Protein Levels and Seizures?

Q: I have a 37-year-old Welsh Mountain Pony mare who has been having seizures on and off for about two years. I have noticed that when her protein levels have been increased with feeding, especially in the springtime when the new grass appears, the seizures appear more frequently. Is it possible that the high protein levels could cause a seizure, or is it just coincidence and there might be something else going on? My vet seems to think there is nothing I can do for the pony because she is so old, and she might hurt herself badly during a seizure, so the best option would be euthanasia.

She is in good health apart from the seizures, which pass after about three minutes, then she begins to tuck into her food. She is obviously underweight--she has very few teeth left and can only eat soft, short-chopped food. Is there anything we can do to manage this condition and keep her comfortable? --Jacky Montgomery, Herts, England

A:It is understandable that you are concerned about your pony's recurrent seizures, and your veterinarian is justified in communicating the risk of potentially serious trauma that she could sustain during a seizure. So yes, there is certainly your pony's quality of life to consider.

There are a few conditions that could be causing your pony's seizures, but they are unlikely to be related to the protein in her feed. The more likely possible causes in a horse of her age include a cholesteatoma (or cholesterol granuloma) in the brain, or a large pars pituitary adenoma (Cushing's disease). Other less-common causes would be a brain abscess, brain cancer, some other space-occupying mass in the brain, or epilepsy.

Alternatively, she could be suffering from liver failure, which could be worsened by higher protein intake. Feeding more dietary protein does not directly result in increased protein levels on a blood test unless the protein is low to begin with. Increased protein on a blood test in a nondehydrated horse is either due to elevated globulins or fibrinogen (indicating chronic inflammation or infection), or excess fat in the blood (called hyperlipemia). Therefore, the increase in blood protein you are seeing that appears to be associated with increasing seizure activity is most likely a reflection of the underlying disease rather than the feed itself; although the change in feed (carbohydrates, proteins, or fats) could be contributing to increasing seizure activity.

The best course of action is to investigate possible causes of the seizures with veterinary examination, complete blood tests (hematology and biochemistry) to rule out organ failure or infection, and testing for Cushing's disease (which is very common in older horses). The most definitive test would involve a CT scan or MRI of the brain, but this might not be very practical, available, or affordable. Seizures can be controlled with certain medications, but these are best prescribed after the cause of the seizures has been investigated.

My advice would be to consider your pony's quality of life carefully, trying to leave emotional attachment aside. If you are noticing that certain pastures or feed increase the frequency of her seizures, then it is certainly worth managing her feed to avoid these changes. Your pony has led a long and happy life, and it is not likely that you will cure the cause of her seizures at this advanced stage. If you don't want to go through thorough veterinary investigation, I would recommend managing her as best as you can, and when you believe she is not her happy self as often, then you will need to make the decision for humane euthanasia.

About the Author

Darien J. Feary, BVSc, MS, Dipl. ACVIM, ACVECC

Darien J. Feary, BVSc, MS, Dipl. ACVIM, ACVECC, is a Lecturer in Equine Medicine at the University of Sydney, Australia.

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