Larynx

Question 1

List the cartilages of the larynx

Answer 1

• Epiglottic
• Thyroid
• Cricoid
• sesamoid
• interarytenoid
• paired arytenoid

Question 2

List the processes of the arytenoid cartilages

Answer 2

• Cuneiform
• Corniculate
• Vocal
• Muscular

Question 3

List the extrinsic and intrinsic muscles of the larynx

Answer 3

Extrinsic (constrict the caudal part of the pharynx)
- Thyropharyngeus
- Cricopharyngeus

Intrinsic
- Cricoarytenoideus dorsalis (arytenois abduction)
- Cricoarytenoideus lateralis (Pivots arytenoid inwards to close rima glottidis
- Thyroarytenoideus - Gives rise to ventricularis and vocalis muscles
- Arytenoideus transversus
- Hyoepiglotticus (draws epiglottis downwards)
- Cricothyroideus (tenses the vocal cords)

Question 4

How does the feline laryngeal anatomy differ from dogs?

Answer 4

• The arytenoid cartilages lack a cuneiform and corniculate process and try aryepiglottic folds are absent (mucosa connects sides of epiglottis directly to the cricoid lamina)
• Vocal cords are thick and rounded
• Ventricles are absent

Question 5

List the three functions of the larynx

Answer 5

• Larynx is pulled cranially during swallowing to block laryngeal opening
• Controls airway resistance
• Voice production

Question 6

What % of dogs with BOAS will have:
- Stenotic nares
- Elongated soft palate
- Everted saccules
- Laryngeal collapse

Answer 6

• Stenotic nares 43-85%
• Elongated soft palate 86-96%
• Everted saccules 55-66%
• Laryngeal collapse 8-70%

Question 7

What are the three stages of laryngeal collapse?

Answer 7

• Stage I - Everted laryngeal saccules
• Stage II - Cuneiform process losses its rigidity and becomes medially displaced
• Stage III - Corniculate process collapse, resulting in loss of dorsal arch of rima glottidis

Question 8

What are the options for a patient with laryngeal collapse who does not respond to surgical management of BOAS and medical management?

Answer 8

• Permanent tracheostomy
• Laryngeal tieback

Question 9

Damage to what structures can cause lar par?

Answer 9

• Nucleus ambiguus
• Vagus nerve or its branches
• Cricoarytenoideus dorsalis muscle

Question 10

What causes congenital lar par?
What breeds are overrepresented?

Answer 10

• Progressive degeneration of neurons within the nucleus ambiguus and Wallerian degeneration of laryngeal nerves
• Bouvier des Flandres, Bull terriers, dalmations, Rottweilers, Leonberger

Question 11

What breeds are overrepresented for acquired lar par?

Answer 11

• Lab and Golder Retrievers
• St Bernards
• Irish Setters

Question 12

What % of dogs with lar par have pre-op aspiration pneumonia?
Oesophageal dysfunction?

Answer 12

• Aspiration pneumonia 7.9%
• Oesophageal dysfunction 11.4% - assoc with an increased risk of post-op complications

Question 13

What is doxapram?

Answer 13

CNS stimulant which causes an increased resp rate and tidal volume by increasing the electrical activity in the inspiratory and expiratory centers of the medulla

Question 14

What are the surgical options for the Tx of lar par?

Answer 14

• Unilateral or bilateral arytenoid lateralisation
• Ventricular cordectomy and partial arytenoidectomy
• Modified castellated laryngofissure
• Permanent tracheostomy

Question 15

What is the reported increase in rima glottidis opening using cricoarytenoid and thyroarytenoid lateralisation?

Answer 15

• Cricoarytenoid - 207%
• Thyroarytenoid - 140%

Question 16

What is the prognosis after tieback?

Answer 16

• 90% will improve
• 70% alive at 5yr

Complications 10-58%
- Aspiration pneumonia 8-21%
- Persistent or recurrence of signs in up to 33%
- Failure (suture breakage or cartilage fracture
- Laryngeal webbing
- etc

Bilateral complication rate 89% with 8/9 dogs developing asp pneumonia and 5/9 dying within 5 months

Question 17

What are the 2 approaches for a partial laryngectomy?

Answer 17

• Intra-oral
• Ventral (less risk of webbing as can close the mucosa primarily)

Removing vocal cord and corniculate and vocal process of arytenoid (cuneiform process left intact)

Question 18

What is the rate of aspiration pneumonia and laryngeal webbing formation with intraoral partial laryngectomy?

Answer 18

• Aspiration pneumonia 6-33%
• Laryngeal webbing - 8-14%

Question 19

When is a permanent tracheostomy a good option for lar par?

Answer 19

Dogs at a high risk for aspiration pneumonia drom myopathy, megaoesophagus, hiatal hernia, GI disorder etc