Collapsing Trachea in a Miniature Horse

A three year-old miniature stallion presented to PHD Veterinary Services for the complaint of open mouth breathing and a "honking" sound during respiration. At presentation, the stallion was agitated and was continuously pawing at his muzzle with his mouth open. The stallion was mildly sedated for the endoscopic exam and interestingly, his breathing became more normal. The most proximal trachea (Figure 1) appeared normal in diameter however the lumen quickly became narrowed (Figure 2). The trachea was nearly completely collapsed for approximately 6 cm at the level of the thoracic inlet. Distal to this area, the trachea appeared normal (Figure 3).

Figure 1

Figure 2

Figure 3

Normally, the lumen of the trachea is continuous, extending from the larynx to the primary bifurcation of the trachea (Figure 4). Unfortunately, the miniature horse breed is predisposed to the condition known as collapsing trachea. The condition is often diagnosed shortly after birth or can develop later in life if the horse is allowed to gain excessive weight. A common clinical complaint is that of a "honking" sound during heavy respiration. The severity of the collapsing trachea depends on the location and the extent of the narrowed lumen. The closer the area of collapse is to the chest cavity, the worse the prognosis. There are reported cases of collapsing tracheas in miniature horses that were repaired via intra- and extra-luminal stents. Unfortunately, they are short term fixes and often do not provide a long term solution.

Figure 4

Resolved Aspiration Pneumonia

Approximately 2 months ago a young warm blood gelding presented for a 4-6 month history of chronic coughing, bilateral nasal discharge, poly-synovitis, and failure to thrive. At presentation, the gelding was in poor body condition and there was a moderate amount of nasal discharge which consisted of mucus mixed with feed/hay. Auscultation of the thorax noted abnormal lung sounds, bilaterally.  As I reported previously, endoscopic exam revealed feed material within the larynx and trachea (Figure 1 and 2). The feed material was noted through out the entire trachea and a trans-tracheal wash revealed the presence of feed material and bacteria in the cranial ventral lung lobes! The gelding was diagnosed with dysphagia and aspiration pneumonia.

Figure 1

Figure 2

Based on the trans-tracheal culture results the gelding was treated with oral antibiotics for 30 days. In addition, he was treated with systemic anti-inflammatory medication and systemic anti-arthritic medication. Once the antibiotic treatment was started, the coughing episodes subsided but were not completely abolished. The gelding began to gain weight and for the first time was seen laying down to sleep and roll in the pasture! A follow-up endoscopy performed at the end of 30 days of antibiotics revealed feed material within the larynx (Figure 3) and an intermittent dorsal displacement of the soft palate (Figure 4). Mild to moderate ulcerations were noted along the caudal edge of the soft palate when displaced. At this point, we were not sure what was going to happen once we stopped treating with antibiotics however based on the continued presence of feed material in the pharynx, it was assumed that a recurrence of aspiration pneumonia was soon to follow.

Figure 3

After discussing the limited options with the owner, it was decided to pursue acupuncture as a potential source of treatment. Dr. Marilyn Maler was asked to examine the gelding and provide her expert opinion and treatment options. She immediately instituted an acupuncture regiment that was directed at treating the horse's difficulty with swallowing among other points of interest. According to the owner, the gelding's cough improved significantly and in a short period of time was completely absent! The gelding continued to gain weight and has been eating "normally" for over 4 weeks. A follow-up exam was performed 2 days ago and the gelding's condition has improved so dramatically that I did not even recognize the horse!  Endoscopic exam noted NO feed material in the pharynx and normal lung sounds!! The gelding has a long way to go but our conversation has shifted from when might it be time to "do the humane thing" to when might it be time to ride him!!  This case is a strong reminder of the benefits of acupuncture for treating chronic diseases and I wish to extend a special thanks to Dr. Maler for all her help!!

Figure 4

Final note: On the day of the most recent exam, the gelding was feeling so good that he played hard to get. So, he was enticed with several hand fulls of feed just prior to the endoscopic exam. This happens to be a crude method of detecting dysphagia in horses and the gelding passed with flying colors!!

Figure 5

Dysphagia and Aspiration Pneumonia in a horse!!

The endoscopy images below were from a young gelding that presented for a history of coughing while eating. In addition, an intermittent nasal discharge was present and the gelding was described as a "hard keeper". In Figure 1, a small amount of feed material was noted along the floor of the soft palate, just in front of the epiglottis. In addition, feed particles were noted on the epiglottis and the walls of the pharynx. These findings alone are not 100% indicative of a dysphagic (difficulty swallowing) horse however, generally speaking there should NOT be any feed material in the pharynx or larynx. 

Figure 1

When the endoscope was passed through the larynx into the trachea (wind pipe) copious amounts of feed material mixed with mucus was noted on the walls of the trachea. In Figure 2, green and brown feed material  can be seen adhered to the wall of the trachea. As the endoscope was pass further down the trachea, feed material mixed with mucus remained present in significant amounts. 

Figure 2

At the very end or deepest region of this image (Figure 3) is the primary bifurcation of the trachea which occurs just in front of the heart. The presence of feed material at this level of the airway is consistent with aspiration and a trans-tracheal wash was performed to confirm pneumonia.  

Figure 3

Dysphagia and aspiration pneumonia are quite uncommon in horses and may be secondary to a neuropathy affecting the nerves that control the swallow reflex. The most common disease processes in horses that may affect these nerves include equine protozoal myeloencephalitis (EPM), cervical spine trauma, trauma to the guttural pouches, temporohyoid osteopathy (THO), strangles, encephalitis, and basisphenoid bone fracture. Unfortunately, the prognosis is poor for horses with this condition. The likelihood that they will recover their normal swallow reflex, regardless of the cause, is low!  In addition, the aspiration pneumonia that results from the dysphagia  is a recurring problem that typically results in their failure to thrive!

Displaced Soft Palate!!

Figure 1

The image above is an endoscopic pic of a middle-aged gelding that presented for a history of exercise intolerance. Apparently, during low level, forced exercise, the gelding would begin to make loud "gurgling" noises and become short of breath! In addition, the gelding would cough on a regular basis, especially when eating in the stall. 

Figure 2

 The image above is that from a normal horse. The yellow arrow is pointing to the epiglottis which is not visible in Figure 1 and Figure 3 due to the dorsal displacement of the soft palate. Normally, horses breathe through their nasal passages. The epiglottis helps keep the soft palate in position thus keeping the oral pharynx separate  from the nasal pharynx. However, when the soft palate becomes displaced and covers the epiglottis, the nasal pharynx and oral pharynx communicate directly. When this occurs, the horse suddenly begins to breath through its oral cavity which results in a gurgling sound and exercise intolerance.

Figure 3

The cause of the chronic dorsal displacement of the soft palate in this case is in part due to chronic inflammation of the soft palate (yellow arrow) and potentially an abnormal epiglottis (blue star). The epiglottis was not visualized in this exam and may require an oral endoscopy and skull radiographs to better determine if  there is a structural problem with the epiglottis. Management of this condition involves treating with systemic anti-inflammatory medications and medicated throat wash. If the soft palate remains displaced, surgical consultation is recommended. Yet another example of the benefit of an endoscopic exam for a horses that suffer from coughing, exercise intolerance, or nasal discharge.

Equine Pharyngitis!!

The image above was from a 10 year old gelding that presented for a history of coughing and mild nasal discharge. The cough was intermittent and would vary from day to day. Recently, the cough had worsened as had the summer heat! Based on the history, the most likely cause was predicted to be heaves (AKA: COPD). However, when the endoscope was introduced into the gelding's upper airway it was clear that we were dealing with something quite different. There was evidence of pharyngeal scarring (cicatrix) and active pharyngeal ulceration  in a 360 degree (red circle below) range.  These findings were consistent with active inflammation and chronic changes. In addition, there was chronic, active inflammation of the arytenoids (green arrow).

The cause of pharyngeal inflammation/ulceration varies and is often never determined. In some cases, it may be complicated by bacterial infection. In some cases, the inciting cause is presumed to be an environmental irritant that the horse is chronically exposed to. The chronic inflammation results in scarring or cicatrix formation that can result in narrowing of the pharynx. Pharyngeal cicatrix formation is a serious complication that has no reliable remedy!  As such, a chronic couch (>2 weeks) should be evaluated via endoscopy prior to the development of scarring. Pharyngeal inflammation is typically treated with forced rest and topical antibiotics/steroids in the form of a nasal flush. 

Cleft Palate!

Image 1

The first two images are from a yearling thoroughbred that presented for a long history of nasal discharge, coughing while eating, and the presence of water exiting from nostrils while drinking. The filly had been treated with antibiotics prior to the exam. Endoscopic exam revealed a defect within the soft palate that extended nearly the entire length of the soft palate. In addition, the epiglottis was entrapped by the aryepigltottic fold. 

Image 2

 The defect within the soft palate is known as a "cleft palate" and most likely has been there since birth. Fortunately, this is a relative rare condition! Normally, the palate plays the role of separating the nasal passages from the oral passage. Hence, a horse is an obligate nasal breather and the palate keeps water and feed from entering the airway. When a cleft palate exists, there is communication between the air passage and oral passage resulting in feed and water going the "wrong way". This may consist of feed material exiting the nostril and/or traveling down the trachea into the lungs. If these horse go undiagnosed they are typically "poor doers" with failure to thrive secondary to chronic respiratory infections. Sadly, there is little to be done to help such a severe cleft palate. Less severe cases may be addressed with surgical intervention with mixed results. 

Image 3

The third image if that of a "normal" horse. The epiglottis is visible and is resting on top of the complete soft palate. Diagnosis of a cleft palate is often made immediately after birth during a thorough post-foaling exam. The veterinarian should palpate the length of the hard and soft palate with their finger to make sure it is normal. If missed at foaling, the diagnosis can be made quite simply with an endoscopic exam.