While these tumors may be rare, it’s important to recognize warning signs when they do occur.

If you’re a horse lover who listens to National Public Radio, you might have enjoyed a segment in the fall of 2006 about a race horse named Precisionist.

The 26-year-old American Hall of Fame Thoroughbred earned an Eclipse Award as a champion sprinter, was also a distance runner, and accumulated almost $3.5 million in winnings throughout his career. The focus on Precisionist in the NPR piece was part of a larger story about Old Friends, a non-profit retirement community for thoroughbreds near Georgetown, Ky., where champions are honored, loved and cared for until their deaths.

In the climax of the piece, a now 29-year-old veterinarian named Holly Aldinger administers the injections that end Precisionist’s life. The reporter of the story observes Aldinger tenderly kissing the animal after she pushes in the plunger, but the story behind the animal’s death, indeed, the very reason for Precisionist’s euthanization, is left unexplored.

Don’t blame NPR. After all, the normal listening audience couldn’t care less about equine sinus issues, much less the fact that Precisionist’s death was due to an inoperable tumor in his sinus cavities. (The reporter did report that fact later.)

And it’s not exactly a condition that affects an inordinate number of horses. Tumors in equines are thankfully rare, and most large veterinary practices may only see one or two horses a year with sinus tumors, though other conditions such as sinusitis and cysts in the sinus cavities occur with a bit more regularity.

“In the grand scheme of horse health issues, sinus problems are not high on the list,” said Shauna Spurlock of Spurlock Equine Associates in Lovettsville, Va.

The surgery practice she runs with her husband, Gary Spurlock, has about 3,000 equine patients in its database, and a good number of them are active cases.

“It’s an interesting topic that most people don’t want to deal with,” Spurlock added, “but, it’s a really big issue for anyone that’s had a problem with them.”

Though sinus problems may occur randomly and less commonly than say, joint issues, they’re still a big enough health concern to warrant attention, as many people are unfamiliar with symptoms of sinus disorders and potential treatments.

In Precisionist’s case, Aldinger wasn’t even sure what she was dealing with right away.

She was called to Old Friends because the elderly stallion had a foul odor coming from his mouth. An examination with a speculum revealed a pocket on one of his teeth that looked like it could be harboring infection, and a round of antibiotics took the smell away.

When the smell came back, Aldinger took a skull radiograph, which looked fairly normal. But bleeding from the horse’s nose made her suspect that Precisionist had guttural pouch mycosis, a fungal infection that occurs in part of the canal that connects the throat cavity to the inner ear. The infection can erode the nearby internal carotid artery, the main supplier of blood to a horse’s brain.

“I had difficulty getting the scope through his nasal canal,” Aldinger recalled. “It turned out there was a mass in there, and the nasal septum had deviated. We took a biopsy and it came back as squamous cell carcinoma.”

A malignant tumor, squamous cell carcinoma is one of the most common equine tumors, and treatment is generally unsuccessful. Younger horses sometimes respond to radiation or chemotherapy, Aldinger said, but it would have been too hard on the old race horse.

A tracheotomy kept Precisionist comfortable for a few more days, but Aldinger ultimately put the horse down on Sept. 27, 2006.

Potential Complications

Equine sinuses are unique machinery. The cavities are located between the eyes and the bridge of the nose, and they stretch from the top of the face all the way down to the roots of the teeth. Combined, the compartments could hold a full liter of fluid, said David Freeman, a surgeon and researcher at the University of Florida College of Veterinary Medicine.

“The sinuses are so big that it’s easy for something small in there to grow into something big,” Freeman said. “The best way to deal with these and bring about successful treatment is early diagnosis.”

Persistent nasal discharge from one nostril frequently indicates a problem in the sinuses.

“Nature has given horses pretty good defenses,” said Gary Spurlock. “Snot is a mucous secretion the body makes to carry bacteria out of those sinuses, and horses are pretty effective at it. Every once in a while, though, they need help, and we can facilitate that by flushing the sinuses out with a sterile solution.”

If the discharge persists, commonly the issue inside is sinusitis, which is caused by either an inflammation or infection in the sinus, or from a tooth infection or facial fracture. Left untreated, a blocked sinus can cause so much swelling inside the head to eventually deform a horse’s face.

“Often, sinusitis, or an infected sinus, is caused from infected teeth,” said Jose Garcia-Lopez, an assistant professor in the department of clinical sciences at the Cummings School of Veterinary Medicine at Tufts University in Massachusetts. He performs about 20 sinus surgeries a year.

“Because horses’ tooth roots are in their sinuses, you can get a tooth root abscess, but it’s usually an older horse condition that happens in horses older than 7,” said Garcia-Lopez.

Diagnosing the problem requires an X-ray of the head, and Garcia-Lopez said it’s frustrating for some owners because even horses with a history of clean dental exams can be afflicted with sudden tooth root infections.

Even a simple crack in tooth can cause these, and the characteristically foul odor that accompanies the infection is usually strong enough for other people in the barn to notice.

“The bread and butter of sinus problems we see are, in order of frequency: sinusitis, sinus cysts and tumors of no known origin,” added Garcia-Lopez.

Largely A Mystery

As far as cysts and tumors are concerned, nobody knows what causes them to grow in some horses’ sinuses, though the former is usually more treatable.

Garcia-Lopez said the cysts can be a growth with a bony core, or they can be like an eggshell filled with mucus.

“A film [X-ray] of the head will show what looks like a big egg,” he said.

Back in Virginia, Gary Spurlock said the cysts they’ve treated have occurred mostly in young horses and seem to be a congenital condition affecting yearlings and 2-year-olds. It’s the older horses, he said, where you see the tumors.

Another tumor-like mass that, for unknown reasons, can grow in a horse’s sinuses is ethmoid hematomas.

The condition usually originates from bleeding in the horse’s sinuses, and an endoscopy is needed to diagnose the problem.

According to some literature, ethmoid hematomas occur more commonly in Thoroughbreds, warmbloods and Arabians. Freeman, however, said he hasn’t seen a pattern based on breed or discipline.

“Ethmoid hematomas can be surgically removed, but the most successful treatment appears to be a formalin injection right into the hematoma,” Freeman said.

The procedure is performed on a sedated horse and is usually accomplished with a needle-like instrument attached to the end of an endoscope. If removed through surgery, ethmoid hematomas often grow back.

Worst-Case Scenario

Sinus tumors, or the condition that afflicted Precisionist, are one of the most severe and problematic upper respiratory issues a horse can contract, and most veterinarians agree it’s fortunate that the condition is fairly rare.

“Sinus tumors are difficult to deal with and come with a high mortality,” Freeman said. “We see them in a wide variety of horses, and by the time diagnosis is made, there’s little you can do for them, though some can be treated surgically or with radiation.”

As in Precisionist’s case, squamous cell carcinoma is the most common tumor to occur in the equine sinus (in humans, squamous cell carcinoma is the second most common form of skin cancer). According to Freeman, the tumors usually invade a large portion of the sinuses and are difficult to remove because they can infiltrate both bone and soft tissue.

“They’re also sporadic and don’t appear to have any predisposing cause,” Freeman said.

As far as early detection is concerned, the good news is that almost all sinus issues start with some kind of discharge from one nostril, making it easier for the observant owner to notice that something  might be wrong. Further diagnosis is accomplished through radiographs, which can reveal masses or fluid lines, an endoscopy or sometimes a CT scan or MRI.

Sinus surgeries, when necessary, are fairly major and involve the removal of the bone flap above the sinus, after which the surgeon can get a better look at what’s inside.

“The sinuses have thin shells of bone over them, and you peel that back to see what’s there, whether it’s a tumor or cyst,” said Shauna Spurlock. “Because horses’ heads are very vascular, they like to bleed a lot, and you have to have a blood donor available just in case.”

Afterward, Spurlock said, the patient ends up “looking a bit like a prize fighter who just lost a fight,” but Gary Spurlock added that the horses usually end up healing well cosmetically after the swelling subsides.

If a tooth is causing the infection, the Spurlocks carefully consider the options and the owner’s commitment to the animal, as removing a tooth can lead to other health problems inside the mouth even if it solves the sinus infection.

“If you’re going to remove a tooth, you need to make sure the owner is committed to being attentive to that horse’s needs for the rest of its life,” said Shauna Spurlock.

Teeth and sinus issues sort of go hand-in-hand, but an overall pattern for sinus infections and sinus tumors is still elusive, Spurlock added.

She said simply: “It’s just sort of bad luck.”