SEIZURE DISORDER IN DOGS
Watching your dog experience a seizure is both frightening and disturbing, especially if it is unexpected. There is collapse, involuntary movement, and often loss of consciousness followed by a period of daze and disorientation. Prolonged seizure activity constitutes an emergency. You are presumably reading this because your dog has had some kind of involuntary fit and you want to understand what it means and what can be done to prevent future episodes so let's cover some basics.
WHAT IS A SEIZURE AND HOW DO YOU KNOW IF YOUR DOG HAS HAD ONE?
A seizure results from excessive electrical activity in the cerebral cortex of the brain. The electrical activity starts in one area (called the "seizure focus") and spreads outwards through the brain causing involuntary movements and loss of normal consciousness. Classically, the patient loses consciousness, collapses, becomes stiff at first and then begins paddling or struggling but seizures can take many forms. Any involuntary behavior that occurs abnormally may represent a seizure. Seizures are classified into several categories.
GENERALIZED (GRAND MAL) SEIZURES
FOCAL SEIZURES (ALSO CALLED PARTIAL MOTOR SEIZURES)
PSYCHOMOTOR SEIZURES (ALSO CALLED COMPLEX PARTIAL SEIZURES) Psychomotor seizures are focal seizures where the seizure is more like an episode of abnormal behavior than an actual convulsion. The pet's consciousness is disturbed by this type of seizure as the pet appears to be hallucinating or in an altered state. The seizure may include episodes of rage or aggression where the pet does not recognize family members or may be as simple as a brief episode of disorientation or "spacing out." Fly-biting is an example of a psychomotor seizure.
Seizures (neurological events) are often difficult to tell from fainting spells (cardiovascular events). Classically, true seizures are preceded by an aura, or special feeling associated with a coming seizure. As animals cannot speak, we usually do not notice any changes associated with the aura. The seizure is also typically followed by a post-ictal period during which the animal appears disoriented, even blind. This period may last only a few minutes or may last several hours. In contrast, fainting animals are usually up and normal within seconds of the spell, with no post-episode disorientation.
*** POST-ICTAL DISORIENTATION IS THE HALLMARK OF THE SEIZURE ***
CAUSES OF SEIZURES AND DIAGNOSTICS:
There are many potential causes of seizures: toxins, tumors, genetic disease such as epilepsy, infections, even scarring in the brain from past trauma. Seizures resulting from metabolic problems or toxicity (i.e. when the brain itself is normal) are called Reactive Seizures. Seizures resulting from identifiable brain abnormalities are called Structural Seizures. Seizures for which no clear cause can be found are called Primary Seizures and the patient is said to have Epilepsy.
It turns out that dogs of certain age groups tend to have common causes for their seizures. This means that certain diagnostic tests are especially important in dogs of one age group while other tests are going to be more important for dogs in another age group. Here are some basic concepts concerning how age is an important consideration:
ANIMALS LESS THAN AGE SIX MONTHS
Particularly important in small dome-headed breeds (Pomeranian, chihuahua etc.) would be congenital disease such as hydrocephalus, where abnormal fluid drainage from the brain creates damage.
ANIMALS BETWEEN AGES 6 MONTHS AND 6 YEARS
Schnauzers, Basset hounds, Collies, and Cocker spaniels have 2-3 times as much epilepsy as other breeds. Labrador retrievers and Golden retrievers are also predisposed to epilepsy but tend to begin their seizures relatively late, closer to age five.
ANIMALS MORE THAN AGE FIVE YEARS
WHEN TO BEGIN TREATMENT:
In 2016, the American College of Veterinary Internal medicine published a consensus statement on this very subject. If the dog fits into any of these criteria, medication to suppress seizures should be initiated:
It should be noted that the German Shepherd dog, Border collie, Australian shepherd, Golden retriever, Irish setter, and Saint Bernard breeds are notorious for difficulty in seizure control. It is best not to wait for frequent seizures in these cases as each seizure makes the next more difficult to control. Often medication is started in these individuals after the first seizure. The more seizures the patient experiences, the more difficult control becomes in the future.
TREATMENT CHOICES: MEDICATION
There are presently four main medications that are used in suppressing seizures in dogs in the United States: phenobarbital, potassium bromide, levetiracetam, and zonisamide. If adequate control cannot be achieved with one medication, often two or even three are combined. The ideal first line anti-convulsant medication is effective, reasonably priced, convenient to administer, and has limited side effects potential. Most dogs are started on either phenobarbital or potassium bromide but we will take a moment to review the pros and cons of all four of these medications.
This has been the first line therapy for canine seizure control for decades as it is effective, reasonably priced, and can be given twice daily which is relatively convenient. When dogs with seizures are started on phenobarbital, approximately 31% of them can be expected to become seizure-free. Approximately 80% of dogs on phenobarbital will experience a >50% decrease in seizure frequency. Approximately 20-30% of dogs on phenobarbital will require a second anti seizure medication to achieve acceptable seizure control.
Side effects of the drug include sedation, which is usually temporary during the first 1-2 weeks of medication use and wanes as the patient's body adjusts. The patient is likely to be unusually hungry and thirsty on phenobarbital. These side effects can be objectionable. Some lab test changes are associated with phenobarbital usage and need to be recognized as such. Phenobarbital is removed from the body by the liver so good liver function is essential for phenobarbital use and phenobarbital can alter the metabolism of numerous other medications. For more details on phenobarbital, click here.
This medication was used for human seizure control nearly 100 years ago but was eclipsed by the development of phenobarbital. It turns out that while phenobarbital may be a superior seizure drug for people, potassium bromide may be superior for dogs. When dogs with seizures are started on potassium bromide, 52% of them can be expected to become seizure free. Approximately, 70% will have >50% reduction in seizure frequency.
Potassium bromide is associated with pancreatitis and probably should not be used in patients with a history of that disease. Potassium bromide takes many months to reach a stable blood level which could leave the patient vulnerable to seizures during that time. As with phenobarbital, there are monitoring tests associated with potassium bromide use and sedation is a side effect. For more information on potassium bromide, click here.
This drug is popular for refractory epilepsy in dogs because it has been shown to be fairly reliable and has minimal side effects potential. It appears to work best in combination with other seizure medications rather than as a sole therapy but many dogs are able to use it as a single agent. There are no monitoring tests recommended for its use and an extended release formula allows for twice daily use. For more information on levetiracetam, click here.
This drug is a sulfa class anti-seizure medication that is rapidly becoming a first line treatment choice but might also be used to supplement more traditional therapies. Because it is a sulfa, it is vulnerable to the side effects associated with sulfa antibiotics: mostly tear production/dry eye issues but also some immune-mediated reactions. (Sulfa side effects are reviewed more completely in our pharmacy library under the sulfa antibiotics such as trimethoprim sulfa). Zonisamide can be used twice a day in dogs but lasts long enough in the cat to possibly be used once daily.
For more information about zonisamide, click here.
SEIZURES AT HOME (WHEN IS IT AN EMERGENCY?)
A Single Breakthrough Seizure
It is a lucky pet that never has another seizure after beginning medications; but an occasional breakthrough seizure (as disturbing as it may be to watch) is rarely of serious concern. In most cases, one can simply give an extra dose of the oral anti-seizure medication that has been in use and consider the episode over with. The veterinarian should be appraised of the situation and the medication regimen evaluated to see if adjustments should be made to prevent further breakthrough seizures in the future.
A Second Breakthrough Seizure within 24 hours
If a second seizure occurs within 24 hours, one might consider bringing the pet to the vet's office for a "seizure watch" (which means the pet can receive medication to interrupt any further seizures) as well as for re-evaluation of the current medication protocol.
Since emergency care can be expensive, one might consider rectal administration of diazepam (valium®) as a means of first aid and tiding the pet over until one's regular veterinarian is available. In anticipation of late night seizing, one can request a set-up for rectal diazepam to keep on hand. The injectable product is delivered rectally with a special syringe that can be kept at home. The rectal route avoids any danger of being bitten while trying to administer medication.
Recently compounding pharmacies have been able to produce diazepam rectal suppositories which may be easier to use than the syringe method, however, absorption rates are unknown with these products and most neurologists prefer using the injectable product. Rectal diazepam administration has been used successfully for many years in epileptic children; the technique has adapted well to veterinary patients. Diazepam can also be given nasally but there is a greater chance of being bitten.
EITHER OF THESE SITUATIONS IS CALLED "STATUS EPILEPTICUS" AND IS
THIS IS CONSIDERED "CLUSTER SEIZURING"
CAN SEIZURE MEDICATION BE DISCONTINUED EVENTUALLY?
While there is some risk to discontinuing seizure medications, this may be appropriate for some patients. Dogs should be completely seizure-free for at least a year before contemplating stopping treatment. In breeds for which seizure control is difficult, it is probably best never to stop medication (German Shepherds, Siberian Huskies, Keeshonds, Golden retriever, Irish Setter, St. Bernard). Phenobarbital is a medication that cannot be suddenly discontinued; if you are interested in discontinuing seizure medication, be sure to discuss this thoroughly with your veterinarian.
The Epilepsy Genetic Research Project
Veterinary Neurologists at several universities are looking for a genetic answer to epilepsy. They seek DNA samples from epileptic dogs and their close relatives if possible. For more information, visit
Canine Epilepsy Network
Affiliated with the Veterinary School at the University of Missouri at Columbia, this site reviews canine seizure disorders, treatment, history and more.
This is a support and news group for owners of seizuring dogs. The group has a substantial library of useful resources which can be viewed at:
Page last updated: 11/8/2021