(4) Re-innervation of CAD muscle + dynamic prosthetic laryngoplasty

Question 20

Which surgical option for laryngeal hemiplegia results in a major improvement of airflow mechanics?

Answer 20

Prosthetic laryngoplasty

Question 21

Which surgical option results in elimination/significant improvement of abnormal noise and some improvement of airflow dynamics?

Answer 21

Ventriculocordectomy

Question 22

What is the most commonly performed surgical treatment for laryngeal hemiplegia in a horse and what procedure is it frequently combined with?

Answer 22

Prosthetic laryngoplasty + ventriculocordectomy

Question 23

T/F The abnormal respiratory noise is removed with a prosthetic laryngoplasty

Answer 23

F: a ventriculocordectomy is the procedure that treats the abnormal noise

Question 24

What type of horses are most commonly treated with a prosthetic laryngoplasty?

Answer 24

Horses performing at high speeds

Question 25

What is the prosthesis made out of for a prosthetic laryngoplasty?

Answer 25

1-2 strands of non absorbable suture

Question 26

Does a prosthetic laryngoplasty or a ventriculocordectomy cause more complications?

Answer 26

Prosthetic laryngoplasty

Question 27

What are the complications that can be caused by a prosthetic laryngoplasty?

Answer 27

(1) Dysphagia (avoid over abduction) (2) Chronic coughing (3) Prosthesis failure (4) Seroma (5) Wound infection (6) Arytenoid condritis

Question 28

What is the scale used to measure post-op abduction after a prosthetic laryngoplasty?

Answer 28

Dixon

Question 29

What is the most common indication for a ventriculocordectomy?

Answer 29

Sports horses where the primary complaint is noise and w/ minimal or no exercise intolerance

Question 30

What are the sx techniques that can be used for a ventriculocordectomny and which is preferred?

Answer 30

(1) Via laryngotomy or (2) trans-endoscopically (preferred)

Question 31

How is re-innervation of the CAD muscle done?

Answer 31

Branch of C1 is identified, isolated and fed through the CAD muscle

Question 32

What does C1 innervate?

Answer 32

C1 innervates the accessory respiratory muscles

Question 33

What is the time frame for re-innervation for the CAD muscle?

Answer 33

4-5 months at the earliest to 12 months

Question 34

When can't re-innveration of the CAD muscle be performed?

Answer 34

If the horse already underwent a laryngoplasty, there is fibrosis of the CAD muscle, or there is C1 disruption

Question 35

What is the usual signalment for development of sub epiglottic cysts?

Answer 35

Young TB and SB, usually congenital

Question 36

What are the CS of sub epiglottic cysts in foals and older horses?

Answer 36

Foals: dysphagia -> coughing and pneumonia Older horses: dysphagia if large, resp noise

Question 37

How do you diagnose a sub epiglottic cyst?

Answer 37

(1) endoscopy | 2) oral endoscopy/palpation (speculum

Question 38

Describe sub epiglottic cysts

Answer 38

* 1.5 - 5 cm, round, pink, mucosa-covered, smooth mass * Asymmetric elevation of epiglottis * +/- concurrent epiglottic entrapment * Lift epiglottis as some cysts might slip under soft palate

Question 39

What happens if you puncture and drain a sub epiglottic cysts?

Answer 39

It will refill rapidly

Question 40

What is a two options for treatment for sub epiglottic cysts?

Answer 40

(1) Formalin injection | (2) Surgical excision

Question 41

If you remove too much sub-epiglottic tissue when you excise a sub epiglottic cyst, what does that put the horse at risk for?

Answer 41

DDSP

Question 42

With a surgical excision of a sub-epiglottic cyst, what do you administer post op?

Answer 42

IV dexamethasone, NSAIDs, and throat spray

Question 43

What does 4-BAD stand for?

Answer 43

4th branchial arch defects

Question 44

What are the 4 abnormalities that can exist in 4-BAD

Answer 44

(1) Lateral wings of the thyroid cartilage (2) Crycoarytenoid articulation (3) Crycothyroid (4) Thyropharyngeus and cricopharynxgeus mm

Question 45

CS of 4-BAD are rare but they include.....

Answer 45

(1) collapse of soft tissues or cartilage -> exercise induced respiratory noise. Normal CAD but ineffective due to abnormal joint (2) dysphagia might be present (3) Chronic colic due to dysfunction of cranial esophageal sphincter

Question 46

How do you differentiate 4-BAD from LLH or chondrites?

Answer 46

4-BAD more commonly affects the right side while LLH or chondritis more commonly affects the left side