Remember the last time you rolled out of bed in the morning feeling like you must have slept with your neck contorted like a noodle? The lingering stiffness lasts all day, making simple things like dressing and driving a pain. Now, imagine you’re a horse with neck pain–consider how uncomfortable it would be to move in a frame, on the bit, to flex and bend and be expressive in your gaits, while battling an ache that just doesn’t go away.
Sue Dyson, VetMB, PhD, FRCVS, head of Clinical Orthopaedics at the Animal Health Trust in Newmarket, England, spoke on neck pain in sport horses at the Florida Association of Equine Practitioners (FAEP) Promoting Excellence Symposium, held Sept. 27-29, 2007, at the Atlantis resort on Paradise Island, the Bahamas. She noted that neck pain can manifest itself through a wide variety of clinical signs, which can make correct diagnosis difficult. This pain can result from a number of factors, including trauma, muscle injury, fracture or displacement of a vertebra, or osteoarthritis.
Some of the more typical clinical signs horses with a neck problem might present include stiffness, muscle atrophy, patchy sweating, shortened forelimb stride, forelimb lameness, and abnormal head carriage. Dyson also noted that she’s seen cases of horses getting their necks "stuck" in a fixed, low position, unable to move and exhibiting considerable distress. (These horses might resolve spontaneously, or they can sometimes be "released" through manipulation. She noted that this is typically associated with enlarged facet joints–the articulating surfaces between the vertebrae– with some remodeling.)
During examination, Dyson said she considers the posture of the horse’s head and neck, their reaction to palpation and manipulation, and their sensitivity at acupuncture points. She also assesses neck flexibility and watches the horse eating from the ground, as well as observing the horse moving naturally on the longe and when ridden.
To assess neck flexibility, Dyson uses passive manipulation (in which the horse flexes itself, as with "carrot stretches," rather than being physically moved into a position), watches the horse turn small circles to the left and right, and watches the horse moving freely on the longe. She said she prefers to promote and watch free, spontaneous movement, as horses will brace against forced stretching.
Observing a horse’s ability to flex freely can help determine whether he’s experiencing neck pain.
However, "There are some horses that are naturally stiffer than others, and that may not be associated with any particular pain," she cautioned. Additionally, not all neck radiographs will look the same–it’s important to know "normal" for the individual horse, as there can be natural variance between individuals that is not associated with any problem. Dyson also noted that the cranial and caudal cervical vertebrae (the neck vertebrae at each end) have greater uptake of radioactivity during nuclear scintigraphy, and that this is normal and should not necessarily be interpreted as indicative of inflammation in the area.
"In mature horses it’s quite common to see remodeling of the caudal cervical facet joints, and it’s quite commonly asymptomatic," Dyson said.
Some of the more common causes of neck pain include remodeling in the vertebrae or facets, loss of joint space due to disk problems, trauma to nerve roots, or primary soreness of the brachiocephalicus muscles (muscles that run from the bicep to the back of the skull and provide lateral flexion of the neck).
Dyson used case examples to illustrate some of the difficulties that can be encountered when evaluating a horse with neck pain.
In one case, which Dyson presented using video of the horse’s evaluation, a dressage horse worked nicely on contact under saddle during most of the evaluation, but it would suddenly stop, fling its head, and refuse to move forward. This horse would become difficult to control as it evaded contact. Radiographs of this horse’s neck showed bone remodeling on the back of the skull in the poll area. Dyson blocked the horse’s poll (with diagnostic nerve blocks), and the horse became compliant under saddle, indicating she’d found the source of the problem.
Dyson noted that she often sees forelimb lameness associated with primary neck pathology. In the next case she reviewed, a dressage horse was evaluated for fluctuant forelimb lameness. The lameness got worse as time under saddle went on. The lameness occurred when the horse was moving either direction, irrespective of the position of the horse’s head and neck. The horse would bend in either direction with no apparent stiffness. As the forelimb lameness became more apparent, the horse’s head carriage was less consistent and it began fussing with its mouth. All nerve blocks and ultrasonography of the limb, shoulder, and elbow were negative. Scintigraphy yielded no result, nor did radiographs of the shoulder or ribs. Radiographs of the neck did show remodeling of the facet joints of the 6th and 7th cervical vertebrae. These were injected with local anaesthetic solution and resulted in an improvement in clinical signs, and the horse was subsequently treatmented successfully via an ultrasound-guided injection of the joint.
However, Dyson noted that, in this case, daily under saddle evaluations at the clinic had their own effect–this horse was typically ridden in a very short, tight frame by its trainer. The staff at the clinic utilized a longer contact, and, over the period of time the horse was in the clinic, its way of going had already improved dramatically under saddle before the physical cause was pinpointed and medical treatment initiated.
"I think that the way in which horses are worked can produce neck stiffness in some horses," Dyson noted.
Wrapping up, Dyson noted that there are many different clinical manifestations of neck pathology, and that careful clinical evaluation, correlated with imaging, is important for getting to the bottom of these cases.