Assessment of survey radiography as a method of diagnosing bilateral laryngeal paralysis in dogs

The gold standard for diagnosis of laryngeal paralysis is laryngoscopy under light anesthesia. This prospective analytical cross-sectional study aimed to determine whether a radiographic assessment of the larynx could be used as a non-invasive screening tool for diagnosing laryngeal paralysis in non-sedated animals, as the laryngeal ventricles may appear wider in affected animals. The laryngeal ventricles of 18 dogs with bilateral laryngeal paralysis composing the affected group and 25 non-sedated dogs presenting no respiratory abnormality composing the control group were evaluated using right lateral radiography of the larynx. Three observers measured the ratios of the maximal ventricular length and surface to the body length of the third cervical vertebra (MVL/LC3 and VS/LC3, respectively). They also subjectively assessed the ventricular shape as either normal or rounded. The most accurate criterion was found to be MVL/LC3, as the respective areas under the ROC curves were 0.96 (95% confidence interval [CI]: 0.95-0.97), 0.89 (95% CI: 0.87-0.91), 0.80 (95% CI: 0.65-0.95) for MVL/LC3, VS/LC3, and ventricular shape evaluation, respectively. Based on ROC curve analysis, two thresholds of clinical interest were set for the MVL/LC3; bilateral laryngeal paralysis was very unlikely for values < 0.3 and very likely for values > 0.5. The findings of this study support the use of lateral laryngeal radiography as a screening tool for diagnosing bilateral laryngeal paralysis. However, further diagnostic tests remain required if MVL/LC3 lies between these threshold values or if clinically indicated. Further studies are warranted to explore the use of laryngeal radiography in unilateral paralysis and other laryngeal or oropharyngeal diseases.

Mechanical ventilation in dogs and cats with tick paralysis

Respiratory failure from tick paralysis (TP) is an important cause of mortality in cats and dogs in Australia, occurring from a combination of respiratory muscle paralysis, upper respiratory tract obstruction and pulmonary disease. Patients may require positive-pressure ventilation in management of any combination of hypoxemia, hypoventilation or respiratory fatigue, but may also require airway management due to laryngeal paralysis. No single ventilation strategy is recommended due to the heterogenous disease presentations. Lung protective ventilation should be used in patients with pulmonary disease. Due to local and systemic effects of TP, patients are at higher risk of complications such as aspiration pneumonia and corneal ulceration and may have additional intravenous fluid and nutritional considerations. Treatment with hyperimmune serum is associated with improved outcomes. Prognosis is considered good with documented survival to discharge (STD) of 52.6-77% for animals with TP ventilated with lung disease and 90.5% for animals without lung disease. Median reported duration of ventilation for TP ranges from 23 to 48 h (range 3 h-10 days). The severity of individual neuromuscular signs and the presence of associated conditions such as aspiration pneumonia and laryngeal paralysis may necessitate longer periods of mechanical ventilation. This review aims to summarize the current recommendations regarding indications, management and prognosis of cats and dogs undergoing MV for TP and to identify areas for future research.

Laryngeal paralysis secondary to cervical bite injuries in five dogs

CASE HISTORIES

Medical records of a veterinary hospital in Belgium were reviewed for dogs (n = 5) that presented between 2016 and 2019 with laryngeal paralysis secondary to bite wounds to the cervical region received while fighting with other dogs. The time elapsed between the trauma and presentation was from a few hours up to 5 days.

CLINICAL FINDINGS AND TREATMENT

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. One dog with bilateral laryngeal paralysis was treated medically as no signs of dyspnoea were present. Surgical management was elected in 4/5 dogs based on evaluation of their clinical status and lesions revealed by endoscopic examination of upper gastrointestinal and respiratory tracts. Dogs underwent surgical procedures that were determined to be appropriate for treatment of the lesions identified on clinical examination, diagnostic imaging, and endoscopy. The cervical region was explored through a ventral midline approach in 2/4 cases, to close tracheal perforations. Temporary tracheostomy was performed in 2/4 cases. Procedures to correct brachycephalic airway obstructive syndrome were performed in 2/4 cases. Cricoarytenoid lateralisation was performed in 2/4 dogs. Dogs were hospitalised for 2-10 days and received antimicrobial therapy before surgery and for 2-3 weeks after surgery. Physical examination and respiratory function were normal in 3/5 dogs 4-6 months after discharge. Information regarding outcomes for two cases was obtained from the owners by telephone assessment 1-6 months after surgery. The owner of each dog reported the respiratory function to be excellent.

DIAGNOSIS

Uni- or bilateral, transient or permanent laryngeal paralysis with concomitant oesophageal, tracheal, or laryngeal lesions following cervical dog bite injuries diagnosed by endoscopic examination of upper gastrointestinal and respiratory tracts.

CLINICAL RELEVANCE

This case series describes the diagnosis and management of dogs with laryngeal paralysis secondary to cervical dog bite injuries. To the authors' knowledge, this is the first published report documenting bilateral laryngeal paralysis secondary to cervical dog bite injuries. 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. Upper airway and digestive endoscopy are recommended for complete assessment of cervical traumatic injuries.

Effect of doxepin on quality of life in Labradors with laryngeal paralysis: A double-blinded, randomized, placebo-controlled trial

Background

Laryngeal paralysis commonly affects older Labrador retrievers. Currently, dogs with severe disease require surgical intervention, most commonly arytenoid lateralization. Anecdotally, doxepin has been proposed to help dogs with laryngeal paralysis.

Hypothesis

Doxepin will improve quality of life measures assessed by owners of Labrador retrievers with laryngeal paralysis not requiring emergency surgery.

Animals

Twenty‐two Labrador retrievers with laryngeal paralysis.

Methods

Dogs were randomized to receive doxepin (3‐5 mg/kg q12h PO) or placebo for 28 days. Owners completed quality‐of‐life assessments before and after completing the study. Data were compared between groups using Rank‐Sum tests or Fisher's exact tests.

Results

The 2 groups of dogs did not differ at baseline except for owner‐perceived degree of ataxia (owners of dogs receiving doxepin considered them more ataxic than owners of dogs receiving placebo). After 28 days, owner‐assessed quality of life measures did not differ between dogs receiving doxepin or placebo (dogs worsening: doxepin = 2, placebo = 1; dogs unchanged: doxepin = 6, placebo = 7; dogs improved: doxepin = 4, placebo = 2; P = .84). Dogs receiving placebo had a greater improvement in client‐assessed overall health than dogs receiving doxepin (mean ranks: doxepin = 4.36, placebo = 6.64; P = .04). The study was terminated at this interim analysis.

Conclusions and Clinical Importance

Doxepin did not appear to improve any measures of owner‐assessed quality of life in Labrador retrievers with laryngeal paralysis.

A CNTNAP1 Missense Variant Is Associated with Canine Laryngeal Paralysis and Polyneuropathy

Laryngeal paralysis associated with a generalized polyneuropathy (LPPN) most commonly exists in geriatric dogs from a variety of large and giant breeds. The purpose of this study was to discover the underlying genetic and molecular mechanisms in a younger-onset form of this neurodegenerative disease seen in two closely related giant dog breeds, the Leonberger and Saint Bernard. Neuropathology of an affected dog from each breed showed variable nerve fiber loss and scattered inappropriately thin myelinated fibers. Using across-breed genome-wide association, haplotype analysis, and whole-genome sequencing, we identified a missense variant in the CNTNAP1 gene (c.2810G>A; p.Gly937Glu) in which homozygotes in both studied breeds are affected. CNTNAP1 encodes a contactin-associated protein important for organization of myelinated axons. The herein described likely pathogenic CNTNAP1 variant occurs in unrelated breeds at variable frequencies. Individual homozygous mutant LPPN-affected Labrador retrievers that were on average four years younger than dogs affected by geriatric onset laryngeal paralysis polyneuropathy could be explained by this variant. Pathologic changes in a Labrador retriever nerve biopsy from a homozygous mutant dog were similar to those of the Leonberger and Saint Bernard. The impact of this variant on health in English bulldogs and Irish terriers, two breeds with higher CNTNAP1 variant allele frequencies, remains unclear. Pathogenic variants in CNTNAP1 have previously been reported in human patients with lethal congenital contracture syndrome and hypomyelinating neuropathy, including vocal cord palsy and severe respiratory distress. This is the first report of contactin-associated LPPN in dogs characterized by a deleterious variant that most likely predates modern breed establishment.

The Influence of Anaesthetic Drugs on the Laryngeal Motion in Dogs: A Systematic Review

Simple Summary

Laryngeal paralysis is secondary to a loss of normal function of the larynx. Older dogs are particularly affected, with normal breathing becoming difficult. A successful diagnosis typically relies on the visualisation of either, complete, or partially absent, laryngeal movements. The use of anaesthesia drugs to provide sedation and stress relief is most commonly necessary during the diagnosis of laryngeal paralysis. While, the excessive administration of anaesthesia drugs may result in absent movements, the ideal anaesthesia regime remains unknown, and the use of sedation is questionable, given the potential for absent laryngeal movements, even in healthy dogs. In this systematic review, we found a potential benefit from using sedation during the evaluation of laryngeal function when compared to injectable anaesthetics only. The respiratory stimulant doxapram was effective in differentiating normal dogs from dogs with laryngeal paralysis but has associated safety hazards.

Abstract

Anaesthetic drugs are commonly used during the evaluation of laryngeal function in dogs. The aim of this review was to 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. PubMed, Google Scholar, and EMBASE databases were used for the literature search up to November 2019. Relevant search terms included laryngeal motion, anaesthetic drugs and dogs. Studies were scored based on their level of evidence (LoE), according to the Oxford Centre for Evidence-based Medicine, and the quality was assessed using the risk-of-bias tool and SIGN-checklist. 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.

Laryngeal stent for acute and chronic respiratory distress in seven dogs with laryngeal paralysis

Background:

Laryngeal paralysis, failure of arytenoid cartilage, and vocal fold abduction are commonly seen in older medium to large breed dogs. Observation of laryngeal function in dogs and cats is performed by transoral visualization. There are a variety of surgical techniques; aspiration pneumonia is the most common complication associated with surgical correction of laryngeal paralysis. The aim of this case series is to report on the placement of a laryngeal silicone stent in seven dogs with laryngeal paralysis and its use as an alternative treatment of respiratory distress caused by laryngeal paralysis and/or its use for laryngeal stenosis as complication of laryngeal paralysis surgery.

Case description:

Seven dogs presented with either episode of gagging, mild-to-severe inspiratory distress, or cyanosis because of a laryngeal paralysis or laryngeal stenosis. In each case, the laryngeal paralysis was diagnosed by direct laryngoscopy. They were treated with a silicone laryngeal stent (Stening^®) that substantially improved the clinical signs. Each dog had a different outcome because of other pathologies; however, the laryngeal pathology was successfully treated with the stent.

Conclusion:

The placement of the laryngeal stent is an easy technique to learn and practice, it could avoid the life-threatening complications of the laryngeal paralysis at the acute phase, and it could be a noninvasive and long-term alternative therapy for laryngeal paralysis in dogs. The results in these clinical cases are encouraging for considering the laryngeal stent as a therapeutic alternative.

Examination of laryngeal function of healthy dogs by using sedation protocols with dexmedetomidine

OBJECTIVE

To determine the ability to evaluate laryngeal function under sedation with dexmedetomidine alone or in combination with opioids.

STUDY DESIGN

Randomized, crossover, blinded study.

ANIMALS

Eight adult research hounds weighing 8 to 22.5 kg.

METHODS

Dogs were sedated with propofol, dexmedetomidine, dexmedetomidine and butorphanol, or dexmedetomidine and hydromorphone. Digital images were collected with video laryngoscopy before and after doxapram administration. Maximal inspiratory normalized glottal gap (GGA_n ) and laryngeal motion were compared between and within protocols before and after doxapram by using a difference of least squares mean.

RESULTS

Normal laryngeal function was confirmed in all dogs with all protocols except propofol, which resulted in two false positive results. No difference between protocols was detected for predoxapram GGA_n . Postdoxapram GGA_n was greater than predoxapram GGA_n for all four sedation protocols (P ≤ .0030). Compared with propofol, postdoxapram GGA_n was greater for all three dexmedetomidine protocols (P ≤ .0420).

CONCLUSION

Dexmedetomidine alone or in combination with opioids was an effective sedation protocol for laryngeal examination, producing sufficient immobilization to prevent jaw motion and without affecting arytenoid abduction.

CLINICAL SIGNIFICANCE

Dexmedetomidine sedation does not inhibit normal laryngeal motion. Laryngeal examination with propofol alone can produce false positive results.

Laryngeal paralysis associated with a muscle pseudotumour in a young dog

An 18-month-old male entire Bloodhound dog was presented with a six-week history of progressive inspiratory dyspnoea, stridor, dysphonia and exercise intolerance. CT scan performed elsewhere had revealed the presence of an unencapsulated nodular mass (3x1x5 cm) dorsal to the larynx and first tracheal rings. Laryngoscopy demonstrated the presence of bilateral laryngeal paralysis and distorted laryngeal architecture suggestive of extraluminal compression. Histopathology results of incisional biopsies from the mass were suggestive of a benign non-neoplastic muscular lesion. Surgery was performed to manage laryngeal paralysis and attempt mass excision. A second histopathology examination confirmed an inflammatory and dysplastic lesion suggestive of a pseudotumour. All clinical signs resolved after surgery and at the 13 months follow-up the dog remains asymptomatic. To the authors’ knowledge, this is the first report of a case of laryngeal paralysis caused by a muscle pseudotumour in a young dog.