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. The prevalence of epilepsy
in the general dog population has been estimated at .5 to 5.7%.
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. The definitions
below are helpful in distinguishing types of epilepsy.
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. 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.
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,
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 generalized 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).
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.
1) 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.
2) The aura signals the start of the seizure. Signs include restlessness,
nervousness, whining, trembling, salivation, affection, wandering,
hiding, hysterical running, and apprehension.
3) 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.
4) 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.
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.
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.
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.
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.
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.
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.
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).
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.
