WHAT IS A SEIZURE?
By Wendy C. Brooks, DVM, DipABVP
Educational Director, VeterinaryPartner.com
Any involuntary behavior that occurs abnormally may
represent a seizure. Seizures are classified into several categories.
GENERALIZED (GRAND MAL) SEIZURES - This is the most common form of
seizure in small animals. The entire body is involved in stiffness and possibly
stiffness/contraction cycles (tonic/clonic action). The animal loses
consciousness and may urinate or defecate.
PARTIAL SEIZURES - This form of seizure originates from some specific
area in the brain and thus involves the activity of a specific region of the
body. Partial seizures may generalize to involve the whole body.
PSYCHOMOTOR SEIZURES - This type of seizure is predominantly behavioral
with the animal involuntarily howling, snapping, circling, etc. The abnormal
behavior may be followed by a generalized 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
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. Fainting animals are usually up and normal within seconds of the
spell.
!!! POST-ICTAL DISORIENTATION IS THE HALLMARK OF
THE SEIZURE !!!
CAUSES OF SEIZURES AND DIAGNOSTICS
Seizures may be caused by situations within the brain, such as trauma or
infection; or by situations centered outside the brain, such as low blood sugar,
hypothyroidism, circulating metabolic toxins, or external poisons. The first
step is to rule out situations centered outside the brain, easily done with a
blood test. An ophthalmic exam may also be performed as the retina may show
signs of a brain infection. If these tests are negative, the next step is
determined by the age of the pet.
ANIMALS LESS THAN AGE 1 YEAR - Seizures are usually caused by infections
of the brain. (Canine distemper would be the classic cause of seizures in a
puppy.) Analysis of cerebrospinal fluid, obtained by a tap under anesthesia,
would be important.
ANIMALS BETWEEN AGES 1 AND 5 - In these animals, usually no cause can be
found and the term epilepsy, which simply means seizure disorder, is applied. If
seizures are occurring frequently enough, medication is used to suppress them.
Schnauzers, Basset hounds, Collies, and Cocker spaniels have two to three times
as much epilepsy as other breeds.
ANIMALS MORE THAN AGE 5 YEARS - In this group, seizures are usually
caused by a tumor growing off the skull and pressing on the brain (a meningioma*).
Most such tumors are operable if found early. A CAT scan or MRI would be the
next step. Special referral is necessary for this type of imaging. For patients
where surgery is not an option, corticosteroids may be used to reduce swelling
in the brain. Treatment to suppress seizures may also be needed (see below).
Epilepsy is the name given to seizure disorders for which no cause can be found.
It is not a unique disease in and of itself.
Seizures resulting from metabolic problems or toxicity (i.e., when the brain
itself is normal) are called
REACTIVE SEIZURES
Seizures resulting from an identifiable brain abnormality are called
SECONDARY SEIZURES.
Seizures for which neither of the above problems apply (i.e., when no cause can
be found) are called PRIMARY SEIZURES.
MEDICATION TO SUPPRESS SEIZURES: PHENOBARBITAL
Treatment of any seizure disorder is aimed at suppressing the seizure with
medication. The drug of choice is phenobarbital.
WHEN TO BEGIN TREATMENT:
When seizures occur in clusters, that is, one after the other.
When isolated seizures occur once a month or more.
When special circumstances exist regarding how often the animal is observed. (If
an animal cannot be observed, there is no way of knowing how frequently its
seizures are occurring. It may be best to play it safe.)
The German Shepherd dog, Golden retriever, Irish setter, or 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.
WHAT YOU SHOULD KNOW ABOUT PHENOBARBITAL
This medication is a long-acting barbiturate capable of suppressing seizure
activity in the brain. It is an inexpensive drug though the monitoring necessary
amounts to about $300 per year.
It takes 1 to 2 weeks to build up a blood level capable of suppressing seizures.
This means that the effectiveness of a given dose cannot be assessed before this
period. After this time, a phenobarbital blood level should be run to determine
the effectiveness of the dose being used. Phenobarbital blood levels, once
therapeutic, are checked every 6 months or sooner if breakthrough seizures
occur.
Twenty to thirty percent of epileptic dogs cannot be controlled with
phenobarbital alone. If an animal on phenobarbital continues to seizure, a blood
level must be drawn. Before adding other drugs, however, it must be shown that
the maximum therapeutic phenobarbital blood level has been ineffective; most
animals are no where near the maximum level and simply require a dose higher
than what they are receiving. If phenobarbital is simply not effective or has
unacceptable side effects, potassium bromide may be used to complement
phenobarbital at a lower dose.
Another important part of monitoring regards the toxicity of phenobarbital. This
medication can be harmful to the liver thus liver function is periodically
checked. A bile acids liver function test and a phenobarbital blood level are
recommended twice a year.
COMMON SIDE EFFECTS
SEDATION - animals may become quite stuporous as they get used to this drug.
This effect is temporary, lasting until the patient's metabolism adjusts
(usually no longer than a few days).
EXCESSIVE THIRST AND APPETITE - These side effects are annoying and,
unfortunately, permanent if they occur. If these side effects become too
objectionable, the phenobarbital dose will have to be lowered and another
medication added for seizure control.
WHAT IF PHENOBARBITAL DOESN'T WORK OR CAUSES UNACCEPTABLE SIDE EFFECTS?
This can happen and in such cases, potassium bromide (often abbreviated KBr)
becomes the next best choice. The phenobarbital dose is generally cut back and
potassium bromide is given at a high dose for a day or two before dropping to a
maintenance bromide dose. Potassium bromide is felt to be an investigational
treatment by the FDA and special permission is needed to use it; still, 85% of
phenobarbital failures can be controlled with potassium bromide. Bromides reach
therapeutic levels very slowly (months), thus in most cases, bromides and
phenobarbitol are used in combination. Due to the success of seizure control
with potassium bromide, many neurologists begin therapy here instead of with
phenobarbital.
SEIZURES AT HOME (WHEN IS IT AN EMERGENCY?)
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. It is important not to put yourself in danger around
a seizuring pet. You may get bitten during involuntary jaw snapping, and in the
period of post ictal disorientation the pet may not recognize you and may snap.
There are, however, some emergency situations:
SEIZURE ACTIVITY NON-STOP FOR 5 MINUTES OR MORE
(this is called status epilepticus)
MORE THAN 3 SEIZURES IN A 24-HOUR PERIOD
If a particularly bad seizure occurs at home or if either of the above
emergencies occur, a special first aid technique can be used: Rectal
administration of valium. In initial studies the injectable product was
delivered rectaly with a special syringe that could be kept at home. The rectal
route avoids any danger of being bitten while trying to asminister medication.
Recently compounding pharmacies have been able to produce valium rectal
suppositories which may be easier to use than the syringe method. Rectal valium
administration has been used successfully for many years in epileptic children;
the technique has adapted well to veterinary patients.
CAN SEIZURE MEDICATION BE STOPPED?
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 retreivers, Irish
setters, St. Bernards). 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.
OTHER INFORMATION
*At the 2004 meeting of the American College of Veterinary Internal Medicine, a
study by Mikszewski's group from the University of Pennsylvania presented a
retrospective study on 171 canine brain tumor cases. They found 46% of tumors to
be meningiomas, 17% astrocytomas, 15% oligodendrogliomas, 7% choroid plexus
tumors, and 4% were cases of lymphoma arising in the brain. The average age at
diagnosis was 9.5 years. Most dogs were mixed breeds but the second most common
breed was the Golden retriever (and third most common breed was the Boxer). The
most common symptom bringing the dog to the veterinarian was seizures. Enough
of the patients studied had abnormalities on chest radiographs or abdominal
ultrasound for the researchers to recommend these procedures prior to expensive
brain imaging or surgery.
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
http://www.canine-epilepsy.net/cerc.html
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.
Epil-K9
This is a support and news group for owners of seizuring dogs. The group has a
substantial library of useful resources at:
Copyright 2001 - 2007 by the
Veterinary Information Network, Inc. All rights reserved.
This work was originally published by Veterinary Information
Network, Inc. (VIN) and is republished with VIN's permission.
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