Ch 101 Larynx Flashcards
List the cartilages of the larynx
Epiglottic
Thyroid
Cricoid
sesamoid
interarytenoid
paired arytenoid
List the processes of the arytenoid cartilages
Cuneiform
Corniculate
Vocal
Muscular
Extrinsic muscles
- Thyropharyngeus
- Cricopharyngeus
constrict the caudal part of the pharynx.
innervated by glossopharyngeal and vagal nerves
intrinsic muscles of the larynx
- 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)
anatomy
- suspended ventrally from the skull by the hyoid apparatus > mastoid process of the temporal bone via tympanohyoid cartilage and thyroid cartilage via thyrohyoid bone
- epiglottis is attached by hyoepiglotticus muscle to the middle of the body of the hyoid bone
- ventricular ligament and ventricularis muscle attach to cuneiform process
- corniculate process forms the dorsal margin of the laryngeal inlet, muscular process insertion site for cricoarytenoideus dorsalis
- Mucosal-covered folds of everted mucosa known as a ventricle or laryngeal saccule
Blood supply
- branches of the cranial and the caudal thyroid arteries.
Lymphatic
- medial retropharyngeal lymph nodes
How does the feline laryngeal anatomy differ from dogs?
- 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
List the three functions of the larynx
- Larynx is pulled cranially during swallowing to block laryngeal opening
- Controls airway resistance
- Voice production
Innervation
- cranial and caudal laryngeal nerves (from vagus n.)
- cranial laryngeal nerve > supplies the cricothyroideus muscle
- The left recurrent laryngeal nerve arches around the aorta, ascends along the trachea before terminating as the left caudal laryngeal nerve.
- The right recurrent laryngeal nerve loops around the right subclavian artery and ascends along the trachea to end as the right caudal laryngeal nerve.
- provide motor supply to all intrinsic laryngeal muscles except for the cricothyroideus.
Laryngeal Neoplasia
- rare in dogs and cats, with most information from individual case studies
- Most laryngeal tumors are locally invasive with a potential to metastasize
- Presenting signs: respiratory stridor, exercise intolerance, dysphagia, gagging, coughing, voice change, and dyspnea
- diagnosis confirmed with laryngeal examination and mass biopsy, may be visible on radiographic or ultrasonographic evaluation of the head and neck region
- Thoracic radiographs > detection of metastasis and aspiration pneumonia.
tumor types in dogs
rhabdomyoma/sarcoma,
osteosarcoma, chondrosarcoma,
melanoma,
carcinoma, SCC
fibrosarcoma,
mast cell,
plasmacytoma
tumors in cats
lymphoma and SCC most common,
adenocarcinoma,
thyroid carcinoma,
round cell tumor reported
treatment
Lymphoma
- radiation therapy or chemotherapy
surgery
transoral approach or through a ventral laryngotomy
- Larger or more aggressive tumors can be treated with partial or a complete laryngectomy
Partial Laryngectomy
- for tumors invading one side of the larynx
- ventral midline incision, and the thyroid cartilage
- Small cartilage defects > primarily closed by sliding the cranial part of the thyroid cartilage caudally.
- If removal of cricoid, the defect reconstructed by advancing the trachea cranially
- Large cartilage defects > use of free tissue implants (costal cartilage, buccal mucosa) or local muscle flaps.
rotary door” procedure
- - An island skin flap based on the sternohyoideus muscle with skin attached to underlying muscle, cranial thyroid blood vessels spared provide blood supply to the flap. After the laryngeal resection is completed, epidermis is shaved off to remove hair follicles and The flap is rotated so dermis is facing inward and flush with the mucosal lining.
MOSER 2022: Partial laryngectomy for the management of laryngeal masses in six cats. JFMS
Four cats showed varying degrees of respiratory distress in the short-term postoperative period. A temporary tracheostomy tube was placed in two cats
Four cats were still alive at the time of writing. These cats survived at least 252 days
Total Laryngectomy
complete laryngectomy with a permanent tracheostomy
- - few reports of complete laryngectomy in dogs and cats> success rate of this surgery is unknown
- The trachea is brought through the sternohyoideus muscles and anastomosed
-
Matz 2021:. Total laryngectomy and permanent tracheostomy in six dogs. Vet Comp Oncol.
six dogs (rhandomyoma, SCC, STS, neurofibroma
The procedure resulted in postoperative quality of life similar to permanent tracheostomy alone. Surgical margin status was evaluated in five of six cases and was complete in those five. All dogs survived to discharge from the hospital. Complications were mostly related to tracheostomy occlusion or collapse
Survival time ~ or>1000d in 4/6 dogs.
What % of dogs with BOAS will have:
- Stenotic nares
- Elongated soft palate
- Everted saccules
- Laryngeal collapse
Stenotic nares 43-85%
Elongated soft palate 86-96%
Everted saccules 55-66%
Laryngeal collapse 8-70%
long AND hyperkastic soft palate > consdier primary (though studies on newborn BOAS requiredm though hyperlasia present in grade I BOAS)
What are the three stages of laryngeal collapse?
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
- Stage II and III collapse reported in dogs as young as 4.5 months
BOAS pathophys
- chronic upper airway obstruction causes increased airway resistance and increased negative intraglottic luminal pressure.
- in order to bring sufficient oxygen to the lungs, an increased negative pressure is needed to overwhelm the primary stenosis and soft tissues are drawn into the lumen and become hyperplastic (Koch et al., 2003). The elongated soft palate and the everted saccules in brachycephalic dogs are the origin of dynamic non-fixed obstruction of the pharynx and larynx.
- Over time, this results in laryngeal collapse caused by cartilage fatigue and degeneration.
decreased diameter of the left main bronchus with partial or almost complete closure of cartilages was present in 70% of the brachycephalic dogs
Tokunaga 2020: Histological and mechanical comparisons of arytenoid cartilage between 4 brachycephalic and 8 non-brachycephalic dogs: A pilot study. PLoS ONE
report histological and mechanical features in arytenoid cartilage of brachycephalic dogs. We identified the arytenoid cartilage in brachycephalic dogs presented degenerative histological characteristics and decreased load to failure and stiffness compared to that in non-brachycephalic dogs. Together, these observations suggest that degenerative condition of arytenoid cartilage in brachycephalic dogs could contribute to chondromalacia and mechanical weakness of arytenoid cartilage and result in cause of failure after arytenoid lateralization.
treatment
- laryngeal collapse represents a secondary condition, the initial treatment is focused on surgical correction of the primary disease
- In one study, moderate and severe laryngeal collapse benefited from surgical correction of the primary condition and removal of laryngeal saccules, with life-threatening clinical signs resolved or severely reduced in all cases.130
Torrez 2006: Results of surgical correction of abnormalities associated with brachycephalic airway obstruction syndrome in dogs in Australia. J Small Anim Pract
- In one study, moderate and severe laryngeal collapse benefited from surgical correction of the primary condition and removal of laryngeal saccules, with life-threatening clinical signs resolved or severely reduced in all cases.130
sacculectomy
- Saccules may not regress
- development of laryngeal webbing post sacculectomy
- recent study, retrospective, brachycephalic dogs undergoing laryngeal sacculectomy in addition to staphylectomy and nares resection were more likely to develop complications compared with brachycephalic dogs receiving staphylectomy and nares resection alone
Hughes 2018: Complications following laryngeal sacculectomy in brachycephalic dogs. J Small Anim Pract
- Norwich terriers: specific breed > redundant supraarytenoid folds, laryngeal collapse, everted laryngeal saccules, and narrowed laryngeal openings
What are the options for a patient with laryngeal collapse who does not respond to surgical management of BOAS and medical management?
3
- Permanent tracheostomy
- Laryngeal tieback
- Epiglottectomy and Ablation of Unilateral Arytenoid Cartilage
permanent tracheostomy
In a study of 15 brachycephalic dogs with severe laryngeal collapse receiving permanent tracheostomy, there was a high risk of severe complications and postoperative death; however, a long-term (>5 years) good quality of life was reported in 5 of those dogs.
Gobbetti 2018: Long-term outcome of permanent tracheostomy in 15 dogs with severe laryngeal collapse secondary to brachycephalic airway obstructive syndrome. Veterinary Surgery.
- median survival time was 100 days. Major complications were diagnosed in 12 of 15 (80%) dogs, resulting in death in 8 (median survival time 15 days) and revision surgery in 4 dogs
- long-term survival (exceeding 5 years) with a good quality of life was documented in 5 of 15 dogs.
laryngeal tie back
- technique should be used with caution because the opposite cartilage may continue to collapse medially postoperatively leading to progressive airway obstruction.
- 12 dogs with stage II or stage III collapse with continued airway obstruction after primary sx, a left unilateral combined cricoarytenoid and thyroarytenoid lateralization
- Ten of the dogs survived to discharge and were alive and well at the time of follow-up (median, 3.5 years)
- Consider Tokunaga 2020 where abnormal cartilage may be reason why tie-back may fail in brachycephalics
Epiglottectomy and Ablation of Unilateral Arytenoid Cartilage
aim of increasing the air passage through the larynx, decreasing negative intraglottic pressure, and reducing airway resistance.
Collivignarelli 2022: Subtotal Epiglottectomy and Ablation of Unilateral Arytenoid Cartilage as Surgical Treatments for Grade III Laryngeal Collapse in Dogs. Animals
- One year after surgery, the owners of 12 patients rated their dogs as follows: excellent in five cases, good in five cases, and fair in two cases.
- epiglottectomy associated with the photoablation of unilateral arytenoid cartilage increases airway flow, and thus may be considered a valid surgical procedure to treat dogs affected by grade III laryngeal collapse.
Laryngeal Paralysis
- vagus nerve (originates from caudal nucleus ambiguus in the medulla) and its branches (recurrent laryngeal nerves) provide motor function to laryngeal muscles.
- recurrent laryngeal > caudal laryngeal > cricoarytenoideus dorsalis contraction and abduction of arytenoid during inspiration.
- dogs and cats, unilateral or bilateral and congenital or acquired. Male dogs are approximately two to three times more affected than female dogs
Damage to what structures can cause lar par?
Nucleus ambiguus
Vagus nerve or its branches
Cricoarytenoideus dorsalis muscle
causes of LA Pa (main groups - 5)
Congenital
trauma
surgical trauma (v-slot, cranial thoracic sx, thyroidectomy)
cervival/thoracic neoplasia
neuromuscular disease (GOLPP, endocrine, myasthenia gravis, polyneuro)
What causes congenital lar par?
What breeds are overrepresented?
Progressive degeneration of neurons within the nucleus ambiguus and Wallerian degeneration of laryngeal nerves
- Bouvier des Flandres, Bull terriers, dalmations, Rottweilers, Leonberger
- onset of clinical signs > usually before 1 year of age
What breeds are overrepresented for acquired lar par?
Lab and Golder Retrievers
St Bernards
Irish Setters
eitiology of aquired
possible causes
- chronic endocrine (hypothyroidism – atrophy type II twitch fibres) > concurrently in 30%, although a direct causal link has not been established
- infectious, or immune-mediated polyneuropathy,
- surgical or traumatic damage to the vagus or recurrent laryngeal nerve,
- lead or organophosphate toxicity,
- retropharyngeal infection,
- polyradiculoneuritis,
- cranial mediastinal mass
GOLPP (stanley 2010)
- In many dogs the cause remains undetermined and traditionally classified as idiopathic;
- recently been shown that many dogs with acquired laryngeal paralysis develop systemic neurologic signs within 1 year following diagnosis which is consistent with a progressive generalized neuropathy
- Abnormalities of electrodiagnostic tests and histopathology of nerve and muscle biopsy reflecting generalized polyneuropathy
cats
- reported in cats (median age, 10 to 16 years)
- Cats >bilateral thyroidectomy, PDA ligation, cervical bite wounds, and head trauma
Clinical Findings
- acute is usually secondary to exacerbation of chronic disease (heat stroke)
- change in voice, gagging + coughing
- Progression slow, months-years > exercise intolerance + laryngeal stridor is noted during inspiration > develops severe respiratory distress.
- accompanied by dysphagia and megaesophagus which significantly enhance the probability of aspiration after surgical correction of laryngeal paralysis
- unilateral laryngeal paralysis are usually asymptomatic unless they are exercising heavily.
- Cats > tachypnea or dyspnea most common, dysphonia, inspiratory stridor
- Because cats and dogs with acquired laryngeal paralysis are old, concurrent disease is common
- polyneuropathy > muscle atrophy or peripheral neurologic abnormalities (decreased postural reactions, spinal reflex deficits, and cranial nerve abnormalities)
lab
- - heatstroke > coagulation panels and immediate evaluation of packed cell volume, glucose, and electrolytes + supportive treatment. Heatstroke can progress to DIC, multiorgan failure, and death
- myasthenia gravis is suspected, acetylcholine receptor antibody titers are measured (association not clear)
What % of dogs with lar par have pre-op aspiration pneumonia?
Oesophageal dysfunction?
Aspiration pneumonia 7.9%
Oesophageal dysfunction 11.4% - assoc with an increased risk of post-op complications
Thoracic radiographs
- rule out other causes of dyspnea, detect underlying etiologies (cranial mediastinal masses); and search for concurrent pathology such as aspiration pneumonia, noncardiogenic pulmonary edema, megaesophagus.
- In cats > hyperinflation of the lungs; caudal displacement of the larynx; and air in the pharynx, larynx, esophagus, and stomach
- Dogs that developed aspiration pneumonia also had worse esophageal function Stanley 2010
pre-op aspiration pneumonia
- Aspiration pneumonia >7.9% of dogs with laryngeal paralysis.82 If present, surgical intervention should be delayed until the aspiration pneumonia is resolved because it increases the risk of postoperative complications
Laryngeal examination
- direct visualization of the larynx with a simple laryngoscope,
- oral video-endoscopic laryngoscopy,
- transnasal laryngoscopy (TNL),
- ultrasonography (echolaryngography),
- computed tomography (CT).
- Ultrasonography
- In one study, 30 of 30 dogs had asymmetry or absence of motion
CT
CT
- failure to abduct the arytenoid cartilages and collapse into the rima glottis on presumed inspiration, stenosis of the laryngeal inlet,and air-filled lateral ventricles.19
- Regardless of method, false-positive results are common because of the influence of anesthetic agents on laryngeal function. Ultrasound, Transnasal Laryngoscopy, and CT avoid the need for heavy sedation and general anesthesia; however, methods not shown to be superior to traditional oral laryngeal examination for definitive diagnosis
oral exam
- A videoendoscope is useful for examination because it is less likely to require ventral epiglottic retraction
- The animal should be anesthetized to the point at which the mouth can be easily opened but a laryngeal reflex is still present.
- Edema and erythema of the arytenoid cartilage mucosa are usually present on the dorsal part of the larynx
dx
- lack of arytenoid abduction during inspiration.
- confounded by paradoxic movement of the arytenoids, resulting in a false-negative result.
- The arytenoid cartilages move inward during inspiration because of negative intraglottic pressure created by increased respiratory effort against an obstruction
Anesthetic Regimens
propofol
- significant respiratory depression often occurs, with apnea related to dose, speed of injection, and use of concurrent premedications.
ketamine
- shown to preserve laryngeal function better in people, a study in dogs found no benefit for laryngeal examination when combining propofol and ketamine;
Alfaxalone
- Although causes respiratory depression, apnea has been shown to be less likely compared with propofol.23
propofol versus alfaxalone vs premeds
- propofol or alfaxan induction for laryngeal examination in healthy dogs, the addition of premedications (acepromazine and butorphanol) improved the quality of the laryngeal examination regardless of the induction agent. This study did not recommend the use of propofol or alfaxalone alone
- in contrast, alfaxalone alone resulted in the best respiratory function and quality of examination compared with propofol alone and alfaxalone or propofol used with premedications.
- Another study, established that alfaxalone impacted laryngeal motion significantly more than propofol
Doxapram
- increase respiratory rate and effort and improve intrinsic laryngeal motion (central nervous stimulant) and may improve the ability to determine normal versus abnormal function,
- results are mixed in studies regarding these benefits
-** Ranninger 2020: The Influence of Anaesthetic Drugs on the Laryngeal Motion in Dogs: A Systematic Review. Animals**
systematically analyse the literature describing the effects of anaesthetic drugs and doxapram on laryngeal motion in dogs and to determine which drug regime provides the best conditions for laryngeal examination. Studies were scored based on their level of evidence. In healthy dogs, premedication before laryngeal examination provided better examination conditions and maintained overall adequate laryngeal motion in 83% of the studies. No difference in laryngeal motion between induction drugs was found in 73% of the studies but the effects in dogs with laryngeal paralysis remain largely unknown. Doxapram increased laryngeal motion in healthy dogs without serious side effects, but intubation was necessary for some dogs with laryngeal paralysis. Methodological characteristics varied considerably between studies, including the technique and timing of evaluation, number of assessors, study design, drug dose, combinations, route and speed of administration.
Emergency Treatment
improving ventilation, reducing laryngeal edema, and minimizing stress.
treatment
- oxygen supplementation,
- short-acting steroids (dex 0.1–1 mg/kg IV)
- sedatives (eg, ace0.02 mg/kg IV or butorphanol 0.2 mg/kg IV),
- appropriate cooling procedures to redcue temp 38.9
temporary tracheostomy
- negative prognostic indicator following definitive surgery >were more likely to experience major complications
- Tube requires intensive monitoring to avoid life-threatening complications.
- Complications: 86% of cases
Translaryngeal percutaneous arytenoid lateralization
- alternative to temporary tracheostomy
- a mattress suture is placed through 1 arytenoid cartilage via an oral approach and exited through the skin ventral to the jugular
Further studies are needed to determine the clinical utility of this method.
Hardie 2016
Medical Management
- dogs with unilateral laryngeal dysfunction are typically not surgical candidates.
- bilateral > decision to recommend surgery is based on the quality of life of the dog, severity of clinical signs, and time of year.
- conservative management: environmental changes, reduction of daily exercise, owner education, weight loss
- medical treatment is insufficient for long-term management.
FELINE LARYNGEAL PARALYSIS
- Clinical presentation is similar to that in dogs in that it occurs most often in middleaged to older cats (mean, 9–14 years), and both unilateral and bilateral conditions have been documented.
- Unlike dogs, cats with unilateral dysfunction can have significant clinical signs and require surgical intervention.
- cause often remains undetermined > trauma, neoplastic invasion, and iatrogenic damage
assessment:
- alfaxalone has been evaluated compared with propofol and midazolam/ketamine, All 3 protocols provided similar conditions to evaluate laryngeal motion
Conservative management: weight loss and minimization of excitement and rigorous exercise.
Surgical:
- successful unilateral arytenoid lateralization has been described in several small studies.
- Complications are noted in 50% to 54% of cats after unilateral or bilateral arytenoid lateralization
- aspiration pneumonia (15%), postoperative dyspnea requiring temporary tracheostomy, increased inspiratory noise, Horner’s syndrome, pulmonary edema, and laryngeal stenosis
- Few studies of long-term results are available. In one study, the mean and median survival times of 10 cats 406 and 150 days
What are the surgical options for the Tx of lar par?
Unilateral or bilateral arytenoid lateralisation
Ventricular cordectomy and partial arytenoidectomy
Modified castellated laryngofissure
Permanent tracheostomy
stent
Unilateral arytenoid lateralization
- very consistent outcome
- Bilateral seems to be associated with more complications than unilateral, and the latter technique is sufficient to resolve clinical signs
- Several variations of unilateral arytenoid lateralization have been described. The most common technique involves suturing the cricoid cartilage to the muscular process of the arytenoid cartilage, which mimics the directional pull of the cricoarytenoideus dorsalis muscle and rotates the arytenoid cartilage laterally.
- the thyropharyngeus muscle is transected.
- Some clinicians separate the cricothyroid junction; however, this is not usually necessary and may destabilize the larynx, decreasing the glottic diameter
- nonabsorbable suture (2-0 polypropylene on a taper needle in dogs; 3-0 in cats)
- Some surgeons pass two sutures before tying.74 If cartilage is calcified or friable, holes for needle passage can be predrilled with 18 gauge hypodermic needles
- the final glottic opening will be no larger than that of the animal with the endotracheal tube in place. Assistant can observe per os
Thyroarytenoid lateralization
with or without cricoarytenoid lateralization has also been described. The purpose of the thyroarytenoid suture is to achieve lateral displacement of the arytenoid without caudal displacement.
- one study of clinical cases, the rima glottidis area was significantly greater after cricoarytenoid lateralization (207%) than thyroarytenoid lateralization (140%); however, there was no difference clinically in dogs treated with either technique
- Drudi 2022
What is the reported increase in rima glottidis opening using cricoarytenoid and thyroarytenoid lateralisation?
Cricoarytenoid - 207%
Thyroarytenoid - 140%
tie back
- increasing the surface area of the rima glottidis beyond the edges of the epiglottis could put the animal at higher risk of aspiration.
- According to Poiseuille’s law, resistance to flow is inversely related to the radius to the fourth power. Because of this, a small increase in glottic area dramatically reduces airway resistance and improves airflow
- Limited lateral displacement of the arytenoid might decrease the risk of postoperative aspiration pneumonia.
- Experimental cadaver study: recommend sutures be tied without overabduction and caudodorsal displacement > primary functions are to keep the arytenoid in a normal position at rest
less invasive approach
- A recent surgical description >less invasive approach to include less than 25% transection in length of the thyropharyngeus muscle and preservation of the cricopharyngeus muscle, cricothyroid articulation, and sesamoid bands
Von Pfeil 2014
- A recent surgical description >less invasive approach to include less than 25% transection in length of the thyropharyngeus muscle and preservation of the cricopharyngeus muscle, cricothyroid articulation, and sesamoid bands
- However, in a separate study, there was no significant difference in risk of aspiration pneumonia or survival times between a standard technique and one that preserves laryngeal anatomy
Perez Lopez 2019
- However, in a separate study, there was no significant difference in risk of aspiration pneumonia or survival times between a standard technique and one that preserves laryngeal anatomy
outcome
- Improvement is expected in 90% of animals undergoing unilateral arytenoid lateralization, and 70% of dogs are still alive 5 years after surgery
- quality of life 6 months after surgery was thought to be improved by 93% of owners of large dogs and 55% of owners of small dogs
Complications (9)
10% to 58% of dogs (7-23% perez lopez 2019)
- seroma,
- intramural hematoma,
- aspiration pneumonia (8% to 21% of dogs, days to years after unilateral arytenoid lateralization )
- persistent coughing or gagging,
- persistent or recurrent signs (up to 33% )
- residual stridor on auscultation,
- surgical failure from suture breakage or arytenoid cartilage fragmentation,
- laryngeal webbing
- progression of generalized neurologic signs
Bilateral arytenoid lateralisation
- depend on the type of surgery performed
- one study, the complication rate 89%, with 8 of 9 dogs developing aspiration pneumonia or respiratory distress
- study of 67 dogs with bilateral and vocal fold excision, major complication 12% and minor 33%. long-term follow-up, 3 of 40 dogs developed aspiration, and 6 of 40 dogs had recurrence of clinical signs that required additional surgery
Perioperative management
- sedative – low dose ACP and opiod
- supplemental oxygen – box, nasal
- cool room, or active cooling if hyperthermic
- steroid – dexamethasone short acting IV
- diuretic if any non-cardiogenic pulmonary oedema
- nebulisation with adrenalin
Franklin 2021: Nebulization of epinephrine to reduce the severity of brachycephalic obstructive airway syndrome in dogs Vet Surg
Partial laryngectomy
- various techniques for vocal cord excision and partial arytenoidectomy (only corniculate process) to increase the diameter of the glottis > transoral, ventral approaches, laser
- Unilateral usually adequate (and reduce aspiration)
- High complication rates have been reported by some investigators; however, bilateral vocal fold resection alone resulted in fewer complications and better postoperative outcome than other partial
laryngectomy techniques - Electrocautery is avoided because of the risk of postoperative swelling and granulation tissue formation.101
- Bilateral ventriculocordectomy > reasonable longterm (>6 months) outcome with a low incidence of major complication (7%)
- a direct comparison of outcomes between dogs treated with either unilateral arytenoid lateralization or bilateral ventriculocordectomy found that dogs undergoing bilateral ventriculocordectomy were more likely to have chronic (lifelong) respiratory complications
- a small cadaveric study of canine larynges, bilateral ventriculocordectomy did not seem to reduce laryngeal airway resistance
- Video-Assisted Photoablative Laryngectomy > Use of a diode laser for unilateral arytenoid photoablation was reported for the treatment of laryngeal paralysis in 20 dogs.
- No complications were reported in the immediate postoperative period, and all dogs were improved 1 month after surgery. Aspiration pneumonia developed in 2 of 18 dogs more than 12 months after surgery
outcome laryngectomy
Outcome
- In general, the outcome is good
- Satisfactory in 86% and in the long term in 90%
- Complications: 40-50% > laryngeal webbing, scarring + aspiration pneumonia (6-33%).
- 25 dogs that underwent bilateral ventriculectomy via oral approach, 48% of dogs had long-term complications, primarily respiratory distress from cicatrix formation
Castellated Laryngofissure
- Offset closure of a stepped, or castellated, incision of the thyroid cartilage results in enlargement of the ventral laryngeal ostium. Use for treatment of laryngeal paralysis is rare because of the difficulty of the procedure and the lack of additional benefits to the patient compared with other techniques
- opens the rima glottidis as much as a bilateral arytenoid lateralization but does not reduce postoperative airway resistance to the same degree
- severe postoperative laryngeal bleeding and edema that may require a temporary tracheostomy tube for 2 to 3 days
Permanent tracheostomy
- is considered a salvage procedure for dogs most at risk of aspiration pneumonia (myopathy, megaesophagus, hiatal hernia etc)
- associated with a high rate of major and minor complications and requires diligent postoperative and long-term care.
- 21 dogs with permanent tracheostomies:
50% major complications
20% required revision surgery
26% acutely died at home, most likely from airway obstruction
Prognosis
- In the absence of surgical complications, unilateral arytenoid lateralization results in reduced respiratory distress and stridor and improved exercise tolerance. Owner satisfaction with this procedure is excellent, with most owners believing that the quality of the dog’s life was improved dramatically.
- One-year 93% + 4 yr 75% (83% and 25% if aspiration post-op)
Aspiration pneumonia
- most common 10% to 21% (arytenoid lateralization)
- most likely in the first few weeks following surgery
- at risk for the rest of their lives
- megaesophagus and post-op opioid = significant risk factors for development of aspiration pneumonia.
gastrointestinal motility modifiers
- Metoclopramide increases lower esophageal sphincter (LES) tone
- prospective multicenter clinical trial >perioperative administration of metoclopramide did not affect the incidence of aspiration pneumonia in the short-term post-op postoperative period
- A retrospective evaluation of a cisapride infusion suggested a positive effect on postoperative aspiration pneumonia, but definitive conclusions not drawn because of low numbers in the study
negative risk factors
- preoperative aspiration pneumonia
- oesophageal dysfunction
- progression of generalized neurologic signs Stanley 2010
- temporary tracheostomy placement
- concurrent neoplastic disease.
Laryngeal stent
- use of laryngeal silicone stents to treat canine laryngeal paralysis in dogs
- Results
- Six dogs > showed improvement in clinical signs immediately after the procedure.
- One dog was suspected of aspirating water while drinking, but the signs disappeared after repositioning the stent.
- One dog relapse of stridor due to caudal migration of the stent. This dog underwent arytenoid lateralization surgery because larger stents are not commercially available.
- between 7-13 month, four dogs owners report a satisfactory quality of life.
- Conclusions
- alternative for treating dogs with acquired laryngeal paralysis
- stent placement can be a temporary solution to stabilize these dogs until a permanent surgical treatment can be performed.
Théron 2022:
Epiglottic Retroversion
- normal dog, epiglottic tip rests on the dorsal surface of the soft palate
- hyoepiglotticus muscle (innervated by the hypoglossal nerve)
- draws the epiglottis downward >bkeeping the nasopharyngeal airway patent.
pathophys
- Muscle laxity + combined with extreme inspiratory effort, may result in retroversion of the epiglottis into the laryngeal ostium and subsequent airway obstruction.
Dx
- Epiglottic entrapment > coughing, gagging, dyspnea, and collapse
- detected on inspiratory cervical fluoroscopy and confirmed on laryngoscopy.
Treatment:
- epiglottopexy (temporary or permanent) or partial/subtotal epiglottectomy
- Epligottopexy failure is reportedly common
- Pexy post-op complications 54% vs ectomy 25%, intra-op complications uncommon
- Good long term survival (median >700d) MULLINS 2019
Laryngeal Cysts
- cause of dyspnea and wheezing in cats.112
- diagnosis > ultrasound + histologic analysis
- Treatment > surgical excision.
completely excised. No recurrence was noted
Inflammatory Laryngeal Disease
Cats
- partial airway obstruction from lymphoplasmacytic inflammation and lymphoid hyperplasia of the laryngeal mucosa over the arytenoids or vocal folds.21,66
- cause unknown
- On laryngoscopy, laryngeal inflammation may appear as a discrete mass or diffuse vocal fold thickening
- biopsy samples to differentiate from lymhoma
- Treatment: glucocorticoids and antibiotics.
- Temporary tracheostomy is often required until inflammation resolves
- Prognosis is considered poor for cats that are presented with severe clinical signs.
Granulomatous laryngitis (dogs)
- Brachycephalic dogs
- vocal folds concurrent with other conditions of BOAS.
- recurred after resection with a CO2 laser/topical treatment with mitomycin or corticosteroids
- Surgical resection may therefore require ventral laryngotomy, vocal fold removal, and primary mucosal closure.
- Antacid therapy may be beneficial in some animals
Laryngeal Trauma
- Causes: bite wounds, choke collars, foreign bodies, gunshot wounds, and traumatic or long-term intubation.
- Dyspnea and exercise intolerance > acutely (swelling or cartilage displacement) or develop over time dt stenosis
- Diagnosis> examination, laryngoscopy, radiography, and computed tomography
Treatment
- Conservative if minimal displacement
may require partial arytenoidectomy or tie-back
traumatic wounds > intubation or tracheostomy tube placement, wound exploration, debridement, drainage or managed open.
- evaluated for secondary laryngeal paralysis or stenosis
- stents has been reported
- Fractures of the laryngeal cartilages may result in acute or insidious onset of clinical signs.
- Iatrogenic cuneiform process fracture, hit by a car cricoid cartilage fracture (Dx on CT)
Laryngeal Web Formation
- Stenosis secondary to laryngeal web formation
- causes included oral ventriculocordectomy (10 of 15 dogs), arytenoid lateralization, unilateral arytenoidectomy, and bilateral laryngeal sacculectomy
- Clinical signs developed 1 to 4 months after sx
- Treatment > transoral laser or blade excision or bougienage of scar tissue was unsuccessful
Tube tracheostomy was required perioperatively in 5 dogs. ventral laryngotomy for web transection/resection and primary mucosal closure
One dog required permanent tracheostomy. All dogs survived the immediate postoperative period, and 6 of 9 dogs were free of clinical signs at long-term follow-up (mean, 2.7 years)
Temporary Tracheostomy
- When commercially available tubes are not available, an endotracheal tube can be trimmed to an appropriate size
- multiple variations in tracheal incisions and flaps
- None has been shown to be particularly advantageous
- Successful use of silicone tracheal stoma stents was in 18 dogs
- either between two tracheal rings in a horizontal (transverse) manner or through 2-3 rings in a vertical (longitudinal) manner.
- The length of the transverse > not exceed half the circumference of the trachea
- stay sutures are placed
- An appropriate tube > outer diameter of the tracheostomy tube not exceed 75% of tracheal diameter
- tube size should be large enough to provide flow through the tube but small enough to allow ample room for airflow around the tube. This helps to prevent silent death from occlusion of the tube lumen
- intensive management and 24-hour observation of the patient are essential >a nurse should be designated
TT management
- The cuff should not be inflated
- Cuffed result in a significant increase in airway pressure compared to uncuffed tubes.
- tracheostomy results in inspiration of cool, dry air (bypasses the upper airway,)
- Tracheobronchial tree responds > increasing mucus > collects around and within the tube and stoma.
- single-lumen tubes must be removed and replaced every time
- double-lumen tubes have a removable cannula that can simply be exchanged.
- tubes should be replaced twice daily; exchange can be required as frequently as every 4 to 6 hours
- cleaned and soaked in 2% chlorhexidine and rinsed with sterile saline before replacement.
- Airway suctioning is another means used to keep the tube patent and is performed as frequently as necessary
- no more than 10 to 12 seconds > Uninterrupted suction can lead to severe atelectasis and hypoxia. A vagal response may also be elicited, resulting in gagging, retching, or bradycardia
- adequate humidification of the airway saline or nebulization
The decision to remove the tube
- typically coincides with resolution of the inciting event
- prudent to occlude the tube and stoma with an occlusive dressing for 15 to 20 minutes under direct observation to ensure that respiratory distress does not ensue.
- Tracheostomy wounds heal by second intention within 7 to 10 days
Complications
Acute complications
- 50%
- plugging with debris, inadvertent tube removal, gagging, coughing, vomiting, subcutaneous emphysema, pneumothorax, infection, and respiratory distress
- plugging of the tube 18% to 25% of cases.
- Cats > higher risk of occlusion because of greater mucus production. 87% had complications. However, 91% of cats with benign disease were discharged
long-term complication
- stenosis.
- Two areas > at the stoma site itself and at the level of the cuff or tube tip
- The advent of high-volume, low-pressure cuffs has reduced the incidence
- documented in dogs > average loss of 18% to 24.7% of luminal area has been noted, regardless of the type of tracheostomy created.
Overall
- complications as high as 86% in dogs – 81% management but only 60% dogs survived discharge.
- The outcome for cats is more guarded, with only 43% of cats being discharged from the hospital in one study
Permanent Tracheostomy
laryngeal masses in cats, laryngeal paralysis or collapse in dogs
Surgery technique
- The sternohyoideus muscles can be apposed dorsally to the trachea using mattress sutures to help elevate the trachea
- The ventral half of the cartilage of 3 or 4 tracheal rings is removed with a #11 blade
- simple interrupted or continuous pattern of fine (3-0 or 4-0) absorbable suture material is used to appose the mucosa to the skin.
- Dahm and Paniello documented significantly higher mortality rates (57%) when the stoma was placed below the 12th tracheal ring
- skin fold occlusion is a prime concern > excise excessive skin
Management
- Care = temporary tube tracheostomies
- cleaning, humidification, and suctioning every 4 to 6 hours
- skin surrounding the site is protected from secretions by applying a thin layer of antibiotic ointment
- healing occurs typically over 2 weeks
- undergoes squamous metaplasia > excessive mucus production can result in obstruction
- should be cleaned frequently
- Typically, secretions are minimal 1 month after surgery.
complications
Dehiscence
change in phonation
aspiration pneumonia
need for revision
death (obstruction)
stenosis
tracheal collapse
- Immediate similar to tube tracheostomy
- most common: aspiration pneumonia and the need for revision surgery
- study of 21 cats > mucus plugs > death by asphyxiation in 5 cats.
- median survival times for cats 20.5 - 42 days.
- major complications in 10 of 20 dogs 4 dogs requiring revision of the stoma site.
- median survival time 328 days.
- Acute death following discharge > 26% and presumed to be the result of airway obstruction.
Stenosis
- less than 10% significant
- Hedlund et al, all animals affected to some degree
- tracheal collapse may occur if the stoma is too large
- preexisting collapse > reinforced with extraluminal polypropylene rings.
- The tracheal mucosa undergoes squamous metaplasia > inflammatory infiltrates 0 - 4 weeks
- - more normal by 16 weeks
environmental modifications
- necessary for a successful outcome:
- healthy weight to ease exercise and reduce excess folds,
- keep the hair clipped around the stoma
- no swimming.
A lateral surgical approach to the larynx may impair
cervical esophageal function in dogs
Two dogs in
each treatment group developed moderate to severe cervical esophageal paresis. This did not occur in control dogs.
no evidence to support our hypothesis that muscle-sparing laryngoplasty results in less severe changes
in swallowing function compared to a standard technique
Fluoroscopic evaluation of laryngopharyngeal anatomic variations attributable to head posture in dogs
Results indicated that head posture significantly affected the laryngopharyngeal structures in dogs. Fluoroscopic examination of the upper respiratory tract of a dog should be performed with an NHP to minimize posture-induced changes in measurements
Evaluation of two unilateral
laryngoplasty techniques and
their effect on arytenoid cartilage
abduction in cats
Bonanno and White 2023
Left cricoarytenoid abduction (lateralisation) was performed in 20 ex vivo cat larynges; 10 following complete cricoarytenoid disarticulation (group LAA-dis) and 10 following no cricoarytenoid disarticulation
The mean percentage increase in LAA
- 311.5% (complete disarticulation)
- 199.4% no cricoarytenoid disarticulation
- no evidence of a lack of epiglottic coverage of the entrance of the larynx for any of the postoperative
larynges.
The clinical significance of the difference in outcome between left cricoarytenoid
abduction following complete cricoarytenoid disarticulation and abduction following no cricoarytenoid disarticulation
remains unclear, and both might be considered appropriate for the surgical management of laryngeal paralysis
in the cat.
Clinical presentation, treatment and
outcome in 23 cats with laryngeal or
tracheal lymphoma
Ignasi Rodriguez-Piza 2024
retrospective multicentre study
Debulking surgery was performed in 26% of cases. All cats received chemotherapy
35% had a partial response and 65% a complete response
Median PFS and OS were
909 days (range 23–1484) and 909 days (range 23–2423), respectively.
B-cell phenotype, could be of a low-to-medium grade, and
may respond to surgical and medical treatment with a longer survival time than has previously been reporte
Laryngeal paralysis secondary to cervical bite
injuries in five dogs
PP Picavet
NZVJ
Bilateral laryngeal paralysis was identified in three dogs and
unilateral laryngeal paralysis in two dogs via endoscopic assessment of laryngeal function. The
primary concomitant lesions included tracheal injury in 3/5 dogs and oesophageal injury in 1/5
dogs.
Clinicians should be aware of this pathology and the importance of
investigating laryngeal function in dogs presenting with cervical bites, particularly those
with inspiratory dyspnoea
Outcome following elective unilateral arytenoid lateralization performed in an outpatient manner is comparable
to hospitalization for dogs with laryngeal paralysis
Shubert 2023
44 client-owned dogs.
PROCEDURES
Medical records were retrospectively reviewed
The overall complication rate was 22.7% (10/44), with 35% (7/20) being in the inpatient group and 12.5% (3/24) being in the outpatient group. The overall mortality rate was 6.8% (3/44).
outpatient management of dogs with laryngeal paralysis treated with elective unilateral arytenoid lateralization is an appropriate method of postoperative management with no difference in complication or mortality rates. Further prospective studies with standardized surgical, sedative, and antiemetic protocols are warranted to evaluate more definitely.
Another multicenter randomized clinical trial found no significant differences in the rate of development of aspiration pneumonia when a metoclopramide constant rate infusion was used.16 Given the minimal effects that prokinetic therapy had on the incidence of aspiration pneumonia, patients without a history of frequent regurgitation or vomiting likely wouldn’t benefit from hospitalization. Instead, it is possible that hospitalization may cause anxiety and distress,
did any almost die before disharge?
Description of a cricotracheostomy technique for
permanent tracheostomy in eight dogs
Jordan D. Pieczynski | Bryden J. Stanley 2024
Short case series.
Animals: Eight client-owned dogs.
The stomata did not
show any evidence of dorsal wall collapse or stenosis. Four dogs required further
skin fold resection.
Comparative clinical investigation of the
CT technique with traditional permanent tracheostomy techniques is indicated
traditional level (approximately 3–5 tracheal rings caudal
The high position of the
stoma appears to be very functional, easy to maintain
and may even be less prone to obstruction than the traditional
lower permanent tracheostomy sites, as the laryngeal
portion is large and sturdy, and the cranial trachea is
wide and the cartilages thicker at its most cranial
aspect
larynx becomes
significantly more superficial when the sternohyoideus
muscle bellies are separated and the cricothyroideus muscle
bellies are removed.
The importance of bilateral cervical skin fold resections cannot be overemphasized
It may be thought that
brachycephalic breeds, with tracheal hypoplasia, may be
at higher risk of obstruction due to clots and exudate, but
this was not found in the three brachycephalic breeds
three patients remain
alive with the remainder deceased due to health concerns unrelated to the CT
Description and evaluation of a novel transoral endoscopic
arytenopexy in canine cadavers
Kaitlyn L. McNamara 2022
Canine cadaveric model.
Animals: Fifteen medium- to large-breed canine cadavers
rima glottis area (RGA) and laryngeal epiglottic-glottic
seal (LEGS)
A custom endoscopic gag port (EGP) facilitated the
TEA, performed by suturing the lateral aspect of the left arytenoid soft tissues
to adjacent pharyngeal wall across the piriform recess.
The mean baseline RGA was 0.52 ± 0.28 cm3 and mean post-TEA
RGA was 0.78 ± 0.37 cm3 (p-value < .0001). The LEGS remained intact post-
TEA in all cadavers.
The mean percent change in RGA after TEA was 157.00%
The ideal increase in RGA to treat canine laryngeal
paralysis would achieve decreased airway resistance
without increasing the risk of subsequent aspiration
pneumonia,
Over the years,
the literature has shifted practice away from procedures
which dramatically increase the RGA to those that provide
a moderate increase in order to lessen the risk of
aspiration through better preservation of the
LEGS.11,14,20,21,23,27 The Hagen-Poiseuille equation
describes the impact of airway radius on the physics of
laminar gas flow, principally, that airway resistance is
inversely proportional to the airway radius to the fourth
power. Based on our results, the average increase in RGA
following a TEA would equate to an estimated 84%
decrease in airway resistance using this calculatio
Comparison of immediate and short-term outcomes
of cricoarytenoid and thyroarytenoid lateralization
in dogs with idiopathic laryngeal paralysis
Dario Drudi 2022
A prospective, clinical trial.
Animals: Fourteen client-owned
The rima glottidis area increased by a mean of 152% at t0 and 127%
at t1 for the TAL group and 205% at t0 and 199% at t1 for the CAL group compared
Cricoarytenoid lateralization and TAL were both effective for
surgical abduction of the arytenoid cartilage. Although a reduction (P < .05)
in the rima glottidis area occurred in the TAL group at t1, we observed no
associated clinical signs.
Clinical significance: Cricoarytenoid lateralization and TAL result in good
short-term outcomes in dogs with laryngeal paralysis.
This suggests that, although CAL
resulted in a larger increase in the rima glottidis area
(P < .05), it provided no short- or medium-term advantage
over TAL.Some studies have suggested that CAL may
increase the risk of aspiration pneumonia because the epiglottis
does not cover the entire rima glottidis.8,10,32–34 None
Partial laryngectomy for the
management of laryngeal masses
in six cats
Jasmine Moser 2022
findji
In all cats, a full-thickness portion of one or several laryngeal cartilages
was resected, including thyroid cartilage alone (n = 2), thyroid cartilage and arytenoid (n = 2), and arytenoid
cartilage and epiglottis (n = 2).
Four cats showed varying degrees of respiratory distress in the short-term postoperative
period. A temporary tracheostomy tube was placed in two cats. No other postoperative complications were noted
in the short or long term. Four cats were still alive at the time of writing. These cats survived at least 252 days.
Unilateral Laryngeal Paralysis Secondary to Otitis
Media/Interna in Two Cats
Influence of doxapram and intermittent 10% carbon dioxide
inspiration on cardiovascular and laryngeal functions in
anesthetized dogs
Sakai 2021
Study Design: Experimental study.
Animals: Six healthy adult dogs.
An intermittent tachycardic effect of up to 79% increase in HR was observed with
doxapram.
However, anesthetic drugs such as
propofol decrease laryngeal motion,4 and this introduces
a confounding factor to the examination, potentially creating
a false positive diagnosis for laryngeal paralysis
All treatments were effective respiratory stimulants in anesthetized
dogs; however, doxapram caused hypertension and tachycardia
Neither hypertension nor tachycardia was observed with I-CO2
The combination
of acepromazine and dexmedetomidine as a sedative
combined with propofol has not been previously evaluated;
however, our results align with the previous findings
that some dogs had absent or insufficient arytenoid
motion prior to each respiratory stimulation
Respiratory stimulants, such as doxapram and carbon
dioxide, improve the quality of the laryngoscopy5,6; however,
they can cause adverse cardiovascular effects.7
inflititrative disease of larynx > inflammatory condiditions common in dogs
many had relpase and only fair QOL
Vocal fold granulomas in six
brachycephalic dogs: clinical,
macroscopical and histological features
D. Sarran1, A. Caron and J. P. Billet
lesions were exclusively unilateral, exophytic, approximately 3-mm wide ulcerated mucosal nodules,
arising from the vocal cord. Histopathological examination mainly revealed chronic inflammatory changes
In brachycephalic breeds, chronic inspiratory efforts and air
turbulences and gastro-esophageal reflux are suspected to result in chronic laryngeal inflammation.
All dogs were assigned a respiratory clinical score of
1 which corresponds to a marked clinical improvement. No dog
required additional surgical or medical treatment.
one had local recurrence on EUS
Examination of laryngeal function of healthy dogs by using
sedation protocols with dexmedetomidine
Whitney D. DeGroot 2020
Randomized, crossover, blinded study.
Animals: Eight adult research hounds weighing 8 to 22.5 kg.
Dogs were sedated with propofol, dexmedetomidine, dexmedetomidine
and butorphanol, or dexmedetomidine and hydromorphone
propofol, which resulted in two false positive results
Postdoxapram GGAn was greater
than predoxapram GGAn for all four sedation protocol
Dexmedetomidine sedation does not inhibit normal laryngeal
motion. Laryngeal examination with propofol alone can produce false positive
results
Dexmedetomidine
is reversible, can be titrated to the desired level of sedation,
does not cause significant respiratory depression, and allows
opening of the mouth and exteriorization of the tongue
Future studies examining the use of
dexmedetomidine for laryngeal function examinations in
dogs with confirmed laryngeal paralysis are warranted
Twenty-three of 24 examinations performed
with dexmedetomidine protocols resulted in a “pin
and pant” phenomenon after doxapram administration. > assume maximum abduction indicated laryngeal function
Effects of preoperative cisapride on postoperative aspiration pneumonia in dogs with laryngeal paralysis
J. Ogden 2019
serotonin 5-HT4 receptor agonist, cisapride
One of 50 dogs in the cisapride group and six of 52 dogs in the historical group developed aspiration pneumonia within the immediate postoperative period
Preoperative treatment
with a cisapride CRI does not appear to dramatically influence
the rate of postoperative aspiration pneumonia but further stud
ies
are needed..
study supports the use of butorphanol with
acepromazine in the preoperative period and buprenorphine for
postoperative analgesia, because these therapies appeared associ
ated
with lower rates of aspiration pneumonia
Theron 2022 – laryngeal silicone stent for laryngeal paralysis in 6 dogs
- immediate improvements in 6/6 post-op
- 2/6 stent malposition/migration; 6/6 satisfactory QOL
Perez Lopez 2019 – standard UAL vs anatomic preservation technique
- complications: standard: minor 22%, major 7%
anatomic preservation: minor 26%, major 23%
- aspiration pneumonia: standard 7%, anatomic preservation 17% - not different
- 18% recurrence overall
- MST: standard 636d, anatomic 1067d
Conclusions In this study, there was no significant difference in risk of aspiration pneumonia or survival time following arytenoid lateralisation by either an ST or an APT.
Mullins 2019 – retrospective of 50 dogs with sx (78 procedures) for epiglottic retroversion (ER)
- 15 primary ER, 35 concomittant (concurrent/historical airway disorder)
- intra-op complications: 2/78 (2.6%) procedures
- post-op major complications: 36/74 (48.7%) procedures
- 7/12 (58.3%) nonincisional epiglottopexy
- 23/43 (53.5%) incisional epiglottopexy
- 2/4 (50%) partial epiglottectomy; 2/12 (16.7%) subtotal epiglottectomy
- 2/3 (66.7%) other
- epiglottopexy failure most common (41.8%)
- aspiration pneumonia: overall 4/74 (5.4%)
- epiglottopexy procedures: higher incidence (30/55, 54.5%) vs epiglottectomy (4/16, 25%)
- survival: 60% at median 928d; MST not reached after median 716d
