Diagnosis and treatment of neck pain

Neck disorders in horses, leading to cervical pain and/or dysfunction, have diverse and unspecific clinical presentations being the diagnosis frequently challenging. History of trauma or complaints such as limb paresis, ataxia, inability to bend the neck or neck stiffness are common to this region, but subtle changes such as poor performance, behavioral changes, stumbling or complex forelimb lameness, abnormalities on hind limb gait, inefficient impulsion or resistance to the bit are also reported by trainers and/or owners.

Cervical pain and dysfunction can be present simultaneously or individually in horses and these are associated to a broad-spectrum of clinical signs. Horses with a painful neck may manifest sings of discomfort on palpation or when different types of movement are requested or performed (active motion on work, stretching, etc.). Cervical dysfunction, on the other hand, may be present without overt pain, and in such cases, more subtle limitations are present (e.g.: muscle atrophy).

The variety of clinical presentations owns to the different structures that can be involved and therefore, a comprehensive knowledge is necessary for a better understanding of each case. Pain and/or dysfunction can be originated from changes on bone, soft tissues, or nervous system components (central or peripheral) and many steps can be followed in attempt to distinguish which are the structures involved.

Osseous sources leading to neck pain/dysfunction can include articular process joint disease, morphologic variations affecting the vertebrae and fractures, while soft tissue sources include densification and fibrosis of cervical fascia, cervical muscles changes, nuchal ligament desmopathy, nuchal bursitis, intervertebral disc disease, joint capsule fibrosis and synovitis. A neurologic source may also be involved such as nerve roots changes leading to impingement risk or radiculopathy (similar to human cases), or, more commonly, cervical vertebral compressive myelopathy, leading to spinal cord compression.

Among the cited disordes, there is a crescent concern in relation to the pathologic changes of the articular process joints (APJs), which involves both bone and soft tissues sources that can lead to pain and dysfunction, being also associated to neurologic structures that can trigger spinal cord compression and nerve root damage. Osteoarthritis (OA) of the APJs has been the disease that we have most diagnosed and treated in our clinical routine. Therefore, due to the limited time available for this lecture, we chose to approach it with greater emphasis.

Post-mortem studies have shown high prevalence of osseous changes within APJs along the cervical spine from horses of different breeds and ages and cervical OA was shown to be highly prevalent in dressage and showjumping horses.

Diagnosis of APJ OA is usually difficult and even sometimes, frustrating as morphologic changes of APJ are not always related to clinical signs. Even so, it relies on the association of clinical presentation and findings from physical examination and diagnostic imaging tools.

Usually, for equine cervical evaluation, we start with static inspection, aiming to identify changes in head and neck positioning, localized sweating spots and muscle atrophies. Myofascial examination also can be used at this time, but we do not have experience with this approach. In sequence, a dynamic inspection is performed, with horse at walk and trot, aiming to identify lameness or ataxia. After that, we start with the palpation of the oblique cervical cranial and caudal muscles, splenium and semispinatus capitis, rhomboid, serratus cervical, cervical trapezius, omotransverse and brachiocephalic and subclavian muscles. Then we performed the passive mobilization test, in order to evaluate sensibility or reduced range of motion of the atlanto-occipital flexion, altanto-axial rotation and lateroflexion between the following segments from C2-C3 to C7-T1. Finally, we evaluated the presence of thoracic limb paresis.

Regarding imaging tools that are allies in the diagnosis of cervical pain/dysfunction in horses, the radiographic examination is usually the first choice. It has been employed for years and there are several studies in the current literature that investigated its diagnostic power. It has shown to be a good screening tool despite having low specificity. Ultrasonography is also employed in conjunction to the radiographic examination. Ultrasonographic images were reported to have a good concordance with anatomic transverse slides in an ex vivo study, but this technique is mostly reported as an auxiliar for intra-articular injections of the APJs for treatment. Findings of ultrasonographic changes were recently reported and aims only the caudal cervical APJs.

Another complementary diagnostic imaging modalities includes nuclear scintigraphy, electrodiagnostic evaluation, computed tomography (CT), CT myelography and magnetic resonance imaging (MRI) but among these, CT and MRI are the mostly employed for diagnosis of APJs disorders.

Treatment of APJ OA relies on a multimodal approach, including non-steroidal anti-inflammatory drugs, muscle relaxants and amitriptyline. Some authors also recommend the use of bisphosphonates. Physiotherapy must be associated, and we usually recommend therapeutic exercises, acupuncture, and elastic therapeutic tape. In some specific cases, mesotherapy, electrotherapy and extracorporeal shockwave therapy are also employed. The authors do not have experience with chiropractic as treatment for APJ OA.

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