Chapter 101 Larynx Flashcards
Label the diagram:
Name the six cartilages of the larynx
- Epiglottis
- Thyroid
- Cricoid
- Arytenoid
- Inter-arytenoid (between arytenoid cartilages and cricoid, caudo-dorsal to sesamoid)
- Sesamoid (connecting corniculate processes)
Which two nerves innervate the thyropharyngeus and cricopharyngeus muscles? (both muscles innervated by same two nerves)
Glossopharyngeal (CN IX) and vagus (CN X)
- Which muscle is responsible for abducting the arytenoid to open glottis?
- Where does it insert?
- How is it innervated?
- Cricoarytenoideus dorsalis
- Muscular process of arytenoid
- Caudal laryngeal nerve (terminal segment of recurrent laryngeal) provides motor supply to all intrinsic laryngeal muscles except cricothyroideus
(Cranial laryngeal n (branch of vagus) supplies cricothyroid m.)
Label the diagram:
Name the bones of the hyoid apparatus, from craniodorsal to caudoventral.
Which is un-paired?
Stylohyoid
Epihyoid
Ceratohyoid
Basihyoid (unpaired)
Thyrohyoid
“Sick Elephants Can Be Treated”
What is the blood supply to the larynx?
Cranial and caudal thyroid arteries
List 3 differences between dog and cat larynx:
- Cats lack corniculate and cuneiform processes
- Cats lack ventricles
- Cats have thick rounded vocal folds
- Cats lack true aryepiglottic fold
What are the three functions of the larynx?
- Block laryngeal opening during swallowing
- Control airway resistance
- Voice production
In cats, what are the two most common types of laryngeal neoplasia?
List 3 other types that have been reported:
Lymphoma and SCC most common
Adenocarcinoma, invasive ectopic thyroid, round cell reported
List 8 types of laryngeal neoplasia reported in dogs
- Adenocarcinoma
- SCC
- Rhabdomyoma
- Rhabdomyosarcoma
- Osteosarc
- Chondrosarc
- Fibrosarc
- MCT
- Plasmacytoma
- Granular cell myoblastoma
N.B. Not lymphoma!
List three methods of excision of laryngeal neoplasia:
- Local excision
- Partial laryngectomy (can be supported with rotatory door myocutaneous flap based on sternohyoid m and cr thyroid artery i..e scrape epidermis to remove hair follicles then twist muscle 180° so skin facing intraluminally in larynx).
- Total laryngectomy + permanent tracheostomy (consider gastrostomy for post-op management)
Describe stage I, II and II laryngeal collapse
- Stage I, laryngeal saccule eversion.
- Stage II, the cuneiform process of the arytenoid cartilage loses its rigidity and becomes medially displaced.
- Stage III, the corniculate processes collapse, resulting in loss of the dorsal arch of the rima glottidis and subsequent airway obstruction.
What percentage of BOAS dogs present with pneumonia?
13.6%
List 3 surgical options for severe laryngeal collapse, above and beyond usual BOAS stuff.
- Laryngeal tie-back (combined cricoarytenoid and thyroarytenoid)
- Permanent tracheostomy
- Partial arytenoidectomy (?if any literature exists re this. Swelling common advise temp trach)
Where does the vagus nerve originate?
Caudal nucleus ambiguus
List 4 common breeds for congenital laryngeal paralysis
- Bouvier des Flanders (+ huskies = degeneratioon of neurons in nucleus ambiguus –> Wallerian degeneration of laryngeal nerves)
- Bull Terriers
- Dalmatians
- Huskies
- Rotties (neuronal vacuolation and axonal degeneration)
MAy see bilat pelvic limb foot drop due to cranial tibial muscle paralysis
List 4 breeds that get aquired laryngeal paralysis
- Labrador
- Golden Retriever
- St Bernard
- Irish Setter
List 5 possible causes of aquired laryngeal paralysis
- Chronic endocrine disease
- Chronic infectious disease
- Immune mediated polyneuropathy
- Idiopathic “polyneuropathy”
- Trauma to vagus/recurrent laryngeal nerve
- Polyradiculoneuropathy
- Organophosphate toxicity
- Retropharyngeal infection
- Rabies
- SLE
- Bronchogenic carcinoma
- Brainstem lesion
- Laryngeal myopathy
- Paratracheal mass
What is the most common clinical signsin cats with lar par?
Tachypnoea or dyspnoa
What percentage of dogs with lar par are diagnosed with concurrent aspiration pneumonia?
And with pre-op pesophageal disease?
- 9% pneumonia
- 4% oesophageal disease
(both associated w increased risk of post-op complications)
List 4 surgical procedures for management of lar par
- Unilateral Arytenoid lateralization
-
Partial arytenoidectomy/laryngectomy (swelling common advise temp trach) - remove corniculate process + vocal cord
- Transoral approach
- Ventral laryngotomy approach. Benefits:
- Allows mucosal apposition
- Cricoarytenoid dorsalis and thyropharyngeus muscles undisturbed
- Modified castellated laryngofissure
- Permanent trach
In what percentage of dogs undergoing unilateral cricoarytenoid lateralization is improvement seen?
90%
List 5 possible complications of arytenoid lateralization
- Aspiration pneumonia
- Cartilage/suture breakage
- On-going gagging/coughing/stridor/resp signs
- Laryngeal webbing
- GDV
- Progression of neuro deterioration
- Seroma
- Intramural haematoma
List 3 factors associated with development of complications after unilateral cricoarytenoid lateralization:
- Pre-op aspiration pneumonia (post op occurs in 8-21%)
- Post-op megaoesophagus (this also associated with death)
- Tracheostomy tube
- Presence of neurologic comorbidity (OR 4. Bookbinder, VetSurg, 2016)
Which muscle is responsible for moving epiglottis ventrally? What is it’s innervation?
Hyoepiglotticus, innervated by hypoglossal nerve (CN XII)
How can epiglottic retroversion be diagnosed?
How is it treated?
Fluoroscopy, laryngoscopy.
Epiglottopexy. If that fails, partail epiglottectomy reported
(Mullins VETSURG 2020 reported fewer post op complications with epiglottectomy)
Name an unusual potential component of BOAS, reported in 14 brachys and 5 Chow Chows
Displacment of glossoepiglottic mucosa (Schabbing, JAAHA 2017)
Tx: Likely resolved with usual BOAs treatment or can be resected + primary closure of mucosa.
