Seizures (Epilepsy)

 

One of the most disturbing things to witness in an animal is a seizure, the most common neurologic problem we see in our hospital. It can traumatize the person witnessing it, and always seems to go on forever. Unfortunately, it is not uncommon for animals to have seizures, particularly dogs. Fortunately, the overwhelming majority of seizures are not life threatening, and most dogs can live a relatively normal life. Cats and other species also get seizures, but not as frequently as dogs. This page will give you a complete explanation as to the cause of these traumatic episodes, and how we diagnose and treat them. The overwhelming majority of dogs have epilepsy, so we will emphasize this disorder when discussing treatment.

We have a few short videos on this page, you will need QuickTime from www.apple.com to view them


Here are some medical terms we will be using in this page:

neuron- nerve cell ictus- an actual seizure
idiopathic- unknown cause postictus- period immediately after a seizure
hypoglycemia- low blood glucose (sugar) status epilepticus- continuous or clusters of seizures
hypocalcemia- low blood calcium level epilepsy- brain disorder characterized by seizures
aura- initial manifestation of a seizure EEG- electroencephalogram
syncope- a heart problem that mimics a seizure Depression- not as alert as usual
Dementia- dull or emotionless Stupor- semi conscious, asleep often, hard to arouse
Coma- Unconscious, unable to arouse at all CSF (cerebrospinal fluid)- normal fluid in the brain and spinal cord

Normal Anatomy & Physiology

The profound complexity of the brain precludes us from going into significant detail regarding anatomy and physiology. You would need to be a neuroanatomist to even begin to understand its basics. The basic unit of the brain is called a neuron, which is a specialized nerve cell. Some of these nerve cells process information, others cause a reaction. For example, your eyes, which are an extension of your brain, process images. Other neurons cause the muscles in your eyes to move in response to movement. In all cases, there are millions upon millions of neurons in the brain, all with complex connections to each other. It is these connections that leads to the complexity and the sophistication of the mammalian brain. Unfortunately, when a neuron has a problem, these connections can let this problem spread elsewhere. If the problem an individual neuron has is a seizure, the seizure activity in this one neuron can easily and instantaneously spread to other neurons, leading eventually to a generalized seizure.

As a rough comparison, the mammoth power failure that occurred in the Northeast U.S. in august of 2003 shows how a small problem in one area can rapidly spread to other areas. Multiply all those electrical lines and power stations with their connections by a million times, and you start approaching what occurs every second in the mammalian brain.


Pathophysiology

Seizures (fits, convulsions) are caused by abnormal activity in the brain cells, particularly in the frontal and temporal lobes of the cerebral cortex. When a neurons fires off in a seizure, it sets off a chain reaction in other neurons, and the seizure spreads. If this chain reaction stays within a specific location, a partial seizure might occur. If it spreads to occur on both sides of the cerebral cortex, a generalized seizure, the most common type of seizure, might occur.


Characteristics

Aura

Behavior just prior to a seizure. Typical behaviors include panting, pacing, barking, and restlessness. Ranges from several minutes to several hours prior to the actual seizure.

Ictus

The actual seizure, characterized by involuntary muscle tone and movement. Lasts from seconds to minutes, although it seems like hours when you are observing it.

Postictus

Period immediately after seizure, characterized by disorientation, unusual behavior, appetite change, or weakness. It can last up to several days.


Classification

Generalized

This is the most common seizure encountered in dogs and cats. Nerve cells on each side of the cerebral cortex start discharging, causing all parts of the body to be affected. Even though the original source of the seizure is usually only a small number of neurons on one side of the cerebral cortex, the discharge of these neurons causes other neurons to discharge also, eventually causing the seizure to be generalized.

Partial (focal)

This seizure also starts as a small number of neurons, yet in this case it does not spread far beyond these initial neurons. Symptoms that are seen depend on which neurons are discharging. It can affect motor areas, causing involuntary movement, or it can affect areas of the brain involved with behavior, causing intermittent behavioral changes. Eventually this type of seizure can progress to a generalized seizure.

This movie is typical of a pet having a partial seizure. Double Click on it to play

twitching eye


Cause

Idiopathic (epilepsy, primary, genetic, true, inherited)

The word “idiopathic” means the cause is unknown. It is also known as epilepsy in humanoids. It is a diagnosis of exclusion- if all the other causes of seizure are eliminated, then this is the cause. This is the most common type of seizure, and occurs in up to 2% of all dogs, relatively rare in cats. Any dog breed can be affected, with the larger breeds having more severe seizures. In general, we see it more often in purebred animals. The more common breeds are:

Alaskan Malamutes

Cocker and Springer spaniels

Beagles

Collies

Boxers

Dachshunds

Dalmations

German Shepherds

Golden and Labrador retrievers

Irish Setters

Mastiffs

Schnauzers

Poodles

Saint Bernards

Siberian Huskies

Vizslas

In the large breeds seizures tend to be more severe.

Secondary

Secondary seizures causing epilepsy occur when there is a structural abnormality in the brain.

Hydrocephalus

This disorder, sometimes know by its more common name of “water on the brain”, occurs in small breed dogs and sometimes cats. It is the excessive accumulation of cerebrospinal fluid (CSF) in the brain. The pressure from the fluid causes the seizures. It is not a problem that is easily corrected, and usually requires lifetime medication. Surgery can be used in select cases, but is not always effective. Pets with severe symptoms early in life have a guarded prognosis.

Common dog breeds that get hydrocephalus:

Chihuahua

Yorkshire Terriers

Maltese

Pomeranian

Lhasa apso

Toy Poodle

Pug

Pekingese

Boston Terrier

The most common symptom with this disorder is behavioral. If seizures occur, they start early in life.

Brain Tumor

We tend to encounter brain tumors in middle aged and older pets. Some arise directly from brain tissue, others spread to the brain via the bloodstream (since the brain has an extensive blood supply). Strangely enough, its not the neurons (brain cells) that become cancerous, it is the cells supporting the neurons, called glial cells, that cause the problem.

Tumors that arise directly from the brain include:

astrocytoma

oligodendroglioma

Symptoms of brain tumor depend on exactly where in the brain they arise, and how fast they grow.

Brain tumors are best diagnosed with an MRI.

Most brain tumors are treated medically- surgery is used only on rare occasion.

The progress is poor if your pet has a brain tumor.

 


Trauma

Pets that have fallen and hit their heads can develop scar tissue in the brain when they heal, leading to seizures later in life.

Stroke

More correctly called “vascular disorders”, they involve damaged blood flow to the brain. The neurons that are normally nourished by these blood vessels can now have a problem.

Viral Disease

Rabies and Distemper are both viral diseases that can cause seizures in dogs.

Reactive Seizures

In this type of seizure the brain is reacting to a problem elsewhere in the body.

Hypoglycemia (low blood sugar)

This puppy has coccidia parasite, causing its blood sugar to plummet.


Hypocalcemia (low blood calcium) This video shows an Iguana with twitching muscles caused by hypocalcemia. It is not a seizure. We show it to give an idea of how the bodies neurologic system is affected by hypocalcemia. You can learn more about this Iguana’s problem, which is called Metabolic Bone Disease.

iggietwitch


Hypothyroidism

A low thyroid level, called hypothyroidism, can precipitate seizures.

Kidney disease

The buildup of waste products in the bloodstream, called uremia, can cause seizures. Our Kidney Pagehas extensive detail on this problem.

Liver disease

Hepatic encephalopathy, a disorder of blood flow into the liver, can cause seizures. Our Liver Pageexplains it in much more detail.

Poisons

The vast number of toxins that can cause seizures precludes us from going into detail on each one. One of the most common ones we encounter in our practice is Metaldehyde, also know as snail bait poison.

Snail Bait Poison The active ingredient in this product is metaldehyde, a potent drug that will cause seizures in animals. There is no specific antidote- pets need to be sedated to stop the seizures, induced to vomit to rid the stomach of this poison, and even have their stomach flushed if necessary. After this initial treatment to prevent further absorption of the metaldehyde, we will give your pet intravenous fluids, sedate and even anesthetize it, check a blood panel for damage to internal organs, and monitor its life signs. If a dog that eats snail bait poison is brought to us immediately we can usually help them. This is a short movie of Eddie the morning after he was treated for snail bait poisoning. Notice how unsteady he is (called ataxia) when he lands after jumping up. His seizures are gone but he is still suffering the effects of the poison the next day

ataxia


Other toxins that can cause seizures include: Lead Poisoning-found in old paint, putty, tile, linoleum, used motor oil, drapery weights, bullets, and fish sinkers

Organophosphates and Carbamates – found in many different insecticides

Pyrethrins- found in insecticides

Strychnine- found in rat poison

Ivermectin- found in antiparasiticides

Mitaban- found in Demodex mange mite treatment

Caffeine- found in chocolate and NoDoz

Ethylene Glycol- found in antifreeze

Fungus

Some fungi can affect the brain and cause seizures. One of them is called cryptococcus.

 


Non epileptic Seizures

Syncope

Dogs that have heart disease with an abnormal heart beat (called an arrhythmia), can pass out in a manner that looks just like a seizure. Sometimes syncope can be difficult to differentiate from a seizure. In syncope a dog does not usually exhibit the motor activity (paddling) or urination/defecation symptoms seen in a seizure. This is one of the may reasons we follow a rigorous approach to the diagnosis of any disease.

Seizures in Cats

Cats have seizures much less commonly than dogs, and they don’t seem to have generalized seizures as often. Seizure symptoms that might occur in cats include:

Facial twitching

Salivation

Attacking invisible objects (although this can be normal behavior in some cats)

Running frantacially as if something unknown is chasing them

Colliding with objects (also ban be a normal behavior)

Secondary epilepsy tends to be more common in cats. In addition to the causes in dogs, common causes in cats might also include:

Thiamine deficiency

FIP (Feline Infectious Peritonitis)

FIV (Feline Immunodeficiency virus)

FeLV (Feline Leukemia virus)

Toxoplasmosis and Roundworms

Feline Hyperesthesia Syndrome

Food allergy

Depending on the cause, they are treated in a similar fashion.

In both dogs and cats we also classify seizures as to their cause when making a diagnosis. Those that occur directly in the brain are called intracranial. Examples include brain tumors, CNS infections and inflammations. Those that occur primarily outside the brain are called extracranial. Examples include hypocalcemia and hypoglycemia

Symptoms

Seizures commonly start while your pet is sleeping. Typical symptoms in a severe, or grand mal seizure, include: Falling

Loss of Consciousness

Extension of the limbs

Paddling of the limbs

Chomping at the jaws

Dilated pupils

Excess salivation

Defecation

Urination

Behavior changes during a milder seizure include:

Fear

Hysteria

Aggression

Barking or meowing

Hiding or cowering

In milder seizures your pet might remain conscious, and appear anxious or walk like it is drunk. Even though people like to compare this to “petit mal” seizures in people, it is not the same thing. Milder seizures might last for a few minutes, or could go on for hours, maybe even leading to a generalized seizure.

Pets appear to have an aura (preictal) prior to a seizure. They might be restless, seek attention, try to hide, whine, or tremble. After their seizure (postictal) they might show similar symptoms, even blindness, aggression, or sleepiness. The postictal stage lasts a variable period of time, up to hours after the seizure.


Diagnosis

In most cases, by the time we examine a pet that has seizures, the seizures are no longer present. It is important to follow the tenets of the diagnostic process closely when making a diagnosis of seizures, especially since the syncope that occurs with heart disease mimics a seizure. A large part of the diagnosis in this disease is based on history, which you learned about when your linked to thediagnostic process page.

Signalment

Idiopathic seizures occur in any age dog or cat, particularly the breeds previously mentioned. Usually a dog with idiopathic epilepsy is between 1-3 years of age. Dogs not in this age range have a greater potential for secondary seizures as their cause.

History

Exposure to toxins, a prior history of head trauma, or concurrent diseases like liver and kidney disease, give us a clue to seizures and their cause. It is important to differentiate syncope from seizure, since some cases of syncope can look like your pet is having a seizure. If we suspect syncope we will perform tests to analyze the heart and lungs. You will find these tests in our heart page.

Physical Exam

In most cases the physical exam is normal. This is because most seizures are caused by idiopathic epilepsy. If your dog has a seizures caused by a brain tumor or infection/inflammation in the central nervous system (CNS), we might see neurologic signs like uneven pupils.


This is a picture of an adult dog with diseased teeth, which might be an indication of Distemper when it was younger.


In some cases of Distemper the pads might be thickened.


As part of the physical exam on of our doctors might feel a need for a more detailed neurologic exam. Things that might be checked are: Mental status- alert, depressed, unresponsive to stimuli, comatose, circling, head pressing, behavior change and disorientation.

Cranial Nerves- menace response, pupillary light reflex (PLR), eyeball deviations (strabismus, nystagmus), oculocephalic reflex,.

Double click on this movie and you will see an example of nystagmus

nystagmus


Postural reflexes- conscious proprioceptive (CP), tremors, gait, extensor thrust, and wheelbarrowing.

Spinal reflexes- pelvic limb (patellar reflex and perineal reflex), thoracic limb triceps reflex and biceps reflex).

Muscle- mass and tone

Pain and tactile reflexes- deep pain and light touch reflexes

Cutaneous trunci reflex

Tail tone

Diagnostic Tests

Blood Panel and Urinalysis They might give us a clue as to the secondary or extracranial cause of seizures. Careful interpretation is needed. If a dog has a low blood sugar (hypoglycemia) on the blood panel, it might be because the seizure activity has depleted its stores of glucose, not because it has hypoglycemia. This is why sometimes its a good idea to perform the exam well after a seizure has occurred and the body has a chance to get back to normal.

Our routine blood panel also includes a thyroid check to make sure the level is not too low, which can precipitate a seizure.

Radiographs

Radiographs of the head of dogs and cats is complex compared to humanoids. There is a much smaller brain to view, the bones are more massive and overlapping, and there is great degree of variation among breeds. They can be used to diagnose hydrocephalus, trauma, or cancer, although they can’t be relied upon in most cases.

They can help us identify a secondary cause of seizures like an enlarged liver or kidney. We can sometimes see cancer on a radiograph as it has spread from its primary location to other parts of the body, particularly the lungs and lymph nodes. We might note fluid in the abdomen (ascites), an indication that a cat has FIP.

CSF Pressure

When a pet has a brain tumor there will be increased pressure within the central nervous system (CNS). This increased pressure, when it occurs, is measure by performing a spinal tap, and measuring the pressure with a manometer. Fluid that is obtained this way (called cerebrospinal fluid) can also be analyzed for inflammation and infection by our pathologist. This is how we diagnosis meningitis and encephalitis.

MRI

One of the most accurate and efficient ways to diagnoses the cause of a seizure, especially if there is a brain tumor, is Magnetic Resonance Imaging (MRI). It is also used to diagnose hydrocephalus, and blood vessel problems in the brain. If you double click on the picture below you will view a series of “slices” of the brain. The first picture shows a side view of a dog’s brain, and gives you an idea of the “slices” as the pictures continue on through the brain. This dog’s nose is on the far left. In slices 6-10 it will be obvious there is a problem when you see the large white mass in the middle of the brain – that is a tumor.

mrisequence


Treatment

In most cases by the time you can bring your dog to us for treatment the seizure has subsided. If your pet experiences a seizure, move any furniture out of the way, move things like lamps that might fall, remove other pets from the area, make sure it cannot fall down any stairs, and let the seizure run its course. Most will run their course within 1-2 minutes. Do not put your hands in your pets mouth to prevent it from swallowing its tongue- all that will do is get you bitten severely. If your pet turns blue during a seizure it is because its muscles of respiration (ribs, diaphragm) are locked, and it is not breathing temporarily. This problem will resolve itself, unless the rare occurrence of status epilepticus is present. Have a crate or airline carrier present to bring your dog to your veterinarian.

One rare but serious type of seizure is called status epilepticus, where the seizure lasts more than 5 minutes, it doesn’t stop at all , or it stops but returns soon after. This is a medical emergency, and requires the use of injectable medication, and even general anesthesia, to prevent it from progressing to a life threatening problem. If your dog is experiencing this problem call us immediately. If we are not available for some reason, you should have information at hand for a 24 hour emergency hospital close to you that will take care of you.

Idiopathic

Idiopathic epilepsy cannot be cured, only controlled, and once treatment is started, it is lifelong. Most dogs respond well to anticonvulsant medication give orally. Deciding when to treat idiopathic epilepsy is just as important as how to treat. Some dogs only have 1 or 2 seizures per year, and don’t require treatment. Some dogs have seizures weekly or daily, and require treatment. Other dogs can be in the gray zone. They might have a seizure every 1-4 months, so making a determination to treat them is not so clear cut. If these dogs with infrequent seizures start having them more frequently, then we recommend anticonvulsant medication. In many breeds the seizures will increase in severity, so it is wise to treat when seizures first appear and try to prevent this problem.

Every dog is different, and what works in one dog might not work in another. Doses sometimes need to be adjusted, and even combination therapy with several different medications might be need to control the seizures. These medications will take several days to take affect, so a seizure during that time might occur. Never abruptly discontinue them. Our goal is to balance seizure control with quality of life, using minimal medication. In most cases of idiopathic epilepsy we are able to achieve this goal, at least initially. Some dogs with epilepsy do not respond to medication.

Phenobarbitol

One of the most common medications for epilepsy is phenobarbitol, given twice to three times daily. The overwhelming majority of dogs are maintained at twice daily dosing in our hospital. It takes several weeks for the blood level of phenobarbitol to reach adequate levels, so there might be an occasional seizure during that time. Phenobarbitol works in the majority of dogs, is inexpensive, and safe, so it is widely used. The dose of this drug has a wide range, so if your dog is not responding to phenobarbitol, and the blood level of the drug is low to normal, we might increase the dose. Doses are changed gradually since it takes time for the effects of this drug to become apparent. an injectable version of this drug given intravenously (IV) to stop status epilepticus.

Never give your dog oral phenobarbitol if it is experiencing status epilepticus as described above- it needs to be seen by a veterinarian immediately.


Some dogs will be sedated initially, but may eventually return to normal activity. Other dogs might drink and urinate more than usual, and have an increased appetite. In rare cases the liver will become toxic due to this drug. This is why we check a full blood panel every 6 months while your pet is on this medication.

Phenobarbitol levels can be measured in the bloodstream, and are a guide to proper dose of this drug. This will help us look for side effects to the medication (rare) and to make sure we are at adequate levels in the bloodstream.


We recommend performing the phenobarbitol check every few weeks to months for the first few months of therapy in order to get an idea of how your pet reacts to the medication. The phenobarbitol level is interpreted in conjunction with the amount of seizures that is occurring. All adequately controlled dogs on long term phenobarbitol should have an exam, blood panel with urinalysis, and phenobarbitol level checked every 6 months at least. Dogs can become refractory to phenobarbitol, so it is imperative you give the medication as prescribed and monitor carefully so we can decide the best course of action in this case. It is not uncommon to have to increase the dose in some dogs.

When giving this medication on a twice daily basis it is important for busy households to give the medication as directed. Using a dedicated calendar to help you know when the next dose is due, along with monitoring seizure activity, is the best way to prevent inadequate dosing, especially when several people are involved with treatment. It is not unusual for dogs to spit out the pill on occasion, so always verify it went down the hatch. If you have trouble at any time giving this medication our nurses will assist you. They can review proper administration techniques, and will even give the medication for you in our hospital if necessary.

If your dog has gone over 1 year without a seizure me might slowly lower the medication over several months, and even stop it completely on a trial basis. This does not apply to every breed of dog.

Potassium Bromide

If phenobarbitol is not adequately controlling seizures, even as we increase the dose, we will sometimes add this drug to the treatment regimen. This medication is used usually in combination with phenobarbitol since it does not do well by itself in most cases. It can sometimes take several months for this drug to achieve enough potency in the bloodstream to prevent seizures. Whenever we have a dog on both medications we start dosing conservatively, and make changes gradually so the body has time to adjust.

It is also monitored with a blood sample periodically in a similar fashion to phenobarbitol.

Side effects can be similar to phenobarbitol, and also include an unsteady gait and inflamed pancreas (called pancreatitis). Liver toxicity to this drug is not usually a problem, so we can use it in cases where phenobarbitol is working but might be affecting the liver. Give it with a meal to prevent an upset stomach, and don’t change your dogs diet abruptly because salt in the diet influences how potassium bromide is absorbed.

Valium

Valium is given intravenously (IV) to dogs with status epilepticus. It is usually the drug of choice in status epilepticus because it is so effective. We might also give you a valium solution, to be given via rectum if your dog starts the continual seizure seen in status epilepticus. This gives you an effective treatment at home if this occurs, although if it does not work you need to seek medical care immediately.

In cats we sometimes use oral Valium (diazepam) as the first drug to control seizures. It is inexpensive and works well, although it might cause sedation.


Miscellaneous Medications

Since seizures have been around for many years, well intentioned people have postulated many treatment regimens that range from high doses of vitamins to herbal treatments, all in the name of being better than drugs because thely are “natural”. These claims are yet to be proven, and until proper clinical trials are performed, these claims have no basis in fact, and are just a repeat of anecdotal evidence that has been around so long and repeated in print so often that it has become fact. Many of these “natural” remedies are drugs themselves, drugs in which no studies have been performed to see if they work and to make sure there are no toxic effects. Herbal treatments contain drugs, and just because they are natural does not mean they are not toxic.

Change the fat content of a dog or cat’s diet does not induce ketoacidosis as found in humanoids, so this treatment will not work.

Accupuncture, when performed by an experienced veterinarian, has been know to be of benefit.

Several drugs used in humanoid medicine are being investigated for use in the dog. We might use them if the standard medications are not working, although they are too new to know for sure how they react in the dog or cat.They have the ptential to be more toxic than the use of phenobarbitol and valium.


Long Term Plan

Everything regarding your pets seizures she be noted on a calendar. It will help us look for trends, and let us know if the medication is working. You should also note the dates your pet needs to return for an exam or blood sample.

Never discontinue medications just because your pet has not had a seizure in a while.

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