Excision of Intralaryngeal Granulation Tissue in 25 Horses Using a Neodymium:YAG Laser (1986 to 1991)

Granulation tissue masses arising from the axial surface of the arytenoid cartilage in 25 horses were excised using a contact neodymium:yttrium aluminum garnet laser. A technique that eliminated the need for general anesthesia or laryngotomy was developed for transen-doscopic removal of the masses in standing horses. Nineteen racehorses made abnormal upper respiratory tract noises or their performance was decreased, whereas six horses not used for racing had a history of stertor (five horses) or epistaxis after nasogastric intubation (one horse). Thoroughbreds were significantly (p = .0126) overrepresented compared with the hospital population. The granulation tissue masses were successfully excised and the defect healed in all 25 horses, although a second excision of granulation tissue regrowth was necessary in four horses. In 21 horses, the underlying chondrosis did not progress appreciably. In four horses with preexisting moderate arytenoid cartilage thickening and concurrent laryn-geal abnormalities, the surgery site healed but the underlying chondrosis progressed substantially. Twelve of 19 (63%) racehorses returned to race at least three times after the surgery. Of the 19 racehorses, five had only slight arytenoid cartilage involvement whereas 14 had moderate cartilage thickening or concurrent laryngeal pathology. All five horses with slight apparent arytenoid cartilage involvement and no concurrent laryngeal pathology returned to racing. Seven of the 14 horses (50%) with moderate underlying cartilage thickening or concurrent laryngeal pathology returned to racing. The six horses not used for racing returned to their previous activity without further respiratory problems.     

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.     

Surgical and Conservative Management of Bilateral Dynamic Laryngeal Collapse Associated with Poll Flexion in Harness Race Horses

Objective— To test the hypothesis that in bilateral dynamic laryngeal collapse associated with poll flexion, vocal fold collapse (VFC) is the initial abnormal event that induces further laryngeal collapse, and that racing performance would therefore be substantially improved after bilateral ventriculocordectomy in affected individuals.
Study Design— Retrospective study.
Animals— Twenty-six horses.
Methods— Medical records (1998–2006) of harness racehorses admitted for high-speed treadmill videoendoscopy (HSTV) that had bilateral dynamic laryngeal collapse associated with poll flexion were reviewed. Race records, owner interviews, and follow-up HSTV were used to evaluate outcome after either surgical treatment including bilateral ventriculocordectomy or conservative management.
Results— Bilateral dynamic laryngeal collapse, defined as bilateral VFC with concurrent arytenoid cartilage collapse (ACC), was identified in 26 horses. Norwegian Coldblooded Trotters (NCT) were overrepresented. Sixteen horses had surgical treatment and 10 were treated conservatively. Return to racing and racing performance was not improved within or between groups after the treatment. On follow-up HSTV of 6 surgically treated horses, there was no residual soft tissue collapse in the ventral portion of the rima glottidis; however, ACC and other abnormalities were still evident.
Conclusion— Bilateral ventriculocordectomy resolved VFC, but failed to stabilize the arytenoid cartilages or to significantly improve racing performance.
Clinical Relevance— Bilateral dynamic laryngeal collapse associated with poll flexion is a serious performance-limiting upper respiratory tract disorder that is overrepresented in NCT racehorses. Our results suggest that VFC is not the initiating event in this complex obstructive airway disorder for which there is currently no consistently effective treatment.     

Postoperative Race Performance is Not Correlated with Degree of Surgical Abduction After Laryngoplasty in National Hunt Thoroughbred Racehorses

Objectives— To (1) assess the degree of arytenoid cartilage abduction lost after laryngoplasty (LP) in Thoroughbred National Hunt racehorses and (2) to correlate postoperative racing performance with degree of arytenoid abduction after LP. Study Design— Case series. Animals— National Hunt Thoroughbred racehorses (n=68). Methods— Grade of postoperative arytenoid abduction for National Hunt racehorses that had LP with ventriculocordectomy was assessed at 1 day, 6 days, and 6 weeks after LP. Race records were analyzed to ascertain if there was correlation between the degree of arytenoid cartilage abduction and various measures of race performance (return to racing postoperatively, total earnings in 5 races immediately postoperatively, and lifetime number of starts postoperatively). Results— Median postoperative arytenoid abduction was grade 2 on day 1 but had decreased to grade 3 by 6 weeks. Horses with grades 1, 2, and 3 abduction 1 day after surgery had median losses of 1, 1, and 0.5 abduction grades, respectively, at 6 weeks. Horses with grade 1 abduction on day 1 were significantly more likely to lose abduction by day 6 after surgery than horses with grade 3 abduction on day 1. There was no statistically significant correlation between the postoperative grade of arytenoid abduction at any time point and earnings in 5 races after surgery, likelihood of racing postoperatively, or total number of lifetime race starts postoperatively. Conclusions— Horses with maximal (grade 1) surgical arytenoid abduction are significantly more likely to suffer postoperative loss of abduction than those with grade 3 abduction. Postoperative grade of abduction does not appear significantly correlated with markers of racing performance in National Hunt racehorses; however, very few horses with poor (grade 4 or 5) abduction were included and thus conclusions regarding racing performance in such horses cannot be drawn from this study. Clinical Relevance— Seemingly, most horses with grade 3 laryngeal abduction can race successfully and perhaps surgeons should not be disillusioned by the appearance of only moderate (grade 3) abduction in the long term after LP in racehorses.     

Endoscopic assessment of airway function as a predictor of racing performance in Thoroughbred yearlings: 427 cases (1997-2000)

OBJECTIVE: To compare endoscopic findings of the upper portion of the respiratory tract in Thoroughbred yearlings with their subsequent race records to determine whether subjective assessment of airway function may be used as a predictor of future racing performance. DESIGN: Retrospective study. ANIMALS: 427 Thoroughbred yearlings. PROCEDURES: Endoscopic examination findings were obtained from the medical records and the videoendoscopic repository of the Keeneland 1996 September yearling sales. Racing records were requested for the yearlings through the end of their 4-year-old racing season (1997-2000). Twenty-nine measures of racing performance were correlated with endoscopic findings. Subjective arytenoid cartilage movement grades were determined, using a 4-point grading scale (grade 1 = symmetrical synchronous abduction of the arytenoid cartilages; grade 4 = no substantial movement of the left arytenoid cartilage). RESULTS: Of the 427 Thoroughbred yearlings included in this study, 364 established race records, and 63 did not. Opinions regarding suitability for purchase, meeting conditions of the sale, and the presence of epiglottic abnormalities had no significant association with racing performance. Arytenoid cartilage movement grades were significantly associated with many of the dependent variables. However, palatine abnormalities were not predictive of inferior racing performance. CONCLUSIONS AND CLINICAL RELEVANCE: Thoroughbred yearlings with grade-1 and -2 arytenoid cartilage movements had significantly better racing performance as adults, compared with yearlings with grade-3 arytenoid cartilage movements. In contrast, epiglottic and palatine abnormalities were not predictive of inferior racing performance. Therefore, evaluation of laryngeal function, but not epiglottic or palatine abnormalities, using the 4-point grading system, should be the major factor in developing recommendations for prospective buyers.     

Long-term study of partial arytenoidectomy with primary mucosal closure in 76 Thoroughbred racehorses (1992-2006)

REASON FOR PERFORMING STUDY: The effectiveness and best method to perform a partial arytenoidectomy in racehorses is unclear. This study was performed to evaluate the success of and complications that can occur after a unilateral partial arytenoidectomy with primary mucosal closure in Thoroughbred racehorses. HYPOTHESIS: Partial arytenoidectomy is an effective surgical procedure to return Thoroughbred racehorses, afflicted by arytenoid chondropathy or a failed laryngoplasty, to preoperative levels of performance. METHODS: Seventy-six Thoroughbred racehorses admitted to the New Bolton Centre between 1992 and 2006 were assessed. Information was obtained from the medical records about the horse, laryngeal abnormalities, surgery and other findings during hospitalisation. Racing information was evaluated relative to those independent variables by an analysis of variance with a level of significance of P<0.05. RESULTS: Arytenoid chondropathy was the presenting complaint in 54 horses and failed laryngoplasty in 22 horses. Thirteen horses (17%) underwent a second surgery for laser excision of intralaryngeal granulation tissue at the arytenoidectomy site. Seventy-three horses were discharged from the hospital and racing outcome was evaluated. Sixty horses (82%) raced after surgery and 46 horses (63%) raced 5 or more times after surgery. The median time from surgery to the first start was 6 months. The average earnings/start was not significantly different before and after surgery. There was no association between earnings after surgery and age, gender, location of lesion, type of lesion, duration of tracheal intubation or undergoing a second surgery. CONCLUSIONS AND POTENTIAL RELEVANCE: A Thoroughbred racehorse is likely to race after a unilateral partial arytenoidectomy with primary mucosal closure and return to a preoperative level of performance.     

Performance after partial arytenoidectomy without mucosal closure in 27 Thoroughbred racehorses

OBJECTIVE: To examine the effect of partial arytenoidectomy without mucosal closure on postoperative racing performance and long-term complications in Thoroughbred racehorses treated for laryngeal hemiplegia, arytenoid chondropathy, or failed laryngoplasty. STUDY DESIGN: Retrospective study. ANIMALS: Twenty-seven Thoroughbred racehorses. METHODS: Medical records of Thoroughbred racehorses that had partial arytenoidectomy without mucosal closure between 1992 and 2002 were reviewed. Horses were divided into groups: horses that had not raced (Group 1) and those that had raced (Group 2) before surgery. Lifetime race records were compared between groups. A standard starts index (SSI) and performance index (PI) were used for Groups 1 and 2, respectively, to objectively evaluate each horse's postoperative performance. Telephone interviews of owners and trainers were used for subjective performance evaluation and to determine prevalence of long-term complications. RESULTS: Eleven (61%) Group 1 and 7 (78%) Group 2 horses raced and earned money after surgery. All Group 1 horses that raced performed at a level lower than the national average. Only 1 Group 2 horse had an improved PI score postoperatively. CONCLUSIONS: Thoroughbred racehorses have a fair prognosis for racing successfully after partial arytenoidectomy without mucosal closure. CLINICAL RELEVANCE: This technique may be a practical alternative to primary mucosal closure, would decrease surgical time, and avoid some problems reported with primary mucosal closure.     

Racing Performance in 72 Racehorses Treated with Prosthetic Laryngoplasty for Laryngeal Hemiplegia

The purpose of this study was to compare racing performance before and after prosthetic laryngoplasty for treatment of laryngeal hemiplegia in inexperienced (horses without at least one start before surgery) and experienced (horses with at least one start before surgery) Thoroughbred and Quarter Horse racehorses. Medical records of 54 Thoroughbred and 18 Quarter Horse racehorses or horses intended for racing treated with prosthetic laryngoplasty and unilateral ventriculectomy for laryngeal hemiplegia were reviewed. Signalment, age at the time of surgery, resting endoscopic grade of laryngeal function, surgical procedure, and type of suture were recorded. Median performance index (PI), earnings, distance, and Beyer speed figure (BSF) per start for three races before and after surgery were compared, and factors associated with improved postsurgical performance were evaluated. Seventy-three percent of horses that had not raced before surgery and 84% of horses that competed in at least one race before surgery were able to return to racing after surgery. Fifty-nine percent and 27% of Thoroughbreds and Quarter Horses, respectively, were able to improve their PI after surgery. Sixty-two percent and 20% of Thoroughbreds and Quarter Horses, respectively, significantly increased their distance after surgery. Additionally, 61% and 66% of racehorses were able to increase their earnings and BSF after surgery, respectively. Horses treated with laryngoplasty and unilateral ventriculectomy have a good prognosis for return to racing. Inexperienced racehorses have a better prognosis for improvement after surgery than do experienced racehorses. Thoroughbred racehorses have a better success rate than Quarter Horse racehorses.     

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.     

Placement of a long term tracheal cannula in a Thoroughbred racehorse with bilateral laryngeal dysfunction

A Thoroughbred horse with bilateral laryngeal dysfunction was treated by placement of a long term tracheal cannula in order to restore full athletic function. The horse initially presented with right-sided arytenoid dysfunction that was considered to be due to a congenital malformation of the laryngeal cartilage. This was corrected by a right-sided laryngoplasty and ventriculectomy. The horse re-presented 1 year later with idiopathic left laryngeal hemiplegia. The decision was made to place a long-term tracheal cannula due to the low success rate and high complication rate associated with other surgeries used to correct bilateral arytenoid dysfunction. A three-piece tracheotomy cannula and stopper were positioned under general anaesthesia. The horse rapidly adjusted to the tracheal cannula and no post-surgical complications were encountered. The horse resumed training 4 weeks postoperatively. Due to the rules governing racing in Australia the horse was exported to New Zealand where he continued his racing career. It was concluded that tracheotomy is a straightforward technique associated with minimal complications and can provide an excellent prognosis for return of full airway function in racing horses. It is recognised that many issues need to be considered prior to more general acceptance of this technique, including assessment of animal welfare issues and public perception. In appropriate cases consideration should be given to using long term placement of a tracheotomy cannula as a treatment option to restore maximal airflow in horses with upper airway obstruction.     

The effect of recurrent laryngeal neurectomy in conjunction with laryngoplasty and unilateral ventriculocordectomy in thoroughbred racehorses

OBJECTIVE: To investigate the effects of recurrent laryngeal neurectomy (RLN) in combination with laryngoplasty and ventriculocordectomy on the postoperative performance of Thoroughbred racehorses treated for grade III left laryngeal hemiparesis (LLH). STUDY DESIGN: Retrospective study. SAMPLE POPULATION: Fifty-five Thoroughbred racehorses. METHODS: Medical records for Thoroughbred racehorses treated surgically by laryngoplasty and laser ventriculocordectomy with or without RLN between June 1993 and December 1996 were reviewed. Outcome was evaluated subjectively by assessment of performance obtained from telephone interviews with owners and trainers, and objectively by assessment of racing performance for 3 races before and after surgery using a performance index (PI). RESULTS: Fifty-five Thoroughbred racehorses with resting endoscopic grade III LLH were treated by laryngoplasty and ventriculocordectomy either with (39 horses) or without (16 horses) RLN. For RLN horses, respondents for 38 horses believed performance was improved in 19 horses, unchanged in 16 horses, and decreased in 3 horses. For horses without RLN, respondents for 9 horses reported that performance was improved in 5 horses, unchanged in 2 horses, and decreased in 2 horses. PI scores were improved in 18 RLN horses and in 6 horses without RLN; there was no statistical difference in outcome. CONCLUSIONS AND CLINICAL RELEVANCE: Use of RLN in combination with laryngoplasty and ventriculocordectomy for treatment of grade III LLH may not improve postoperative racing performance.     

Dynamic obstructions of the equine upper respiratory tract. Part 1: observations during high-speed treadmill endoscopy of 600 Thoroughbred racehorses

REASONS FOR PERFORMING STUDY AND OBJECTIVE: To review the prevalence of single and complex forms of dynamic airway obstructions within a large group of Thoroughbred horses in training referred for investigation of poor performance. METHODS: Video-endoscopic recordings of the upper respiratory tract made during a standardised treadmill exercise test of 600 Thoroughbred racehorses were reviewed and analysed in real time and slow motion to identify dynamic collapse by the tissues bordering onto the pharyngeal and laryngeal airways. RESULTS: Dynamic collapse within the nasopharynx or larynx was confirmed in 471 of the 600 horses. Dorsal displacement of the soft palate (DDSP; 50%) and palatal instability (33%) were the disorders most frequently identified. It was concluded that deglutition is not a significant event in the triggering of DDSP. Complex forms of dynamic collapse were present in 30% of the horses with upper respiratory tract obstructions. A significant influence of age on the prevalence of DDSP and dynamic laryngeal collapse was identified. There was an increased risk of DDSP in younger horses, and of laryngeal collapse in older horses. No association with gender or format of racing was identified. CONCLUSIONS AND POTENTIAL RELEVANCE: Palatal instability and DDSP comprised the most frequently encountered forms of dynamic collapse within the upper respiratory tract of the Thoroughbred racehorses in this study and are probably expressions of the same nasopharyngeal malfunction. Complex obstructions, i.e. where more than one structure collapses into the airway, occur frequently and therefore treatments that address solitary disorders may often be unsuccessful. Younger horses were found to be at greater risk of sustaining DDSP while older horses seemed more at risk to vocal cord collapse but not to collapse of the arytenoid cartilage itself.     

Ventroaxial luxation of the apex of the corniculate process of the arytenoid cartilage in resting horses during induced swallowing or nasal occlusion

OBJECTIVE: To report ventroaxial luxation of the apex of the left or right corniculate process of the arytenoid cartilage under the contralateral corniculate process during resting endoscopic examination, and morphologic features of the larynx of 1 affected horse. STUDY DESIGN: Retrospective study. ANIMALS: Horses (n=8). METHODS: Horses had endoscopic examination as part of a survey of Clydesdale horses (n=7), or investigation of poor performance in Thoroughbred horses (1). One Clydesdale was euthanatized and the larynx examined; 4 cadaver larynges from normal horses were also examined. RESULTS: Ventroaxial luxation of the apex of the left or right corniculate process of the arytenoid cartilage was not detected during quiet breathing but was induced by swallowing or nasal occlusion. Prevalence in Clydesdales was 5.2% (7/133). A Thoroughbred with identical endoscopic appearance of the larynx at rest had progressive ventroaxial luxation of the apex of the arytenoid cartilage during high-speed treadmill endoscopy, associated with abnormal respiratory noise. Necropsy examination of an affected Clydesdale larynx revealed an excessively wide (10 mm) transverse arytenoid ligament that allowed easy separation of the apices of the corniculate processes. In normal cadaver larynges, the apices could not be separated with abaxial traction. CLINICAL RELEVANCE: The clinical relevance of this laryngeal observation in resting horses is unclear. Ventroaxial luxation of the corniculate process of the arytenoid cartilage during induced swallowing or nasal occlusion in resting horses or during high-speed treadmill exercise may be caused by an abnormally wide transverse arytenoid ligament.     

Equine laryngeal hemiplegia part II: Some clinical observations

Some clinical features of laryngeal hemiplegia in 127 horses are described. Possible aetiologic factors were found in only 11% of affected animals. The onset of clinical signs was either sudden or insidious. The majority of cases were presented because of an abnormal respiratory noise made at exercise. Other clinical signs, particularly those usually attributed to laryngopalatal dislocation, were observed in a substantial proportion of affected animals. In all cases surveyed the left arytenoid was affected, although in 3 animals a bilateral laryngeal dysfunction was noted. Thirty of 65 animals examined with a fibreoptic endoscope had other upper respiratory tract abnormalities in addition to abnormal arytenoid movements. Electrocardiographic examination of 45 affected horses did not reveal a significantly higher incidence of abnormalities than that observed in the racing population. The majority of haemograms taken from affected animals were also within normal limits.     

Frequency distribution of carpal osteochondral fragmentation in a population of flat racing Thoroughbreds in the UK

Lameness associated with osteochondral fragmentation of the carpus is a common injury in racing horses. Frequency distributions of sites of fragmentation have previously been published in racehorses in the USA, Australia, New Zealand and Japan but not in racing Thoroughbreds in the UK. The objectives of the study were to document sites of osteochondral fragmentation in the carpus of a population of Thoroughbred flat racehorses in the UK and compare these with other Thoroughbred populations globally and other flat racing breeds. This study was a single centre retrospective observational study; case records of flat racing Thoroughbreds with sites of carpal bone fragmentation that underwent arthroscopic surgery at Newmarket Equine Hospital between 2008 and 2013 were reviewed. A total of 291 sites of fragmentation were identified arthroscopically within the carpal joints of 174 horses. This involved 135 (75%) middle carpal (MCj) and 44 (25%) antebrachiocarpal joints (ABCj), which differs from other populations reported. The most common sites of fragmentation were dorsodistal radial carpal bone (DDiCr) (49%), dorsoproximal third carpal bone (DPrC3) (22%), dorsodistal radius (DDiR) (15%), dorsoproximal radial carpal bone (DPrCr) (5%) and dorsoproximal intermediate carpal bone (DPrCi) (4%). The dorsodistal radial carpal bone is also the most common site in American (US) Quarter Horses (QHs) and Thoroughbreds (TBs) and Australian (AUS) TBs, while DPrC3 has a greater prevalence in US Standardbreds (SBs). Thereafter the frequency distribution differs between the reported study groups. Although all horses underwent bilateral radiographic examination, 45% of the total population had unilateral arthroscopic evaluation. This may therefore underestimate the total number of sites of fragmentation reported. In summary the frequency distribution of carpal fragmentation in flat racing Thoroughbreds in the UK appears to differ from other populations of racehorses.     

Endoscopic observations on laryngeal symmetry and movements in young racing horses

An endoscopic survey of young race horses was performed to examine the prevalence and character of laryngeal movements during quiet respiration. The main aim was to determine whether those arytenoid movements which could possibly reflect the efficiency of left dorsal cricoarytenoid muscle function changed over a period of time. Of the 452 horses examined, 439 were Thoroughbreds and 23 were Standardbreds, 250 were less than 2 years of age (6-21 months), and 202 were 2 years old. One hundred and nine of these horses were examined again 16 months later. Arytenoid movements were given one of four grades. Grades 1 and 2 were considered normal and unlikely to be the result of abnormal left dorsal cricoarytenoid muscle function, whilst grades 3 and 4 were considered likely, or almost certainly, the result of abnormal left dorsal cricoarytenoid muscle function. The percutaneous prominence of the muscular process of left and right arytenoid cartilages, endoscopic arytenoid movement on left and right sides, age, sex and breed was recorded. Chi squared analysis was used to determine the association between age, breed, sex and the other recorded variables, and the presence or absence of abnormal laryngeal movements. At the first examination, 48% of the horses had grade 1, 37% grade 2, 15% grade 3 and 0.2% grade 4 left laryngeal movements. Of the horses examined I6 months later, 52% had grade 1, 33% grade 2, 14% grade 3 and 1% grade 4 left laryngeal movements. Fifteen percent of horses with grade 1 and 9% with grade 2 initially were found to be grade 3 at the subsequent examination. Conversely, 53% of horses with grade 3 initially were found to be grade 1 and 21% grade 2 at the subsequent examination. One horse that was grade 3 at the initial examination was grade 4 at the subsequent examination. Overall, 43% of horses were graded the same, 29% were given a better grade and 28% were given a worse grade. Age and sex were not associated with abnormal left laryngeal movements. The presence of abnormal arytenoid movements was significantly less in Standardbreds, but significantly higher in those horses that had a more prominent muscular process of the left arytenoid cartilage. The number of grade 2 and 3 laryngeal movements recorded on the left side was significantly higher than the right. It was concluded that asymmetrical laryngeal movements are common in young race horses; at this age laryngeal movements may interchange between what is considered normal and abnormal; the proportion of young horses with normal or minor variations in their left arytenoid movements that develop more obvious degrees of asynchrony is low (12%); and the proportion of horses considered to have endoscopic evidence of deficient left abductor muscle function that eventually develop laryngeal hemiplegia is also low (5%).     

Laryngoplasty With or Without Ventriculectomy for Treatment of Left Laryngeal Hemiplegia in 230 Racehorses

Objective —The purpose of this study was to examine the influence of laryngoplasty on racing performance and to determine if any of the following variables had a significant effect on outcome: breed (Thoroughbred v Standardbred), endoscopic grade of laryngeal function, ventriculectomy versus no ventriculectomy, type of prosthetic suture used, and number of prostheses placed. Study Design —Retrospective study of laryngoplasty with or without ventriculectomy for treatment of left laryngeal hemiplegia in racehorses between 1986 and 1993. Animals or Sample Population —230 horses (174 Thoroughbreds, 56 Standardbreds). Methods —The medical records of racehorses or horses intended for racing were reviewed. Signalment, admitting complaints, physical examination findings, resting endoscopic grade of laryngeal function, type of prosthetic suture material used, number of prosthetic sutures placed, presence or absence of ventriculectomy, and postoperative complications were recorded. Results —Upper respiratory tract noise and exercise intolerance were the most common presenting complaints. Two horses had a laryngeal grade of 2, 109 horses a laryngeal grade of 3, and 119 horses a laryngeal grade of 4. Two double-strand braided polyester sutures were used in 147 horses, a single double-strand polyester suture was used in 49 horses, and a single double-strand nylon suture was used in 34 horses. Ventriculectomy was performed on 186 horses. The most common complication recognized during hospitalization was coughing in 50 horses. Telephone follow-up was obtained for 176 horses. For 168 horses, respiratory noise after surgery was decreased in 126 horses, the same in 28, and increased in 14. After hospital discharge, coughing occurred in 43 of 166 horses, and a nasal discharge occurred in 26 horses. Postoperative racing performance for 167 horses was subjectively evaluated by respondents as being improved in 69% of the horses. Overall owner satisfaction with the outcome after surgery was 81%. Of 230 horses, 178 raced at least one time after surgery. Overall, 117 horses raced three or more times before and after surgery, and 65 of these horses had improved performance index scores. None of the variables of surgical interest affected performance index scores. Conclusions and Clinical Relevance —Laryngoplasty with or without ventriculectomy allowed 77% of the horses to race at least one time after surgery, improved racing performance in 56% of the horses that completed three races before and after surgery, and improved subjectively evaluated racing performance in 69% of the horses.     

Career racing performance in Thoroughbreds treated with prosthetic laryngoplasty for laryngeal neuropathy: 52 cases (1981-1989)

OBJECTIVE: To compare racing performance before and after prosthetic laryngoplasty for treatment of laryngeal neuropathy in inexperienced and experienced Thoroughbred racehorses. DESIGN: Retrospective study. ANIMALS: 52 Thoroughbred racehorses treated with prosthetic laryngoplasty for laryngeal neuropathy. PROCEDURE: Lifetime race records were analyzed by use of a verified regression model. Individual race records and hospital records were also reviewed. RESULTS: Experienced horses had a decline in performance, as measured by performance index, earnings percentage, and mean prediction error, during the 6-month period before prosthetic laryngoplasty. Performance improved after surgery, relative to performance in 1 to 4 races immediately before surgery, but did not attain previous baseline values for performance index and earnings percentage, although racing speed was restored to baseline values. Factors associated with failure to attain baseline levels of performance included other racing-related injuries and disorders, major complications of surgery, and age. Individually, however, many horses had long and successful careers after surgery. Performance of inexperienced horses after surgery was at least equal to that of experienced horses. CONCLUSIONS AND CLINICAL RELEVANCE: In addition to warning clients of the complications associated with prosthetic laryngoplasty, it may be prudent to provide a guarded prognosis for full restoration of racing performance in older horses, unless they are especially talented and are free of other racing-related problems.     

Equine laryngeal hemiplegia part II: some clinical observations

Some clinical features of laryngeal hemlplegia in 127 horses arc described. Possible aetiologic factors were found in only 11% of affected animals. The onset of clinical signs was either sudden or insidious. The majority of cases were presented because of an abnkmal respiratory noise made at exercise. Other clinical signs, particularly those usually attributed to laryngopalatal dislocation, were observed in a substantial proportion of affected animals. In all cases surveyed the left arytenoid was affected, although in 3 animals a bilateral laryngeal dysfunction was noted. Thirty of 65 animals examined with a fibreoptic endoscope had other upper respiratory tract abnormalities in addition to abnormal arytenoid movements. Electrocardiographic examination of 45 affected horses did not reveal a significantly higher incidence ot abnormalltles than that observed in the racing population. The majority of haemograms taken from affected animals were also within normal limits.     

Race Performance After Laryngoplasty and Ventriculocordectomy in National Hunt Racehorses

Objective— To evaluate the effect of laryngoplasty (LP) on race performance in longer distance (National Hunt) Thoroughbred racehorses. Study Design— Case‐control study. Animals— National Hunt Thoroughbred racehorses (n=71) and race‐matched controls (n=126). Methods— Race records for National Hunt racehorses that had LP and ventriculocordectomy were analyzed and racing performance was compared with race‐matched controls. Results— Sixty‐three of 71 cases were matched with controls. Postoperatively, 78% of cases raced, 47% improved their individual performance and cases were as likely to start in 1 or 3 races as controls. In the 5 preoperative races, case horses earned less prize money than race‐matched controls but there was no difference in prize money earned in 5 postoperative races between groups. Cases started in significantly fewer total (lifetime) races both before and after the date of surgery compared with controls. Conclusions— LP seemingly restored short‐term postoperative racing performance of National Hunt horses to a level comparable with that of a matched control population; however, the career “longevity” of case horses appears to be shorter than that of control horses. Clinical Relevance— LP appears to be a suitable treatment for recurrent laryngeal neuropathy in National Hunt racehorses.