Catherine Lawton sensed that something was amiss last autumn when her otherwise healthy 14-year-old gelding Eric suffered a few minor nosebleeds. Endoscopy revealed an ethmoid haematoma, a solid build-up of blood and mucus in a sinus compartment.

“The mass was quite difficult to get to, but my vet suggested a series of formalin injections to try to break it down,” says Catherine. “Eric coped well with the injections, although sometimes blood and mucus would come out of a nostril, which needed cleaning up.”

In spring, Eric underwent a computed tomography (CT) scan to check the size of the mass.

“The haematoma was not responding well to treatment,” explains Catherine.

“It was decided that the best option was to treat it through a trephine site [a hole made in the skull] with multiple formalin injections. Eric came home with a big plaster on his head, but when it came to re-dressing the site I nearly fainted. The hole was the size of a £2 coin and you could see inside the skull and the haematoma itself!

“A further attempt to eradicate the mass by laser removed only 40% of it and unfortunately the dexamethasone he was given for the swelling at the trephine site triggered steroid laminitis.

Treatment has been on the back-burner, but the lameness is now under control.

“We hope that the haematoma is growing slowly, otherwise we may consider more injections through the trephine site.”

Identifying the mass
Ethmoid haematomas are thankfully relatively rare. While it can affect horses of any age, most cases have been seen in middle-aged (around 10 years old) thoroughbreds.

The most common clinical sign is that of mild, intermittent blood trickling out of one nostril only. This can be accompanied by an abnormal respiratory noise, especially if the haematoma is large and is occupying a substantial part of the nose.

In really severe cases, the haematoma can start to deform the horse’s skull. This causes swelling of the head, which can be painful and may result in head shaking, head shyness or any behaviour associated with a horse having a headache.

Occasionally, in cases of fast-growing or long-standing disease, the haematoma may actually grow so large that it appears at the nostril.

The quickest and easiest way to diagnose the problem is for the vet to perform an endoscopy examination, which is when a flexible camera is passed up the horse’s nose to visualise the nasal cavities and upper airway. Not all ethmoid haematomas can be seen, however, so additional diagnostic imaging such as X-rays may highlight an opacity consistent with the condition.

The most accurate diagnostic method is a CT scan of the horse’s head. It is highly likely that any soft tissue mass in the region of the ethmoid turbinates is a haematoma, but other possibilities include abscesses, sinus cysts or – very rarely – tumours.

Shrink or burn?
The progressive nature of an ethmoid haematoma means that it will keep on growing, making treatment a necessity. The three main options are all aimed at removing the mass and destroying its origin.

A relatively cheap and risk-free option is intra-lesional injection of the mass with formalin. This substance destroys the mass so that it gradually shrinks in size. The formalin is injected via a needle attached to a catheter, which is fed down the working channel of an endoscope.

While this method is minimally invasive and can be carried out on an outpatient basis, the treatment must be repeated – usually every 3-4 weeks until the mass has been resolved. Up to 18 treatments have been required in some cases, but most cases resolve with between three and five injections.

An alternative treatment is laser ablation, which is also performed via an endoscope and is recommended for small haematomas measuring less than 5cm in diameter.

The laser is used to “burn” the haematoma until the all of the tissue has been destroyed. Treatment usually has to be repeated and is checked at seven-day intervals.

Surgical options
Surgical removal (resection) of the mass is carried out under standing sedation. There are a number of different ways in which the mass can be approached, depending on its size and exact location.

Essentially, a hole must be created in the horse’s skull to access the sinuses and the mass. This can be a small hole, a larger trephine hole or a large, hinged bone flap.

The large trephine or flap is my preference, so that the entire mass can be dissected out and removed completely. Smaller trephines, as in Eric’s case, however, are ideal if access to the base of the haematoma is all that is required.

Surgical resection can cure the problem in one fell swoop, but there are some risks to consider. Bleeding is a genuine danger and can occasionally be severe. It is always sensible to have access to edonor blood in case a transfusion is required, even if this is very unlikely.

Dehiscence, or splitting, of the surgical incision and the trephine hole is also a potential risk, as is failure of the trephine hole to fill in. Unfortunately, there is nothing that can be done to predict that this might occur, or indeed do anything to reduce the chance of it happening.

It would appear that sometimes the bone is reactive and swells following surgery and then just fails to heal up. Thankfully, this is very rare.

The prognosis is poor if an ethmoid haematoma is left to grow unchecked, but the chances of recovery are good with appropriate care.

Eric’s case highlights the fact that a combination of treatments may be necessary to successfully eradicate the encapsulated mass in its entirety.

Multiple treatments are often necessary and recurrence is relatively common (in up to 43% of cases). Regular endoscopic checks are a good idea so that any re-growth can be detected and dealt with promptly.

This article was first published in Horse & Hound magazine (2 October 2014)