Comparison of immediate and short-term outcomes of cricoarytenoid and thyroarytenoid lateralization in dogs with idiopathic laryngeal paralysis

OBJECTIVE

To compare the immediate and short-term outcomes of thyroarytenoid lateralization (TAL) and cricoarytenoid lateralization (CAL) for the treatment of canine laryngeal paralysis in dogs.

STUDY DESIGN

A prospective, clinical trial.

ANIMALS

Fourteen client-owned dogs referred to our hospital because of bilateral laryngeal paralysis.

METHODS

Dogs with confirmed laryngeal paralysis were randomly assigned to the CAL or TAL group. Video images of the rima glottidis obtained preoperatively, immediately postoperatively (t0), and 15 days postoperatively (t1) were digitized. The rima glottidis area was measured using image-analysis software. An increase in the rima glottidis area was expressed as a percentage of the preoperative area.

RESULTS

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 with preoperative values. The increase in the rima glottidis area differed (P < .05) between the 2 groups at all postoperative time points. A reduction of the area occurred at t1 in both groups. There was no difference between t0 and t1 (P > .05) in the CAL group but there was a large difference (P < .05) in the TAL group.

CONCLUSION

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.

Influence of doxapram and intermittent 10% carbon dioxide inspiration on cardiovascular and laryngeal functions in anesthetized dogs

OBJECTIVE

To compare the effects of two doses of doxapram intravenous injection and carbon dioxide inhalation on the cardiovascular and laryngeal functions of anesthetized hounds.

STUDY DESIGN

Experimental study.

ANIMALS

Six healthy adult dogs.

METHODS

In a Latin-square design, the mean arterial blood pressure (MABP) and heart rate (HR) were recorded continuously. The inspiratory normalized glottic gap areas (iNGGA) were measured before and after each stimulation with 0.55 mg/kg of doxapram (L-DOX), 2.2 mg/kg of doxapram (H-DOX), or 90 s of inhalation of 10% carbon dioxide in oxygen (I-CO₂ ). The stimulations were tested in duplicate or triplicate. Video clips of the laryngeal movement were scored by board-certified surgeons masked to the treatment.

RESULTS

The MABP increased with L-DOX and H-DOX up to 81% (both p < .001 compared to I-CO₂ ), and persisted during the other stimulations (both p < .001). An intermittent tachycardic effect of up to 79% increase in HR was observed with doxapram. The HR following H-DOX was higher than L-DOX and I-CO₂ (both p < .016). Neither hypertension nor tachycardia was observed with I-CO₂ . The iNGGA increased with all treatments (p < .001). The iNGGA was greater with H-DOX than L-DOX and I-CO₂ (both p < .007). All treatments received higher scores (all p < .001) with acceptable inter- and intra-observers Krippendorff's alphas.

CONCLUSION

All treatments were effective respiratory stimulants in anesthetized dogs; however, doxapram caused hypertension and tachycardia.

CLINICAL SIGNIFICANCE

Carbon dioxide inhalation might improve arytenoid motion without cardiovascular effects in dogs during clinical airway examinations.

A RAPGEF6 variant constitutes a major risk factor for laryngeal paralysis in dogs

Laryngeal paralysis (LP) is the inability to abduct the arytenoid cartilages during inspiration, resulting in a partial to complete airway obstruction and consequent respiratory distress. Different forms of LP with varying age of onset exist in dogs. Hereditary early onset forms were reported in several dog breeds. In most breeds, hereditary LP is associated with other neurologic pathologies. Using a genome-wide association study and haplotype analyses, we mapped a major genetic risk factor for an early onset LP in Miniature Bull Terriers to a ~1.3 Mb interval on chromosome 11. Whole genome sequencing of an affected Miniature Bull Terrier and comparison to 598 control genomes revealed a 36 bp insertion into exon 15 of the RAPGEF6 gene (c.1793_1794ins36). The imperfect genotype-phenotype correlation suggested a complex mode of inheritance with a major genetic risk factor involving a recessive risk allele. Homozygosity for the insertion was associated with a 10- to 17-fold increased risk for LP. The insertion allele was only found in Miniature Bull Terriers and Bull Terriers. It was absent from >1000 control dogs of other dog breeds. The insertion sequence contains a splice acceptor motif leading to aberrant splicing in transcripts originating from the mutant allele (r.1732_1780del). This leads to a frameshift and a premature stop codon, p.(Ile587ProfsTer5), removing 64% of the open reading frame. Our results suggest an important role of RAPGEF6 in laryngeal nerve function and provide new clues to its physiological significance.

Laryngeal paralysis (LP) leads to respiratory distress in affected dogs and can be fatal in severe cases. Many different forms of LP with different etiologies exist. Striking breed predispositions suggest that genetic factors contribute to some forms of LP. During the last years, dog breeders noticed an increased prevalence of an early onset LP in Miniature Bull Terriers. We mapped a major risk locus for this specific form of LP to a ~1.3 Mb interval on dog chromosome 11. Whole genome sequence analysis of an affected dog and comparison to 598 control genomes revealed a single protein-changing genetic variant in the critical interval. This variant, a 36 bp insertion into a coding exon of the RAPGEF6 gene, creates a cryptic splice site and leads to the expression of an aberrantly spliced transcript with a premature stop codon. This suggests that the insertion results in a loss-of-function allele. Dogs that are homozygous for the insertion have a 10- to 17-fold increased risk to develop LP. The genotype-phenotype association is not perfect, suggesting that other genetic and/or environmental factors also contribute to the development of LP. Our results suggest an important role of RAPGEF6 in laryngeal nerve function.