"All the most acute, most powerful, and most deadly diseases, and those most difficult to be understood ... fall upon the brain."
--Hippocrates

Epilepsy was recognized in ancient times and was undoubtedly one of the "difficult" diseases Hippocrates referred to. Understanding what causes seizures, how epilepsy is treated and how current research may help decrease the incidence of the disease, will help you deal with the condition in your pet.

See your veterinarian

Your veterinarian is the person to ask what's best for your pet.

• Your veterinarian will be your best source for advice about your pet's health. They know your pet, what treatments have been tried in the past, what was found on examination, and your pet's other medical problems.
• Be an intelligent consumer. Educate yourself about your pet's disease and don't be afraid to ask questions. If you don't understand why a test is being run or a treatment recommended, your veterinarian will be able to explain why this will help your pet.
• Remember anyone can post anything on the Internet so there is no guarantee the information is valid unless it comes from a reputable source. Share what you learn with your veterinarian. They can help you distinguish information that may be helpful from ideas that may be useless or even dangerous for your pet's individual needs.
• The information in this site is provided to help you understand the things your veterinarian will be discussing with you and may help stimulate discussion of the options available.
• We cannot directly advise you on how to treat your pet. If your pet is having serious problems, you may wish to ask your veterinarian to refer you to a nearby Veterinary Neurologist (a specialist in diseases of the nervous system like epilepsy). To find a Board Certified Neurologist near you, go to the American College of Veterinary Internal Medicine homepage and search the "Find an ACVIM specialist near you" database. Information about the neurology service at the University of Missouri, College of Veterinary Medicine can be found at http://www.vmth.missouri.edu/

Key points

If you have a pet with epilepsy, these are some of the key points for you to remember. They are discussed in more detail elsewhere:

• Don't change or discontinue medication without consulting your veterinarian.
• See your veterinarian at least once a year for follow-up visits.
• If your pet has a seizure longer than 5 -10 minutes or 3 seizures in a day, seek veterinary care immediately.
• Be skeptical of exorbitant claims of treatments.
• Remember, live with epilepsy not for epilepsy. With appropriate treatment, most dogs have far more good days than bad ones. Enjoy all those good days! Enjoy your life and your pet. They have a serious disease, but don't let that keep you from enjoying the time you have with them.

What is epilepsy?

Epilepsy refers to repeated seizures over time. Idiopathic means we can't find an underlying cause of the seizures.

Epilepsy simply refers to repeated seizures. Seizures may occur as a one time event in an animal from a variety of causes, but only if the seizures repeat again and again over a period of time do we call it epilepsy. Seizures are a sign of brain disease the same way a cough is a sign of lung disease. Saying an animal has epilepsy is like saying it has a chronic cough; it is a sign of a problem which isn't going away. Anything which damages the brain in the right area can cause epilepsy. If we can identify the cause of the seizures, say a brain tumor or a stroke, then we say the pet has symptomatic (or secondary) epilepsy. That is, the seizures are a symptom of a disease process we've been able to identify. If we've looked and can't find the cause, then we call it idiopathic (or primary) epilepsy. The term idiopathic simply means that we don't know the cause. It may be that the cause has escaped our attention; for example, a stroke that is too small to detect with routine brain scans or damage that occurred during whelping.

Many of the idiopathic epileptics have inherited epilepsy: epilepsy caused by a mutation in a specific gene which they inherited from their parents. Dogs with idiopathic epilepsy frequently begin seizing at between one and three years of age, and certain breeds are predisposed to develop epilepsy. A few breeds have proven hereditary epilepsy, while in most it is just a strong suspicion. One of the goals of the Canine Epilepsy Project is to identify genes responsible for epilepsy in dogs. This will allow us to positively diagnose the hereditary form and take steps to decrease the incidence of epilepsy in dogs.

How common is epilepsy?

Epilepsy is one of the most common neurologic diseases in dogs, but no one knows for sure just how common it is. Some studies estimate up to 4% of all dogs are affected. In some breeds, the incidence may be higher and some families may have up to 14% epileptics. Epilepsy occurs less frequently in cats and other pets, presumably because they do not have a hereditary form of the disease.

What determines when my pet will have seizures?

No one knows what it is that determines when an epileptic will have seizures. The only thing we can predict about epilepsy is that it's unpredictable. Some pets appear to have seizures very regularly, while in others, the seizures appear to be precipitated by specific events such as stress, or changes in the weather. However, when we try to use what's happened in the past to predict when the next seizure may occur, we usually aren't very successful. For many epileptics, there is no pattern to their seizures.

How do we diagnose idiopathic epilepsy?

Idiopathic epilepsy is a diagnosis by elimination. That is, we look for other causes of seizures and if we can't find any, we make the diagnosis of idiopathic epilepsy. How aggressively we search for an underlying cause is a matter of clinical judgement. We always recommend a minimum work-up for any dog having seizures. This will provide us with clues to a possible underlying disease and provide the baseline from which to watch for potential side effects of antiepileptic drugs.

Since your veterinarian may not witness one of your pet's seizures, they are very dependant upon your description of the episode. This will help them decide whether these events are indeed seizures. Other problems such as fainting or dizzy spells can also come and go like seizures and may look similar to the untrained eye. Thus, your veterinarian will need a clear description of what you observe during the episode to help make that distinction. They will also be determining what type of seizure your pet is experiencing. Write down a description of what you saw as soon as possible after the episode. If you can, make a videotape of the episode to show your veterinarian or the neurologist.

In order to rule out some diseases, we would need further tests. If the animal is outside the 1-3 year old range when idiopathic epilepsy typically starts, or has any abnormalities on examination that hint of a cause, we strongly recommend such testing. Your veterinarian may refer you to a neurologist for some of these tests. Even if an animal is within the "idiopathic epilepsy" age range, we can't be sure it's idiopathic unless we perform the full compliment of tests. One study (Podell 1995) showed that over 1/3 of the dogs between 1 and 5 years of age had an identifiable cause for the seizures. Thus we can make a case for aggressive testing in any epileptic dog, but need to weigh the additional cost involved into the equation.

The electroencephalogram (EEG) is a useful tool in diagnosing epilepsy, but has serious drawbacks in animals. When we see abnormalities in the EEG, that tells us this is indeed a seizure and may help us pinpoint the source. The trouble is, those EEG abnormalities, like the seizures, can come and go. If they don't happen while we are recording the EEG, we will not see them. Recording an EEG in an awake animal is difficult, so we often have to sedate or anesthetize them to get an adequate recording. The drugs used for the sedation/anesthesia also affect the EEG. Thus, we often make the diagnoses of epilepsy based on the clinical signs and don't require EEG confirmation of the disease.

Thyroid function and epilepsy

There is a great deal of controversy (largely unnecessary) about the role of the thyroid in canine epilepsy. The thyroid hormones regulate metabolism. Too much thyroid activity, and the metabolism runs too fast. The result is weight loss, nervousness, high blood pressure, and so on. Too little thyroid activity, and metabolism runs too slow. This results in weight gain, lethargy, high cholesterol levels, and so on. Normally, dogs don't develop atherosclerosis: the hardening of the arteries that predisposes people to heart attacks and strokes. The high cholesterol that accompanies hypothyroidism (too little thyroid hormone) can, however, lead to atherosclerosis and strokes in dogs. Likewise the high blood pressure that accompanies hyperthyroidism (too much thyroid hormone) can also predispose the dog to stroke. So the dog needs "Goldilocks levels" of thyroid hormone: not too much, not too little, but just right. If the levels are outside that range, then we could have problems which could cause epilepsy.

Thyroid function tests are affected by many things, including stress and medications. Several recent studies have demonstrated that phenobarbital therapy causes falsely low values on some thyroid tests. Recent seizures will also cause false lowering of the values, presumably due to the stress they cause. So test results need to be interpreted with these caveats in mind. If an animal tests truly low on thyroid function, then a trial of thyroid supplementation is indicated. If an animal has normal thyroid tests or fits with what we expect from the effects of the medication or seizures, then there is no reason to supplement thyroid hormones.

What about liver shunts?

In this radiograph, blood (shown in white) flows through a shunt (arrow) bypassing the liver (star).

One of the jobs of the liver is to ensure that only the good stuff from the food we eat gets into the body. Dogs are notorious for eating disgusting things, such as the moldy cheese out of the garbage, and their liver is responsible for keeping toxins from affecting the body. In addition, the action of bacteria in the intestines on food can produce toxic byproducts which the liver deals with. All the blood coming from the intestines goes through the liver first, where it is cleansed of toxins before going around the rest of the body. When an embryo is safe in the mother's womb, the mother's liver takes care of that job, and the embryo doesn't need to worry about it. As a result, the blood from the intestines bypasses the liver in the embryo through a separate vessel called a shunt. When the pup is born, however, the liver needs to switch gears and start doing it's job of cleaning the blood from the intestines. So the shunt closes down and blood is run through the liver to be cleansed before it gets to the brain.

If the shunt fails to shut down like it should, then blood will continue to bypass the liver. A shunt that is present from birth is called a congenital shunt. The liver then doesn't get a chance to remove the bad stuff until it's already circulating around the body. Many of the toxins that the liver would normally clean up can affect the brain, and seizures can be one of the effects.

Shunts can also be acquired later in life. If the liver is diseased, blood may have a hard time flowing through the sick liver, leading to a back-pressure in the vessels coming from the intestines. If that back-pressure gets high enough, the blood may find an alternative, less resistant, pathway. The result is the same as the congenital shunt; blood bypasses the liver and toxins affect the brain.

Both because liver problems can cause seizures and because many of the medications used to treat epilepsy can injure the liver, we recommend liver function tests as part of the initial work-up and as part of the regular check-ups. The liver enzyme tests which are part of a routine chemistry profile may not be adequate to detect liver shunts and liver function tests, such as bile acids or ammonia, are necessary.

Other tests may be necessary

Depending upon your pet's age, type of seizure, and findings on the minimum work-up, your veterinarian may also recommend further tests. Advanced imaging, such as MRI or CT scans, is necessary to be able to actually see the brain. Regular radiographs (X-rays) can tell us about the bones of the skull, but not the brain itself. Such imaging is becoming more readily available for animals at referral centers. By imaging the brain, we can diagnose diseases such as brain tumors or hydrocephalus (water on the brain) which can cause seizures.

Infection of the brain (encephalitis) can cause seizures. Canine distemper is the most common cause of encephalitis in dogs and one of the reasons to keep your pets current on their vaccinations. A spinal tap and serum antibody titers will enable your veterinarian to tell if distemper or one of the other causes of encephalitis is the reason for your pet's seizures. Additional blood tests including toxin screens may also be indicated.

Last updated: 4/19/02