101. Larynx

Question 1

structures of the hyoid apparatus

Answer 1

S E C B Ts. stylohyoide. epihyoidc. ceratohyoidb. basihyoidt. thyrohyoid

Question 2

cartilages of the larynx

Answer 2

epiglotticthyroid (largest)cricoid (complete ring)arytenoid (corniculate, cuneiform, vocal and muscular process)sesamoid (connect the paired corniculate processes of the arytenoid)

Question 3

muscle attaching the epiglottis to the middle of the body of the hyoid apparatus

Answer 3

hyoepiglotticus musclecontraction pulls the epiglottis downintrinsic muscle of the larynx

Question 4

neurovascular structure in the rostral notch of the thyroid cartilage

Answer 4

cranial laryngeal nervelaryngeal artery

Question 5

insertions site of what muscle to the muscular process of the arytenoid

Answer 5

cricoarytenoideus dorsalis musclemost important intrinsic muscle of the larynxabducts arytenoid cartilage to open the glottisrecurrent laryngeal nerve (caudal laryngeal branch) innervation

Question 6

extrinsic muscles of the larynx

Answer 6

thyropharyngeus mcricopharyngeus mboth fx to constrict caudal pharynxunder glossopharyngeal (9) and vagus (10) nerve stimulation

Question 7

innervation to the larynx

Answer 7

cranial and caudal laryngeal nerves that originate from vagus (10)the caudal laryngeal nerve is the branch of the left recurrent laryngeal nervethe caudal laryngeal nerve provides all the intrinsic muscle innervation EXCEPT cricothyroideus muscle

Question 8

blood supply to the larynx

Answer 8

cranial and caudal thyroid artery branches

Question 9

what is different about the feline arytenoid cartilage

Answer 9

lacks cuneiform, corniculate processes and aryepiglottic folds

Question 10

three function of the larynx

Answer 10

1. pulls cranially during swallow to protect rima glottis under epiglottis and prevent aspiration 2. helps control airway resistance with abduction of the arytenoid cartilages during inspiration 3. voice production by changing tension on vocal cords

Question 11

characteristic of most laryngeal tumors

Answer 11

malignantmet slowly but very locally aggressivesmall tumors can be excised with ventral laryngotomy or transoral approachlarge tumors: partial or complete laryngectomy (with permanent tracheostomy)

Question 12

percentage of BCAS dogs that have some form or laryngeal collapse and what are the stages of collapse

Answer 12

50-70%I. eversion of laryngeal saccadesII. collapse of cuneiform process of arytenoidIII. collapse of corniculate process of arytenoid in combo with stages I and II

Question 13

percentage of occurrence of BCAS components in brachycephalic dogs

Answer 13

mostly based on Fasanella et al JAVMA 2010elongated SP > 90%stenotic nares 80%eversion of laryngeal saccades 70%eversion of tonsils 60%(historical accounts of hypo plastic trachea in 40%)

Question 14

tx of laryngeal collapse

Answer 14

–wt loss–exercise restriction–cool environment–antianxiety drugs–antiinflammatories (GCC or NSAID)–staphylectomy or palatoplasty–nares wedge resection (rhinoplasty), alapexy, etc–laryngeal tie back (cricoarytenoid, or lateral arytenoid)–permanent tracheostomy

Question 15

techniques for partial laryngectomy

Answer 15

intra oral approachor ventral approachorvideo assisted photoablative

Question 16

sex predisposition for laryngeal paralysis

Answer 16

males are 2-3 times more affected than females

Question 17

congenital laryngeal paralysis

Answer 17

—siberian huskies–bouvier de flanders–dalmatians–bull terriers–rottweilers–pyrenean mountain dogsprogressive degeneration of neurons within nucleus ambiguous, with subsequent Wallarian degeneration of laryngeal nerves before 1 yr of agealso see hind limb muscle atrophy (cranial tibial muscle)

Question 18

causes of acquired laryngeal paralysis

Answer 18

older labs, goldens, setters, st. bernards–polyneuropathy–idiopathic **–iatrogenic from cervical surgery–trauma–OP toxicosis–laryngeal myopathy–polyradiculoneuritis–cranial or mediastinal mass (neoplasia, cysts, abscess, granulomas)atrophy of type II muscle fibers (normally fast contracting fast fatigue)

Question 19

incidence of aspiration pneumonia in laryngeal paralysis dogs

Answer 19

8%

Question 20

most common radiographic changes in cats with airway obstruction

Answer 20

–hyperinflation of the lungs–caudal displacement of the larynx–air in the pharynx, larynx, esophagus and stomach

Question 21

diagnostic approach to laryngeal paralysis patient

Answer 21

–complete PE, ortho and neuro exam (to rule in or out other causes of weakness and polyneuropathy–CBC/Chem/UA +/- T4 (not because hypoT causes LarPar but often they are concurrent)–if unstable gain access to airway and run coag screening if heatstroke–thoracic imaging (8% aspiration pneumonia and RO masses, megaesophagus 12%)–esophagram for dysmotility– laryngeal US–electromyography (young as 12 weeks of age)–GA and airway examination

Question 22

According to Stanley 2010 what conclusions were made about laryngeal paralysis dogs and esophageal dysfunction

Answer 22

–Esophagram scores in dogs with ILP were significantly higher in each phase compared to the controls, most notably with liquid –Dysfunction more pronounced in the cervical and cranial thoracic esophagus. –dogs w aspiration pneumonia had significantly higher esophagram scores than the dogs that did not develop aspiration pneumonia–30% dogs with ILP had generalized neurologic signs upon enrollment and 100% developed neurologic signs over 1 year

Question 23

laryngeal examination in dogs with laryngeal paralysis

Answer 23

–normally should abduct during inspiration and at rest there should be a gap btwn arytenoid cartilages–erythema and laryngeal edema should be noted as well as presence of everted saccules or other causes for airway obstruction (masses)–note paradoxical movement (inspiration move medially expiration forced open–doxapram 1 mg/kg give IV if needed to stimulate respirations

Question 24

ER treatment for airway obstruction (ex. BCAS, laryngeal paralysis)

Answer 24

–cool–oxygen–sedate (butorphenol, acepromazine)–antiinflammatories (severe–GCC, mild–NSAID)–fluids–temporary tracheostomy if needed (but may be a poor px indicator and lead to more complications)

Question 25

surgical methods for laryngeal paralysis

Answer 25

–unilateral cricoarytenoid lateralization–unilateral thyroidarytenoid lateralization–bilateral ventriculocordectomy (ventral approach vs intramural approach)–modified castellated laryngofissure–partial arytenoidectomy w ventriculocordectomy–permanent tracheostomy–muscle-nerve pedicle transposition (reinnervation)

Question 26

post op complication rate and outcome in dogs with laryngeal paralysisaccording to MacPhail 2001 JAVMA 140 cases

Answer 26

Postoperative complications 34% (OVERALL)Aspiration pneumonia was the most common complication 24%. Dogs that underwent bilateral arytenoid lateralization were significantly more likely to develop complications and significantly less likely to survive than were dogs that underwent unilateral arytenoid lateralization or partial laryngectomy. Factors that were significantly associated with a higher risk of dying or of developing complications included age, temporary tracheostomy placement, concurrent respiratory tract abnormalities, concurrent esophageal disease, postoperative megaesophagus, concurrent neoplastic disease, and concurrent neurologic disease70% alive at 5 years90% improve clinical signs

Question 27

T/Fthe degree of clinical improvement in post op laryngeal paralysis dogs has NOT been related to the glottic diameter change

Answer 27

TRUEcricoarytenoid 207% (can go up to 240% with TA combo)thyroarytenoid 140%NO clinical differenceTA may be faster than CA

Question 28

Pouiselles law conclusions in terms of flow and resistance

Answer 28

FLOW is directly proportional to radius to the fourth powerresistance is INVERSELY proportional to radius to the fourth powerthus, only small increases in glottic area are needed to improve airway flow

Question 29

reported complications following cricoarytenoid lateralization

Answer 29

1, seroma2, infection3. failure of suture/recurrence of signs4. aspiration pneumonia (24%)5. gagging retching6. persistent stridor 7. progression of neurologic signs

Question 30

factors associated with the development of post op complications for cricoarytenoid lateralization in laryngeal paralysis dogs

Answer 30

–temporary tracheostomy–preop aspiration pneumonia–post op megaesophagus

Question 31

percentage reported of recurrence of respiratory signs and inspiratory stridor –post op

Answer 31

33%seen mores in small dogs

Question 32

complication rate of BILATERAL cricoarytenoid lateralization

Answer 32

much higher with bilateral than unilateral90% bilateral30% unilateral

Question 33

complication rate following partial laryngectomy

Answer 33

40-50% (higher than for tie back CAL; associated with more mortality than with CAL)aspiration pneumoniapersistent coughlaryngeal webbing (esp if bilateral vocal fold resection done)complications may be lower for more experienced surgeonsprocedure can be done intraoral, ventral, or video assisted photoablative

Question 34

benefits of a ventral approach vs intramural approach for partial laryngectomy

Answer 34

ventral approach allows for primary mucosal apposition and closure to limit second intention healing, scar, and laryngeal webbing; also allows greater exposure and spacedisadvantage is orientation is difficult to appreciate with ventral approach

Question 35

bilateral ventriculocordectomy via ventral approach for tx of lar par according to Zikes et al 88 dogs

Answer 35

Zikes et al JAAHA 20123 % major complications short term7% major complications long termsatisfactory 93%low incidence of complications

Question 36

bilateral ventriculocordectomy via ventral approach vs unilateral arytenoid lateralization results based on Bahr et al JAAHA 2014

Answer 36

Bahr et al JAAHA 2014 45 dogsno sign difference in post op complication rate (50-60%)UAL were more likely to suffer from short term acute respiratory distress/aspiration pneumonia complications where as BV were more likely to have chronic respiratory/aspiration pneumonia complicationsREVISION 24% BV10% UAL

Question 37

castellated laryngofissure

Answer 37

opens ventral laryngeal ostiumpots op edema and hemorrhage are highopens the rims but does not reduce airway resistance more than unilateral lateralization therefore no real benefit

Question 38

methods of devocalization

Answer 38

removal vocal folds on vocal process—transoral vocal cordectomy–ventral laryngotomy with vocal cordectomy (allows mucosal apposition)–laser vocal fold resectionpreserve ventral portion to avoid scar formation/laryngeal webbingchitosan > mitomycin C antifibrotics to decr scar formation

Question 39

miscellanous conditions of the larynx

Answer 39

—cysts—foreign body–trauma (dog bites, electrical cords, intubation)–inflammatory disease (lymphoid hyperplasia in cats; granulomatous in BCAS dogs)–neoplasia—webbing

Question 40

epiglottic retroversion

Answer 40

muscle: hyoepiglottis muscle innervated by caudal laryngeal nerve (branch of recurrent laryngeal n)diagnostics: laryngeal examination of epiglottis into laryngeal ostium, cervical fluoroscopy, laryngoscopytx: epiglottopexydifferentiate from epiglottic entrapment, glossoepiglottic mucosa laxity, redundancy, and displacement