Log in for access

Logging in to the private area gives you access to protected parts of the site and enables you to interact with the portal

Log in not working?

Contact us via e-mail or fill in the help form

User login

Search by term

Search by Subject

Laryngeal paralysis in dogs and cats: management and complications (Part II)

Last updated November 12, 2013

Acquired laryngeal paralysis (LP) may be related to trauma, neoplasia, polyneuropathies or hypothyroidism. However, the idiopathic form is the most common diagnosis. Medical management with sedatives, oxygen supplementation, cold environment, rest and steroids, when needed, can temporarily alleviate clinical signs. Surgery is considered to be the most effective means of treating and palliating the signs associated with laryngeal paralysis. Different surgical techniques for correction of laryngeal paralysis yield variable results and whereas no one technique is seemingly superior, unilateral arytenoid lateralisation is generally considered the gold standard. Most dogs experience significant improvement in respiration following surgery; however, they have an increased risk of aspiration pneumonia for the remainder of their lives.

 

MEDICAL VERSUS SURGICAL MANAGEMENT


Patients presented with acute cyanosis or collapse as a result of LP have to be stabilised with emergency medical treatment. These animals should be placed in a cold environment with oxygen supplementation. Patients with hyperthermia may require an ice water bath. Stressed animals may benefit from sedation with acepromazine (0.02 mg/kg IV). However, acepromazine may cause hypotension; therefore an intravenous catheter should be promptly placed for fluids and drug administration. Fluid therapy should yet be used with caution because some animals with severe upper respiratory tract obstruction may develop pulmonary oedema. In these cases, diuretics are indicated. Corticosteroids such as prednisolone (1mg/kg IV q 24h) or dexamethasone (0.1 to 0.2 mg/kg IV or IM q 12 to 24h) can also be administered to reduce laryngeal inflammation and oedema. If the patient’s demeanour deteriorates, an emergency tracheostomy is recommended. However, it has been reported that temporary tracheostomy in dogs with LP was associated with more postoperative complications and was a negative prognostic indicator for long-term survival. In fact, the presence of a tracheostomy tube results in diffuse loss of cilia, epithelial ulceration, sub-mucosal inflammation and retained secretions. The trachea becomes colonised with bacteria within 24 hours after tracheostomy placement. These conditions may increase the risk for complications such as pneumonia following the surgical correction of LP. In the case of rapidly deteriorating conditions it is also possible to take the animal immediately to surgery for a laryngeal procedure. Dogs that are asymptomatic at rest or mildly affected can be managed with weight loss, stress reduction, exercise restriction and avoidance of high temperature environments. The owners of conservatively managed patients should be aware that the condition is progressive and that signs will likely worsen with time.

Unilateral laryngeal “tie-back” surgery is currently the most widely used technique to correct LP in dogs and cats and to manage symptoms. The purpose of laryngeal tieback is to enlarge the rima glottidis by surgical retraction of the arytenoid cartilage on one side of the larynx and decrease airway resistance.2

Laryngeal “tie-back” refers to one of two possible surgical techniques:

  • Tyro-arytenoid lateralisation

       or

  • Crico-arytenoid rotation

For laryngeal tieback surgery the patient is placed in lateral recumbency with a soft support underneath the neck and an incision is made ventral to the jugular vein (Fig. 1). After dissection through the subcutaneous tissue, the thyreopharyngeal muscle is incised along the dorsal edge of the wing of the thyroid cartilage and this is retracted with a fine wound hook or with Allis tissue forceps. The muscular process of the arytenoid cartilage can be easily identified by palpation and therefore the cricoarytenoideus dorsalis muscle inserting on the process can be transected. It is at this point that a sample of this muscle and of the muscular branch of the RLN can be collected for histopathological examination. The crico-arytenoid joint is opened partially with Metzenbaum scissors, which are inserted with cranial direction between the laterally located muscular process and the medially located cricoid cartilage. While during tyro-arytenoid lateralisation complete disarticulation of the arytenoid cartilage and attachment to the thyroid cartilage is achieved, in the crico-arytenoid rotation minimal dissection of the crico-arytenoid articulation followed by anchoring the muscular process of the arytenoid cartilage to the caudo-dorsal border of the cricoid cartilage is performed (Fig. 2).

The purpose of tyro-arytenoid lateralisation is to achieve lateral displacement of the arytenoid without caudal displacement. One suture of 0 (for large dogs) or 3-0 (for small dogs and cats) monofilament non-absorbable material such as polypropylene with a taper-pointed needle is passed medially to laterally through the articular surface of the muscular process of the arytenoid and then through the caudo-dorsal border of the wing of the thyroid cartilage. An alternative and more physiologic suturing technique involves placing the tieback suture from the muscular process of the arytenoid to the dorso-caudal border of the cricoid in a medio-lateral direction (crico-arytenoid rotation). The needle is first passed around the caudal border of the cricoid cartilage and then through the muscular process from the crico-arytenoid joint surface. Suture tying up is a critical phase and a common problem for inexperienced surgeons as it may result in either inadequate enlargement of the glottis opening or over-abduction of the arytenoid cartilage.

Sutures are tied up so that the final glottis opening will be no larger than that of the patient with the endotracheal tube in place. It is advisable to ask an assistant to observe the size of the opening achieved during tying up to ensure that correct abduction of the laryngeal cartilages has been obtained. It is also recommended to extubate and then re-intubate the patient during this delicate phase for adequate observation. In elderly dogs laryngeal cartilages could be calcified or friable. To reduce the risk of cartilages fracture, holes for needle passage can be pre-drilled with an 18-gauge hypodermic needle.

Griffith and others (2001) reported that the glottis opening was significantly greater after crico-arytenoid lateralisation (207%) than thyro-arytenoid lateralisation (140%); however, there was no clinical difference in dogs treated with either technique.3 Demetriou and others (2003) demonstrated that a combined technique of crico-arytenoid and tyro-arytenoid cartilage lateralisation does not significantly increase the rima glottidis compared with crico-arytenoid cartilage lateralisation alone.4

According to a law of physics (Poiseuille’s law), resistance to flow is inversely related to the radius to the fourth power. This explains why a small increase in glottis opening dramatically reduces airway resistance, improving airflow and therefore significantly reducing clinical signs of airway obstruction due to LP. It is also true that if the rima glottidis is enlarged beyond the edges of the epiglottis, part of it remains uncovered by the epiglottis, increasing the risk of aspiration during swallowing. Therefore, the arytenoid cartilage abduction should be limited, so that laryngeal resistance to air flow is reduced leading to improvement of the symptoms and the rima glottidis is almost completely covered by the epiglottis, decreasing the risk of aspiration pneumonia.

 

COMPLICATIONS AFTER LARYNGEAL “TIE-BACK”


White (1995) reported that tieback surgery has a high success rate (90%) providing immediate relief of the clinical signs (Figs. 3a and b) (Videos 1 and 2).5 On the contrary, Mac Phail and Monnet (2001) found a high incidence of complications  (34%) and a high mortality rate (19%) in 140 dogs undergoing surgical treatment of LP in a long term follow up (13 years).1 Dogs that underwent bilateral arytenoid lateralisation were significantly more likely to develop complications and less likely to survive than dogs that underwent unilateral arytenoid lateralisation. Factors associated with a higher risk of complications or death included age, temporary tracheostomy, concurrent respiratory tract or oesophageal abnormalities, and concurrent neoplastic or neurologic disease.1

Video 1. One day postopVideo 2. Two months postop

 

A number of intra- post-operative and long –term complications can develop in dogs undergoing laryngeal lateralisation.

Intra-surgical complications include haemorrhage, arytenoid cartilage fragmentation and failure to achieve adequate opening of the rima glottidis.

Haemorrhage may occur from dissection and mainly from transection of the cryco-arytenoid muscle and the crico-arytenoid joint capsule. Meticulous haemostasis throughout the procedure is therefore recommended as haematoma developing around the tieback site could lead to avulsion of the suture or could cause acute airway obstruction if around the vocal folds.6

Over-manipulation of the arytenoid cartilage and the use of cutting needles for passing the suture could lead to fracture of the cartilage leading to the impossibility to conclude the procedure. In these cases, a contralateral tieback is usually the safer solution. Inadequate glottis opening may be secondary to incomplete inter-arytenoid separation, misplacement or inadequate tensioning of the suture. Revision may be feasible in some cases even though contra-lateral procedure is recommended.6

Post-operative complications include rima glottidis over-abduction, haematoma, oedema or seroma development and aspiration pneumonia (Figs. 4a and b). Excessive enlargement of the glottis opening and thyropharyngeus muscle dysfunction may predispose to dysphagia and aspiration. These complications are normally evident within 24 hours. Avoiding over-abduction and minimal dissection of the thyreopharyngeus muscle can reduce the incidence. Depending on the degree of over-abduction patients may cope with the complication or revision to reduce the degree of opening or arytenoid release with contralateral tieback may be required. Poor haemostasis or dead space management may lead to peri-laryngeal haematoma, or oedema which may require tracheostomy since revision is not helpful.6

Long-term complications include arytenoid suture pull-through and contralateral arytenoid collapse. Patients with severe airway obstruction prior surgery tend to develop a collapse towards the rima of the non-abducted arytenoid and vocal fold over the weeks following the surgery. Management entails a staged contralateral tieback.6

Major complications after bilateral arytenoid lateralisation are aspiration pneumonia and surgical failure. It is generally accepted to avoid bilateral laryngeal tieback to reduce the incidence of aspiration pneumonia complication. In cases where indicated, bilateral surgeries require a delay of 2-3 weeks between the first and the second procedure.

The incidence of complications in cats after laryngeal tieback is of around 54% and includes aspiration pneumonia, post-operative dyspnoea requiring temporary tracheostomy, Horner’s syndrome and laryngeal stenosis.7

 

OTHER SURGICAL OPTIONS FOR LP CORRECTION


A variety of surgical procedures different from laryngeal tieback have been described. These are generally aimed at removing one or both vocal folds and arytenoid cartilages to provide a functional airway and include transoral partial laryngectomy, video-assisted photoablative (diode laser) laryngectomy and ventral laryngotomy for partial laryngectomy.8

Transoral partial laryngectomy is often performed in combination with unilateral or more rarely bilateral vocal cord excision. Two to three mm of the medial border of the corniculate process of the arytenoid cartilage is removed resulting in enlargement of the laryngeal opening. A unilateral partial laryngectomy usually provides an adequate opening, minimising the risk of aspiration pneumonia. Long instruments such as long thumb forceps, Metzenbaum scissors and scalpel handles facilitate the procedure. With the patient placed in sternal recumbency, the head suspended by the maxilla and mouth opened with a mouth gag or a tape, the corniculate process is grasped and retracted medially with the forceps. The process is excised smoothly using the scalpel blade. It is also possible to incise the mucosa on the rostral rim of the corniculate process and then remove piece by piece the corniculate cartilage without resecting the mucosa. The cuneiform process is left intact and the mucosal defect is either left to heal by second intention or is sutured with a 5-0 or 6-0 monofilament, rapidly absorbable material in a continuous pattern. With unilateral partial laryngectomy the vocal process and the entire vocal fold on one side are also removed. If both vocal cords are excised, the ventral and the dorsal commissure of the glottis, where the vocal folds meet ventrally and join the arytenoid cartilage dorsally, are preserved to minimise scar tissue webbing across the rima glottidis. Bilateral arytenoid resection is not recommended. Intra-operative bleeding can be controlled by direct pressure with swabs in conjunction with topical epinephrine. Electro cautery should be avoided since its use in this area may lead to post-operative swelling and granulation tissue formation. In general, the outcome for animals with LP undergoing this procedure is good. Complications have been reported in 40-50% of the cases and include aspiration pneumonia, persistent cough, vomiting, and laryngeal webbing.2 This last complication can be serious and life threatening and is most likely to occur when bilateral vocal folds resection is performed.

Olivieri and others (2009) described transoral partial arytenoidectomy using video-assisted diode laser ablation. It was reported thatthe use of this technique seemed to lead to fewer complications than standard intraoral partial arytenoidectomy and enhanced precision of cartilage resection because of the magnification afforded by the endoscope. The diode laser promotes coagulation from local thermal action created over the cartilaginous tissue during photovaporisation. This dramatically decreases post-operative intramural oedema and haematoma formation, which are other potential complications of standard intraoral techniques. Reported advantages of using laser are accuracy, rapid re-epithelisation, and prevention of scar or granulation tissue formation.9

In theventral laryngotomy for partial laryngectomy, the ventral approach to the larynx provides better exposure and more operative space than a transoral approach. It also permits primary mucosal closure. The patient is placed in dorsal recumbency and the larynx is approached ventrally. The cricothyroid membrane and thyroid cartilage are incised on the midline, the edges are maintained opened by stay sutures and retractors. The endotracheal tube is left in place. A gentle retraction of the thyroid cartilage edges exposes the arytenoid cartilage and the vocal folds. The mucosa is incised over the corniculate, cuneiform and vocal process of one arytenoid and the structures are excised with scissors or scalpel blade. The redundant mucosa is removed and the mucosal defect sutured with fine absorbable monofilament, in a continuous pattern. The thyroid cartilage incision is then reapposed with non-absorbable interrupted sutures that do not penetrate the laryngeal lumen.

Zikes and others (2012) modified this last technique performing a bilateral ventriculocordectomy via ventral laryngotomy in 88 dogs and the results were considered very satisfactory in 93% of cases. The technique uses the above described ventral approach to the larynx and includes a bilateral sharp dissection with complete excision of the vocal folds. The mucosal defect is then closed with absorbable suture material elevating a mucosal flap from the lateral wall of the laryngeal ventricle. The authors concluded that bilateral ventriculocordectomy via a ventral laryngotomy approach requires less extensive dissection than unilateral arytenoid lateralisation and creates no disruption to either the thyreopharyngeus or cricoarytenoideus muscles. This procedure may in fact actually lead to less post operative complications in those patients considered at increased risk for developing aspiration pneumonia.10

 

POST-OPERATIVE MANAGEMENT


Patients undergoing laryngeal corrective surgery for LP should not be offered water and food until fully awake. They should also not be heavily medicated with analgesics or sedatives during recovery so as to maintain the swallowing reflex. It is recommended to hand-feed meatballs not earlier than 24 hours after surgery and offer water only after the animal can swallow the meatballs. Owners should carry on hand-feeding the animal for the 2 weeks after surgery and rest should be recommended for the following 4-6 weeks. The use of a harness instead of a neck collar is also recommended.

 

CONCLUSION


The long-term outcome after treatment of acquired idiopathic LP is generally good even though dogs treated for this condition are at risk for aspiration pneumonia for their entire life. When successful, laryngeal surgery  reduces or resolves the respiratory signs in most patients; however it does not address the underlying cause.

 

References


  1. MacPhail CM & Monnet E.  Outcome of and postoperative complications in dogs undergoing surgical treatment of laryngeal paralysis: 140 cases (1985–1998). Journal of American Veterinary Medical Association 2001;218:1949–1956.
  2. Millard RP & Tobias KM. Laryngeal paralysis in dogs. Compendium on Continuing Education for the practicing veterinarians 2009;31:212-219.
  3. Griffiths LG, Sullivan M & Reid SWJ. A comparison of the effects of unilateral thyroarytenoid lateralization versus cricoarytenoid laryngoplasty on the area of the rima glottides and clinical outcome in dogs with laryngeal paralysis. Veterinary Surgery 2001;30:359-365.
  4. Demetriou JL & Kirby BM. The effect of two modifications of unilateral arytenoid lateralization on rima glottides area in dogs. Veterinary Surgery 2003;32:62-68.
  5. White RAS. Unilateral arytenoid lateralization: an assessment of technique and long term results in 62 dogs with laryngeal paralysis. Journal of Small Animal Practice 1995;30:543-549.
  6. White RAS. Technical failures and complications in laryngeal tie back surgery. ECVS proceedings, 2010:253-254.
  7. Thunberg B & Lantz GC. Evaluation of unilateral arytenoid lateralization for the treatment of laryngeal paralysis in 14 cats. Journal of the American Animal Hospital Association 2010;46:418-424.
  8. GriffinJG & Krahwinkel DJ. Laryngeal paralysis: pathophysiology, diagnosis and surgical repair. Compendium on Continuing Education for the practicing veterinarians 2005;27:857-868.
  9. Olivieri M, Voghera SG & Fossum TW. Video-assisted left partial arytenoidectomy by diode laser photoablation for treatment of canine laryngeal paralysis. Veterinary Surgery 2009;38:439-444.
  10. Zikes C & McCarthy T. Bilateral ventriculocordectomy via ventral laryngotomy for idiopathic laryngeal paralysis in 88 dogs.  Journal of the American Animal Hospital Association 2012;48:234-244.

Vetpedia is translated by a team of expert scientific translators coordinated by Alberto Scalcerle (InterMed - Italian Association Medical Interpreters - coordinator) and Rachel Stenner (MA (Cantab) MB BS (Lon) - lead translator). 
For further information please contact: alberto.scalcerle@alice.it  www.scalcerle.net

Latest publications

Image of the day

Paraprostatic cysts are one or more large, encapsulated fluid collections found close to the prostate

Events

The BIBLIOVET project is supported by Bayer HealthCare  
   
Bayer is a multinational with key expertise in various fields including health, wellbeing and nutrition.
Bayer’s mission is to supply products and services that improve the quality of life of people and animals.