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Equine Skull
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Smarty Jones
As the trainer encouraged the colt to step into the starting gate the young chestnut racehorse suddenly reared up and slammed his head on an unpadded iron bar.
As if in slow motion, the colt's legs buckled beneath him, his head swung down between his front legs and he collapsed forward. The sun shone down on the glossy and motionless shoulders of the horse as a widening pool of blood darkened the track around him. The colt known as Quasimodo survived his devastating injuries in the hands of veterinarian Patricia Hogan. "We knew by looking at the x-rays that the skull was in too many pieces to count but other than an eye that had been jarred back behind the sinus, there weren't many visible signs of damage," Dr. Hogan declared. "Within hours, though, the entire head was swollen to horrific proportions and all we could do was wrap him in huge white padded wraps, medicate him and hope for the best."
Fortunately very few horses ever suffer head pain to the extent that Quasimodo did, but Robert Cook, FRCVS, PhD, Professor of Surgery Emeritus of Tufts University, Massachusetts, suspects that head pain is the root cause of what many consider to be behavioral or performance problems in many horses.
If you suspect your horse suffers from head pain, Dr. Cook suggests a physical evaluation of the horse's skull and soft tissues to further pinpoint the source of the problem. "It is important to provide for your veterinarian a thorough description of the symptoms and behaviors that indicate a problem," says Dr. Cook.
Begin by evaluating the structure of the head for symmetry. Expose the incisors by simply lifting the lips but not shifting the jaws to determine the placement of the lower jaw in conjunction with the skull. Visually inspect the head from the front for unevenness in the ears. Compare the lateral sides of the head for placement of the cheekbones. Palpate the bony structures of the skull and poll, watching for areas that are soft, have protuberances, feel hot to the touch, or areas that stimulate a reaction in your horse when they are compressed. Look at and apply pressure to the temporalis (forehead) and masseter (cheek) muscles to establish if these are asymmetrical or show sensitivity. The hyoid apparatus and inside chewing muscles (pterygoids -- opposite the masseters) should also be checked. Standing in front of your horse reach back to the ears and apply pressure on both sides of the temporomandibular joint (TMJ). Anatomically, the TMJ refers to the area of the cranium where the jaw (the mandible), contacts and articulates with the temporal bone. The temporal bone is the area of the skull where the ear resides (see Diagram A). Examine the ears and the lower jaw for unevenness or tenderness.
"In addition to physical manifestations of head problems, a host of other symptoms contribute to identifying discomfort or disease in the skeletal, muscular or dental structures of the head," clarifies Dr. Cook. Other symptoms to watch for include head shaking, swelling of the throat or the hollow between the lateral sides of the jaw bone, biting problems, ear sensitivity, drainage from the eyes, ears or nostrils, foul breath, vertigo, loss of 'bloom' to the coat and behavioral isDental issues are frequently to blame for head pain in horses. According to Spencer LaFlure, Orthodontic EqD, the structure of a horse's teeth and lower mandible are configured with the lower set of teeth slightly more narrow and offset from those on the top. This arrangement allows for efficient grinding of the feed but also creates the opportunity for the edges of some teeth to be unused in the process. Because a horse's teeth continue to grow throughout his lifetime to allow for this grinding action, the unworn edges of some teeth form enamel projections often referred to as points or ramps. "To compensate for the poor function of these teeth, horses often develop an even more exaggerated chewing motion that results in strain to the muscles and joints in the head," explains LaFlure. "The points also often create abrasions where they contact the tongue or the inside of the horse's cheek." Prompt annual dental exams are recommended to forego this common cause of head pain.
TEMPOROMANDIBULAR JOINT DISEASE
Temporomandibular Joint Disease, or TMD, is a term often used in conjunction with discussions of dentistry. Dr. Dwight Bennet, DVM, describes TMD as the general diagnosis to describe dysfunction and pain of the TMJ. Misalignment of the jaw itself, often the result of inadequate dental care, causes wear damage to the cartilage that makes up the articular disc. This disc is responsible for the correct function of the singular but critical joint in the horse's head. "To alleviate the pain of TMD it is important to address dental issues but also to treat and correct the resulting soreness in the soft structures of the head," says Dr. Bennet. Massage therapy is a tool often used to relax the constricted muscles, tendons and ligaments that support the TMJ. Myofascial or craniosacral therapies work directly on the structures of the head to realign the bony structures and break up strictures in the muscle tissues. Closely monitoring your horse for dental issues or other mouth or facial injuries that may create an irregular chewing motion can allow medical professionals to intercede and correct problems before TMD becomes a chronic affliction.
SYSTEMIC INFECTIONS
Systemic infections and diseases of the head are less common than structural maladies but typically create more pronounced symptoms and are often more pernicious. The horse's moveable upright ear requires the inclusion of a guttural pouch as part of their audile and intranasal configuration. Eustachian tubes serve the vital function of regulating the pressure on the eardrums and (unique to equines) are attached guttural pouches that trap and detain bacteria and debris before it reaches the inner ear. The objective of the guttural pouches makes them vulnerable to disease as a result of the very bacteria they detain.
Dr. Kim Sprayberry, DVM, and staff member of the American Veterinary Medical Association explains that the infection of the guttural pouch is described as one of three disorders. Guttural Pouch Tympany involves damage or infection of the pharyngeal opening, allowing air into the pouch but not allowing it to escape, causing distention of the pouch. Guttural Pouch Empyema is a bacterial infection that pools in the bottom of the pouches creating a cottage cheese-like substance called Chondroids that cannot be flushed out through the tubes. Guttural Pouch Mycosis is a fungal infection of the wall of the pouch itself and is by far the most difficult to resolve.
PAIN IN THE NECK
It is important to consider that some of the same symptoms that are indicative of pain within the head can reflect dysfunction in the poll area or the neck. Although symptoms are somewhat ambiguous from the muzzle to the withers, veterinary examination can typically pinpoint the source of your horse's discontent. Occasionally a headache is simply a pain in the neck.
A horse's neck is comprised of seven vertebrae (see diagram B). Above and below the vertebrae are large muscles responsible for neck and head movement along with forward movement of the forelimbs. The crest region is formed by the nuchal ligament, which attaches to the occipital bone on the back of the head and runs along the top of the neck to the withers. The nuchal ligament then forms a hood across the area of the withers and continues down the entire length of the spine as the supraspinous ligament. Because the top line of the horse is somewhat of a 'suspension bridge' construction, it is easy to see why neck pain has a negative effect on the entire mechanism and therefore the entire horse.
According to Gerd Heuschmann, DVM, the poll offers but a single safety feature to protect the vital nuchal ligament in the region of the poll. The Atlantal Bursa is a small fluid-filled pouch that works as a shock absorber for the ligament as it attaches to the occipital bone. Traumatic injury to this area is very common but often erroneously overlooked as 'just a bump on the head.' Bruising of the bursa can cause infection and necrosis of the tissue, too often resulting in the rupture of the pouch. This condition is still known by its colloquial name Poll Evil because of the unpleasant behavior displayed by horses suffering from this condition and the complexities of its treatment.
The neck itself between the poll and the withers is typically free of chronic ailments and systemic illness, although it frequently falls victim to traumatic injury or repetitive stress pain. The muscle most commonly affected is the brachiocephalicus, which runs along both sides of the neck from the forelimb to the back of the head. Damage to one of these muscles can result in lameness, whereas most neck injuries cause stiffness and possibly a restricted forelimb gait.
Other signs of neck pain include the horse standing with its neck in an unusually low position and being reluctant to move the head and neck through the full range of normal movement. If there is pain at the base of the neck, the horse may straddle its forelimbs to eat off the ground.
Identifying and treating dysfunctions of the head and neck can bring real rewards to the owner of any horse who suffers from these maladies. Improved performance, resolution of behavioral issues and enhanced physical conditioning as well as knowing your horse feels his best are among these rewards.
Quasimodo, who is registered with the jockey club as Smarty Jones, recovered fully from his injuries. Having earned $7,613,155 in his racing career following the accident, Smarty Jones is one of only three undefeated winners of the Kentucky Derby and Preakness. When freed from the confines of pain, as Smarty Jones was, your horse will be the real winner.
A horseowner since age 13, Brenda Thoma has shown competitively for nearly three decades. Always curious about what lies beneath the exterior of horses and people, she is interested in alternative health therapies, psychology, yoga and distance running. Recently, at age 40, Brenda resigned her "office job," simplifying her life to include her passion for writing. She and husband David have a son, Grant, 15, and daughter, Lauren, 13. They live in Annandale, Minnesota.