Idiopathic mucosal lesions of the arytenoid cartilages of 21 Thoroughbred yearlings: 1997-2001

Clinical and Pathological Features in Horses With Advanced Arytenoid Chondritis

Equine arytenoid chondritis causes airway obstruction and abnormal upper airway noise due to a space-occupying lesion(s) and decreased abduction. Our objective was to compare clinical scores and ultrasonographic findings with gross and microscopic lesions of naturally occurring arytenoid chondritis, in order to guide surgical treatment. Seventeen naturally affected horses with advanced/severe chronic arytenoid chondritis and 4 control arytenoid cartilages were evaluated after partial arytenoidectomy. Cartilages were sectioned caudal to the corniculate process and the body of each arytenoid was measured. We assessed total gross area (TA), percentage of viable cartilage (VC), percentage of viable cartilage on the lateral wall, and medial expansion. Retrospectively, the gross lesions were used to suggest 2 preferred surgical management (SM) groups: those requiring partial arytenoidectomy and those amendable to focal medial resection (a conservative SM). TA of horses with arytenoid chondritis was significantly larger than controls (P = .005), due to a layered lesion composed of cavitation, granulation tissue, fibrosis, inflammation, hemorrhage, and edema, with relatively equal medial and lateral expansion that distorted the geometry of the affected cartilage. The increased TA paralleled the presence of immature cartilage with disorganized primitive mesenchymal cells. TA and SM were positively correlated (P = .01). All cases showed varying degrees of cartilage degeneration or necrosis, more severe medially; those appearing amenable to focal medial resection arytenoid group had significantly more viable cartilage on the lateral wall (P = .02). The gross and histopathologic findings suggest a new surgical approach-focal medial resection-that may save the lateral wall of the arytenoid.

Antimicrobial susceptibility of bacterial isolates from 33 thoroughbred horses with arytenoid chondropathy (2005-2019)

OBJECTIVE

To describe the prevalence and antimicrobial susceptibility of bacterial isolates cultured from surgical specimens of infected arytenoid cartilage and granulomas.

STUDY DESIGN

Retrospective cohort study.

ANIMALS

Thirty-three thoroughbred horses.

METHODS

Hospital records were retrieved for all horses admitted to a referral hospital for arytenoid chondropathy surgery that had samples submitted for culture and sensitivity between 2005 and 2019. Descriptive analyses were performed.

RESULTS

In total, 56 bacterial isolates were obtained. Gram-positive bacteria (58%), Gram-negative bacteria (54%), and anaerobes (33%) were cultured from samples. Fifty-eight percent of horses had multiple bacteria isolated. Streptococcus spp were the most common (32%), followed by Enterobacteriaceae (13%). Bacterial isolates were sensitive to ceftiofur (83%), followed by ampicillin (64%), tetracycline (48%), enrofloxacin (45%), trimethoprim-sulfamethoxazole (41%), and gentamicin (18%). Multidrug resistance (MDR) was present in 44% of bacterial isolates.

CONCLUSION

A wide variety of bacteria was cultured, providing evidence that secondary opportunistic infection by common respiratory bacteria is likely a factor in arytenoid chondropathy. Multidrug resistance was higher than what has been previously reported in equine respiratory samples. Trimethoprim-sulfamethoxazole had low effectiveness.

CLINICAL SIGNIFICANCE

Because culture and sensitivity testing is not available in the diagnosis of mild to moderate arytenoid chondropathy, the information from this study may allow for more targeted broad-spectrum antimicrobial treatment to limit disease progression when the disease is first identified. The antimicrobial susceptibilities and MDR found in this study emphasize the importance of following current antimicrobial guidelines and highlight the requirement for surgical intervention rather than continued medical treatment in cases that do not resolve with initial antimicrobial therapy.

Vocal fold granulomas in six brachycephalic dogs: clinical, macroscopical and histological features

Vocal cord granulomas are rarely observed in brachycephalic breeds but often reported in humans as contact granulomas. Six French bulldogs were included in this retrospective descriptive study. Endoscopic laryngeal examinations were performed on all dogs under general anaesthesia. Vocal cord lesions were exclusively unilateral, exophytic, approximately 3-mm wide ulcerated mucosal nodules, arising from the vocal cord. Histopathological examination mainly revealed chronic inflammatory changes on the laryngeal epithelium which were consistent with laryngeal granulomas described in humans, except for the location: vocal cord in dogs versus vocal process in humans. In humans, granulomas result from chronic physical or chemical insult to laryngeal mucosa (chronic cough or throat clearing, vocal abuse, gastro-esophageal reflux). In brachycephalic breeds, chronic inspiratory efforts and air turbulences and gastro-esophageal reflux are suspected to result in chronic laryngeal inflammation.

Imaging diagnosis--equine nasal septal thickening due to chronic chondritis

We describe the use of computed tomography (CT) in a 6-year-old mare with upper airway obstruction due to an abnormally thick nasal septum. Upon CT imaging, multifocal, expansile cyst-like lesions were detected in the nasal septum. The histopathologic diagnosis was chronic dissecting chondritis. Resection of the abnormal nasal septum resulted in resolution of the clinical signs.

Prevalence of pharyngeal and laryngeal abnormalities in Thoroughbreds racing in Australia, and their association with performance

REASONS FOR PERFORMING STUDY

Little information is available regarding the prevalence of abnormalities of the upper airway and their association with performance in the general population of Thoroughbred racehorses.

OBJECTIVES

To describe the prevalence of selected abnormalities of the upper airway and their association with performance in Thoroughbred racehorses in Australia.

HYPOTHESIS

That abnormalities of the upper airway of Thoroughbred racehorses are associated with poor race performance.

METHODS

Rhinolaryngoscopy was performed after racing and presence and characteristics of abnormalities of the larynx and pharynx were recorded in a prospective cross-sectional study of Thoroughbred horses racing in Victoria, Australia.

RESULTS

Rhinolaryngoscopy was performed once on each of 744 horses over 35 months. Fifty abnormalities of the upper airway were detected in 47 horses (6.3%, 95% confidence interval [CI] 4.7-83%). Epiglottic entrapment was detected in 7 horses (0.9%, 95% CI 0.4-1.9%) and was significantly (P = 0.015) associated with superior performance. Grade 2 asymmetry (4 grade scale) of the left arytenoid cartilage was detected in 9 horses (1.2%, 95% CI 0.5-2.4%) and was also associated with superior performance (P<0.001). Ulceration or erosion of the mucosa of the axial surface of one or both arytenoids was detected in 18 horses (2.4%, 95% CI 13-3.8%) and was not associated with alterations in exercise performance (P = 0.31).

CONCLUSIONS

Epiglottic entrapment, Grade 2 laryngeal asymmetry and mucosal erosions detected in Thoroughbred racehorses were not associated with impaired performance; therefore, surgical correction and concern over laryngeal function in horses with Grade 2 asymmetry may not be necessary in individuals performing to expectation.

Racing performance after combined prosthetic laryngoplasty and ipsilateral ventriculocordectomy or partial arytenoidectomy: 135 Thoroughbred racehorses competing at less than 2400 m (1997-2007)

REASONS FOR PERFORMING STUDY

The success of combined prosthetic laryngoplasty with ipsilateral ventriculocordectomy (LPVC) has not been compared to that of partial arytenoidectomy (PA) in a clinical population.

HYPOTHESES

In Thoroughbred (TB) racehorses: (1) earnings after LPVC are unaffected by the severity of recurrent laryngeal neuropathy (RLN) (laryngeal grade III vs. grade IV); (2) LPVC and PA yield similar results in the treatment of grade III RLN; (3) performance outcome following PA is independent of diagnosis (RLN vs. unilateral arytenoid chondritis [UAC]); and (4) neither LPVC nor PA returns horses to the level of performance of controls.

METHODS

Medical and racing records of 135 TB racehorses undergoing LPVC or PA for the treatment of grade III or IV RLN or UAC were reviewed. Racing records of age and sex matched controls were also reviewed.

RESULTS

After LPVC, horses with grade III RLN performed better compared to those with grade IV RLN. Furthermore, horses treated for grade III RLN by LPVC showed post operative earnings comparable to controls. Rate of return to racing were similar for PA and LPVC, although LPVC resulted in higher post operative earnings. Performance after PA was similar regardless of diagnosis (UAC or RLN). Finally, neither LPVC when performed for grade IV RLN, nor PA performed for either diagnosis restored post operative earnings to control levels.

CONCLUSIONS

Thoroughbred racehorses treated by LPVC for grade III RLN show significantly better post operative earnings compared to horses treated for grade IV disease. In grade III RLN, LPVC returns earning potential to control levels. PA and LPVC lead to similar success in terms of rate of return to racing, but PA leads to inferior earnings after surgery.

POTENTIAL RELEVANCE

Laryngoplasty should be recommended for all TB racehorses with grade III RLN to maximise return to racing at a high level. This contradicts the common approach of waiting for complete paralysis.

Arytenoid mucosal injury in young Thoroughbred horses — investigation of a proposed aetiology and clinical significance

AIM

To determine whether trauma to the larynx caused by nasotracheal intubation induced mucosal ulceration of the arytenoid cartilages of adult horses, and to determine the incidence of such ulceration in yearling Thoroughbred horses and its effect on athletic performance.

METHODS

Laryngeal trauma was induced in a group of 21 adult horses by introduction of a nasogastric tube into the trachea three times within 5 min. Injury to the arytenoid cartilages or vocal cords was subjectively assessed immediately after intubation, and thereafter at weekly intervals for 10 weeks. The outcome and athletic performance of 33 Thoroughbred yearling horses with idiopathic disease of the arytenoid cartilages, diagnosed at the yearling sales, were evaluated and compared to those of control horses of the same gender and age, from the same sale.

RESULTS

Mucosal injury was noted immediately after intubation in every horse. Evidence of injury to the vocal or corniculate processes of the arytenoid cartilages or vocal cords was still apparent in 10/21 (48%) horses 1 week after intubation, five of which developed persistent lesions that remained present and unchanged from 28 days following intubation until the end of the 10-week observation period. All persistent lesions were nodules or focal swellings of the vocal cords or arytenoid cartilages, and there was no evidence of mucosal ulceration, infection or discharge. Mucosal ulceration of the vocal processes was the most common abnormality detected in the yearlings, affecting 16/33 (48%) that were diagnosed with idiopathic arytenoid disease at the yearling sales. Five of the 33 (15%) horses were diagnosed with arytenoid chondritis at the time of sale and were excluded from the performance outcome analysis. Of the 28 horses diagnosed with arytenoid abnormalities excluding chondritis, 19 (68%) raced with no history of respiratory-related problems, two (7%) were subsequently diagnosed with laryngeal hemiplegia, and seven (25%) were lost to follow-up. The case animals were 2.7 times more likely to race than control horses, but there was no difference between cases and controls in the likelihood of starting more than three times.

CONCLUSIONS

This study showed that nasotracheal intubation in adult horses could result in immediate mucosal trauma, persistent swelling, and focal scarring of the arytenoid cartilages, but this did not mimic mucosal ulceration or chondritis of the arytenoid cartilages observed in yearling Thoroughbred horses. The population studied, however, may not accurately represent the population in which idiopathic disease occurs. In this study, arytenoid mucosal ulceration detected at sale did not commonly progress to arytenoid chondritis. However, a study of a larger population of horses with untreated, naturally occurring disease is required to confirm these findings.

CLINICAL RELEVANCE

It is unlikely that trauma from nasogastric intubation caused arytenoid mucosal ulceration, therefore this procedure should not necessarily be discouraged. This study did not find evidence that horses diagnosed with arytenoid mucosal ulceration at yearling sales had a reduced performance history, therefore it is reasonable to continue to pass horses with uncomplicated arytenoid mucosal ulceration during post-sale endoscopic examination. However, monitoring of the lesions and treatment, if required, may be indicated in the post-sale period.