Endoscopy of the upper respiratory tract during treadmill exercise: a clinical study of 100 horses

SUMMARY: Endoscopy of the upper respiratory tract was performed in 100 horses during high speed treadmill exercise. Reasons for endoscopy were a history of an abnormal noise during exercise in 75 horses, poor performance in 17 horses and to evaluate the results of upper respiratory tract surgery in 8 horses. Of the 75 horses with a history of an abnormal noise during exercise the cause was determined in 67 (89%). Endoscopic abnormalities were detected at rest in 40 of these 75 horses (53%). In these 40 horses, a similar diagnosis as to the cause of the abnormal noise was made at rest and during exercise on the treadmill in 19 cases, while in the remaining 21 the endoscopic findings during exercise varied from that seen at rest. This included 3 horses in which a diagnosis was made at rest but no abnormalities were detected during exercise. Some of the findings during treadmill endoscopy included laryngeal dysfunction, grades 3, 4 and 5 (22 cases), dorsal displacement of the soft palate (20), epiglottic entrapment (8), epiglottic flutter (4), aryepiglottic fold flutter (4), pharyngeal collapse (3), arytenoiditis (3), vocal cord flutter (3), false nostril noise (2), pharyngeal lymphoid hyperplasia (2), soft palate haemorrhage (1) and positional arytenoid collapse (1). More than one abnormality was observed during exercise in 7 horses. A complete and correct diagnosis based on the resting endoscopy findings alone was made in 19 (25%) of these 75 cases. In the 17 horses examined because of poor performance, no abnormalities were detected during treadmill endoscopy that were not evident at rest. None of these 17 horses presented with a history of an abnormal respiratory noise, although one, diagnosed as having grade 4 laryngeal function at rest and exercise, did make a characteristic inspiratory noise during treadmill exercise. Eight horses were evaluated after surgery for correction of laryngeal hemiplegia, as the post-operative performance or the amount of respiratory noise present was considered unsatisfactory. Of these, 3 were found to have a satisfactory airway during exercise and other reasons for poor performance were detected; 3 had insufficient abduction; and 2 had intermittent dorsal displacement of the soft palate. Endoscopy of the upper respiratory tract was found to be a useful technique for evaluating the cause of abnormal respiratory noise in most cases. We concluded that treadmill endoscopy in horses presented for poor performance, without a history of an abnormal respiratory noise, was of little value. The technique, in conjunction with arterial blood gas measurements, was useful in determining the efficacy of surgical treatment of laryngeal hemiplegia.     

Use of transendoscopic contact neodymium:yttrium aluminum garnet laser to drain dorsal epiglottic abscesses in two horses

A submucosal abscess, located on the dorsal surface of the epiglottis, was diagnosed in 2 Thoroughbred racehorses by use of endoscopy. Both horses had exercise intolerance. One horse had intermittent dorsal displacement of the soft palate, coughed while eating and galloping, and made an abnormal respiratory noise. Both abscesses were drained transendoscopically by use of a contact neodymium:yttrium aluminum garnet laser. Eleven days after surgery, the surgical sites appeared to have healed. Clinical signs resolved permanently, and both horses returned to successful racing careers.     

Poor performance due to epiglottic retroversion in a Standardbred trotter

A 3-year-old Standardbred trotting gelding presented to the Atlantic Veterinary College for diagnostic work-up of poor performance and abnormal respiratory noise during exercise. Physical examination was unremarkable, and no significant findings were identified on standing endoscopic examination of the upper respiratory tract. Treadmill endoscopy was utilised for dynamic evaluation of the upper respiratory tract; a diagnosis of epiglottic retroversion was confirmed. The owner requested euthanasia of the gelding, and a post-mortem evaluation was completed. Despite thorough gross and histological examination of the head and neck on post-mortem examination, no evidence was identified to support the postulated aetiologies for epiglottic retroversion currently found in the literature. This case represents the first reported findings from a post-mortem examination of a horse with epiglottic retroversion.     

Exercising upper respiratory videoendoscopic evaluation of 100 nonracing performance horses with abnormal respiratory noise and/or poor performance

Reasons for performing study: Although well documented in racehorses, there is paucity in the literature regarding the prevalence of dynamic upper airway abnormalities in nonracing performance horses. Objective: To describe upper airway function of nonracing performance horses with abnormal respiratory noise and/or poor performance via exercising upper airway videoendoscopy. Methods: Medical records of nonracing performance horses admitted for exercising evaluation with a chief complaint of abnormal respiratory noise and/or poor performance were reviewed. All horses had video recordings of resting and exercising upper airway endoscopy. Relationships between horse demographics, resting endoscopic findings, treadmill intensity and implementation of head and neck flexion during exercise with exercising endoscopic findings were examined. Results: Dynamic upper airway obstructions were observed in 72% of examinations. Head and neck flexion was necessary to obtain a diagnosis in 21 horses. Pharyngeal wall collapse was the most prevalent upper airway abnormality, observed in 31% of the examinations. Complex abnormalities were noted in 27% of the examinations. Resting laryngeal dysfunction was significantly associated with dynamic arytenoid collapse and the odds of detecting intermittent dorsal displacement of the soft palate (DDSP) during exercise in horses with resting DDSP was only 7.7%. Exercising endoscopic observations were different from the resting observations in 54% of examinations. Conclusions: Dynamic upper airway obstructions were common in nonracing performance horses with respiratory noise and/or poor performance. Resting endoscopy was only helpful in determining exercising abnormalities with recurrent laryngeal neuropathy. Potential relevance: This study emphasises the importance of exercising endoscopic evaluation in nonracing performance horses with abnormal respiratory noise and/or poor performance for accurate assessment of dynamic upper airway function.     

Retroversion of the Epiglottis as a Complication of Endotracheal Intubation in the Horse A Pilot Study

As part of a study of possible causes of postoperative pulmonary complications of general anesthesia in the horse, lateral cervical radiographs were taken after endotracheal intubation in nine randomly selected horses. The epiglottis was found to be retroverted in three. Subsequently, the effects of epiglottic retroversion during anesthesia on postoperative laryngeal function were investigated experimentally in three horses by fluoroscopy. No untoward sequelae were observed. Prophylaxis and potential adverse effects of this previously unreported complication of endotracheal intubation in the horse are discussed.     

Laryngoplasty with ventriculectomy or ventriculocordectomy in 104 draft horses (1992-2000)

OBJECTIVE: To evaluate efficacy and safety of laryngoplasty with vetriculectomy (VE) or ventriculocordectomy (VCE) for treatment of laryngeal hemiplegia (LH) in draft horses. STUDY DESIGN: Retrospective study. SAMPLE POPULATION: One hundred four draft horses used for competitive hitch competitions. METHODS: Medical records and postoperative endoscopy for competitive hitch draft horses diagnosed with left LH and treated with laryngoplasty and VE or VCE between January 1992 and December 2000 were reviewed. Follow-up information was obtained from telephone interviews with owners and trainers, and performance scores of 1 to 3 were assigned in which 1 was defined as a horse that was unable to perform (abnormal respiratory noise with or without exercise intolerance), 2 was able to perform but not for its intended use (exercise tolerant but abnormal respiratory noise), and 3 was performing as expected for its intended use (exercise tolerant, no abnormal respiratory noise). RESULTS: One hundred four horses that had 111 laryngoplasty procedures were included. All horses had preoperative performance scores of 1. Follow-up information was available for 79 horses. Improvement in postoperative performance (exercise tolerant, with or without abnormal respiratory noise) was reported in 92% of horses. Respiratory noise was eliminated in 72% (57 horses) of horses. Postoperative performance scores were the following: 3 in 57 (72%) horses, 2 in 16 (20%) horses, and 1 in 6 (8%) horses. There was no significant difference in postoperative performance based on preoperative grade of LH. There was a trend for horses with >/=70% of possible maximal abduction postoperatively to have a performance score of 3. Postanesthetic complications included prolonged recovery (4 horses, 4%) and myopathy or neuropathy (7 horses, 7%). One of these horses was killed because it did stand; triceps myopathy and encephalopathy were confirmed on necropsy. CONCLUSIONS: Laryngoplasty with VE or VCE is an effective and safe procedure for the treatment of LH in the draft horse. Repeat laryngoplasty can be performed successfully, with good performance outcome after laryngoplasty failure. Complications associated with general anesthesia and laryngoplasty in draft horses are higher than reported for light breed horses under similar conditions. CLINICAL RELEVANCE: For LH, laryngoplasty with VCE or VE under general anesthesia is recommended to eliminate abnormal respiratory noise and improve performance in most competitive hitch draft horses.     

Endoscope-guided, transoral axial division of an entrapping epiglottic fold in fifteen standing horses

Objectives— To describe and evaluate the use of a transoral, endoscope-guided technique for transection of an entrapping epiglottic fold in sedated standing horses.
Study Design— Retrospective study.
Animals— Horses (n=16) with epiglottic fold entrapment (EFE).
Methods— Medical records (2005–2006) of 16 horses with EFE were reviewed to determine history, physical and endoscopic examination findings, postoperative complications, and outcome after axial division of EFE using a hooked bistoury, under an endoscopic-guided, transoral approach.
Results— EFE was confirmed by endoscopy. Axial division was successfully performed in 15 sedated, standing horses. One horse had to be anesthetized to complete the procedure. None of the horses made abnormal respiratory noise after surgery and all returned to their intended use. After surgery, 1 horse had a short, deformed epiglottis.
Conclusions— EFE can be axially divided safely and effectively using an endoscope-guided, transoral approach, with the horse sedated and standing.
Clinical Relevance— Endoscopic-guided, transoral axial division of EFE in sedated standing horses is an alternative choice to performing this procedure under general anesthesia.     

Transendoscopic, laser-assisted ventriculocordectomy for treatment of left laryngeal hemiplegia in horses: 22 cases (1999-2005)

OBJECTIVE: To determine long-term effects of transendoscopic, laser-assisted ventriculocordectomy (LAVC) on airway noise and performance in horses with naturally occurring left laryngeal hemiplegia. DESIGN: Retrospective case series. ANIMALS: 22 horses with left laryngeal hemiplegia treated by means of LAVC. PROCEDURES: Medical records were reviewed and initial complaint, intended use of the horse, duration of abnormal airway noise, preoperative performance level, endoscopic findings, surgical procedure, postoperative treatment, and complications were recorded. Follow-up telephone interviews with owners and trainers were conducted to determine time for return to intended use, level of postoperative performance, and percentage reduction in airway noise. RESULTS: All horses were examined because of excessive airway noise; 10 (45%) had concurrent exercise intolerance. Left ventriculocordectomy was performed in all 22 horses; bilateral ventriculocordectomy (right ventriculocordectomy was done 1 year later) was performed in 1 horse (5%). Complications occurred in 3 (14%) horses. Twenty (91%) horses returned to their intended use. Excessive airway noise was eliminated after surgery in 18 (82%) horses; exercise intolerance improved postoperatively in 8 of 10 horses. Three racing Thoroughbreds returned to racing; 1 additional racehorse returned to racing but required a laryngoplasty 1 year later to continue racing. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that LAVC was an effective procedure for elimination of excessive airway noise and improvement of performance in horses with left laryngeal hemiplegia.     

Persistent dorsal displacement of the soft palate attributable to a frenulum of the epiglottis in a racing Thoroughbred

CASE DESCRIPTION: A 7-year-old sexually intact male Thoroughbred racehorse was evaluated because of exercise intolerance, respiratory tract noise, and coughing when eating. CLINICAL FINDINGS: A persistent dorsal displacement of the soft palate was identified during endoscopic examination of the upper portions of the respiratory tract. Radiography of the pharyngeal and laryngeal regions revealed a hypoplastic epiglottis that was ventral to, and not in contact with, the soft palate. The horse was anesthetized, and an oral endoscopic examination revealed a subepiglottic frenulum that had resulted in the dorsal displacement of the soft palate. TREATMENT AND OUTCOME: The frenulum was transected transendoscopically by use of a diode laser. Twenty-four hours following surgery, repeat endoscopic and radiographic examinations revealed that the epiglottis had returned to its correct anatomic position in relation to the soft palate. Four weeks after surgery, endoscopy of the upper portions of the airway revealed recurrence of the dorsal displacement of the soft palate. CLINICAL RELEVANCE: A subepiglottic frenulum should be considered as a cause of persistent dorsal displacement of the soft palate in horses. An endoscopic examination of the oropharyngeal region should be performed in horses prior to undertaking any surgical interventions to treat persistent dorsal displacement of the soft palate.     

Subepiglottic cysts in 15 horses

Subepiglottic cysts (SECs) are an infrequent cause of upper respiratory tract noise and exercise intolerance in horses. They may also be associated with no clinical signs and be an incidental finding during routine upper airway endoscopy. The aim of this study was to assess the effect on performance of horses undergoing surgical removal of SECs. The case records of 15 horses (1995–2009) diagnosed with SECs were retrieved. Eleven (73%) of the 15 horses included in the study were Thoroughbred racehorses. Eleven (73%) of the 15 horses had no preoperative clinical signs related to the SECs, with the remaining 4 (27%) having a respiratory noise (n = 4), nasal discharge (n = 1), difficulty swallowing (n = 1) or a cough (n = 1). Endoscopic examination in the standing horse was diagnostic in 93% (n = 14) of horses. Nine (82%) of the 11 Thoroughbred horses were yearlings, of which only one horse (11%) presented with clinical signs consisting of a respiratory noise and nasal discharge. Four of the 11 (36%) Thoroughbred horses were found to have concurrent epiglottic entrapment. Surgical removal was successful in all cases. Eight of the 11 (73%) Thoroughbred horses in this study raced following SEC removal. The majority of SECs are identified during routine endoscopic examinations and are not associated with clinical signs. The prognosis following surgical removal of SECs is good and future performance does not appear to be affected.     

Epiglottic augmentation by use of polytetrafluoroethylene to correct dorsal displacement of the soft palate in a standardbred horse.

A 2-year-old 400-kg Standardbred colt with a history of exercise intolerance was determined to have dorsal displacement of the soft palate (DDSP). Standing endoscopy revealed a soft, flaccid, and hypoplastic epiglottis and arytenoid cartilages that moved symmetrically and abducted fully. Lateral laryngeal radiography was used to calculate a corrected thyroepiglottic length of 6.48 cm. Videoendoscopy during exercise on a high-speed treadmill at standardized treadmill speeds was performed weekly for 3 consecutive weeks. The soft palate dorsally displaced at each examination. A sternohyoideus/sternothyroideus myectomy was followed by 2 weeks of stall rest and 2 weeks of treadmill training. Because endoscopy during exercise at standardized treadmill speeds caused the horse to dorsally displace the soft palate once a week for 3 weeks after the myectomy, this surgery was deemed ineffective in this horse. Epiglottic augmentation was performed by injecting 7 ml of polytetrafluoroethylene into the ventral submucosal space of the epiglottis. After 21 days of stall rest and 5 weeks of pasture rest, the horse was placed on a 2-month treadmill conditioning program. Using endoscopy at standardized treadmill speeds, exercise efforts to encourage DDSP were unsuccessful, which suggested that epiglottic augmentation by use of polytetrafluoroethylene was an effective surgical treatment to correct dorsal displacement of the soft palate in this horse. It is believed that polytetrafluoroethylene increases the rigidity of the epiglottis, allowing it to maintain the ventral position of the soft palate.     

Nasal Septum Resection in the Horse

The nasal septum was surgically removed from 22 horses with upper airway obstruction caused by thickening and/or deviation of the septum. The most common presenting complaints were a low-pitched, snoring, respiratory noise and respiratory difficulty during exercise, which usually occurs in young horses. Abnormalities of the septum were most commonly congenital defects or caused by trauma or inflammation secondary to severe respiratory infection.
Diagnosis was made based on history, clinical signs, and results of physical examination. Radiography and endoscopy were useful adjuncts in some horses.
Under general anesthesia, the septum was removed by scalpel and osteotome (19 horses) or by obstetrical wire and osteotome (1 horse). In two horses, the rostral one third of the septum was removed by scalpel alone.
In three horses, the alar folds and floor of the nasal diverticula were removed in an attempt to relieve airway obstruction caused by flattening of the bridge of the nose following removal of the nasal septum.
Follow-up was obtained on 18 horses: persistent noise during exercise continued in 90%; however, 50% returned to usefulness.     

Interpretation of laryngeal function tests in the horse

Idiopathic left-sided laryngeal paralysis was present in 14 of 169 horses on a thoroughbred horse farm (8.3 per cent). In nine animals, it was evident only after exercise and arytenoid abduction and adduction were normal at rest. Asynchronous movement of the arytenoid cartilages was observed in 94 horses at rest (55.6 per cent), 86 of which were considered to be normal after exercise. Conversely, synchronous movement of the arytenoids was noted when at rest in six of the 14 animals diagnosed as having laryngeal hemiplegia after exercise. An abnormal inspiratory noise during exercise was detectable in 11 of these 14 horses, but not in the remainder. An abnormal noise on inspiration was also produced by nine horses in which laryngeal hemiplegia was not diagnosed.     

Laryngeal dyskinesia in a horse

A 3-year-old Warmblood gelding was evaluated for intermittent respiratory distress and an inspiratory noise. These signs were mainly observed at exercise but sometimes occurred at rest as well. At the age of 2 months, a severe episode of respiratory distress had necessitated a temporary tracheotomy, which had then healed uneventfully. Examination of the patient and resting endoscopy revealed no structural laryngeal alterations. Exercise endoscopy revealed episodes of active bilateral laryngeal adduction during inspiration. Spirometrically, a corresponding impairment of inspiratory airflow was identified. These abnormalities were most pronounced at the trot but they occurred at magnitudes of inspiratory airflow lower than those inducing dynamic arytenoid collapse in horses with recurrent laryngeal neuropathy. Therefore, the diagnosis of a laryngeal dyskinesia characterised by an active bilateral arytenoid adduction during inspiration was made. No specific treatment was implemented. Three years later, the owner reported that the condition was markedly improved and the horse was used for pleasure riding.     

Correlation of resting and exercising endoscopic findings for horses with dynamic laryngeal collapse and palatal dysfunction

Reasons for performing study: To correlate resting and exercising endoscopic grades of laryngeal function in horses undergoing high‐speed treadmill endoscopy (HSTE) using the Havemeyer grading system. To correlate dorsal displacement of the soft palate (DDSP) seen at rest with palatal function during exercise. Methods: Records of horses that underwent HSTE examination (1999–2009) were reviewed. Resting laryngeal function score and other abnormalities noted on resting endoscopy were recorded as were results of HSTE. Results of resting and exercising endoscopic findings were correlated. Results: 281 horses underwent HSTE. There was significant correlation between grade of laryngeal function at rest (grades 1–4) and exercise (ρ= 0.53, P<0.001) and between resting subgrades 3.1, 3.2 and 3.3 and exercising grades of laryngeal function (ρ= 0.43, P = 0.0017). DDSP was observed at rest significantly more often in horses that developed DDSP during HSTE than those without DDSP during HSTE (RR = 4.1, P<0.001). The sensitivity and specificity of DDSP seen during resting endoscopy as a test for DDSP occurring during exercise were 25.5 and 95.1% respectively (positive predictive value 0.57, negative predictive value 0.83). Conclusions and potential relevance: The results of the current study support the use of the Havemeyer system for grading laryngeal function in the resting horse, and corroborate findings of previous studies correlating resting and exercising palatal abnormalities. Studies that use the presence of spontaneous DDSP during resting endoscopic examination as an inclusion criterion for investigating efficacy of treatments for DDSP are likely to have a low proportion of horses with false positive diagnoses.     

Use of successive dynamic videoendoscopic evaluations to identify progression of recurrent laryngeal neuropathy in three horses

CASE DESCRIPTION: 3 racehorses were evaluated because of poor performance or abnormal noise originating from the upper portion of the respiratory tract. CLINICAL FINDINGS: During maximal exercise, initial dynamic videoendoscopy of the upper respiratory tract revealed complete arytenoid cartilage abduction in 2 horses and incomplete but adequate abduction of the left arytenoid cartilage in 1 horse. Subsequent exercising endoscopic evaluation revealed severe dynamic collapse of the left arytenoid cartilage and vocal fold in all 3 horses. TREATMENT AND OUTCOME: 2 horses were treated with prosthetic left laryngoplasty and raced successfully. One horse was retired from racing. CLINICAL RELEVANCE: Idiopathic laryngeal hemiplegia can be a progressive disease. Successive dynamic videoendoscopic upper airway evaluations were used to confirm progression of left laryngeal hemiplegia in these 3 horses. Videoendoscopy of the upper respiratory tract during exercise should be considered as part of the clinical evaluation of horses with signs of upper respiratory tract dysfunction.     

Epidemiologic analysis of factors influencing exertional rhabdomyolysis in Thoroughbreds

OBJECTIVE: To determine incidence, effect on performance, and management practices associated with exertional rhabdomyolysis (ER) in Thoroughbreds. SAMPLE POPULATION: Medical records for 984 Thoroughbreds and a survey of trainers of horses with and without ER. PROCEDURES: Medical records for 984 Thoroughbreds stabled at a midwestern racetrack were examined to determine the incidence of ER during the 1995 racing season. A retrospective questionnaire was administered to trainers to determine management practices associated with ER in 59 Thoroughbreds with ER and 47 control Thoroughbreds in training. Multiple logistic regression was used to determine management factors associated with ER. RESULTS: ER affected 48 of 984 (4.9%) Thoroughbreds. Two-year-old females were most frequently affected, and 36 of 96 (37.5%) trainers had > or = 1 horse with ER. Horses with ER were more likely not to race during the racing season, compared with control horses. For horses that raced, differences were not found with respect to racing performance between ER and control horses. Exertional rhabdomyolysis developed frequently in susceptible horses that had > or = 1 day of rest prior to exercise and that galloped during exercise. Horses with ER were commonly fed > 4.5 kg of grain daily. Nervous and extremely nervous horses were 5.4 times more likely, and horses with some form of lameness were 4.2 times more likely, to have ER. CONCLUSIONS AND CLINICAL RELEVANCE: Exertional rhabdomyolysis is common in Thoroughbreds, and ER can be affected by temperament, sex, age, diet, exercise routines, and lameness. Management that minimizes excitability, particularly when tailored to each horse, may be most effective for controlling ER.     

Dorsal Displacement of the Soft Palate Secondary to Persistent Frenulum of the Epiglottis in Neonatal Foal

Dorsal displacement of the soft palate (DDSP) usually occurs in athletic adult horses. Congenital DDSP in foals secondary to the persistent frenulum of the epiglottis is rarely observed. The aim of this report was to describe a case of a seven-day-old female neonate Quarter Horse presenting dysphagia, milk reflux through the nostrils and mouth, and expiratory dyspnea since 4 days. Thoracic auscultation was indicative of aspiration pneumonia. Diagnosis of DDSP associated with local inflammation was made after endoscopic examination of upper respiratory tract. Radiographic examination was performed to rule out hypoplasia of the epiglottis. No clinical improvement was observed after anti-inflammatory treatment with flunixin meglumine. Oral endoscopy under general anesthesia revealed that the displacement of the soft palate was caused by a persistent frenulum of the epiglottis. Using a 30° rigid endoscope and a curved laparoscopic scissors, the frenulum was transected. After surgery, no dysphagia or dyspnea at rest was observed. However, discreet respiratory noise persisted during exercise for 5 days postoperatively. After discharge, the owner reported that the animal was completely normal during exercise. The animal is currently 3 years old and is developing a normal athletic performance. Persistent frenulum of the epiglottis should be considered while examining neonates with nasal milk reflux associated with expiratory dyspnea. This case report emphasizes the importance of the differential diagnosis for DDSP and for DDSP secondary to the persistent frenulum of the epiglottis in neonatal foals. It also underlines the importance of oral endoscopic examination for diagnosis.     

Transendoscopic contact neodymium:yttrium aluminum garnet laser correction of epiglottic entrapment in standing horses

Fifty-seven Standardbred and 44 Thoroughbred racehorses and 1 Thoroughbred polo mare with primary clinical signs of exercise intolerance or respiratory tract noise or combined exercise intolerance and respiratory tract noise were referred for laser correction of epiglottic entrapment. Significantly (P less than 0.001) more Standardbred than Thoroughbred racehorses were affected, compared with the observed hospital population during the same period. At referral, 14 horses did not have evident epiglottic entrapment and were returned to exercise without development of entrapment after treatment, which consisted of 1 week of rest and administration of anti-inflammatory medication. In 88 standing horses under sedation and topical anesthesia, epiglottic entrapment was corrected transendoscopically by use of a contact neodymium:yttrium aluminum garnet laser. In these 88 horses, 98% of entrapments were persistent, 92% were thick, 97% were wide, and 45% were ulcerated. Thirty-one percent of the horses had endoscopic evidence of epiglottic hypoplasia, and 8% had deviated epiglottic axis. Complete correction was achieved in 97% of the horses, Persistent dorsal displacement of the soft palate in 1 horse and severe epiglottic hypoplasia with thick, chronic entrapping membranes in 2 horses precluded successful transendoscopic correction with the horses in standing position. Most horses were treated on an outpatient basis, and all were able to be returned to exercise after 7 to 14 days of rest and treatment with anti-inflammatory medication. Entrapment recurred in 4 horses (5%), 3 of which had hypoplastic epiglottis. Dorsal displacement of the soft palate developed after surgery in 9 horses (10%) and continued in 4 horses (5%) that had displaced soft palate before surgery. All these horses had epiglottic hypoplasia. Laser correction of epiglottic entrapment in standing horses was safe, well tolerated, and effective. Laser surgery was an alternative to conventional surgery, and eliminated the need for general anesthesia and laryngotomy. It also reduced convalescence and postoperative complications.     

Xylazine-induced attenuation of dorsal displacement of the soft palate associated with epiglottic dysfunction in a horse

An 18-month-old Quarter Horse filly was evaluated because of dorsal displacement of the soft palate associated with epiglottic dysfunction that caused exercise intolerance and an abnormal respiratory noise. The abnormality of the epiglottis was corrected by use of a sedative dose of xylazine hydrochloride. There was no familial predisposition to hyperkalemic periodic paralysis, which may cause similar laryngopharyngeal signs, and the horse did not respond to administration of acetazolamide. There was no known history of trauma that could have caused neuritis, which has also been suggested as a cause of laryngeal dysfunction. It was unusual that a complete response was obtained with xylazine hydrochloride, an alpha2-adrenergic agonist, although this drug has various effects on the respiratory tract in horses. It was also unusual that the response outlasted the sedative effect of the drug.