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Basics ⬇

Outline

BASICS

Definition!!navigator!!

  • A septic inflammatory process of one or both arytenoid cartilages, resulting in the formation of luminal swelling, granulomas, and deformation with enlargement
  • This interferes with the ability of the affected arytenoid cartilage to fully abduct during forced inspiration and/or to resist collapsing airway pressure during inspiration. In addition “kissing lesions” on the medial surface of the opposing arytenoid cartilage may be seen

Signalment!!navigator!!

Racehorses are more commonly affected, although it can be observed in older horses of any breed or function.

Signs!!navigator!!

  • Upper respiratory noise, exercise intolerance, or both
  • The disease usually worsens gradually, with progressive involvement of one or both arytenoid cartilages
  • Can lead to ventilation interference proportional to the loss of abductory function and the mechanical size of the granulomas or affected arytenoid cartilages. The more intense the high-intensity exercise occurs, the earlier the effect of an obstruction is detected (the horse does not “finish” or close well)
  • In show horses, loss of points during competition because of upper respiratory noise may be the main concern; this upper airway noise may resemble that of horses with laryngeal hemiplegia

Causes!!navigator!!

  • Physical trauma to the mucosa of the arytenoid cartilage caused by air turbulence or aspiration of track surface particles during exercise or severe coughing or intubation (e.g. endotracheal, nasogastric) procedures
  • Upper airway infection leading to coughing and contact ulcers on the medial surface of the arytenoid cartilage dorsal to the vocal processes. If the inflammatory condition persists and infection develops, arytenoid cartilage sepsis occurs
  • In many cases, the inciting cause is never found

Diagnosis ⬆ ⬇

Outline

DIAGNOSIS

Differential Diagnosis!!navigator!!

  • Laryngeal hemiplegia
  • Congenital malformation of the laryngeal cartilages (i.e. fourth branchial arch defect)

CBC/Biochemistry/Urinalysis!!navigator!!

In active infection with abscessation, serum amyloid A and fibrinogen may be elevated.

Other Laboratory Tests!!navigator!!

  • Arterial blood gases during exercise
  • Hypoventilation can be evaluated using arterial blood gases—typically at maximal exercise PaCO2 can be >50 mmHg; PaO2 may be <65 mmHg in affected horses

Imaging!!navigator!!

  • Lateral radiography of the larynx may reveal enlarged laryngeal cartilages, sometimes with associated osseous metaplasia
  • Ultrasonographic examination of the larynx using the mid-ventral and caudoventral windows to evaluate for abscess and the caudolateral window to assess the presence of disease in the lateral aspect of the arytenoid cartilage. MRI and CT are rarely indicated but may also reveal the extent of arytenoid cartilage involvement

Other Diagnostic Procedures!!navigator!!

  • The diagnosis is established on the basis of videoendoscopic examination at rest:
    • The body of the arytenoid is irregular and thickened
    • A mass of granulation tissue may protrude from the medial surface of the arytenoid cartilage into the airway. The size or location of the protruding mass has no correlation with the amount of abduction remaining
    • The corniculate process may be deformed
    • Contact (i.e. “kissing”) lesions may be observed on the contralateral arytenoid cartilage
  • Eventually, the condition may lead to decreased or total inability of the affected arytenoid cartilage to abduct during inspiration

Treatment ⬆ ⬇

TREATMENT

  • Medical treatment is indicated only in acute cases with mucosal ulceration and swellings
  • Consider endoscopically guided excision of intralaryngeal granulations if the affected arytenoid cartilage retains sufficient abductory function for intended athletic activity
  • When arytenoid abduction is severely reduced, partial arytenoidectomy (excision of the body and corniculate process of affected arytenoid cartilage) is the treatment of choice to restore exercise capacity and to reduce upper airway noise
  • Permanent tracheotomy can be used in countries where athletic competition is allowed with this procedure and to salvage the animal for breeding purposes

Medications ⬆ ⬇

MEDICATIONS

Drug(s) of Choice

  • Acute case—broad-spectrum antibiotics and NSAIDs
  • Chronic case—none, other than routine perioperative antimicrobial and anti-inflammatory agents
  • Use of nasopharyngeal spray, consisting of various anti-inflammatory and antimicrobial agents (140 mL DMSO, 140 mL glycerin, 266 mL distilled water, and 14 mL dexamethasone 4 mg/mL and often an antibiotic such as nitrofurazone—makes 560 mL, enough for 2 weeks) can be applied (20 mL BID) using a soft rubber feeding tube
  • If the airway is significantly compromised, a temporary tracheotomy may be needed until the swelling resolves

Follow-up ⬆ ⬇

Outline

FOLLOW-UP

Patient Monitoring!!navigator!!

  • Videoendoscopy of the upper airway 2–6 weeks after surgery to monitor patient response
  • Final response to treatment or continuation of monitoring of affected horses is made on the basis of evaluating exercise tolerance and upper respiratory noise
  • Laser resection of the unsupported ipsilateral aryepiglottic fold might be needed to improve airway patency

Possible Complications!!navigator!!

  • Horses undergoing removal of the corniculate and body of the arytenoid cartilage have a slightly increased risk of tracheal aspiration of feed during deglutition. In addition, these procedures do not fully restore the airway diameter, so a mild degree of airway obstruction persists, which may interfere with performance or result in upper airway noise during exercise. Postsurgery dynamic endoscopy is indicated if results are not satisfactory to identify if a soft tissue resection of collapsing tissue is needed
  • Bilateral arytenoidectomy increases the risk for tracheal aspiration of feed during deglutition and for glottic stenosis because of webbing at the resection site

Expected Course and Prognosis!!navigator!!

  • Horses with acute swelling of the arytenoid cartilage may respond favorably to NSAIDs, topical anti-inflammatory agents, and antibiotics
  • Untreated horses exhibit a progressive increase in exercise intolerance and upper respiratory noise
  • Horses with focal elevated granulations on the medial surface of the arytenoid cartilage that maintain abductory function may respond to simple “lumpectomy”; recurrence of granuloma is seen in approximately 20–30% of horses
  • Horses with generalized involvement of an arytenoid cartilage and without surgical treatment often develop contralateral contact or “kissing” lesions
  • Horses with unilateral lesions treated surgically have a fair prognosis (60%) for elimination or significant reduction of exercise intolerance; however, the prognosis is guarded (20%) in horses with bilateral lesions

Miscellaneous ⬆ ⬇

Outline

MISCELLANEOUS

Abbreviations!!navigator!!

  • CT = computed tomography
  • DMSO = dimethylsulfoxide
  • MRI = magnetic resonance imaging
  • NSAID = nonsteroidal anti-inflammatory drug
  • PaCO2 = partial pressure of carbon dioxide in arterial blood
  • PaO2 = partial pressure of oxygen in arterial blood

Suggested Reading ⬆ ⬇

Hay WP, Tulleners E. Excision of intralaryngeal granulation tissue in 25 horses using a neodymium: YAG laser (1986 to 1991). Vet Surg 1993;22:129–134.

Haynes PF, Snider TG, McLure JR, McClure JJ. Chronic chondritis of the equine arytenoid cartilage. J Am Vet Med Assoc 1980;177:1135–1142.

Lumsden JM, Derksen FJ, Stick JA, et al. Evaluation of partial arytenoidectomy as a treatment for equine laryngeal hemiplegia. Equine Vet J 1994;26:92–93.

Parente EJ, Tulleners EP, Southwood LL. Long-term study of partial arytenoidectomy with primary mucosal closure in 76 Thoroughbred racehorses (1992-2006). Equine Vet J 2008;40:214–218.

Radcliffe CH, Woodie JB, Hackett RP, et al. A comparison of laryngoplasty and modified partial arytenoidectomy as treatments for laryngeal hemiplegia in exercising horses. Vet Surg 2006;35:643–652.

Tulleners EP, Harrison IW, Raker CW. Management of arytenoid chondropathy and failed laryngoplasty in horses: 75 cases (1979–1985). J Am Vet Med Assoc 1988;192:670–675.

Witte TH, Mohammed HO, Radcliffe CH, et al. Racing performance after combined prosthetic laryngoplasty and ipsilateral ventriculocordectomy or partial arytenoidectomy: 135 Thoroughbred racehorses competing at less than 2400 m (1997-2007). Equine Vet J 2009;41:70–75.

Author(s) ⬆

Author: Norm G. Ducharme

Consulting Editors: Daniel Jean and Mathilde Leclère