101. Larynx Flashcards
structures of the hyoid apparatus
S E C B Ts. stylohyoide. epihyoidc. ceratohyoidb. basihyoidt. thyrohyoid
cartilages of the larynx
epiglotticthyroid (largest)cricoid (complete ring)arytenoid (corniculate, cuneiform, vocal and muscular process)sesamoid (connect the paired corniculate processes of the arytenoid)
muscle attaching the epiglottis to the middle of the body of the hyoid apparatus
hyoepiglotticus musclecontraction pulls the epiglottis downintrinsic muscle of the larynx
neurovascular structure in the rostral notch of the thyroid cartilage
cranial laryngeal nervelaryngeal artery
insertions site of what muscle to the muscular process of the arytenoid
cricoarytenoideus dorsalis musclemost important intrinsic muscle of the larynxabducts arytenoid cartilage to open the glottisrecurrent laryngeal nerve (caudal laryngeal branch) innervation
extrinsic muscles of the larynx
thyropharyngeus mcricopharyngeus mboth fx to constrict caudal pharynxunder glossopharyngeal (9) and vagus (10) nerve stimulation
innervation to the larynx
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
blood supply to the larynx
cranial and caudal thyroid artery branches
what is different about the feline arytenoid cartilage
lacks cuneiform, corniculate processes and aryepiglottic folds
three function of the larynx
- 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
characteristic of most laryngeal tumors
malignantmet slowly but very locally aggressivesmall tumors can be excised with ventral laryngotomy or transoral approachlarge tumors: partial or complete laryngectomy (with permanent tracheostomy)
percentage of BCAS dogs that have some form or laryngeal collapse and what are the stages of collapse
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
percentage of occurrence of BCAS components in brachycephalic dogs
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%)
tx of laryngeal collapse
–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
techniques for partial laryngectomy
intra oral approachor ventral approachorvideo assisted photoablative
sex predisposition for laryngeal paralysis
males are 2-3 times more affected than females
congenital laryngeal paralysis
—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)
causes of acquired laryngeal paralysis
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)
incidence of aspiration pneumonia in laryngeal paralysis dogs
8%
most common radiographic changes in cats with airway obstruction
–hyperinflation of the lungs–caudal displacement of the larynx–air in the pharynx, larynx, esophagus and stomach
diagnostic approach to laryngeal paralysis patient
–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
According to Stanley 2010 what conclusions were made about laryngeal paralysis dogs and esophageal dysfunction
–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
laryngeal examination in dogs with laryngeal paralysis
–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
ER treatment for airway obstruction (ex. BCAS, laryngeal paralysis)
–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)
surgical methods for laryngeal paralysis
–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)
post op complication rate and outcome in dogs with laryngeal paralysisaccording to MacPhail 2001 JAVMA 140 cases
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
T/Fthe degree of clinical improvement in post op laryngeal paralysis dogs has NOT been related to the glottic diameter change
TRUEcricoarytenoid 207% (can go up to 240% with TA combo)thyroarytenoid 140%NO clinical differenceTA may be faster than CA
Pouiselles law conclusions in terms of flow and resistance
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
reported complications following cricoarytenoid lateralization
1, seroma2, infection3. failure of suture/recurrence of signs4. aspiration pneumonia (24%)5. gagging retching6. persistent stridor 7. progression of neurologic signs
factors associated with the development of post op complications for cricoarytenoid lateralization in laryngeal paralysis dogs
–temporary tracheostomy–preop aspiration pneumonia–post op megaesophagus
percentage reported of recurrence of respiratory signs and inspiratory stridor –post op
33%seen mores in small dogs
complication rate of BILATERAL cricoarytenoid lateralization
much higher with bilateral than unilateral90% bilateral30% unilateral
complication rate following partial laryngectomy
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
benefits of a ventral approach vs intramural approach for partial laryngectomy
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
bilateral ventriculocordectomy via ventral approach for tx of lar par according to Zikes et al 88 dogs
Zikes et al JAAHA 20123 % major complications short term7% major complications long termsatisfactory 93%low incidence of complications
bilateral ventriculocordectomy via ventral approach vs unilateral arytenoid lateralization results based on Bahr et al JAAHA 2014
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
castellated laryngofissure
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
methods of devocalization
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
miscellanous conditions of the larynx
—cysts—foreign body–trauma (dog bites, electrical cords, intubation)–inflammatory disease (lymphoid hyperplasia in cats; granulomatous in BCAS dogs)–neoplasia—webbing
epiglottic retroversion
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
