Equine head injuries — what's the prognosis? *H&H VIP*

“I thought he was dead,” recalls Kate Cook of the day she found her gelding Max lying motionless in the field. The eight- year-old had collided with a tree in a freak accident (see case study, below).

[subscriber-content] “Apparently, he had cantered headlong into an overhanging branch that flipped him over backwards,” Kate explains. “He had a wound between his eyes and blood was pouring from his nose. I touched him and he tried to stand, eventually getting to his feet.”

A bewildered Max was then coaxed to his stable and treated with painkillers and antibiotics. He was unco-ordinated and appeared blind, walking in circles and grinding his teeth. But within two weeks, he had regained his eyesight and enough strength to go back out in the field.

Six weeks later, Max was taken to Bell Equine in Kent for a CT (computed tomography) examination of his skull. The findings stunned the team.

[caption id="attachment_629893" align="aligncenter" width="630"] A CT scan of Max’s head enabled complete evaluation of his injuries. the cranium (the bony shell around the brain) should be a complete circle. However, it is irregular in shape and there are fragments of bone protruding down into the grey tissue of the brain[/caption]

“The scan identified that some of the bony shell of Max’s skull had fractured during the collision, leaving fragments embedded in his brain,” said David Sinclair MRCVS. “His recovery is nothing short of astonishing.”

Kicks and collisions “Blunt” trauma, from a collision or kick, is a typical cause of facial injury in adult horses. Foals are also at risk of being kicked or trodden on by the mare.

The most commonly injured bones include the nasal, frontal and maxillary bones, and the zygomatic process. Fortunately, horses have a large sinus arcade and extensive nasal passages that can normally tolerate a significant amount of damage without life- threatening consequences.

As is seen in Max’s case, however, injury can result in trauma to the brain and eyes. It is usually the damage to the nasal passages and paranasal sinuses that results in severe haemorrhage — although horses have a huge circulating blood volume and can survive large blood loss.

Depression fractures to the frontal and maxillary sinuses typically occur upon impact, causing a profuse but short-term nosebleed. This may lead to intermittent bleeding that can last more than a month in some cases.

If the trauma has resulted in damage to the skin, facial fractures are usually obvious. And occasionally, the offending item — such as a fence post or polo stick — may still be in place, or the fracture may be sizable with a significant skin defect. Otherwise, it is not uncommon to diagnose a fracture many weeks after the event while investigating a small but persistent nosebleed.

An unstable fragment may move when the horse breathes and if the defect is large, then it can even be possible to literally see into the horse’s head. This kind of severe trauma, with extensive bleeding, is usually not nearly as bad as it looks so try not to panic, but seek immediate veterinary attention.

When facial fractures are less obvious, diagnosis may be made by examination. Air can escape under intact skin to cause emphysema, which feels like a piece of bubble wrap popping as you run your hand over the area. And it may be possible to feel crepitus (fracture fragments) moving beneath your fingers.

Radiographs (X-rays) of the skull are often required to reveal the extent of the fracture and endoscopy (scoping) is useful for evaluating the nasal cavities, especially when a nosebleed is the presenting complaint. However, a CT scan presents a “slice by slice” picture that enables complete evaluation of the head and detailed pre-operative planning for any fracture repair.

It is also wise to examine the eyes and perform a neurological assessment to detect any further or more severe damage.

Fracture repair Initial treatment should be aimed at stabilising the horse.

Supportive care ranges from basic wound management to antibiotic therapy and analgesia (pain relief ), usually in the form of phenylbutazone (bute). In most cases, there is no need to repair the fracture immediately — a delay is often useful to allow any wounds to heal and swelling to dissipate. Further treatment will be aimed at reconstructing the bone and mending the fracture. Displaced fractures can rarely be left to heal on their own, as this typically leads to sinus infections.

Sinuses that have been traumatised and are full of blood or contamination may need lavage (flushing out) to prevent any residual infection occurring. Reduction (alignment) can then be achieved in most cases by lifting the fracture fragments and wedging them back into place like a tight-fitting jigsaw puzzle.

More often than not, the soft tissue attachments will provide adequate blood supply and the means for stabilising the fragments, but a more complicated fracture may require further treatment. If the fragments do not reduce snugly, they can be held in place by cerclage (looped) wire sutures.

A complicated fracture may also warrant the use of reconstruction plates and screws, but this increases the risk of infection and makes closure of the facial skin more difficult.

Prognosis for a full return to work is usually good, and factors that might have long-lasting effects — such as damage to the eyes, the nasolacrimal duct (tear duct), salivary duct and the brain — are normally realised before any repair is attempted.

A good cosmetic outcome is usually possible. The best prognosis is with the simplest, least invasive repair. Carbon fibre implants can be used to reshape the face where a depression in the bone has remained, but this is rarely necessary.

If wire sutures or plates, or both, have been used, the skin can remain thickened and bony swellings called nasofrontal suture exotoses can develop. These may be self-resolving or permanent and little can be done to prevent them, other than adhering to the “less is more” mantra when repairing skull fractures. evaluation of the head and detailed pre-operative planning for any fracture repair.

Case study — a survival against all odds Three months after his accident, Max shows almost no signs of neurological problems, other than some very subtle changes to his facial expression. Surgery to remove the bone fragments is not an option, however, due to difficulties with sedation and aftercare, so his future looks uncertain.

[caption id="attachment_629892" align="aligncenter" width="630"] A return to work may be possible for Max, who has started some light lungeing[/caption]

“The literature on equine cranial trauma does not document a single case of a horse surviving such damage to the skull and brain,” explains David Sinclair, “although similar cases of canine skull injury have done very well. Seizures are possible, indeed probable, and also infection of the brain (meningitis and encephalitis) owing to the fact that Max’s cranium (brain cavity) was open to the elements for a while, but we have seen neither of these.

[caption id="attachment_629891" align="aligncenter" width="630"] Max bears the scars, but is currently progressing well[/caption]

“While collapse, seizures and abnormal neurological behaviour in a dog would probably not put its owner at risk, half a ton of horse with these problems is a different matter. We cannot rule out problems, but we can mitigate risks by advising any attempt to try to return Max to some sort of working life is done very slowly, and that any activities are introduced unridden.”

Kate adds: “Max was my daughter Molly’s showjumping horse and such a talented animal, but I wouldn’t put her on him again. His previous owner wants to give him a chance, however, so he has started some light lungeing and is progressing well.”

Ref: Horse & Hound; 24 August 2017

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Equine head injuries — what’s the prognosis? H&H VIP

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