"EPILEPTIC" SEIZURE DISORDERS
Genetics Editor / Sept. 2006
Your dog develops a far-away
look in his eyes, suddenly collapses and begins to tremor and shake
uncontrollably. Before you have a chance to react, the incident is over. He
remains lethargic and weak for a while afterwards. What happened?
Seizures, epilepsy, fits,
Different terms, same condition.
A seizure results from
sudden uncontrolled abnormal firing of neurons in the brain. The brain exists in
a delicate state of chemical and physical balance. This balance can be upset by
a number of factors. If the balance in the brain shifts too far, brain cells
(neurons) may become over stimulated, and a seizure may result. This point at
which seizures occur is known as the “seizure threshold”.
Seizures are commonly
preceded by an “aura” or altered state which may be characterized by
restlessness, nervousness, salivation, and anxiety. The “ictus” or actual
seizure follows next. The dog will become non-responsive, collapse, and
experience involuntary motor movements such as stretching, kicking, or paddling.
The motions may vary in intensity from mild tremors to severe jerking movements.
Seizures place tremendous stress on the heart, lungs and circulation. The body
temperature may get very high from all the muscle activity and the animal may
not breathe adequately. This may result (in rare cases) in brain damage and
death. The actual seizure itself may last only seconds or minutes. A seizure
persisting more than a few minutes is an EMERGENCY, which requires immediate
treatment by the closest veterinary facility. The postictal stage is the period
of time after the seizure; the dog may remain lethargic and weak, and possibly
To be considered a true
seizure, there must be an alteration in the level of consciousness. If the dog
is conscious, responsive, aware of his surroundings, or is awakened easily from
a sleep state, he is not having a true seizure. Heart and lung problems can
sometimes result in weakness and collapse, and middle ear infections can cause
dizziness. Twitching and jerking motions may occur in a sleep state, and this is
considered normal in early neurological development of puppies.
There can also be focal or
partial seizures, which affect a certain part of the body. For instance, the
face or just one limb may be involved. This may progress to involve the entire
body. The fact that the seizure starts in a local area suggests that a specific
area in the brain is damaged, perhaps due to a brain tumor or infection.
Seizures are a sign of
irritation of the brain tissue, just as coughing is a sign of irritation of
the respiratory tract. Any of the factors listed below can trigger uncontrolled
firing of the neurons of the brain. When a seizure is the result of an
identifiable cause, the disorder is known as symptomatic or secondary epilepsy.
Seizures or Convulsions May Be Caused by:
Brain tumors - more common
in dogs over 5 years old.
Stroke-can be caused either
by bleeding in the brain or by deficiency of the blood flow to the brain tissue.
Either condition can be associated with seizures.
Hypoglycemia or low blood
glucose (sugar)-common in toy breeds and especially puppies. Rubbing a small
amount of sugar or syrup on the lips, gums and tongue may be effective in
stopping the seizure if caused by low blood sugar.
Hypoxemia - Low blood
oxygen, with resultant lack of oxygen available to the brain. This can be due to
poor lung function, or an abnormal cardiac or pulmonary shunting process in a
Elevated blood ammonia level
due to liver infection, cirrhosis or a liver shunt.
Inflammatory or infectious
disease of the nervous system, this can include Lyme disease, distemper, rabies,
toxoplasmosis, and Rocky Mountain spotted fever, encephalitis and meningitis.
Ingestion of toxins such as
lead, caffeine, chocolate
Botulism-toxins sometimes produced by bacteria in food.
Exposure to pesticides such
as organophosphates (many flea control products) and metaldehyde (snail bait)
Congenital problems, such as
hydrocephalus, produce increased intracranial pressure.
Intestinal parasites can
cause severe anemia and hypoglycemia. Some parasites also migrate to the liver
and brain in their larval forms.
Low serum calcium or
magnesium levels- for example, eclampsia in a lactating bitch.
Blood sodium or potassium
imbalances can be caused by dehydration or kidney problems.
Genetic predisposition as in
the MDR-1 mutation common to many herding breeds causes a lack of the protein
which exerts a protective function in the blood-brain barrier and limits the
entry of many drugs to the central nervous system. The lack of this protein
renders the dog susceptible to the neurotoxic side effects of several drugs
including Ivermectin, Moxidectin and Loperamide.
Kidney failure and high
levels in the blood of uremic toxins
Hyperthermia as a result of
fever or heat stroke
Thyroid hormone deficiency
or hyperactive thyroid.
Seizures are a common
disorder in dogs. When tests are done and no reason can be found for the
seizure, the disorder is referred to as “idiopathic epilepsy”. The term
“idiopathic” means that there is no cause for the problem, and that the seizures
are not the result of another disease process. This is the type of epilepsy
which is usually considered to have an inherited basis.
Idiopathic epilepsy is the
most common canine seizure disorder, occurring in up to nearly 6% of all dogs.
The problem is more prevalent in some breeds than others. There is a suspected
genetic basis for idiopathic epilepsy in German Shepherds, Belgian Tervurens,
Keeshonden, Beagles, Dachshunds, Pugs, Poodles, St. Bernards, Irish setters,
Siberian Huskies, Cocker Spaniels, Wire-Haired Fox Terriers, Labrador and Golden
Retrievers, and Australian Shepherds. In breeds which are genetically
predisposed, up to 14% of the population may develop epilepsy. As epilepsy has
been shown to be an inherited disorder in humans, baboons, mice, rats, rabbits,
gerbils, and chickens, it seems logical that is can be an inherited disorder in
dogs as well. Test breeding of epileptic dams and sires done by veterinary
researchers have produced incidences of epilepsy in the offspring ranging from
between 38% (affected to nonaffected) to 100% (breeding together of two affected
Hereditary epilepsy commonly
begins between the ages of 1-3 years. Seizures which begin earlier or later in
the dog's life most probably are a result of a disease process such as those
listed above. Your vet will likely want to rule out these conditions before
deciding that your dog has hereditary epilepsy.
If your dog has a seizure,
don’t panic. Check the clock and make a note of how many seconds or minutes the
seizure activity lasts. Keep your dog in a safe environment until the seizure is
over. Note what type of abnormal muscular activity happens, so you can describe
it for your vet. Do not put anything in your dog’s mouth. Remain by your dog to
comfort him. Call your vet for further advice. If the seizure lasts more than a
few minutes, take your dog to the closest veterinary facility for immediate
care. If your dog has recurrent seizures (more than once in 24 hours), again,
seek immediate medical assistance.
Epileptic Seizure Treatment Choices
Determining the cause is
essential for making appropriate treatment choices, and to assist in breeding
decisions. You should seek the advice of your veterinarian. Your vet will obtain
a medical history, and a full exam including a neurological exam. He will do
blood tests, a urinalysis and fecal exam to look for any possible cause for the
seizures. Other exams may include x-ray or ultrasound of the abdomen, EEG to
evaluate brain waves, skull x-ray or head MRI, and a cerebrospinal fluid
analysis if infection is suspected. Treatment will depend upon the cause of the
In the case of idiopathic
epilepsy, if your dog experiences seizures more frequently than once a month,
your vet may decide to place your dog on seizure medication. Antiepileptic drugs
do not cure epilepsy, they simply control the seizures. Life-long therapy may be
expected. The drugs increase inhibition in the brain, decrease the seizure
threshold, and thus make seizures less likely. This often results in side
effects such as sedation, un-coordination of movements and appetite stimulation.
These effects lessen with time as the body becomes habituated to the medication.
The number of dogs who have serious side effects from the medication is small,
and often preventable through careful health monitoring. Regular rechecks are
essential, and a thorough physical should be done at least yearly.
Phenobarbital and Primidone
(Mysoline) are considered first line drugs for idiopathic epilepsy. They are
eliminated by the liver and over time may cause liver damage. Your vet will want
to monitor liver function tests on a regular basis to avoid this problem. Also
blood levels of these drugs are checked to help with deciding on the dosage
required. Bone marrow depression and anemia may occur, so a blood count should
be done yearly as well.
Potassium Bromide can be
used in dogs. Interestingly, it is not well tolerated by humans, as it causes
psychological problems in people. However, this is not a problem for dogs. Salty
foods should not be given with bromide. Bromide can be mixed with food, as it
sometimes can cause an upset stomach.
Valium (diazepam) is
affective in treating the acute phase of seizure activity. It is not as
effective when given routinely, and is usually reserved for emergency
Many of the newer
antiepileptic drugs, such as Dilantin, Tegretol, and Depakote, are metabolized
more quickly by dogs than humans. The need for frequent dosing (and their higher
price tag) makes their use impractical for dogs.
Unless the seizures are due
to low blood sugar or low oxygen due to heart/lung disease, there is no reason
to restrict activity. Most epileptic seizures occur when the pet is relaxed and
quiet, or even sleeping. Most epileptic pets can lead relatively normal lives
with careful monitoring, a healthy diet, plenty of fresh air and exercise, and
their favorite human nearby.
Davol, Pamela A.
"Understanding Canine Epilepsy"
Dvorak, Roy, "Why Does My
Dog Have Seizures"
Thomas K, DVM, "Seizures in Dogs"
O'Brien, Dennis, DVM, PhD.,
"Understanding Your Pet's Epilepsy"
Primovic, Debra, DVM, "Seizure Disorders"
More on epilepsy > Epileptic Seizures - Cause and Treatment