Dorsal Displacement of the Soft Palate (DDSP)

Horse name: Poto madrin
Colour: Bay
Breed: Thoroughbred
Years: 3 years

Introduction

(DDSP) is a condition where the epiglottis becomes positioned above the soft palate.

DDSP may be intermittent (the most common) or persistent. With intermittent displacement, the horse is able to replace the soft palate when swallowing. When a horse is persistently
displaced, the displacement is not corrected when the horse swallows, these horses are not capable of covering the opening of their trachea during eating, which may lead to coughing and ultimately aspiration pneumonia.

Case history and presentation

1. The jockey noted the horse “choking down” or “gurgling”
2. The horse had open-mouth breathing with episodes of loud expiratory gurgling noise.

N/B: Once the soft palate is displaced the horse is unable to breathe sufficiently, which leads to rapid slowing or stopping, at which time, it usually swallow s and replaces the palate into normal position causing the gurgling noise to dissipate and the open-mouth breathing to stop.
3. Substantial exercise intolerance occurs during DDSP due to disruption in airflow. The
exercise intolerance and gurgling noise are due to the soft palate creating an expiratory airway
obstruction because of its abnormal position.

Causes of DDSP

Numerous factors are believed to contribute to this performance-limiting disease.

These factors include:

1. Inflammation of the airway, including the throat and guttural pouches
2. Abnormal epiglottic size and shape
3. Abnormal soft palate rigidity (flaccidity)
4. Abnormal retraction of the larynx
5. Excessive flexion at the poll
6. Neuromuscular disease
7. Excitement and malpositioning of the horse’s tongue over the bit.
Diagnosis of DDSP

Making a diagnosis of DDSP requires a thorough history to be obtained and a complete physical
exam be performed.

During the physical examination, a re-breathing bag may be placed
over the horse’s nostrils to make the horse breathe deeply so that lower airway noises can be better assessed.

In this case endoscopy was used as a diagnostic procedure by Dr. Varma..

1. The horse was sedated with 2ml Detomidine hydrochloride 10mg/ml (preservative-Methyl parahydroxybenzoate 1mg/ml). As shown below…..

image

N/B: Endoscopy is the most useful diagnostic test and is usually performed in the standing horse to visualize the inside of the throat…

2. A nose twitch was used as a method of choice for physical restraint to safely perform upper airway endoscopy while standing  as shown below….

image

3. The procedure involved placing the flexible, fiberoptic endoscope through the left nostril, nasal passages and into the throat as shown below…

image

This enabled thorough examination of the structures of the upper respiratory tract i.e.

a. Normal positioning

Carefully examine the photo below…….

image

Did you see the beautifully positioned arytenoid cartilages?  If you slapped the right thoracic side of the horse while observing, you will see the right arytenoid cartilage being deflected inwards!

This is an endoscopic image of a
horse’s throat demonstrating the normal position of the epiglottis (E) relative to the soft palate (SP).

b. DDSP

Once again, carefully examine the photo below………

image

Kindly compare it to the previous photo….is there any difference? If yes, bravo! Continue reading….if no! Take a look again…

This is an endoscopic image of a horse’s throat demonstrating DDSP. Note that the epiglottis (E), which is evident in Figure above, is not visible. The epiglottis disappears underneath the soft palate (SP), which is displaced above it.

Treatment and Management

Treatment of DDSP involves both conservative and surgical approaches.

1. Alleviate any inflammation by providing the horse with a period of rest and to resolve any respiratory tract infection and/or inflammation that may be present.

2. Application of a tongue-tie and/or a figure-eight noseband. Both of these methods are believed to be effective because they help to counteract the caudal retractile forces that are believed to contribute to DDSP. (this was the management option opted/advised in this case)

3. Switching bits to one that aids in holding the tongue down and in place, and altering the horse’s headset.

4. A staphylectomy (trimming the palate) is a procedure in which the back edge of the soft palate is surgically altered (the scar tissue formed stiffens the back border of the palate and gives it more rigidity, thus making it more difficult for displacement to occur).

5. Myectomy (removing a section of muscle) of the sternothyrohyoideus muscles (strap muscles in the neck), which involves the removal of a portion of muscle that results in the inability to retract the larynx.

6. Epiglottic augmentation,when the epiglotic opening is abnormally small or flaccid. During this procedure, the underside of the epiglottis is injected with medical grade Teflon paste.

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