Of all the injuries your horse may sustain over the course of his life, serious head trauma is one of the least likely. Yet more than a few of us have witnessed a fast-moving horse unexpectedly collide head-on with a tree or other obstacle. And there are those who wince at the remembrance of a rearing horse falling over backward and striking his head on an unforgiving stable aisle. Perhaps the susceptibility of our own brains to concussion heightens our concern for the well-being of any horse who accidentally whacks his head--or worse.
In most instances, the design of the equine skull provides ample protection for the brain so that even extensive damage to the bony capsule leaves the gray matter unscathed. This knowledge may be small consolation, however, when your horse staggers in from the pasture bearing evidence of a herdmate's forceful kick to the face.
An understanding of the anatomy of the equine head as well as an awareness of the signs indicative of superficial to serious trauma will help guide you in your initial handling of a horse with a head injury while also preparing you to talk with your veterinarian about the specific diagnosis, treatment options and prognosis for recovery.
A Basis for Assessment
The equine cranium is a complex series of 16 broad, thin, interlocking bones connected at immobile joints called sutures. The majority of a horse's skull--about three-quarters--encloses and protects the long nasal passages as well as the teeth and mouth; smaller areas encase the eyes and the structures of the inner ear. The brain is contained in a compact space within a series of six bones, called the calvarium or brain box. An almost circular opening in the base of the box accommodates the spinal cord.
In addition to giving the face its substance and structure, the long expanse of the equine skull serves the same protective purpose as the "crumple zone" on a car, absorbing the impact of a collision before the force can reach the brain and do it harm. The design works so well that many veterinarians never will encounter a horse with a true brain injury in the course of their careers. As a horse owner, you're even less likely to see one.
What you may encounter is a routine head injury of some sort, and the sight can be alarming. With its extensive vascular network, the head bleeds easily and copiously so that even a relatively minor wound can look quite serious. But, given proper attention, even badly marred facial flesh and bone will mend over time, in part because of the abundant local circulation.
Unless an injury directly affects the brain, the prognosis for a full recovery typically is very good. Determining whether a blow to the head has affected the brain can be tricky, however, because the look of a wound alone doesn't supply sufficient evidence of its severity. When evaluating any trauma to the head, it's also essential to consider how the horse is behaving.
If you see your horse hit his head or suspect he has, approach and examine him carefully, asking yourself the following questions. The answers may put some of your fears to rest while helping to organize your thoughts for the call to the veterinarian.
1. Can he rise? Don't force a horse with a head injury to get up. Simply watch to see if he attempts it. A horse who rises quickly and stands normally and steadily probably is not suffering from neurological trauma. A horse who is dazed may lie still until he gets his bearings, then he'll slowly but successfully rise. In contrast, a horse with a serious head injury may panic as he attempts to stand and fails. He also may move his head and legs aimlessly or convulsively.
2. Can he see? A horse who follows you with his eyes or reacts when you wave a hand near his face most likely can see, which is an important indication of brain function.
3. Can he walk? Don't force an injured horse to walk. Take stock of his general condition while he's standing still then encourage him to follow you. It's good news if he's able to move in a coordinated fashion. If, however, he refuses to move, check for a mechanical injury, such as fractured withers, that may make walking painful. Suspect neurological trauma if he tries to move and cannot seem to position his legs properly or he collapses.
4. How does he seem to feel? Although subjective, your assessment of your horse's overall demeanor offers valuable insight into his level of awareness and mental function. For instance, a horse who is acting relatively "normal"--taking into account that he's injured--is less likely to have suffered brain trauma than one who is behaving in a completely unexpected manner. An abnormally lethargic horse who does not respond to stimulation is just as worrisome as one who appears panicked and overreactive.
The signs of brain injury usually are immediately apparent, so what you see during your initial assessment will tell you a great deal about your horse's condition. Call your veterinarian, convey the details of the situation and have him come to evaluate your horse.
Diagnosis, Prognosis, Course of Care
During a detailed neurological examination, your veterinarian will determine the extent of brain trauma by focusing both on the physical evidence of injury and on behavioral clues. A dozen pairs of cranial nerves keep the brain informed of developments affecting the senses and muscles of the head. Three pairs of nerves--the optic, olfactory and auditory--serve as couriers of sight, smell and hearing. Five other pairs are responsible for moving the eyes, ears, tongue, jaws and skin.
Damage to the nerves or the brain interferes with the structures' ability to transmit and process information, and the degree of any deficit will reflect the scope and severity of injury. For instance, a horse who is shying and bumping into things may have injured his optic nerve and his eyesight is impaired. To investigate whether that's the case, a veterinarian will test the animal's menace response to see whether he blinks or is startled when a hand is waved in front of his eyes. The practitioner also will evaluate a horse's pupils to gauge their reactivity to light. A pupil that fails to contract may signal damage to that side of the brain or the optic nerve.
Equally telling is a horse's ability to stand and move. Your veterinarian will pay close attention to any missteps or stumbles indicative of damage to the vestibular system, which controls balance. He also will check to see whether there is a peculiar tilt to your horse's head--another sign of vestibular impairment. When a head injury affects the cerebrum--the front part of the brain that directs motor function--a horse may walk compulsively, sometimes in circles; his direction usually points to the location of the injury.
Equine brain traumas fall into three major categories that take into account the severity of the injury, the likely course of veterinary treatment and the role you can expect to play in a horse's recovery.
1. No lasting damage. The first type of brain trauma is a loss of consciousness with no structural damage to the brain. Commonly called a concussion, this injury occurs when a horse bangs his head hard enough against a solid object, such as a barn wall, that the force of the impact causes the brain to suspend its function for a time. The altered consciousness might be so quick and slight that you never notice it, even if you witness the accident, or a horse may be out cold for many minutes before coming to. Generally, a horse with a concussion will be slightly depressed and even dazed for a while following the incident. But he'll usually show no functional neurological deficit once he is fully conscious, and his recovery will be remarkably quick.
Your veterinarian likely will prescribe Banamine, phenylbutazone or another nonsteroidal anti-inflammatory drug for three to five days to make your horse comfortable as he recovers. Your role will be one of watchful vigilance. Keep your horse in a large, quiet space and make no demands of him. Watch carefully for signs of improvement, and consider taking notes on various aspects of his behavior, such as eating, lying down and even showing an interest in you or other animals.
Horses destined for a full recovery exhibit dramatic improvement in attitude and outlook within 24 hours. Even so, your veterinarian probably will recommend a week or two of rest to be on the safe side. If at any point you believe that your horse's condition is declining, call your veterinarian immediately.
2. Serious but possibly survivable. A more serious head injury occurs when the force of impact is strong enough to rupture blood vessels, leading to bruising--edema and hemorrhage--in the brain. Bleeding is always accompanied by swelling, and this is particularly serious when the brain is the site of injury. Confined within the brain box, it has little room to swell, so it quickly experiences the harmful effects of escalating pressure. At the same time, damaged nerve tissues release a rush of neurotransmitters that trigger destructive chemical processes in the brain cells, increasing the damage and swelling. Uncontrolled brain bleeding and swelling can be fatal within minutes to a few hours.
Injuries that lead to brain swelling most often occur when a horse flips over backward while rearing and strikes his head with great force on a concrete aisleway. From a fully upright rearing position, his head, which probably weighs close to 40 pounds, accelerates during the 10- to 12-foot fall to the ground. Similarly, a brain hemorrhage may occur if a horse rears and slams his head into a ceiling beam in the barn. Incidentally, a horse is much less likely to sustain a serious head injury by rearing in a trailer because most trailer ceilings have enough give to soften impact. The worst that is likely to happen is that the horse will suffer a mild concussion.
A horse with a brain hemorrhage usually shows obvious neurological deficits as a result of both the initial injury and the subsequent bleeding. The deficits may become worse as the brain continues to bleed and pressure builds. Changes in the horse's coordination and demeanor will provide insight into the rate at which his condition is progressing, so convey the details of your initial assessment to your veterinarian.
To treat a horse's brain hemorrhage, a veterinarian will concentrate his efforts first and foremost on controlling the swelling. He'll administer intramuscular and intravenous drugs, such as DMSO and mannitol, which removes excess fluid from the brain. He'll also likely give intravenous fluid to keep the horse's blood pressure up, optimizing circulation to the brain. He may or may not choose to use steroids because the practice of treating people's head injuries with high doses of steroids recently has come into question.
Once anti-inflammatory drugs have been given and your horse is stable, your veterinarian likely will turn over care to you. There isn't, however, much to do beyond continuing the medication, watching the horse closely and keeping your veterinarian informed.
Within a couple of days, a brain-injured horse with a good chance of recovery will regain much of the neurological function that he's likely to. Some of the deficits that remain after a few days may be permanent, and you may be faced with the task of making some difficult decisions about your horse's future, depending on the extent of his impairment. For instance, if any of his persistent deficits involve coordination, balance or movement, he no longer will be safe to ride. Deaf horses and even some who are blind can be ridden in a familiar environment, but a horse who is not sure of where his legs are at every moment is unfit to carry a rider, and it would be foolhardy to climb onto his back.
Along the same lines, a horse whose personality has drastically changed--he's far more excitable or periodically "zones out" and seems to be unaware of anyone or anything in his surroundings--can never be considered safe under saddle. Of course, any horse can be moody or inattentive, but one who is that way after a brain injury isn't likely to respond to the usual corrections for such behaviors.
A horse with a minor neurological deficit can be kept in a pasture with one or two quiet companions. Depending on the extent of his impairment, he may be a perfect babysitter for a weanling or a good buddy for a horse convalescing from an injury. Continuous turnout in a safe, open space is a better option than confinement in a small stall that he'll have to enter and exit.
3. Beyond repair or recovery. By far the worst sort of head injury occurs when the skull fractures and bone lacerates brain tissue. Many horses who suffer such severe head trauma go down instantly and never rise and, in some respects, they are the lucky ones.
The bones of the skull can break from direct trauma with varying consequences. For instance, a horse who rears and flips over, landing on his pelvis first, may twist his body in a way that causes his poll to strike the ground at an angle. The resulting damage may not be to the brain but to the bones on the side of the head that house the vestibular system, the balance apparatus. More than half of such injuries are fatal, yet about 25 percent of horses recover completely.
In other instances, hyperextended muscles and ligaments can pull apart or fracture the most fragile bones of the skull. There are rare cases where horses who have gotten their heads stuck in fences have pulled back so quickly and forcefully that they fractured or dislocated the occipital bone connecting the skull to the spine. The injury causes the brain stem to detach from the brain, and death comes within minutes.
It is possible to surgically repair some skull fractures, and many nonmobile bones heal in a surprisingly short time, but damage to the brain can't be undone. A university or referral clinic may offer the option of high-tech diagnostics, such as a computed tomography (CT) scan to locate fractures or magnetic resonance imaging (MRI) to examine the brain itself.
In nearly every case, however, all that can be done is to control pain and swelling, keep a constant watch for at least 36 hours and be prepared to make the ultimate decision if it becomes obvious that euthanasia is the most humane choice.
Fortunately, most of us will never have to deal with a horse who has suffered a brain trauma. We may, however, have ample opportunity to witness firsthand the protection that the equine skull inherently provides. It's always going to be alarming to see a horse hit his head during a harrowing spill. But knowing the trouble signs to look for and the appropriate action to take can help you keep a cool head when you're confronted with a horse who may have injured his own.
EQUUS thanks Robert J. MacKay, BVSc, PhD, professor and chief of large animal medicine at the University of Florida, and Stephen Reed, DVM, Jenne Professor and head of equine medicine and surgery at Ohio State University, for their assistance with this article.
This article first appeared in the May 2005 issue of EQUUS magazine.