The Neurological Examination – Part I
Dr. Melissa Mazan
A neurological examination aims to determine two things: whether a neurological problem exists and, if it does, where does it exist in the neurological system. The ingredients to a successful diagnosis of neurological problems are a thorough knowledge of how the normal horse behaves and moves, a systematic examination and experience.
Your veterinarian will start with a complete medical history. Details such as the age, the breed, and the sex of the horse can be very helpful, because some diseases preferentially affect certain groups of horses. It is very important for your veterinarian to know how your horse is used and how hard he is being used. For instance, if your horse is a pasture potato, he may have had subtle signs for quite some time that you haven't noticed because you haven't challenged your horse with difficult maneuvers, such as going up and down hills, and you haven't spent as much time with your horse.
Your veterinarian will want you to try to pinpoint exactly when the abnormal behavior began, and whether it has progressed rapidly or remained relatively static. Your veterinarian is like a detective, who needs as many clues as possible to solve the mystery – your horse's problem.
Your veterinarian will start by assessing your horse in his usual environment. That usually translates into quietly observing the horse in his stall or paddock. First of all, your veterinarian wants to know if the horse's mental actvity is normal. If you think about it, this is something that you are probably good at assessing yourself. Ask yourself, how does a normal horse act in this situation, and then observe your horse.
Any time that your horse is in a strange situation, he should be alert and bright. His ears should be pricked forward toward any strange sounds, his head should be up, and he should be ready to assess the situation and decide if flight is the right course of action. Your veterinarian will also want to observe the way that your horse moves in the paddock or stall. For instance, does he seem balanced? Does he trip or stumble? Does he bump into things? All of these things could indicate neurological disease.
After the initial observation, your veterinarian will want to do a complete physical examination. This is important for many reasons. There are some systemic diseases, such as liver or kidney disease, that can have neurologic manifestations, that might be picked up on a general physical examination. It is also possible that some of the abnormalities are caused by things that have no neurologic connections at all. Perhaps your horse is tripping because his toes are too long or his shoes are loose.
There may be other indicators of neurologic disease on physical examination. Some neurological diseases cause muscle loss that is asymmetrical. Your veterinarian will look to see if your horse is well muscled, and if that musculature appears the same on both the left and right sides. Some neurological diseases cause foot dragging and stumbling – this will often manifest itself as abnormal wear on the toes of your horse's hooves. Some neurologic diseases may cause the horse to experience seizures – your veterinarian may suspect this if she sees signs of unexplained trauma – scrapes and abrasions that aren't the result of a pasture fight.
As part of that complete physical examination, your veterinarian will often wish to perform a complete ophthalmologic examination. Perhaps he is bumping into things because he is developing a cataract in one of his eyes. It is also possible to examine directly one of the nerves of the central nervous system (CNS) by looking at the back of the eye – your veterinarian can look for any abnormalities in this nerve.
Depending on what your veterinarian has found at this point, she may choose to do bloodwork – usually a complete blood count (CBC) and a serum chemistry profile. The CBC can tell you that there is infection or inflammation in the body, as may be found with meningitis or encephalitis. The serum chemistry profile may tell you that there is liver disease, which can result in abnormal mental activity, or that there are serum electrolyte abnormalities, which can also interfere with the normal function of the brain.