The Systematic Equine Neurologic Exam
Despite best efforts, some cases of equine neurologic disease remain unresolved, without achieving a final diagnosis. The best way to find the answer to your horse’s neurologic issues lies in your veterinarian’s keen eye and methodical approach. A careful history and clinical examination combined with appropriate diagnostic testing help him or her whittle through the long list of potential diagnoses and, ideally, identify the culprit.
Why exactly are neurologic conditions in adult horses so perplexing?
“Horses may be more challenging to diagnose because we are comparatively limited in our diagnostic capabilities, primarily due to size and, in some cases, risk,” says Sarah F. Colmer, VMD, Dipl. ACVIM, a fellow in large animal neurology at the University of Pennsylvania’s New Bolton Center, in Kennett Square.
Kathryn P. Sullivan, VMD, CVA, CVSMT, an assistant professor in New Bolton Center’s Section of Field Service, agrees, adding, “Neurologic diseases in horses are of particular concern due to the size of the animal and the interactions with humans—both in the saddle and in hand.”
In contrast, small animals are much easier and safer to anesthetize and image with computed tomography (CT) or magnetic resonance imaging (MRI).
“Even collecting a cerebrospinal fluid (CSF) sample can be more difficult in the large animal patient from a safety perspective, depending on their degree of ataxia (incoordination),” says Colmer. “Additionally, some relatively common neurologic conditions, like neurodegenerative conditions for example, can only be diagnosed postmortem and, therefore, also present a diagnostic challenge.”
In this article Colmer and Sullivan help us walk rather than stumble through a comprehensive neurologic examination in a methodical, thoughtful, step-by-step manner. Although not specifically addressed in this article, the horse’s history can play an integral role in diagnosing neurologic conditions.
Step 1: Identifying a Neurologic Horse
Not all patients present with classic neurologic signs such as the “dog sitting” of a horse with equine herpesvirus encephalomyelopathy; some cases can have very mild behavior changes and/or ataxia. With mild ataxia, distinguishing between a neurologic and lame horse can be daunting
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