What Causes Seizures in Dogs and How Should They be Treated?
Canine seizures are life threatening and frightening. Here’s what to do if your dog has one.
Dr. Eric Barchas
|Seizures are scary things. In fact, the first seizure I witnessed was one of the most frightening things that had happened in my short life to that point. I remember it vividly.|
My cat (yes, I know this is Dogster, and I swear I’m going somewhere with this) was in the kitchen. She suddenly got a strange look in her eyes, vocalized several times, collapsed, urinated, defecated, and began to convulse. I was convinced that she was dying before my eyes, and I was horrified beyond words. But within a minute or so (it seemed like much longer) the convulsions stopped. My cat was disoriented for about five minutes, and then she returned to normal.
Nobody in my family had any idea what had happened. We rushed to the vet, and, shockingly, he had no idea what had happened either. He told us to keep an eye on her.
That was the end of it until 20 years later when I was in a vet school neurology class. At that point I realized that this traumatic, inexplicable event from my childhood actually was common and had an explanation. My cat had suffered from a classic seizure.
Seizures in cats and dogs (see, I told you I was going somewhere with this) come in three stages. The first is called the pre-ictal stage and it is not always seen, especially since many animals will seize in their sleep. However, when it occurs animals may exhibit vocalization, disorientation, a glazed look in their eyes, and agitation.
Next comes the seizure itself. The animal collapses and goes rigid. Loss of bowel and bladder control may occur. Convulsions occur, usually lasting only a minute or two.
Finally, most animals experience a post-ictal stage lasting anywhere from a few minutes to a several hours or longer. During this time they may exhibit symptoms of blindness, they may vocalize, pant, stagger or fall, behave in a markedly disoriented fashion, and not respond to sensory stimuli.
Most pets then usually get better. These events are called grandmal seizures. (Note that this article is directed towards owners of animals who suffer grandmal seizures; it does not cover less serious petitmal events.)
Our understanding of what should be done when an animal suffers a seizure has been evolving over time. When I first started practicing, it was common for vets to recommend “benign neglect” (a practice in which nothing is done because doing nothing does not harm the patient) in animals who had experienced a single seizure. However, it turns out that neglect in these cases may not be benign.
Seizures are, in effect, electrical storms in the brain. Brain cells transmit electrical impulses along their length; these electrical impulses cause communication with connected cells. When an area of the brain begins to fire electrical impulses excessively, those impulses can spread to the connected brain cells, and to the cells connected to them, and so on until the brain is overrun with electrical activity. The result is a seizure.
Seizures that do not rapidly (within two to three minutes) resolve can cause severe complications including brain damage and high body temperature. Such seizures need to be treated immediately or death could occur rapidly.
However, even short seizures can cause permanent changes in the brain. After the electrical storm of a seizure subsides, additional areas of the brain may be left with residual electrical over-activity — this can lead to escalating seizures in the future. Seizures also appear to have the potential to rewire the brain. Humans with uncontrolled seizure disorders are prone to cognitive and memory problems later in life. These problems are harder to identify in dogs, but there is no reason to believe that their potential to suffer from such issues is any lower.
Also, seizures often come in clusters. After a seizure, those residual areas of extra activity are all left firing away with the potential to trigger more problems. And, just as aftershocks are common after an earthquake, subsequent seizures are common in the period immediately after a seizure has occurred. Unlike aftershocks, however, the subsequent seizures may often be bigger than the original one.
I therefore recommend that dogs who have suffered seizures receive immediate veterinary attention, with two aims in mind. The first is to try to prevent more seizures from occurring. The second to try to identify the cause of the seizures.
Various medications exist that can be used in the short term to prevent further seizures. Diazepam (which has gained no shortage of notoriety for its use and misuse by humans in the form of Valium) is the mainstay of treatment in acute cases, but it appears that supply issues are looming with this medication. Fortunately, other similar medications such as midazolam and lorazepam, and the unrelated medication propofol, also work well.
There are many causes of seizures in dogs. In young dogs less than five years of age, epilepsy is the most common cause. The term epilepsy is rapidly becoming outdated because of the implication that it is a single disease. In fact, epilepsy almost certainly encompasses a spectrum of conditions that cause seizures for unknown reasons in dogs.
Other causes of seizures in young dogs may include, among others, exposure to toxins, liver problems (especially a problem called liver shunt in small breeds), and head trauma.
In older dogs, especially those over seven years of age, the most common cause of seizures is so-called intracranial disease. Intracranial disease includes brain tumors, encephalitis, meningitis, and vascular events similar to strokes. Other problems such as exposure to toxins, liver failure, other metabolic or endocrine disorders, and head trauma also may cause seizures in dogs.
I recommend blood tests, urine tests, radiographs (X-rays), and blood pressure measurement for dogs who suffer seizures. I generally hospitalize them for observation and treatment with diazepam to prevent escalating seizure clusters in the short term. If a cause for the seizure is found, then it is addressed directly. If not, a presumptive diagnosis of epilepsy often is made.
However, in the long term things become trickier for those dogs diagnosed with epilepsy. Many veterinary neurologists recommend starting long-term anti-seizure medications such as phenobarbital, potassium bromide, zonisamide, levetiracetam, or (rarely) gabapentin after any seizure. However, these medications have potential side effects or issues that must be considered, especially in young dogs who might be looking at a lifetime of medication. Phenobarbital works well but can cause liver problems, weight gain, and possibly pancreatitis.
Potassium bromide can cause behavior changes and has been linked to pancreatitis. Levetiracetam and zonisamide may be subject to significant “honeymoon” effects. This means that they works well in most dogs for a while, but then may become less effective. The efficacy of gabapentin is questioned by many. All of the drugs used to treat seizures work by reducing brain activity, and therefore all of them can cause sedation or behavior changes which fortunately in most cases wear off within a few weeks.
In an ideal world, we would be able to identify those dogs for whom the long-term side effects of chronic medication outweigh the risks. Unfortunately, in many cases it is not possible; nonetheless it is still worth trying.
The best option for owners of dogs who have suffered a seizure or seizures is to consult with a large referral center where a veterinary neurologist and a veterinary internist (who can look out for the liver and pancreas) can work together to tailor an optimal protocol. Be aware that the neurologist will probably want to run an MRI and obtain a sample of cerebrospinal fluid for analysis. The internist will probably recommend regular blood work.
Owners for whom such specialist intervention is not feasible due to geographic or financial reasons will have to rely on less information and work with their family vet. At this time most vets are not recommending long-term anti-seizure medications for most dogs who have experienced single seizures. That could change as our understanding of epilepsy changes or as newer and better drugs become available.
Another treatment that may hold some promise is dietary modification. In humans, high carbohydrate diets have been linked to changes in brain electrical activity that seem to promote seizures in some individuals. I have yet to see any evidence of such a link in dogs, but this area of study is definitely something to watch. It is unlikely that switching to a lower carb (but still fully balanced) diet will harm a dog with seizures; therefore this step is one that might not be unreasonable for owners of epileptic dogs who have decided not to start chronic medication (and also for those who have).