Laryngeal hemiplegia in draft horses. A review of 27 cases

Prevalence of Exercise-Induced Pulmonary Hemorrhage, Tracheal Mucus and Recurrent Laryngeal Neuropathy in Competitive Draft Pulling Horses

Respiratory disease is common in the horse population and is often associated with poor performance in equine athletes. Despite their outstanding strength and aerobic capacity, little regard is given to draft horses and the respiratory disorders they may encounter when performing athletic activity. For this reason, the objectives of this study were: (1) to determine the prevalence of exercise-induced pulmonary hemorrhage (EIPH), tracheal mucus (TM) and recurrent laryngeal hemiplegia (RLH) in a population of competitive draft pulling horses, and (2) to determine if there was an association between horse weight, height, age, amount pulled, or competition placing with EIPH, TM or RLH in draft pullers. Results of this study identified EIPH in 26% of the study population, RLH in 32% and TM in 82% of participating horses; however, no risk factors were identified for the development of these problems in draft pulling horses.

Effect of ventriculectomy versus ventriculocordectomy on upper airway noise in draught horses with recurrent laryngeal neuropathy

REASONS FOR PERFORMING STUDY

Little is known about the efficacy of bilateral ventriculectomy (VE) or bilateral ventriculocordectomy (VCE) in draught horses.

OBJECTIVES

To compare the effect of VE and VCE on upper airway noise in draught horses with recurrent laryngeal neuropathy (RLN) by use of quantitative sound analysis techniques.

HYPOTHESIS

In competitive draught horses with grade 4 RLN, VE and VCE reduce upper airway noise during exercise, but VCE is more effective.

METHODS

Thirty competitive hitch or pulling draught horses with grade 4 RLN were evaluated for upper airway sound during exercise. Respiratory rate (RR), inspiratory (Ti) and expiratory time (Te), the ratio between Ti and Te (Ti/Te), inspiratory (Sli) and expiratory sound levels (Sle), the ratio between Sli and Sle (Sli/Sle), and peak sound intensity of the second formant (F2) were calculated. Eleven horses were treated with VE and 19 with VCE. After 90 days of voice and physical rest and 30 days of work, the horses returned for post operative upper airway sound evaluation and resting videoendoscopy.

RESULTS

VE significantly reduced Ti/Te, Sli, Sli/Sle and the sound intensity of F2. Respiratory rate, Ti, Te and Sle were unaffected by VE. VCE significantly reduced Ti/Te, Ti, Te, Sli, Sli/Sle and the sound intensity of F2, while RR and Sle were unaffected. The reduction in sound intensity of F2 following VCE was significantly greater than following VE. After VE and VCE, 7/11 (64%) and 15/18 (83%) owners, respectively, concluded that the surgery improved upper airway sound in their horses sufficiently for successful competition.

CONCLUSIONS

VE and VCE significantly reduce upper airway noise and indices of airway obstruction in draught horses with RLN, but VCE is more effective than VE. The procedures have few post operative complications.

POTENTIAL RELEVANCE

VCE is recommended as the preferred treatment for RLN in draught horses. Further studies are required to evaluate the longevity of the procedure's results.

Ventriculocordectomy as the Sole Treatment for Recurrent Laryngeal Neuropathy: Long-Term Results from Ninety-Two Horses

OBJECTIVE

To evaluate the effect ventriculocordectomy (VC) for treatment of recurrent laryngeal neuropathy (RLN) on exercise performance and owner satisfaction in a mixed-breed population of horses.

STUDY DESIGN

Retrospective study.

ANIMALS

Adult horses (n=92) with a history of abnormal respiratory noise and RLN.

METHODS

Retrospective analysis of horse that had unilateral VC (and contralateral ventriculectomy in 63 horses) for treatment of idiopathic RLN. Owners/trainers completed a questionnaire about complications and outcome at least 1 year after surgery. Performance index was determined using race records for previously raced Thoroughbreds to evaluate outcome.

RESULTS

Clinical signs included abnormal exercise-induced respiratory noises (noises; 52%), poor performance (11%), and noises and poor performance (37%). The median preoperative resting endoscopic grade of laryngeal function was Havemeyer grade III.1 (mild asymmetry). No discharge from the laryngotomy 1 week postoperatively occurred in 62% horses, 22% coughed after surgery, 66% made no noises, 9% continued to make noises at the canter, 21% made noise at the gallop, and 4% of owners were unsure whether noises were present. Ninety-three percent of horses returned to full work after surgery. Overall, 86% of owners considered the surgery worthwhile, 3% did not consider it worthwhile, and 11% were unsure. Surgery had a significantly beneficial effect on the racing performance index in Thoroughbreds (P=.004).

CONCLUSIONS

VC is a useful alternative to laryngoplasty for selected cases of RLN and is associated with a positive effect on exercise performance, a low postoperative complication rate, and a high rate of owner satisfaction.

CLINICAL RELEVANCE

Unilateral VC should be considered as a sole treatment in horses with low grades of RLN.

The Prevalence of Laryngeal Disease in a Large Population of Competition Draft Horses

OBJECTIVES

(1) To determine the effect of age, height, weight, breed, sex, and specific use on the prevalence of idiopathic left laryngeal hemiplegia (ILH) in a population of draft performance horses; (2) to determine the association between tracheal mucus and laryngeal dysfunction, and the prevalence of exercise-induced pulmonary hemorrhage (EIPH) in a population of draft performance horses.

STUDY DESIGN

Cross-sectional.

ANIMALS

Draft horses competing at the 2005 Michigan Great Lakes Draft Horse Show.

METHODS

Endoscopic examinations were performed on horses competing at the 2005 Michigan Great Lakes Draft Horse Show. Signalment, height, and weight were obtained from the owners and trainers.

RESULTS

Belgian, Percheron, and Clydesdale horses (n=183) were studied. Prevalence of ILH was 35%. Horse height was significantly associated with the risk of ILH in Belgian and Percheron horses but not Clydesdales. There was a significantly different prevalence of ILH among the breeds such that 42% Belgians, 31% Percherons, and 17% Clydesdales were affected. Laryngeal disease was a risk factor for increased tracheal mucus. None of the horses had acute evidence of EIPH.

CONCLUSIONS

The prevalence of ILH in draft horses has increased or is higher in competition horses compared with previously studied groups. Tracheal and/or pulmonary inflammation may be more common in draft horses with ILH based on our findings that horses with ILH have more tracheal mucus than horses with normal laryngeal function.

CLINICAL RELEVANCE

Selection pressure for large, taller, longer-necked horses may be responsible for a seemingly increased incidence of ILH in competitive draft horses.

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.

Long-term survey of laryngoplasty and ventriculocordectomy in an older, mixed-breed population of 200 horses. Part 1: Maintenance of surgical arytenoid abduction and complications of surgery

REASONS FOR PERFORMING STUDY

Laryngoplasty (LP) is currently the most common surgical treatment for equine laryngeal paralysis, however, there have been no reports quantifying the degree of retention of arytenoid abduction following LP. Additionally, the complications of LP have been poorly documented.

OBJECTIVES

To record the degree of arytenoid abduction retention following LP and to accurately document all complications of surgery.

METHODS

A study (1986-1998) of 200 horses of mixed breed and workload, median age 6 years (prospective 136 cases and retrospective 64 cases) undergoing LP (using 2 stainless steel wires) and combined ventriculocordectomy was undertaken; 198 owners completed questionnaires, a median of 19 months following surgery. The degree of arytenoid abduction achieved was endoscopically, semi-quantitatively evaluated using a 5-grade system, at 1 day, 7 days, and 6 weeks after surgery.

RESULTS

On the day following LP, 62% of horses had good (median grade 2) arytenoid abduction, 10% had excessive (grade 1), and 5% had minimal (grade 4) abduction (overall-median grade 2). Due to progressive loss of abduction, moderate (median grade 3, range 1-5) abduction was present overall at 1 and 6 weeks after LP. Further surgery was required to re-tighten prostheses in 10% of cases with excessive loss of abduction, or to loosen prostheses in 7% of horses which had continuing high levels of LP abduction and significant post operative dysphagia. LP wound problems (mainly seromas and suture abscesses) were reported to last < 2 weeks in 9% of cases, < 4 weeks in 4% and > 4 weeks in 4%. The (partially sutured) laryngotomy wounds discharged post operatively for < 2 weeks in 22% of cases, < 4 weeks in 7% and for > 4 weeks in 2%. Coughing occurred at some stage post operatively in 43% of cases and its presence correlated significantly with the degree of surgical arytenoid abduction. This coughing occurred during eating in 24% of cases and was not associated with eating (or dysphagia) in the other 19% of cases. Chronic (> 6 months duration) coughing occurred in 14% of cases, but appeared to be due to intercurrent pulmonary disease in half of these horses.

CONCLUSIONS

Suturing the cricotracheal membrane allows most laryngotomy wounds to heal quickly. Laryngoplasty wound problems were of little long-term consequence when stainless steel wire prostheses were used.

POTENTIAL RELEVANCE

A significant loss of LP abduction occurs in most horses in the 6 weeks following surgery and efforts should be made to find ways to prevent such loss. However, excessive LP abduction is associated with post operative dysphagia and coughing.

Neodymium:yttrium aluminum garnet laser ventriculocordectomy in standing horses

OBJECTIVE

To develop a technique for neodymium:yttrium-aluminum-garnet (Nd:YAG) laser ventriculocordectomy in standing horses and document healing in horses undergoing laser ventriculocordectomy.

ANIMALS

6 horses between 2 and 32 years old.

PROCEDURE

Under endoscopic guidance, the left laryngeal ventricle was everted with grasping forceps and excised with an Nd:YAG laser, using 60 watts of power in a noncontact fashion (6,403 to 9,197 Joules). Following removal of the ventricle, the vocal cord was photoablated. Horses were examined endoscopically 2, 7, 14, 21, 30, and 47 days after ventriculocordectomy, and 1 horse was euthanatized on each of these days. At necropsy, the larynx was removed intact and examined grossly. Samples were collected for histologic examination of the ventriculocordectomy site.

RESULTS

Endoscopic examination revealed granulation tissue by day 7, the start of epithelialization by day 21, and healing by day 47. At necropsy, 4 horses were found to have a small amount of ventricular mucosa remaining dorsally and 1 additional horse was found to have a mucocele. Granulation tissue was identified grossly and histologically in the horses euthanatized between 7 and 30 days after surgery. Incipient reepithelialization was evident histologically on day 14, and complete reepithelialization of the surgery site was evident by day 47.

CONCLUSION AND CLINICAL RELEVANCE

Results suggest that ventriculocordectomy can safely be performed with an Nd:YAG laser in standing horses.

Upper respiratory causes of exercise intolerance

The respiratory system is a frequent cause of exercise intolerance in performance horses. Labored breathing, fatigue during performance, and prolonged recovery after exercise are common complaints. Inadequate fitness level and diseases of the cardiovascular system are differential diagnoses that share these complaints and should be ruled out. Generation of increased airway noise is a clinical sign that implicates the upper respiratory system. A careful history from the owner and endoscopy of the upper airway are the most useful diagnostic tools. Endoscopy during exercise on a treadmill is indicated when the airway lesion is not apparent with endoscopy at rest. Treatment of the respiratory obstruction may differ with the level of performance required.

He-Ne laser therapy by fibroendoscopy in the mucosa of the equine upper airway

BACKGROUND AND OBJECTIVE

A study was made of the effects of low-level laser irradiation on the cicatrization of superficial wounds in the pharyngeal mucosa of the horse.

STUDY DESIGN/MATERIALS AND METHODS

Duplicate pharyngeal mucosal ulcers were induced in 12 Spanish horses with submucosal injection of sulfuric acid. A fibroendoscope and an He-Ne laser were used to treat one of the ulcers and the second ulcer in each animal was left untreated, serving as a control. Biopsy samples for the histological study were taken after the seventh laser therapy session from the two animals.

RESULTS

Irradiated lesions cicatrized at 10.5 days and nonirradiated lesions cicatrized at 18.0 days. Statistical analysis revealed highly significant differences (P < 0.0001) between the irradiated and control groups. Histological study of the control samples showed epithelial coagulation necrosis, edema, and microthrombi. However, in samples from the irradiated lesions no inflammatory edema, numerous active fibroblasts, connective tissue, and intensive epithelial regeneration were observed.

CONCLUSION

Macroscopic and microscopic results indicated that laser treatment accelerated the cicatrization. Irradiated lesions cicatrized faster than control. These results suggest beneficial effects of low-level laser irradiation therapy on equine pharyngeal ulcerative lesions.

Blood gas tensions, acid-base status, heart rates, and venous profiles in exercising horses with laryngeal hemiplegia before and after corrective surgery

The physiologic effects of exercise were studied in four horses with complete laryngeal hemiplegia. Right carotid arteries were surgically elevated to a subcutaneous position for percutaneous catheterization. Each horse was fitted with a device designed to obtain multiple arterial samples while the horse was exercised over a 1.6-km course. After each horse completed 10 test gallops, the laryngeal hemiplegia was treated using a laryngeal prothesis and ventriculectomy. The horses were then reconditioned, and the exercise test and sampling were repeated. Horses with laryngeal hemiplegia became acidotic, hypoxic, and hypercapnic compared to normal horses. Surgical treatment improved blood gas and acid-base status, but the values were not equivalent to those in normal horses similarly tested.

Standing surgery of the neck and thorax

Many surgical procedures of the head and neck can be safely performed in the standing horse, with easy access to all aspects of the surgical field. Some procedures, such as tracheotomy, are easier to perform with the horse standing with the head in a more natural position than with the horse under general anesthesia. Procedures of the neck and thorax that require evacuation of purulent and necrotic material from confined spaces, such as occur in horses with esophageal ruptures and extensive intrathoracic abscesses, can be done as standing procedures to avoid the risks of general anesthesia on severely debilitated patients.