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Canine Epilepsy
By Alicia
Aylward Marcinczyk
Alicia is the Health Registry Chair (and Rescue Chair)
of the United Belgian Shepherd Dog Association, the
BSD parent club under UKC. As a layperson, she says,
"I could find little comprehensible information about
seizures or epilepsy, so I decided to research my own
article on the subject and make it available to other
dog owners. The article now appears at several Web sites
and has been published in a number of canine newsletters
and magazines." Email: aliciam@maine.maine.edu
Copyright
©1996, 1997 HomeVet
Introduction
It happened
without warning. One moment my young male Belgian Tervueren
was snuggling against me as I sat on the couch; the
next moment he lost control of his hindquarters and
fell onto his side, unconscious. His lips writhed back
over his teeth; his legs stretched out, then became
rigid; and his head twisted up and back as if an unseen
hand was trying to raise his chin to an impossible height.
It seemed like an eternity, but actually only two minutes
passed before his body relaxed and consciousness slowly
ebbed back. For an hour afterward he seemed exhausted
and disoriented. I was shaken too, never having witnessed
such a seizure before. Yet later that day the dog was
romping about as if nothing out of the ordinary had
occurred.
My dog is lucky.
His seizures have been few and far between. We now believe
they are caused by hypothyroidism. Other dogs are not
so lucky. Seizures can be severe and frequent. They
may occur in "clusters" (several in one day), or progress
to the life-threatening state of status epilepticus.
In extreme cases where seizures cannot be controlled,
a veterinarian may advise euthanasia.
Epilepsy is found
in all breeds and mixed breeds of dogs. Belgian Tervueren
are listed among the breeds for which a genetic factor
is either proved or highly suspected. Other breeds so
listed include the Beagle, Dachshund, German Shepherd
Dog, (Alsatian), and Keeshond. A high incidence of seizure
disorders is also found in Boxers, Cocker Spaniels,
Collies, Golden Retrievers, Irish Setters, Labrador
Retrievers, Miniature Schnauzers, Poodles, Saint Bernards,
Siberian Huskies, and Wire-Haired Terriers. [Oliver,
Seizures]. The prevalence of epilepsy in the general
dog population has been estimated at .5 to 5.7 percent.
[Koestner, Cunningham].
A progress report
on the epilepsy survey conducted by the American Belgian
Tervuren Club in cooperation with John Oliver, Jr.,
DVM in 1983 found that 57 (21 percent) of the 268 Tervueren
studied had suffered more than one seizure. The authors
of that report concluded, "At this time, we believe
there is sufficient evidence for the probable genetic
basis of seizures in Tervuren to warrant concern on
the part of breeders". [Mahaffey]. Unfortunately, this
survey was discontinued.
The term "epilepsy"
can be confusing because some authors use it to describe
recurrent seizures of any etiology (cause), while others
use it to specify recurrent seizures unrelated to brain
disorders or underlying disease processes. [Shell, Understanding.].
The definitions below are helpful in distinguishing
types of epilepsy.
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Types
of Epilepsy
Primary
epilepsy: also known as idiopathic, genetic, inherited,
or true epilepsy. There are no positive diagnostic findings
that will substantiate the diagnosis. It is a case of
ruling out every other possibility. The first seizure
in a dog with primary epilepsy usually occurs between
the ages of 6 months and 5 years. [Oliver, Seizures].
However, a diagnosis of primary epilepsy is not proof
of a genetic defect; only careful breeding studies could
prove that. The breed, the age, and the history may
suggest a genetic basis for primary epilepsy if there
is a familial history of seizures.
Secondary epilepsy
refers to seizures for which a cause can be determined,
and there are many. In dogs less than one year of age,
the most commonly-found causes of seizures can be broken
down into the following classes: degenerative (storage
diseases); developmental (hydrocephalus); toxic (lead,
arsenic, organophosphates, chlorinated hydrocarbons,
strychnine, tetanus); infectious (distemper, encephalitis,
and others); metabolic (such as transient hypoglycemia,
enzyme deficiency, liver or kidney failure); nutritional
(thiamine, parasitism); and traumatic (acute injury).
In dogs 1-3 years of age, a genetic factor is most highly
suspected. In dogs 4 years of age and older, seizures
are commonly found in the metabolic (hypoglycemia, cardiovascular
arrhythmia, hypocalcemia, cirrhosis) and neoplastic
(brain tumor) classes. [Oliver, Seizure]. Dr. Jean Dodds
has mentioned that seizures are also associated with
hypothyroidism, which is a familial (inherited) autoimmune
disease of purebred dogs.
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Types
of Seizures
The types
of seizures most commonly reported are listed below.
If you believe your dog is having a seizure, it is important
to note all the details so that you may accurately describe
it to your veterinarian. Types of seizures include:
Generalized
Seizure: Tonic-clonic (may be Grand Mal or
Mild): In the grand mal seizure, the tonic phase occurs
as the animal falls, loses consciousness, and extends
its limbs rigidly. Respiration also stops (apnea). This
phase usually lasts 10-30 seconds before the clonic
phase begins. Clonic movements include paddling of the
limbs and/or chewing. Other signs that appear during
the tonic or clonic phase are dilation of the pupils,
salivation, urination, and defecation. The mild seizure
involves little or no paddling or extension of limbs,
and usually no loss of consciousness. Generalized seizures
are usually associated with primary epilepsy.
Petit
Mal Seizure (aka Absence Seizure): Depending
on the authority quoted, petit mals are described as
either very rare or usually unrecognized in animals.
Signs are brief (seconds) duration of unconsciousness,
loss of muscle tone, blank stare, and possibly upward
rotation of eyes. According to one authority [Kay],
the term petit mal is misused by veterinarians and should
only be accorded to cases manifesting very specific
clinical signs and EEG abnormalities.
Partial
Seizures: Movements are restricted to one area
of the body, such as muscle jerking, movement of one
limb, turning the head or bending the trunk to one side,
or facial twitches. A partial seizure can progress to
(and be mistaken for) a generalized tonic-clonic seizure,
but the difference can be established by noting whether
or not a seizure starts with one specific area of the
body. Partial seizures are usually associated with secondary
epilepsy.
Complex
Partial Seizures (aka Psychomotor or Behavioral) Seizures:
are associated with bizarre or complex behaviors
that are repeated during each seizure. People with complex
partial seizures experience distortions of thought,
perception or emotion (usually fear), sometimes with
unusual visual, olfactory, auditory and gustatory sensations.
If dogs experience the same things, it may explain the
lip-smacking, chewing, fly biting, aggression, vocalization,
hysterical running, cowering or hiding in otherwise
normal animals. Vomiting, diarrhea, abdominal distress,
salivation, blindness, unusual thirst or appetite, and
flank biting are other signs. There is an obvious lack
of awareness though usually not lack of consciousness.
Abnormal behaviors may last minutes or hours and can
be followed by a generalized seizure. Complex partial
seizures are usually associated with secondary epilepsy.
Cluster
Seizures: Multiple seizures within a short
period of time with only brief periods of consciousness
in between. May be confused with status epilepticus.
Status
Epilepticus: Status can occur as one continuous
seizure lasting 30 minutes or more, or a series of multiple
seizures in a short time with no periods of normal consciousness.
It can be difficult to tell status epilepticus from
frequent cluster seizures; but both are considered life-threatening
emergencies. Most status patients usually suffer from
eneralized tonic-clonic seizures. Though status epilepticus
can occur with either primary or secondary epilepsy,
it may also suddenly arise in dogs with no previous
history of seizures (traumatic brain injury, toxins,
or disease). [Dyer & Shell, Managing].
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What
Is a 'Seizure Threshold'?
Dr. Alexander
de Lahunta of Cornell University and others suggest
that each animal inherits a genetically determined predisposition
to seizures", and that seizures occur when this threshold
is exceeded. [Cunningham, Inherited]. In other words,
a physical condition (see examples under section on
secondary epilepsy above) which may cause seizures in
a low-threshold animal may not cause seizures in a "normal"
animal.
The seizure threshold
is apparently exceptionally low in animals that suffer
from idiopathic (primary) epilepsy. [de Lahunta]. An
animal's threshold can also be altered by other means.
Certain types of tranquilizers (e.g. acepromazine) may
induce seizures in animal with a low threshold. The
medical condition of alkalosis is reported to decrease
the threshold. [Shell, Differential]
Karen R. Dyer,
DVM, PH.D, and Linda G. Shell, DVM, Dilp. ACVIM, note
that there is "convincing experimental evidence" that
repetitive seizures can "irreversibly lower the seizure
threshold" in a process called kindling. William Fenner,
DVM and Julie Haas, DVM, describe kindling as a mechanism
in which epileptic neurons in the brain "recruit" normal
neurons into the original seizure focus, enlarging the
area of the brain that can produce seizures. Linda Shell,
DVM describes kindling as the "increased excitability
of neurons", and notes that normal neurons, sufficiently
stimulated, become increasingly able to cause seizures
independent of outside stimulation.
The mirror focus
phenomenon also deserves mention. Each hemisphere of
the brain is a "mirror image" of the other. A seizure
focus on one side of the brain will show itself as abnormal
wave forms on EEG recordings. Within a period of weeks,
the "normal" side of the brain will start to show similar
EEG abnormalities. In time, the mirror focus becomes
capable of causing seizure activity on its own. Thus,
repetitive, uncontrolled seizures also lower the seizure
threshold in any given animal. That is why early intervention
is so important in the control of seizures.
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Stages
of a Seizure
There
are 4 basic stages to a seizure: 1) the prodome, 2)
the aura or preictus, 3) the ictus or seizure stage,
and 4) the postictus.
- The prodome
may precede the actual seizure by hours or days. It
is characterized by a change in mood or behavior.
Human epileptics experience mood changes, headaches,
insomnia or feelings about the impending seizure.
It is not known whether animals experience a prodome
except for any behavioral changes observed by their
owners.
- The aura signals the start of the
seizure. Signs include restlessness, nervousness,
whining, trembling, salivation, affection, wandering,
hiding, hysterical running, and apprehension.
- The ictus is the actual seizure,
characterized by sudden increase in tone of all muscle
groups. The ictus is either tonic or tonic-clonic,
generally lasting from 1-3 minutes.
- The postictus may be the only sign
of epilepsy the owner sees, particularly since many
seizures occur at night or early in the morning. For
minutes to days after the seizure, the dog may be
confused, disoriented, restless, or unresponsive,
or may wander or suffer from transient blindness.
At this stage the animal is conscious but not functional.
[Shell, Understanding; Kay; Oliver, Seizures].
What can you
do when your dog seizures? Note the time to determine
how long the seizure lasts. Keep the dog as quiet as
possible. Loud or sharp noises may prolong the seizure
or make it worse. Other dogs should be removed from
the area, as they may disturb or attack the seizuring
dog. Should you attempt to comfort the animal? Opinions
on this vary. My own dog is comforted by my presence
and looks for me as he returns to consciousness. I make
a point of calmly maintaining physical and voice contact
with him throughout the seizure and during recovery.
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Diagnosing
Epilepsy
What
do you do if you think your dog has had a seizure? Veterinarians
have a number of diagnostic tools at their disposal.
For dogs who
have had only one isolated seizure, a complete physical
and neurological examination is in order. Owners will
be advised to watch for further seizures if no abnormalities
are found. Medical treatment will not be instituted
until future activity can be noted.
For every patient
having more than one seizure, a minimum data base should
be developed. The data base contains the patient's profile,
history, results of complete physical and neurological
examinations, and basic tests. The profile consists
of the dog's breed, age, and sex. Pertinent history
includes vaccinations, potential exposure to toxins,
diet, any illnesses or injuries, behavioral changes,
and whether seizures occurred in any animal related
to the dog.
Owners are also
asked to give a complete description of the seizures:
frequency, duration, and severity, as well as any behavioral
abnormalities associated with them. An accurate description
is important because there are other conditions with
symptoms that mimic seizures, such as cardiac and/or
pulmonary disease, narcolepsy, cataplexy, myasthenia
gravis, and metabolic disturbances.
Among the recommended
tests are: CBC, urinalysis, BUN, ALT, ALP, calcium,
fasting blood glucose level, serum glucose level, serum
lead level, fecal parasite or ova examination, and others
if indicated. When the results of the examinations and
tests have been analyzed, one of three conclusions will
be drawn: a definitive diagnosis, a potential cause
of seizures requiring further tests to confirm, or no
suggestion of a cause.
When further
tests are required a complete date base should be done.
This may include computed tomography or magnetic resonance
imaging; CSF analysis (cell count, protein levels, pressure),
skull radiographs, and an EEG.
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Treatment
Medical
treatment is generally advised for animals who have
one or more seizures per month. Animals who have cluster
seizures or go into status epilepticus may be treated
even though the rate of incidence is greater than once
per month. Successful drug therapy depends upon the
owner's dedication to delivering the drug exactly as
prescribed, with absolutely NO changes in the dose or
type of medication without veterinary consultation.
Haphazard drug administration or abrupt changes in medication
is worse than no treatment at all, and may cause status
epilepticus.
William Thomas,
DVM, MS feels it important to remember that the goal
of treatment is to decrease the frequency and severity
of seizures and avoid unacceptable side effects. It
may not be possible to stop the seizures altogether.
A number of drugs and some alternative therapies may
be used to control epilepsy. Phenobarbitol and primidone
are the most widely used anticonvulsant drugs, but others
have their place in treatment as well.
Phenobarbitol
is one of the most commonly prescribed drugs. Frey reports
that while dogs rapidly develop tolerance to the sedative
and hypnotic effects of phenobarbitol, at high concentrations
tolerance may be lost and persistent depressive side
effects may appear. Dogs may eat or drink more than
their usual amounts. Liver function can be impaired.
When use of the drug is terminated, signs of physical
dependence (tremors, incoordination, restlessness, seizures)
may develop. There is danger of triggering status epilepticus
during withdrawal. To avoid this, dosages should be
gradually reduced in small steps over a prolonged period.
Primidone's side
effects include sedation when treatment is initiated,
and eating or drinking more than usual. High concentrations
of liver enzymes have been reported with prolonged treatment
at high dosages.
Diazepam (Valium)
is used for treatment of status epilepticus. Phenytoin
(Dilantin), carbamazine, and valproic acid are not currently
recommended for use.
Potassium bromide
(KBr) is gaining new recognition for use in refractory
(difficult to control) canine epilepsy, though used
to treat human epileptics as early as 1857. It is the
anticonvulsant of choice for dogs with liver disease.
Sodium bromide is preferred for dogs with kidney problems.
Combining potassium bromide or sodium bromide and phenobarbitol
may be useful for patients who do not respond well to
phenobarbital or primidone alone.
One recent study
(Pearce) reported that 10 dogs who had uncontrolled
seizures with phenobarbitol alone had improved control
with the addition of potassium bromide to their drug
regimen. The severity of the seizures and the tendency
to cluster were significantly decreased. An earlier
study by Professor Dorothea Schwartz-Porsche [Sisson/LeCouteur]
reported that 5 of 9 epileptics uncontrolled by phenobarbitol
responded to the addition of potassium bromide to either
phenobarbitol or primidone. Podell and Fenner reported
that bromide therapy improved seizure control in 83%
of dogs previously unimproved by phenobarbitol; 26%
of the 83% dogs became totally seizure free.
Bromide is not
approved for use in dogs, nor is it commercially available
at this time. Veterinarians can obtain it from chemical
supply houses as an American Chemical Society reagent,
which dissolves in water and is added to the dog's food.
Dog owners are asked to sign release forms and are advised
to handle the drug with gloves. Thomas notes that some
custom pharmacies will now formulate bromide in capsules
or suspension so the veterinarian doesn't have to.
Side effects
of bromide toxicity (bromism) can include incoordination,
depression, muscle pain, and stupor. There are no dermatologic
or gastrointestinal signs as seen in humans taking KBr.
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Monitoring
Drug Treatment
In order
for any drug therapy to be effective, the amount of
drug found in the body (serum concentration) must be
consistently monitored. No two animals may react to
the same dose in the same way. Farnbach reports a sixfold
variation in the ratio between daily dosage and serum
concentration was demonstrated in a large population
of epileptic dogs. In 3 dogs given roughly the same
dose of phenobarbitol, one dog's condition did not change,
the second dog achieved seizure control, and the third
dog experienced toxicosis. The amount of drug found
in the body correlates much better with seizure control
than daily dosage.
If your dog is
on medication, work with your veterinarian in observing
your dog and testing his/her serum levels to ensure
he/she is receiving the appropriate amount of drug to
achieve control and avoid side effects.
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Why
Treatment Fails
There
are many reasons why medical treatments can fail. The
biggest reason is the owner's lack of proper administration
of the prescribed drug. The progression of an underlying
disease (such as brain tumor) may resist treatment.
Also, gastrointestinal disorders can affect drug absorption,
and tranquilizers may stimulate seizures. Drug interactions
can occur and adversely affect the level of anticonvulsant
drug in the dog's system. And it just might be that
a particular drug may not work for that animal. [LeCouteur].
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Alternative
Therapies
These
range from acupuncture to vitamin therapy. Traditional
acupuncture therapy for epileptic dogs involves the
placement of needles in up to 10 areas of the body.
Needles can be left in place from 20 minutes to over
a month.
Acupuncture is
not usually considered a substitute for drug therapy,
but is used in conjunction with them. Of 5 dogs with
intractable epilepsy, followed after gold bead implants
in acupuncture points, 2 dogs relapsed after five months.
Two reports of epileptic dogs given acupuncture in the
ear (Shen-men point) are more positive. One dog enjoyed
a six-fold increase in time between seizures; the other
was seizure-free for 200 days after a previous history
of monthly seizures. [Joseph, van Niekerk].
Holistic veterinarian
Roger DeHaan, DVM states that some forms of epilepsy
respond to supplementation of vitamin B6, magnesium,
and manganese. Drs. Wendell Belfield and Martin Zucker
stated that "It has long been known that a deficiency
of vitamin B6 or any interference with its function
can cause seizures in any mammalian species, including
man and dog".
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Parting
Considerations
If your
dog is experiencing either mild or severe seizures,
there is help for both of you. Work with a veterinary
professional with whom you feel a good rapport, and
educate yourself on seizures and their treatment. Follow
the vet's instructions, never change medication or dosages
without a consultation, be observant, monitor serum
levels as recommended, have patience and be willing
to try another form of treatment if that seems indicated.
Above all, if your breed club sponsors a health registry
or research project on seizures or epilepsy in your
breed, participate fully in it. New research on epilepsy
is being done each year in an effort to determine how
it's inherited and ultimately, to design a test that
will allow breeders to select against this health defect.
Please note:
The information provided here is meant to supplement
that provided by your veterinarian. Nothing can replace
a complete history and physical examination performed
by your veterinarian. - Dr. Jeff
I greatly value your feedback. Please let me know what
you think of this site and what you would like to see
on it. drjeff@homevet.com
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