Article by Michael Mahaffey
Long a treatment option for humans with a variety of conditions, from removing tumors to correcting bad eyesight, the use of lasers has made its way to equine medicine, and veterinary surgeons are finding more ways in which to use the technology to help their patients.
Dr. Dustin Devine, DVM, MS, DACVS, an Assistant Professor of Equine Surgery at the Oklahoma State University Center for Veterinary Health Sciences in Stillwater, Okla., is at the forefront of the use of lasers in his practice, treating everything from a variety of airway disorders to tumor removal to recurring palmar foot pain issues.
“The laser has afforded us the ability to more conveniently provide treatments for conditions involving the upper airway,” Devine says, “especially conditions that once would require general anesthesia and incision. Now, we can do these things through an endoscopic guided laser.”
Laser assisted surgery provides numerous benefits for the horse—especially geriatric horses or horses that are in the middle to later part of their performance careers—such as a quicker return to performance and avoiding general anesthesia.
“It makes the procedures easier and safer for the horse,” he says.
While the laser is obviously not a cure-all for every ailment a horse may have, in Devine’s practice it is a tool of first choice in the treatment of many airway disorders and certain skin conditions.
Dealing with DDSP
Dorsal Displacement of the Soft Palate (DDSP) is a condition of the epiglottis. The epiglottis is the triangular piece of cartilage located at the base of the tongue that covers the trachea when a horse swallows and prevents food and water from entering the airway. In DDSP, the epiglottis is covered by the soft palate, a flexible area that extends from the back of the throat to the roof of the mouth or hard palate.
The soft palate is meant to be anatomically underneath the opening to the larynx and underneath the epiglottis. A horse with DDSP usually presents with a history of exercise intolerance and a history of “gurgling” or “swallowing his tongue,” as the soft palate becomes displaced up above the epiglottis during work. In this position, the soft palate has the tendency to flutter like a sail when the horse takes a breath.
“The soft palate interferes with the airway and becomes turbulent,” Devine says. “It just kind of sits there and flaps and flutters as the air moves by because it’s not in its normal position underneath the epiglottis.”
Horses will often be scoped while working on a treadmill to give veterinarians the best read on the situation.
“That’s the best diagnostic test we have to date for upper airway problems that occur during exercise,” Devine says.
For many horses with DDSP, the soft palate is too flexible, lacking the appropriate amount of stability required to keep it from shifting position with the epiglottis. A procedure called a “tie forward,” in which the larynx is elevated and brought forward relative to the soft palate, is usually a first option to treat the problem.
However, if the surgeon looks through an endoscope and determines the horse’s soft palate is excessively compliant, then treatment with the laser becomes the primary treatment option.
Using the endoscope to both visualize the area and guide the laser, the surgeon will induce fibrosis in the soft palate by scarring small, pinpoint areas of the tissue with the laser. The scarred tissue draws together more tightly to make the larger surface more rigid. Scar tissue formed by the laser stiffens the back border of the palate, giving it more rigidity and making it harder for displacement to occur.
“The theory is that if we make it firmer, the epiglottis won’t be able to flip down below the soft palate,” Devine says. “Not all horses present with soft palates that are flaccid and have increased compliance, but for the few that do, the laser is very effective.”
Once the problem has been treated with the laser, it doesn’t necessarily mean there will be no further issues with DDSP. On occasion, a tie forward procedure may have to be done as well in order to fully correct the problem.
Devine cautions that a successful surgery to treat DDSP—or any airway condition—does not guarantee that a horse will begin to perform at a higher level, just that it will be more comfortable and will be better able to perform up to its potential. A 3D horse will not suddenly become a 1D superstar. He will simply breathe better and be happier and healthier overall.
DDSP isn’t the only condition in which the normal operation of the epiglottis can be disrupted. Laryngeal tissues called aryepiglottic folds, which extend from near the vocal chords to the epiglottis, when loosely attached, can flip over and trap the epiglottis in its resting position, leading to a problem called epiglottic entrapment.
“Once it becomes entrapped, problems can arise with breathing and swallowing,” Devine says. “The horse can also develop ulcers on the epiglottis from the pressure put on it by the entrapping tissue.”
The condition causes noise when the horse breathes in and out and results in poor performance due to decreasing air intake during exercise. The horse may also develop a nasal discharge.
Epiglottic entrapment can easily be diagnosed through an endoscopic examination while the horse is resting. Treatment involves surgically removing the excess tissue that covers the epiglottis.
Devine says laser surgery is his first choice as a way to treat an epiglottic entrapment because using the endoscope-guided laser not only allows him to see what he is doing, it allows him to be more precise in how he operates.
The surgery is performed while the horse is standing under sedation. During the procedure, Devine uses the laser to cut away the excess tissue and seal the wounds in a single pass.
“I prefer to do it that way personally,” Devine says. “However, the drawbacks are it requires a laser, and it can be a little more technically demanding to do it that way.”
The traditional version of the surgery is performed using general anesthesia—which comes with its own set of risks to the horse’s health—using a curved metal blade called a bistoury that splits the membrane down the middle, releasing the epiglottis.
“You anesthetize the horse, lay the horse down and put the knife inside the mouth and basically hook the tissue that’s redundant and then excise it blindly or by feel,” Devine says of the conventional method. “Then the horse has to recover from anesthesia.”
Recovery time is typically a little faster for horses treated with the laser, with most being out of action for about a month. A follow-up procedure that involves the removal of more tissue may be necessary in some cases.
“They may re-entrap and require a little more resection,” Devine says, “but the majority of them, we get in one fell swoop.”
The reason some follow-ups are necessary is that surgeons try to be conscious not to go overboard when cutting.
“You can’t put tissue back,” Devine says.
Granulomas and Cysts
According to Devine, lasers may be the most effective means of removing growths, such as granulomas, a non-cancerous inflammation in the tissue, sub-epiglottic cysts and other excessive tissue accumulations in the upper airway.
“Anything in the airway as far as masses, growths, granulomas, cysts,” he says. “If you can get to it from the nasal passages [through an endoscope], you can get a laser to it.”
He says traditional surgery using scalpels and other tools in the larynx can be problematic because any cut from the outside of the throat into the larynx automatically becomes a contaminated incision due to the amount of bacteria in a horse’s upper respiratory tract.
“When you make a cut into the airway of any critter, you’re entering a contaminated field,” Devine says, “so they have these draining, weeping wounds underneath their throat latch that have to be cleaned and maintained daily until they heal in about 10-14 days. We don’t even close them. We leave them open to heal. They basically heal naturally without sutures or anything because they are infected incisions.”
By using the laser, Devine says these procedures, which involve either cutting out or burning away the excess tissue, cause less trauma to the horse and have a quicker healing time because you don’t have to deal with the additional wounds and problems that come with a traditional surgical incision.
“The cool thing is the laser lets you get in there and get out what you need out without having to make a big hole and do a lot of whittling and messing around with a lot of blood and tissue,” Devine says.
Guttural Pouch Tympany
Lasers are also very effective at curing a condition that affects young horses called guttural pouch tympany.
“The guttural pouches are chambers that horses have evolved to have in their head that’s equivalent to our Eustachian tubes, they connect the pharynx to the middle ear,” Devine says. “They can abnormally fill up with air and become kind of like balloons, getting tight. It’s a common thing in Quarter Horses and Arabs.”
In a horse with a normally functioning guttural pouch, air passes in and out of the guttural pouch, passing out of the area through a natural opening in the pharynx. However, in horses with guttural pouch tympany, this pharyngeal opening does not work properly, resulting in the ear canal acting like a one-way valve and causing an abnormal amount of air to build-up of air in the guttural pouch.
In most cases, the opening in the pharynx that is supposed to allow the air from the guttural pouch to be expelled is either not big enough or is simply not functioning.
Foals with this condition are often found to snore or gurgle. The may have distended nostrils or swollen cheeks, and may have trouble swallowing food, especially if both guttural pouches are obstructed.
To correct the problem, surgeons create a new opening in the pharynx adjacent to the original, malfunctioning opening the horse was born with. Devine uses the laser to make a new opening in the pharynx, so the guttural pouch can decompress.
“With this particular problem, you’re making a hole from the pharynx into the guttural pouch so the air can escape, bypassing what it is naturally there,” Devine says. “You’re leaving the normal opening alone and creating a new orifice into the pouch.”
While the natural opening is more slit-like, the opening a surgeon like Devine will make is circular and about 1 cm in diameter. The newly created opening will seal up and close if a catheter isn’t maintained in the hole for a week to 10 days, necessitating another surgery.
There is no permanent disfigurement or damage to the pharynx from using the laser, and most horses outgrow the problem by the time they are late weanlings to early yearlings.
Michael Mahaffey is associate editor of Barrel Horse News. E-mail comments on this article to [email protected].