Nutrition, Disease, and Mimi

For years, Mimi has exhibited symptoms of "generalized tremor syndrome." She has nearly continuous tremors of parts or all of her body. The tremors get worse when she is excited or stressed. They are also present when she is sitting quietly and thus relatively relaxed and continue even when she is falling asleep. They disappear only when she is fully in REM sleep. This particular tremor syndrome is usually observed in smaller dogs like the small terrier breeds. The tremors showed up when Mimi was just a few years old, and have been slowly progressive since then. They are not painful and they do not affect her ability to run, eat, play, defecate, or engage in any other normal dog activities. All of these are typical characteristics for this disease.

This tremor syndrome has been fairly well studied. It can't be linked to any infectious agent or toxin. Some dogs have a mild increase of white blood cells in their cerebrospinal fluid, but that isn't observed in all cases. Thus it isn't strictly speaking an inflammatory disease, although it has been described as a type of meningoencephalitis (the -itis is used to describe inflammatory diseases). Instead, the syndrome is thought to be immune-mediated. That means that the immune system got its signals crossed at some point and began to attack a specific part of the body because the immune system thinks it is foreign.

When most dogs with this syndrome are given immune-suppressive doses of corticosteroids, they begin to improve, often within a few days. The tremors may be completely eliminated in some dogs and they can taper off the steroids. Sometimes the tremors return and then the dog has to begin the course of steroids all over again.

Steroids like prednisone are a powerful component of the vet med pharmacopia. But when they are given at immune-suppressive doses, they can have some unpleasant side effects. Heck, they can have unpleasant side effects at the lower anti-inflammatory doses. They are not to be prescribed lightly. Suppressing the immune system is not to be done lightly.

For some months now, I have been reading up on this generalized tremor syndrome and wondering if I should put Mimi on an immunosuppressive course of prednisone. She is much older than the typical dog that is treated for this syndrome, mainly because the tremors don't affect her life and I chose not to treat it earlier. Not all dogs who take prednisone achieve resolution of the tremors. I've been on the fence about this since I can't predict Mimi's response to treatment.

And because Mimi is an old girl (13 years now), I have also been thinking about age-related cognitive decline. Harry experienced a significant cognitive decline during his last two years. So when I ran across Purina's new prescription diet aimed specifically at slowing this kind of cognitive decline in dogs, I was quite interested. To be clear, once neurological damage and cognitive decline are present, they are not reversible. Purina intends for this diet to be fed prophylactically to dogs before they begin to show clinical signs. The diet, called Purina Proplan Neurocare, is only available by prescription. Purina, like Hills and a couple of other food companies, does actual feeding trials for their diets. This makes their claims for their diets much more compelling. They have published some good papers on the diet and it certainly seems to work as they claim it should.

What makes their Neurocare diet different? They increase the levels of omega-3 fatty acids, the vitamin B complex, and the antioxidants Vitamin E and Vitamin C. They also include medium-chain fatty acids (vegetable sourced). These fatty acids are processed by the body using slightly different metabolic pathways than longer chain fatty acids. It's not that long-chain fatty acids are bad. Quite the contrary, the long-chain fatty acids in the omega-3 family are extremely useful and are valuable additions to any diet, including yours. But the normal human and dog diet doesn't include much in the way of medium-chain fatty acids and far too much saturated fatty acids.

Purina, like Hills and Royal Canin and other companies that made veterinary diets, also make similar diets that you can buy without a prescription. In the case of Purina, the grocery-store version of their Neurocare diet is called Purina One Vibrant Maturity. Of course, it is not quite the same formulation as the prescription diet. It lacks the extra omega-3 fatty acids. But it has extra zinc, selenium, and Vitamin E. All three of these are important players in anti-oxidant metabolic pathways. And Vibrant Maturity includes those same medium-chain fatty acids and most of the Vitamin B complex. So there is considerable overlap between the diets.

Since I started working towards this new vet med career, I have been interested in how diet can be used to decrease incidence or susceptibility to disease, to decrease the use of drugs, and to improve performance. These concepts apply to old fox terriers as much as they apply to poultry houses with 120,000 broiler chicks.

On a bit of a whim, I decided to feed Mimi the Purina One Vibrant Maturity kibble just to see what would happen. I have now been feeding it for four weeks, which is generally the length of time we know we have to feed a new diet before we can expect to see changes in whatever clinical sign we are monitoring. I made no other changes to her diet or activities.

With respect to her cognition, all I can say is that she is no worse than she was four weeks ago, although that is a really subjective interpretation that has a high risk of owner confirmation bias. She wasn't exhibiting signs of cognitive decline before I started feeding her Vibrant Maturity, and Purina's claim is that their diet will delay these kinds of changes. So this part of my little experiment is a bit moot at this time.

But here is the amazing part: after four weeks, Mimi's tremors are notably reduced. Her head tremors have almost completely disappeared. Her body tremors are still present, although they are somewhat positional now (her hind legs will tremor more if she stands just so, and will tremor less if she stands another way). To make sure I wasn't seeing changes that I wanted to see, I had two other people look at her who have seen her tremors in the past. They saw the same changes that I saw.

This is the take-home lesson: I was apparently able to alter the course of her tremor syndrome using diet alone. I suspect that Purina is not aware that their diet could have this effect since their focus has been on the cognitive benefits.

These kinds of serendipitous observations are what drive me as a scientist and as a soon-to-be newly minted veterinarian. My mind is swirling with ideas for project designs and funding sources. I'm not likely to follow through with any of them, but you never know what future opportunities might appear!