Dynamic Endoscopy Examinations
Dorsal Displacement of the Soft Palate
Is your horse fading in the last furlong? You may like to consider that the horse has a breathing problem. Respiratory dysfunction is second only to musculoskeletal injuries as a cause of poor performance in racehorses. In most cases, veterinary attention is required to accurately diagnose and effectively manage these issues.
Dorsal displacement of the soft palate (DDSP) is one of the more common physical causes of dynamic respiratory problems. The soft palate is a soft tissue structure that separates the oral cavity from the respiratory passages. In normal horses, the soft palate is displaced dorsally (upward) to facilitate swallowing food and water; however, in some horses, the soft palate moves dorsally during intense exercise and obstructs the respiratory passages. This condition is commonly referred to as “choking up”, “gurgling”, or “swallowing the tongue”. When the soft palate becomes abnormally positioned during exercise, the animal is unable to breathe sufficiently and therefore will slow down or even stop due to lack of oxygen getting to the muscles.
On-board endoscopy. A video is taken of the upper respiratory tract while the horse is undergoing fast work.
DDSP can be diagnosed using resting endoscopy, however, due to the dynamic nature of the condition; many horses will require treadmill or on-board endoscopy to make a definitive diagnosis. On-board endoscopy or Dynamic Respiratory Endoscopy (DRS) can be done by a veterinarian during routine track work. Normal racing pressures can be applied to the animal in order to trigger their breathing problem when undergoing this examination. Dynamic scoping will also allow your veterinarian to differentiate from other upper respiratory tract causes such as roaring (left-laryngeal hemiplegia) and epiglottis issues.
A horse with a displaced soft palate (as seen on endoscopy) A normal Larynx (as seen on endoscopy)
The cause of DDSP is unknown and probably related to a number of issues including the physical size and shape of the larynx and pharynx and the neuromuscular control of the pharyngeal stabilising muscles.
The use of a tongue-tie and figure-of-eight nosebands to keep the tongue under the bit and prevent oral breathing is often tried and are sometimes helpful in preventing DDSP. Young horses, especially 2-year-olds, suffering from lymphoid hyperplasia (throat inflammation) may benefit from a brief spell and or anti-inflammatory medication prior to considering more invasive treatment methods.
Several surgical treatments exist for correcting DDSP. The current gold-standard treatment for a horse with DDSP is the Tie-Forward surgical procedure. This surgery helps position the larynx so that it prevents displacement of the soft palate during exercise. Good success rate is seen with this procedure with horses requiring approximately a 3 to 4-week layoff prior to re-commencing work.
Tie-forward: A prosthetic implant is used to re-position the larynx
In summary, DDSP is a common cause of upper respiratory tract noise and decreased performance in racehorses. In selected cases, this condition can be treated effectively with surgical intervention.