Welcome to this edition of the webinar Vett entitled, Light at the End of the Tunnel, A Review of current upper airway Surgery in the Horse. We're gonna look at some diagnosis and management of upper airway conditions, specifically in sports horses and pleasure horses, and look at surgery of the upper airway as well as some conservative management as well. I am Matthew Sinnovich, a surgeon and layman's diagnostician at the Lipogew Hospital in Hampshire in the United Kingdom.
So the learning objective objective or synopsis is over there, which is upper respiratory conditions, these are common obviously as a cause of poor performance, usually in racing, but we also are just diagnosing more and more of them in sports horses. This webinar will cover the current evidence on the diagnosis and the treatment of equine upper airway disease. I certainly don't have all the answers, but we'll have to share with you the current research and experiences as we look at what is a very complex topic.
So the learning objectives for today's talk are listed here. Right. We'll get off with some anatomy.
The equine upper respiratory tract consists of all respiratory structures from the nose to the extra thoracic trachea, including the larynx and its associated structures. Upper airway obstruction can negatively impact a horse's athletic performance as well as quality of life, and abnormal air flow patterns can result in upper respiratory noise. However, the intensity of the noise does not necessarily correlate with the degree of airway obstruction.
Horses faced with an impaired ventilation use one of three strategies usually to compensate. One is to increase the driving and spiratory pressure. Uncoupling the gait and the respiratory frequency, or changing the duration of inspiratory and expiratory times.
Now those strategies ultimately manifest as the two leading clinical signs suggest of upper respiratory disease which is poor performance and abnormal respiratory noise. So constriction of the AR folds or nay, drainage from the nasal cavities, facial swellings caused by masses or enlargement of the sinuses or asymmetrical air flow through the nostrils are other possible issues veterinarians can face, and these can easily be diagnosed by examining the horse. Further, we can pick up subtle signs associated with neuropathology such as Horner syndrome, where we can get damage to the sympathetic nerve supply in and around the guttural pouch, and that can result in failure of the nervous system to control the nerves associated with the muscles and organs and upset airflow and functionality of the pharynx and larynx.
The larynx, which is composed of a single cricoid, thyroid and epiglottic cartilage, and a paired achnoid cartilage, forms the communicating channel between the pharynx and the trachea. Contraction of the intrinsic laryngeal muscles, so those on the inside, produce changes in the remer glottis, which is the is the hole, and that that and changes that diameter by abducting and adducting the cornicular process of the erachnoid cartilage, and this then tenses the vocal fold. So here we have the normal endoscopic anatomy and as you can see the arachnoids are up at the top and the vocal folds down at the bottom there, and the blue circle shows you the rema glottis, and that basically is the functional airway of the horse.
The paired cricorretinoid dorsal muscles, which are innervated by the recurrent laryngeal branch of the vagus nerve, are the principal abductor muscles that widen the laryngeal opening by abducting the corniculate process of the arachnoid cartilage and thus tensing the vocal fold and keeping the airway open. So the question you're asking is, but isn't airway disease just a thing in racehorses? No, not necessarily.
Re researchers have found that dynamic airway obstruction or UAO is a cause of respiratory noise and often poor performance in sport horses. Rider intervention during ridden exercise, so for example, the various movements a a horse might be asked to perform, influences upper airway morphology and function, and in cases of dynamic obstruction can contribute to increasing laryngeal and or pharyngeal instability, particularly in sports horses. This study here in 91% of horses with sports horses that made noise, they found a dynamic obstruction and in about 71% of poor performance cases, this was also found.
OK, so is it just horses that go fast? Again, not necessarily. The prevalence of disease in draught horses has increased or is higher in competition horses compared with previously studied groups.
So this can often be associated with tracheal or pulmonary inflammation, and that may be more common inh in draught horses which have laryngeal hemiplegia or upper airway obstruction. There's good evidence to show that with a heightened thoroughbreds is correlated to recurrent laryngeal neuropathy or being aurora, and the same is probably true of draught horses, where selection pressure for larger, taller, longer necked horses may be responsible for a seeming increase in. Left-sided paresis.
And in this case, the prevalence was about 35% in some breeds, up to 42% in Belgians. So how do we go about making a diagnosis now that we know our horse or finding out about poor performance and upper airway conditions in our sports horse. So we go through palpation, sound analysis, endoscopy, and then look at dynamic or overground exercise endoscopy, and we can also look at radiographs and ultrasound.
So we employ a range of clinical exams, and all of these need to be done in conjunction to get to the bottom of what's going on. Palpation is a very, very important part of the examination and should never be forgotten. Palpating the normal larynx, there's usually a small space ventrally between the cricoid and thyroid cartilages, and this is usually filled with a cricothyroid ligament with no space palpable laterally, and this is due to the overlap of the thyroid and cricoid cartilages.
In recurrent laryngeal neuropathy or roaring due to atrophy of the crinoidalus dorsalis muscle, the muscular process may be more easily palpable on the affected site, and there may also be an absence of a slap reflex. In conditions like 4th bra brachial arch defects, the most frequent finding identified on palpation of the larynx is enlargement of the cricothyroid notch, and this is due to aplasia or hyperplasia of the thyroid wing. Most commonly, this is unilateral and on the right side, but it can also occur bilaterally.
For years, static endoscopy or standing endoscopy with a flexible scope has been the diagnostic modality of choice. For standardisation, when we are viewing larynxes and pharynxes, we usually perform this via the right nostril, in a. Unsedated horse and this hopefully will give you the best view and best interpretation of what is going on with the larynx.
Sometimes the nares are occluded in order to force inspiration, and this will help you to grade laryngeal function. Lately there have been a number of dynamic or overgrown scopes which have become commercially available. These can be head mounted, such as the case over here, which is the system that we have in Lipo and the one that I'll be showing today.
It's a very light system, it fits completely on the bridle, with a flexible scope as you can see by the grey tube there that then goes up the nostril. Now this is a racehorse obviously on the right and a dressage horse on the left, and what this then does is films in real time to a SIM card, . And there is a Bluetooth link to a screen so we can adjust things and have a look.
That records all of the data and then we can examine it afterwards. There are other systems that are Saddle mounted or rider mounted, and then run a cable up the neck and up between the ears and a very similar setup. As you can see in sports horses, a system like this allows a normal frame, so the rider can get the horse into flexion or extension, do lateral work and do the typical functions that the horse should do.
And this allows us to observe the larynx in a dynamic situation and see where and what the problems are. Very frequently, it's not just one problem, we have a range of conditions that occur simultaneously. And this means that in a dynamic scope, we can assess all of the.
And come up with the So what's better, treadmill, overground or static scoping. So overground or treadmill are superior to standing for all upper respiratory conditions. That's all of them.
Treadmill is a great way for racehorses to reach maximum speeds and pressures and for sports horses to get to their fatigue level where some of these conditions are evident. The problem with treadmill is that it takes some training, and there is obviously the risk of injury. Overground scopes or flexible scopes, dynamic ones are often better for sports horses because you can replicate the rider interactions, and certainly this is the case with ridden horses as well as some carriage horses, so that is often easier than on the treadmill.
And what has come out of a lot of the research, particularly with treadmills, is that up to 30% of dorsal displacement of the soft palate or what we call silent displaces, and these are only seen on overground or dynamic endoscopy or sometimes on treadmill studies. So what does it look like? This here is a video of a horse undergoing a dynamic endoscopy.
You'll see there, the left arachnoid is completely immobile and paralysed. There is some pharyngeal instability as we go through and as the horse gets up to speed, you can see the dynamic phase and what we can see in the with the dynamic scope. In this case, this horse had had a previous hob day, so the vocal cord on the left was taken off, .
As it starts to get up to speed now, you can see that there's some instability of the right vocal cord. But that's a very good idea of the sort of thing we see on dynamic scopes. Radiographs are particularly useful as well, although limited for some of the evaluation of soft tissue.
What we have here is a lateral lateral standing radiograph focused on the pharynx and larynx, and we can see the soft palate over here, has a focal swelling or what we call the classic matchstick appearance, and that's consistent with a cyst in the in the soft palate. Here we have a standing lateral radiograph showing air in the oesophagus, and this is due to aerophagia in the case of a 4th brachial arch defect. Ultrasound has now also been reported and should definitely be performed in cases of RLN.
This here is a normal look at the cricoidalus lateralis muscles, the CAL muscle, and that is a nice normal fibre pattern over there. What happens in. Neuropathy is you get atrophy of that muscle as is evidenced over here, and this then means that you get, you lose the normal appearance so you can see left versus right there, .
The normal one is. On the side and then you can see the changes between the two. It's also very useful for 4th brachial arch defects.
And what we can see there is the abnormal cartilages and their abnormal relations. And that's a transverse view of the same, and then you've got extension of the thyroid cartilage, dorsal to the arachnoid. What does that look like on scoping?
That is a very classic, 4th brachial arch defect. The right side is paralysed and because the cricopharynges and thyropharynges muscles form the upper esophageal sphincters and provide the muscular support to the attachment of the pillars of the soft palate. Their absence or their weakness makes the weakens the attachment and allows these pillars to be displaced rostrally.
So what we have here is rostral displacement of the palatopharyngeal arch, so you see that lipping on the top of the right reinoid, and that's in 1/4 brachial arch defect. So what conditions do we get that can cause poor performance? So constriction of the naries or ala fold collapse.
This happens with increased pressures and is usually associated with an inspiratory noise. We can have epiglottic entrapment. This occurs when the are epiglottic membrane envelops the rostral aspect of the epiglottis and adheres or gets stuck to it.
We can have nasopharyngeal masses. Typically, the diseases here are sub-epiglottic cysts, granulomas, and epiglottic abscesses. .
We need to be able to elevate the head and manipulate these to sometimes with bronchoesophageal forceps when we're scoping them in order to diagnose them. And we can also treat these with transcendoscopic laser. Intermittent displacement of the soft palate and palatal instability.
This is where the caudal aspect of the soft palate becomes displaced from its normal position, ventral to the epiglottis, and it then comes to sit dorsally, creating an expiratory obstruction or flutter as the horse breathes out, . We can also, that can also manifest as just unstable soft palate and flutter and that you can see quite well on the scope. The cause of intermittent dorsal displacement and palatal instability is probably unknown, but it's likely a multifactorial and is most likely associated with neuromuscular dysfunction.
Permanent displacement of the soft palate is a relatively uncommon disease that possibly has a different aetiology to intermittent dorsal displacement and palatal instability. It's sometimes seen as a complication following laryngoplasty and or typhoid procedures. Then RLN is a disease best classified as a mono neuropathy of the left recurrent laryngeal nerve with degenerative changes that are associated with distal axinopathy.
This disease can cause a range of problems ranging from vocal cord collapse to complete paralysis of the left CAD muscle and subsequent collapse of the left arachnoid cartilage. It's also recognised as a more dynamic problem, with overground endoscopy allowing us to make a more accurate diagnosis, and to assess the degree of dysfunction that exists and therefore direct treatment better. Areachnoid chondritis, maybe a later stage, and often, that's classified or generally shown with a thick infected cartilage, sometimes with abscessation or granuloma formation.
So what can we do about these problems? Well, first off, epiglottic entrapment, we have a number of surgical procedures. Endoscope guided or transorial axial deviation of the entrapping membrane.
Endoscopic guided trans nasal axial deviation of the entrapping membrane. Or laser transection of the entrapping membrane. For nasopharyngeal masses, again depending on the type and place, we can do trans-nasal, trans oral or transesophageal endoscopic guided laser resection, or snare resection.
For intermittent dorsal displacement of the soft palate and palatal instability, we can try conservative management. So there classically we try things like tongue ties or the cornell collar. Cornell collar has been shown to work fairly effectively in the early part of this disease.
Tongue ties anecdotally work, although there's not always great, scientific evidence for their efficacy. Then we move on to things like laser thermopylatoplasty or iron the thermopolatoplasty or firing. There is absolutely no evidence that either of these, the laser or the hot iron firing, produce any significant result and certainly most surgeons won't .
Encourage their use. The tieho is probably the better surgical procedure for that. There is a a biy which is used for epiglossic entrapment.
Persistent dorsal displacement of the soft palates, so there you can resect the caudal aspect of the soft palate. This can be done with a laser or a pair of scissors, or a typhoid or a conjunction of the two. When we have medial or axial deviation of the area epiglottic folds, often seen in conjunction with RLN, we can do a trans-nasal video endoscopic laser resection.
And then for RLN itself, so for auroras various forms, so for sports horses, what often helps enough for functionality is a ventricularcorectomy. Now this can be either done under GA standing or with video endoscopic assisted laser. Combined often with a ringoplasty or tie back, and in cases where there's not yet complete paralysis, we can often attempt a laryngeal reinnervation to.
For yochondritis, you can do curettage or partial retinoidectomy. Interestingly, all of these conditions can now be treated by standing surgery and we'll go into those as we walk through the rest of the treatments. Why are we keen for doing standing surgery?
Confidence and familiarity with standing airway surgery is definitely growing, and as you can see by this list, more and more procedures are being performed this way. There are clear advantages of standing surgery, and specifically standing upper airway surgery. Cost is often listed as one, and this can be viewed in a couple of ways, .
Firstly, as cost to the client and second as cost for the required skill and equipment to the practise. But mostly what we, the benefits are the reduced anaesthetic risk. The mobility of airway structures during surgery means that we can manipulate and see things in situ as they are, not with tubes in the way.
We have the ability to visualise abduction properly, again without a tube assisting anaesthetic and affecting the arachnoids, and often we can do. Multiple things as a single procedure, so perform a hop day and a tie back all in one go. But it does require specialist equipment and specialist facilities, and there's definitely an increased surgical skill and confidence or familiarity with the anatomy that's needed before embarking on these types of surgeries.
So, current evidence for what to do about these procedures. For constriction of the nay or AR faults, conservative management, the use of flare strips has been proven to increase airflow and decrease the work of breathing for conservative management. However, in many competitions, and in much racing, certainly in some FEI instances as well, these are prohibited.
So in these instances, a surgical option has been developed, and this is Ela fold resection with bipolar electrosurgical energy, and it's a good alternative to the traditional surgical approaches performed under general anaesthesia. So this was written up by this group over here, . And they had very good outcomes.
Again, the so transcendoscopic correction of epiglosic entrapments. There are a number of ways of doing this, just with laser itself. This is probably a nicer way of doing it with a silicone covered.
Guide that unhooks the membrane and then the diode laser fibre passed through the scope can be used to transect the membrane away as shown by the picture there. In this study, the entrapping membrane was successfully released in all horses. There were mild postoperative complications with some swelling in 12 horses and coughing on mild nasal discharge in 5.
96% of owners and trainers were satisfied with the outcome procedure, and 93% of horses in this study returned to racing. Nasopharyngeal masses, again, there are a number of ways to get at them. This can be trans oral, trans-nasal, with snares and or scopes and lasers.
Another way to get at them is transtracheal. So if there is significant swelling and you can't actually get at them. What we often do is perform a tracheostomy or tracheotomy, get the scope up there, and this is a bilobed cyst, seen on the edge of the soft palate from the trachea.
Those were lasers and lasered and extirpated, and that resulted in resolution of the problem. Laryngeal typhoid has now also been written up in standing sedated horses. In this study, it was performed and evaluated in 5 experimental horses first, and then in 5 clinical cases which were diagnosed with intermittent dorsal displacement of a soft palate.
Was performed under endoscopic guidance with the horses sedated and local anaesthetic put up in the surgical site. It was well tolerated and the procedure was completed in all horses. They'd used radiographic assessment to demonstrate pre and postoperatively that the basic hyoid and temporal hyoid thyroid, and thy thyroid articulation were positioned dorsally at 2 days and repeated dynamic upper respiratory tract endoscopy.
In this study, 3 or 5 horses showed complete resolution and 2 of 5 marked improvement. One horse experienced brief displacement post-surgery, which was associated with severe neck flexion but was corrected after swallowing. Then there is a modified first or second cervical nerve transplant technique for the treatment of recurrent laryngeal neuropathy.
Now this is, has been shown to be a very good procedure, resulting in 11 of 12 cases that became re-innovated and improved in exercise grade in 9 out of 14 horses within 12 months. The problem with this surgery is that you have to have a functional or a CAD muscle. It can't be completely paralysed, or the muscle can't be completely atrofied because even once it is atrofied, you're never going to restore muscular function.
So it's not applicable to horses with complete paralysis. It also takes up to a year to determine whether the reinnovation has been successful. Most of you will have heard about loryoplasty in standing horses.
So this was written up by this group first here, again performed under endoscopic guidance with the horses sedated, surgical site desensitised with local anaesthetic. In this study where it was first written up, it was completed in all the courses, was well tolerated, no hyper abduction was observed. Two horses developed incisional swelling that resolved drainage only and it was.
Resulted in satisfactory improvement in respiration in all but 3 horses. Standing laryngoplasty avoids the risk associated obviously with general anaesthesia and the recovery, and definitely yields comparable results in non-racing horses to those performed with the horses anaesthetized. Then this is a very recent report written up now where in a case of 4th brachial arch defect, it's a bit of a unique case in that it's a left-sided 4th brachial arch defect, not a right sided one.
But in this case, the horse was treated with a laryngoplasty under endoscopic guidance, sedated and standing, and the surgical site was desensitised again with local anaesthetic, was completed and was well tolerated, . And as you can see there, with the cordectomy and corotomy on the other side, resulted in a functional airway. Then we get on to minimally invasive laser treatment for aretinochondritis.
Now traditionally, this has been approached under GA and then curettage or complete removal of the erachtinoid has been performed. But over here it has been written up as a. Standing procedure using a laser to drain granulomas and abscesses and to partially resect arachnoids as needed.
In this case it was tolerated, or in this case series was tolerated well and showed a resolution of the problem again. So I think the take home message here is there are numerous conditions involved in upper airway problems. They are not specifically .
Conditions of racehorses and indeed are more and more prevalent in sports horses and more and more prevalent in performance horses. In the UK we find them quite commonly in the native breeds as well as in the heavy horses and definitely horses exhibiting poor performance there. Part of your examination should be an upper airway examination, and probably including a dynamic endoscopy.
So I'm gonna say thank you for your attention, and we will go from there.
