Seizures in Pets

The diagnosis and treatment of seizure disorders in small
animals are similar in many respects to the diagnosis and
treatment of other ailments: a historical problem arises, a
therapy is started to treat the underlying disease and/or signs
of the disease. In seizure disorders, however, unlike other
diseases, a long period of normal activity may occur between the
seizure event. Even during these normal periods, serious
conditions may still be present as the cause of the seizures.
Knowing which animals are at the highest risk for such problems
is helpful in planning the proper tests and treatment.

First, your veterinarian wants to be sure that an epileptic
seizure has occurred and, if so, the seizure type(s) manifested.
An epileptic seizure is the clinical sign of excessive, abnormal
activity in the brain and the clinical features can be separated
into three components. The aura is the initial manifestation of
a seizure.

During this time period, which can last from minutes to hours,
animals can exhibit recurrent pacing or licking, excessive or
unusual salivation or vomiting, and/or even unusual psychic
events such as excessive barking or increased or decreased
attention seeking. Some owners even report that they know their
dog is going to have a seizure days in advance by changes in the
animal’s behavior. The ictal period is the actual seizure event,
manifested by involuntary muscle tone or movement and/or
abnormal sensations or behavior, usually lasting from seconds to
minutes. After the ictal event is the postictal period. During
this time, an animal can exhibit unusual behavior,
disorientation, inappropriate bowel or bladder activity,
excessive or depressed thirst and appetite, and actual
neurologic problems, such as weakness and blindness.

Seizure types can be classified into two major categories:
partial and generalized. Partial seizures are the result of a
focal abnormal electrical event in the brain. This seizure type
is associated with a higher prevalence of focal disease, such as
a tumor. Animals with simple partial seizures have a sudden
change in activity without any change in awareness, such as
twitching of facial muscles. Animals with complex partial
seizures often show bizarre behavioral activity, such as
“fly-chasing” behavior patterns. Generalized seizures are either
convulsive (“grand mal”) or nonconvulsive (“petit mat”)
seizures. Generalized convulsive seizures are by far the most
common seizure type seen in animals and are characterized by
impaired consciousness coupled with symmetric stiffening,
paddling, or even loss of movement of the limb muscles. The
major form of nonconvulsive seizure is the “absence” variety,
manifested as a “spacing-out” episode. The severity of the
seizure does not necessarily match the cause, as dogs with brain
tumors may have mild partial seizures and dogs with primary
epilepsy may have severe generalized seizures.

The second level of assessment is the diagnosis of the cause of
the seizures. Just as a cough signals a problem in the airway, a
seizure tells us there is a problem in the brain, but not the
cause. The goals of a diagnostic evaluation are to determine the
underlying cause, evaluate the chance for recurrence, and
establish whether medication is necessary for treatment. Primary
epileptic seizure (PES) is diagnosed if no underlying cause of
the seizure can be identified (idiopathic). This term is often
reserved for inherited epilepsy in people, but the genetic
component of epilepsy is difficult to determine in many animals.
Breed-related inherited epilepsy in the dog has been documented
in beagle, Belgian Tervuren, keeshond, dachshund, and Siberian
husky dogs. Other breeds with a high prevalence of an inherited
component of their seizures are German shepherd, border collie,
Irish setter, and golden retriever dogs. A diagnosis of PES is
most common in large breed dogs 1 to 5 years of age and/or when
the interval between the first and the second seizure event is
long (>4 weeks).

Secondary epileptic seizure (SES) is the direct result of an
abnormal brain structure. The conditions involved include
developmental brain problems, inflammation, tumors or strokes.
An animal is categorized as having epilepsy if recurrent PES or
SES is diagnosed, indicating the presence of a chronic brain
disorder.

Reactive epileptic seizure (RES) is a reaction of the normal
brain to transient systemic insults or physiologic stresses. A
patient with recurring RES is not defined as having epilepsy, as
there is not a primary chronic brain disorder underlying the
seizure activity. An underlying identifiable cause (SES or RES)
of the seizures is suspected in dogs that have an initial
seizure when they are younger than 1 or older than 5 years of
age, the initial interval between the first and second seizure
events is less than 4 weeks, or a partial seizure is the first
observed seizure. Cats, in general, do not suffer as frequently
from seizures as dogs. When cats have seizures, there is a high
likelihood that an underlying problem in the brain (SES) is
present, such as inflammation, stroke, or tumor.

Maintaining a seizure-free status without unacceptable adverse
effects is the ultimate goal of antiepileptic drug (AED)
therapy. This is optimal balance is achieved in less than half
of epileptic people and, probably, just as many dogs. Before
starting AED treatment, owners and veterinarians should have a
realistic idea of what to expect over the course of therapy.
First and foremost is that seizure control does not equal
elimination. Decreasing the number and severity of seizures and
postictal complications, while increasing the time period
between seizures, is a realistic goal. Once treatment is
started, you should realize that there is a daily treatment
regimen, reevaluations are required, and there is a potential
for emergency situations to arise, along with the inherent risks
of the drug.

The decision to start AED therapy is based on the underlying
cause, seizure type and frequency, and postictal effects. An
acceptable AED is one that can be given two to three times per
day, has documentable benefit, is well tolerated, and has few
side effects. The two AEDs most widely used in the dog and cat
are phenobarbital and potassium bromide. Bromide has the benefit
of a reduced chance of liver toxicity but may not be as
effective as phenobarbital for stopping all types of seizures or
work as quickly. Periodic measurements of the amount of drug
present in the bloodstream are necessary to determine that an
acceptable level of medication is present. At the same time,
blood test to evaluate liver function may be necessary.

These periodic evaluations are important in trying to maximize
the benefit of drug therapy while monitoring for early detection
of possible complications. Treating each animal as an
individual, applying the philosophy that seizure prevention is
better than intervention, and consulting your veterinarian to
help formulate or revise treatment plans increase chances of
success.

The above is general veterinary information. Do not begin
any course of treatment without consulting your regular
veterinarian. All animals should be examined at least once every
12 months.