Neurology Service: Information for Owners: Seizures
This information is not meant to be a substitute for
veterinary care. Always follow the instructions provided by your
A seizure is defined as a paroxysmal, transitory disturbance
of brain function that has a sudden onset, ceases spontaneously,
and has a tendency to recur. Generalized seizures affect the
entire body. Most commonly, animals will fall to the side, make
paddling movements with the limbs; they will often will urinate,
salivate and defecate during the episodes. Generalized seizures
usually last from several seconds to upwards of a couple
minutes. Focal seizures remain localized to one body region and
are usually shorter in duration, lasting a couple seconds.
Seizures may start focal and then become generalized.
After the veterinarian is convinced that a seizure disorder is
present, the most important question to be answered is whether
the seizure is the result of primary brain disease (intracranial
disease), or the result of a disturbance outside the brain (extracranial
disease), The most common intracranial causes of seizures
include: structural disease including hydrocephalus, head
trauma, inflammatory brain disease (encephalitis), strokes and
neoplasia (brain cancer). The most common causes of
extracranial diseases that cause secondary brain signs include:
toxins and metabolic diseases. Metabolic diseases include:
low blood sugar (hypoglycemia), high blood sugar
(hyperglycemia), liver disease, kidney disease, electrolyte
disturbances, toxins (poisons), anemia.
Idiopathic epilepsy is another common cause of seizures in dogs
and less commonly in cats. It is by definition, seizures
of unknown cause. These episodes are thought to be due to
"mal-wiring" within the brain. Idiopathic epilepsy is seen
in dogs between the ages of 6 months and 6 years of age.
It is more common in certain breeds: border collies,
Australian Shepherds, Labrador retrievers, beagles, Belgian
Tervurens, collies and German shepherds. That being said,
seizures can occur in any breed of dog or cat. To search for the
cause of seizures, a systemic work up is performed (physical and
neurologic exam, blood work, blood pressure, sometimes chest
x-rays, specific liver function test including bile acid
testing). Once an extra-cranial cause of seizures is ruled
out, then the brain is imaged using either a CT scan or an MRI.
Following brain imaging, a cerebrospinal fluid (CSF) tap is
performed in order to look for encephalitis. If an underlying
disease can be found, then primary treatment for that disease
may help to make the seizures stop. If the seizures are
recurrent, anticonvulsant medications are often given. The
choice of medication depends upon the characteristics of the
individual animal's problem. Some of the more commonly used
anticonvulsants are listed below. It is important to remember
that once an anticonvulsant is initiated, it should not be
changed without veterinary assistance. Most animals with
idiopathic epilepsy will require anticonvulsant medication for
the rest of their life.
Drugs Used to Treat Seizures
- Phenobarbital is the most commonly used anticonvulsants
in veterinary medicine because it is effective and also
inexpensive. Side effects include: sedation, incoordination and rear limb weakness, , increased drinking,
urination and appetite. With high dosages or prolonged use,
phenobarbital can cause damage to the liver. Paradoxically, some
animals given phenobarbital may become restless and excitable.
If any of these signs are observed, occurs, consult your
veterinarian for assistance. For best results, this drug needs
to be given consistently (every day) at least twice daily. This
drug should not be altered without veterinary consultation.
- Potassium Bromide is another effective first-line
seizure medication used in veterinary medicine. Due to its
lack of metabolism it is the ideal anticonvulsant for patients
with liver disease. Side effects include: sedation, incoordination,
limb weakness and vomiting. Pancreatitis has also been
described as a possible complication. If any of these
signs are observed, occurs, consult your veterinarian for
- Levetiracetam (Keppra) is a newer anti-convulsant for
use in veterinary medicine. It is also not liver
metabolized making it safe in patients with liver disease.
It is to be given three times daily. Side effects are rare
and include sedation and incoordination.
- Zonisamide (Zonegram) is a newer anti-convulsant for use
in veterinary medicine. It, like phenobarbital, is
metabolized by the liver. It is a sulfonamide medication
and can therefore cause dry eye, decreases in white and red
blood cells. It can also cause liver disease and sedation
- Diazepam (Valium) is a medication to be given on an
emergency basis to halt an active seizure in dogs and cats
because its effects are very short acting. Thus, this
medication is not used on a daily basis. Side effects
include drowsiness, lethargy, and depression and liver disease.
This information was made possible by funds from the
at Washington State University.
Washington State University assumes no liability for injury to you or
your pet incurred by following these descriptions or procedures.