Wind Conditions in racehorses

 

Diagnosis and Treatment

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Whistler or Laryngeal hemiplegia

The horse’s throat region (the pharynx and larynx) can be affected by conditions which physically restrict the amount of air entering the lungs. Probably the best known of these is laryngeal hemiplegia (whistling). The larynx closes to prevent food entering the wind pipe during swallowing and opens up fully during peak exercise to allow air to enter the lungs. Provided that the muscles controlling the larynx are functioning properly it opens to form a diamond shaped structure. It is relatively common for the left side of the larynx to become paralyzed, which results in only half of the larynx opening and causing reduced airflow into the lungs.

 

Diagnosis of laryngeal hemiplegia has traditionally been by listening for a characteristic whistle or roar at exercise in combination with endoscopy of the upper airway at rest to confirm the diagnosis. The degree of laziness or paralysis is graded from 1 to 5. Grades 1 and 2 are considered within the normal range, but grade 3 and higher are abnormal. However, there are a significant number of horses in which the diagnosis is not clear cut. This means there are many affected horses that scope normally, but make a whistle at exercise, and alternatively there are horses that fail on scope but make no noise at exercise.

 

For this reason high-speed treadmill video-endoscopy was introduced.  This enabled the horse’s larynx to be visualised while at fast exercise and was a huge step forward in accurate diagnosis. Troytown Equine Hospital installed the first high-speed treadmill in Ireland in 2002.  It is a very safe and reliable method to accurately diagnose wind conditions in horses.   The overland scope was introduced as a method to perform scope examinations during exercise with a Jockey on its back,

 

 

Treatment for Laryngeal hemiplegia

 

a) Hobday or Ventriculocordectomy

The majority of horses with this condition are within the grade 3 category where a Hobday is likely to be very effective. This surgery has traditionally been done under a general anaesthetic and making a surgical opening into the larynx under the throat to remove both ventricles and the left vocal cord. In essence the technique hasn’t changed for the past 60 years but has been very successful in selected cases.

 

With the introduction of exercise endoscopy and the improvement in laser technology it is now possible to do the same surgery standing under mild sedation. Laser surgery offers a number of benefits over the traditional surgery. It precludes a general anaesthetic, the horses can return to work more quickly, there is no surgical scar under the throat and it is less traumatic for the horse. Another huge benefit of this new technique is that it allows more intricate correction of additional concurrent problems that cannot be dealt with by the old methods. Both traditional and laser surgery are still carried out at Troytown Hospital and both have their place in treatment.

 

b) Tieback Surgery combined with laser surgery

In horses that have got grade 4 or 5 paralysis a laryngeal tieback ,whereby a suture is placed on the left side of the larynx to permanently hold it open, is often the treatment of choice. This is a more involved surgical procedure and potentially prone to more complications (such as failure of the suture, or a persistent cough at feeding time, and sometimes dynamic collapse of other areas of the pharynx and larynx). Tiebacks are less problematical for horses working at slower speeds, such as show jumpers and eventers. In race horses operating at maximum breathing capacity, studies at Cornell University have demonstrated turbulent airflow at the level of the larynx post-tieback. This turbulence can lead to collapse of soft tissue structures within the larynx, such as the right aryepiglottic folds.

 

Troytown Equine Hospital have refined a reported technique for tieback surgery which in our opinion is giving consistently better results. The surgery is done in combination with ventriculectomies by laser surgery rather than the traditional method (which avoids a second scar and possible infection of the tieback site). Laser surgery also enables us very effectively to remove the soft tissue structures that can collapse after tieback, such as the aryepiglottic folds. It is still worth doing this surgery on good horses as there have been many success stories.  Without surgery the horses usually are retired from racing.

 

 

Choking, Gurgling or Dorsal displacement of the soft palate

 

Dorsal displacement of the soft palate or choking is another common condition affecting the upper respiratory tract. This is a difficult condition to diagnose and subsequently find the most appropriate treatment.  At Troytown GreyAbbey it is our opinion that no two cases are the same. Before any surgical or medical treatment should be undertaken it is imperative that a full history and proper diagnosis is made. There is not doubt that the advent of endoscopy and the use of the onboard overland endoscopy systems have improved our ability to diagnose these problems immeasurably.  The overland scope is convenient as it requires no training of the horse on the treadmill. (It is definitely the most convenient first line for investigation). However, in some instances the treadmill exercise test gives superior visualisation and control of the horse as it is easy to re-run horses on the treadmill trying different nose bands and re-positioning the scope to view different areas of the larynx. This enables the diagnosis of conditions which are more difficult to detect.  Race horses adapt to treadmill training very quickly and easily and it is as safe, if not safer, than fast work on all weather gallops. We can facilitate both overland scopes and treadmill tests at a very competitive cost in today’s financial environment.  An accurate early diagnosis is far cheaper in the long term.

 

a) Treatment for Dorsal Displacement of soft palate

Once the diagnosis is made a series of appropriate recommendations can be given.  Many horses will choke up temporarily due to other conditions, such as infection, allergies, EIPH (bleeding) or immaturity.  It could be wrong to operate on some of these horses without trying other methods of treatment first.  Other horses may benefit from minimal surgical intervention such as thermocautery of the soft palate to stiffen it.  Other horses may need surgery to shorten the soft palate or alternatively to do a tie-forward procedure.  There are many other surgical solutions including staphylectomy, myectomy, Llewelyn procedure and epiglottic augmentation.

 

Other Upper Respiratory Conditions

 

The results of the overland endoscopy often will give a completely different diagnosis than expected. Pharyngeal collapse, retroversion of the epiglottis, collapse of the aryepiglottic folds are all conditions which are only identifiable under exercise endoscopy.  There is a myriad of combinations of problems that can be identified concurrently including vocal cord vibration, rostral displacement of the palatopharyngeal arch and overlapping of the corniculate processes of the arytenoid cartilages.  It is not possible in this newsletter to fully explain all these conditions but it is important to be aware that it is far more complicated than previously thought.  It is also worth noting that 25% of horses with upper respiratory obstructions will make no outward noise at exercise.  An accurate diagnosis is therefore vital and we need to get away from the old fashioned approach of guesswork and just doing the standard wind surgeries. Each horse needs an individual tailored plan to treat any underlying medical conditions and then attempt any surgical treatments.  Some horses may need a number of surgeries to completely solve the problem. New surgical techniques including the most up to date laser surgical methods are now available.  There are a small number of horses that have such serious problems in the pharynx and larynx that cannot be cured either medically or surgically. These horses need to find another career.

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