Usually, a horse with neurological disease is a picture of depression, disorientation, staggering and stumbling. A lame horse’s symptoms include heat, swelling, hobbling around, and head bobbing.
But sometimes making the decision about which is which is not that clear cut, creating a diagnostic mess for both owners and their veterinarians. To make matters even more complicated, subtle abnormal gaits either directly related to a neurological problem or adopted by the horse in an attempt to compensate for weakness related to one, can cause secondary strains and injuries in the horse.
What’s Going On
The horse’s nervous system contains a ”sympathetic branch” that controls involuntary body functions such as the senses, heart rate, breathing, sweating and digestive functions. These are things the horse cannot voluntarily turn on or off. This branch also influences the pain threshold and even the immune system.
The voluntary branch of the nervous system contains both afferent and efferent neurons (nerves), which convey information from the body to the brain (afferent) and vice versa (efferent). This system handles information regarding sensations of heat, cold, pain, position and ”stretch” within tendons/ligaments, as well as providing the signals responsible for movement and coordination. The potential for overlap between pain or lameness and neurological problems in causing changes in the horse’s gait and coordination is where problems occur in differentiating between the two.
Let’s take one of the most common situations, a horse that is obviously off behind, has trouble negotiating hills, maybe has some muscle loss, does some odd things with her legs when circled (making you think neurological) and maybe even is less resistant to a tail pull on one side than another. But it isn’t enough to really be convincing as a neurological problem vs. a lameness. Now what' Depending on the veterinarian’s feel for which it is more likely to be, the next step is a thorough neurological or lameness exam.
In some ways, it makes more sense to start with the neurological exam, since finding any neurological abnormalities unrelated to gait/movement, or involving other areas, makes neurological disease a lot more likely.
Neurological testing also aims to put the horse in positions that are specifically designed to exaggerate any movement or sensory deficits the horse might have. It’s important to remember that at this stage of the game the most important thing to be accomplished is to determine if the horse has neurological disease or lameness. Localizing it, or hanging a name on it, will come later. Our chart will help you see how these two problems can overlap and how to begin to differentiate between the two.
In our example of a horse with an ill-defined problem behind, a thorough neurological exam, lameness exam including nerve blocks up to and including the hip and saroiliac joint, as well as a rectal exam by a veterinarian to check for pelvic or circulatory problems, will usually allow for identification of the problem as a lameness or neurological.
If the problem still isn’t diagnosed, more sophisticated testing, such as spinal fluid sampling if neurological is highest on the list, or a bone scan if obscure lameness is highest, may be required. Getting another exam and opinion, even if it means shipping the horse, may also be a good idea.
Although it’s tempting to start trying various treatments and skip the involved diagnostics, in the end this may be both more expensive and less effective than getting the correct diagnosis, and treating it properly as quickly as possible.