Answered by, Kirstin Bubeck, DVM, Tufts University Cummings School of Veterinary Medicine
Question: What would you do with a horse that suffers from palatal instability at exercise but also has crico-tracheal membrane collapse – the whole circumference collapses inwards on dynamic endoscopy giving the appearance of a sphincter behind the larynx?
Answer: The symptom you are describing is seen very rarely and only during high speed exercise. Therefore, it is very important to perform an endoscopy during exercise in some horses as your veterinarian has done. Most likely the sphincter-like prolapse of the crico-tracheal membrane is caused by strong negative pressures within the upper airway due to the palatal (soft palate) instability you are describing. If your horse is a two year old, we normally suggest waiting with racing for one more year. A lot of horses can improve during this extra year of additional training.
Other underlying problems can be muscle tissue disorders, and I would suggest to test the horse for Equine Protozoal Myeloencephalitis (EPM), Vitamin E deficiency, and in the case your horse is a Quarter Horse for the possibility of Hyperkalemic Periodic Paralysis (HYPP).
In case your horse is in good training condition, and the pharyngeal instability is causing dorsal displacement of the soft palate without strong signs of pharyngeal collapse, I would treat it with a tie-forward procedure. If the crico-tracheal membrane continues to prolapse, a surgical imbrication (shortening) of this membrane has been described.
More often a syndrome called axial deviation of the aryepiglottic folds is noted on dynamic endoscopy. These collapsing folds can cause a sphincter like appearance just before (rostral) the larynx. The treatment would be excision of the collapsing tissue with a laser.
Question: Has there been any advancement in the cause, treatment, and prevention of upper airway cicatrix of horses?
Answer: Nasopharyngeal cicatrix syndrome is mostly seen in horses in the south of the United States. During the acute phase, signs of severe inflammation of the upper respiratory tract are seen on endoscopy. In more chronic cases, web-like scar tissue and deformation of the upper airway structures can occur and lead to different grades of respiratory tract obstruction. In patients with strong respiratory distress, permanent tracheostomy (a permanent opening into the wind pipe) is at this time the treatment of choice.
To date, the cause for nasopharyngeal cicatrix syndrome is unknown. Due to the clinical signs and endoscopic findings, inhalation of a direct irritant, allergen or bacteria/virus is thought to be the cause for this disease, but this theory could not be confirmed to this date. A study published in 2013 by a group at Texas A&M, found that horses presented with this disease were turned out on pasture and the disease was found in a higher rate within summer months. They concluded that the possible irritant agent is most likely not airborne and most likely on pasture. Further research will be needed to further investigate the cause for this disease.