Epilepsy In Your Dog or Cat

Canine and feline epilepsy is a disease in which the body is subject to recurrent convulsions called seizures. It is identical in nature to the disease that occurs in human beings. Seizure disorders in cats are relatively rare. An excellent link to information on epilepsy in cats is http://groups.yahoo.com/group/epi-felines/
Seizures in dogs are the most common disease affecting the nervous system. They have a number of causes and not all of them are true epilepsy. It is only when we eliminate all organic causes of seizures that we can label the disease epilepsy, idiopathic epilepsy or primary epilepsy. In epilepsy the root cause of seizures is a defect in nerve transmission within the brain. During an epileptic seizure random impulses are sent from the nerve cells of the brain to muscle tissue throughout the body. In “true” or idiopathic epilepsy the source of these abnormal brain impulses are small areas of abnormal or damaged brain tissue. During a seizure, these tiny areas of abnormal nerves cells or neurons begin sending out electrical impulses that are received by the nerve cells that surround them. This results in a chain reaction in which the surrounding nerve cells are stimulated to fire off a shower of signals of their own to various muscles of the body. These abnormal electrical signals constitute a seizure.

When no organic brain lesion can be located that is responsible for the disease, the condition is called idiopathic epilepsy. Cases of idiopathic epilepsy involve a large element of family heredity. It is common for epileptic adults to produce epileptic offspring. When a brain lesion can be identified the condition is called secondary epilepsy. Secondary epilepsy also frequently occurs due to non-brain events that affect the brain such as overheating (hyperthermia), increased intracranial pressure, low blood glucose, intestinal inflammation and major body organ failure. Regardless of cause, witnessing an epileptiform seizure can be very frightening to a pet owner. If your pet suffers from seizures, try to remember that they look much more terrifying than they actually are to the pet.

Primary epilepsy is over twenty times as common in dogs as in cats. Among dogs certain breeds, such as golden retrievers, are highly susceptible to the disease. Purebred cats are more susceptible to epilepsy than randomly bred cats. Among dogs, collies, poodles, beagles, keeshunds, Labrador retrievers, German shepherds and collies seem more susceptible to the disease.
Epileptic seizures in cats tend to be more serious than in dogs. As opposed to dogs, cats usually have an acquired brain lesion or disease that is responsible for their epilepsy. Because many of these causes are progressive, the long-term prognosis for epileptic cats is not nearly as good as it is for dogs. Once common cause of epileptiform seizures that I see in cats is infection with the virus of feline infectious peritonitis. Another cause is infection with toxoplasmosis. Increases in pressure within the brain, liver and kidney disease, low blood sugar, brain tumors, vitamin B-1 deficiency, feline AIDS, rabies, insecticides, antifreeze and migrating parasites account for most of the other cases of epilepsy in cats.

During an epileptic seizure the pet looses consciousness. Epileptic seizures have been likened to an electrical storm. The location within cerebral cortex of the brain where these impulses originate and the target tissues of the nerve cell impulses define the type epilepsy that occurs. When a defect within the brain can be identified and is the source of these abnormal impulses we call the condition symptomatic or secondary epilepsy. When the whole body is wracked by severe muscle contractions, the seizures are called grand mal. When epilepsy is less severe and affects fewer muscle groups it is called petite mal. Status epilepticus is a term used to characterize severe seizures that occur again and again with little or no rest between convulsive episodes.

Most pets that develop epilepsy have their first seizures between one and five years of age. During a seizure, the pet falls on its side with its legs outstretched and it’s back arched convexly. Most dogs maintain their legs rigidly extended but some paddle as if they were running. Dogs may whine although they are not in pain. They often void their bowels and bladder. Their jaws are clenched during the initial phase of the seizure. If only a portion of the body is affected the seizure is called a focal simple seizure when the dog retains consciousness and focal complex seizures when consciousness is lost. Focal simple seizures often involve the muscles of the face. Some seizures affect portions of the brain that control conscious thought rather than motion. When an area of the brain that controls the conscious process is affected the seizure is called a psychomotor seizure. In humans this form of seizure is called frontal lobe epilepsy. During this altered period of consciousness the pet may show fear, aggression, hyperactivity, repetitive nonsensical behavior, gum chewing or snapping at imaginary insects.

Because so many areas of the brain can give rise to epileptic seizures, not two pets exhibit exactly the same signs. In some instances seizures will be a one-time episode never to occur again. In other pets the problem reoccurs at regular intervals of from every several days to several times a year.

A Typical Seizure
A single seizure event of epilepsy can be broken down into four distinct stages. The first stage is called the prodome, prodromal or warning stage. This stage lasts from several minutes to, in extreme cases, several days prior to the seizure event. During this stage, changes in mood and behavior can be noticed. In people with epilepsy, dogs have been trained to warn their owners during this period that a seizure is eminent.

The second stage of an epileptic seizure is called the aura. In humans, this is the first stage at which the person is conscious that a seizure is eminent. In dogs and cats, restlessness, wandering, pacing, licking, trembling, vomiting and vocalization may occur during this stage.

The next stage is called ictus. This is the time of the seizure itself when the body is subject to uncontrolled movement and thrashing. During this stage the pet is unconscious. Any vocalization is not due to pain. This is the period when dogs and cats often void their urine and bowels. Paddling or swimming movements, clenched teeth, and arched back are common during this stage. In cases where partial seizures occur, the pet may run in circles, and appear blind or deaf. Partial seizures may amount to no more than a twitching of facial or body musculature or the chewing of imaginary gum.

The final stage of an epileptic seizure is called the ictal or postictal stage. This is the stage of gradual recovery. Dogs and cats in the postical stage appear dazed or hung over. They may bump into objects. These pets are exhausted and sleep a lot. They may have a blank expression or appear to stare out into space.

When a seizure occurs in a loved pet, owners tend to over-react. Their first inclination is to rush the pet to an emergency veterinary center. Luckily, most epileptic seizures last only a few minutes. One to three minute seizures are most common. Those that last five to ten minutes are less common. Those that last longer than fifteen minutes can become medical emergencies since these pets may have trouble breathing. This is how a seizure typically progresses: The pet will seem perfectly normal when all of the sudden it begins to wobble. It may back up and sit down with its rear legs extended under its stomach. Then the muscles of its face will begin to twitch. The pets teeth can often be heard to chatter. The pet then begins to drool and salivate with its teeth clenched tightly. It will often foam at the mouth and respiration becomes rapid and labored. This is all very scary. But try to remember that your pet is oblivious to what is happening and remembers nothing of the event. As the seizure progresses the pet usually falls over on its side with its limbs extended and its back arched. After a few minutes breathing returns to normal, the body relaxes and the dog again becomes aware of its surroundings.

What To Do During A Seizure
If your pet or a neighbor’s pet develops a seizure when you are present begin by placing the pet’s head on a soft folded towel or pillow. You may carry the pet in a blanket to a tiled area so as not to soil the carpet or rug. Then remove all objects that surround the pet so it will not injure itself. Do not put your hands into the pet’s mouth or you are very likely to be bitten. It is quite rare for a dog to “swallow” its tongue but if the pet should turn bluish you can use an inverted spoon to manipulate the tongue. If this is not sufficient and the dog is still having difficulty breathing open the mouth by passing two towels through the mouth and pulling on them – one up, one down - to force the mouth open. You can gently stroke and speak calmly and softly to your pet. He will not know you are present until the seizures begin to subside. Keep the room darkened and keep other family members away. You can already position some paper towels and warm soapy water on a wash stand beyond the pet’s reach.

When To Start Medicating My Pet?
Dogs and cats should receive anti-seizure medications when they have two or more seizures within and 8-week period or two or more cluster seizures within a 12-week period. Dogs and cats that show unusually severe ictal or postictal periods should also begin medication.

Medications Used To Treat Epilepsy
Several medications are very effective in preventing epileptic seizures in pets:

This old time standby for epilepsy is dispensed in 50 and 250mg tablets. The accepted dose for this drug is 4-5mg/pound body weight two or three times a day. Through blood serum monitoring the final dose should be adjusted to 5-7.5mg/pound three times a day.

Phenobarbital
Phenobarbital is the most commonly used drug to treat epilepsy in dogs and cats.
The initial dose should be 1mg/pound body weight given twice a day. Dose should then be adjusted based on blood serum levels of the drug. Ideal trough phenobarbital serum levels are 10-20 micrograms/ml. Trough serum level is the level of the drug in the blood just prior to the next subsequent dosage. Side effects are sedation, increased appetite, weight gain, increased thirst and urination and a deleterious affect on the liver over time. This traditional drug is given to dogs at 1-4mg/pound body weight twice a day and to cats at 1-2mg/pound body weight twice a day. The final dose is determined by monitoring serum plasma levels of the drug. Pets on Phenobarbital need to have their liver enzymes tested every few months to check for possible liver damage.

Attempting to protect your pet's liver from damage caused by phenobarbital is a wise action. First, try to use the smallest dose of phenobarbital that controls the problem. This must be done through trial and error as every pet has different requirements. Second, try to lower the phenobarbital dose by combining it with a second anti-epileptic medication such as Potassium Bromide. Some liver protective compounds used in animals and humans are alpha lipoic acid, silymarin (a.k.a. silibinin or milk thistle).

This drug rarely controls seizures on its own. The accepted dose of this drug in dogs is 10-17.5mg/pound body weight given three times a day.

Potassium Bromide
This drug is compounded by a number of special order pharmacies at 200mg/ml. It can be used to lower the dose of phenobarbital given and thus decrease the likelihood for liver damage. The dose should be adjusted to maintain trough serum potassium bromide levels at 100-200mg/decileter (1.0-2.0mg/ml). Concurrently phenobarbital serum level should be maintained at 10-20 micrograms/ml.
It is usually given in combination with phenobarbital to dogs and cats at15-20mg/pound body weight divided into two or three doses. When given alone in an attempt to control seizures, doses of 20-25mg/pound may be required. Dogs taking this drug need to be careful with salt levels in their diet and whenever their brand of dog food is changed

Valium (diazepam)
This medication is only suitable to end prolonged seizures until another medicine can take effect. It is quite good at breaking seizures but when given over longer periods of time the body becomes resistant to its effects. Diazepam’s anti-seizure dose is 0.25mg/pound body weight. In emergencies, wetted tablets can be given rectally.

Some newer drugs used in human epilepsy show promise in dogs. These include clorazepate, felbamate, gabapentin, levetiracetam and zonisamide.
Unfortunately, with the exception of clorazepate in small dogs, all of these medications are quite expensive.

This drug can be used in conjunction with phenobarbital. It is moderately effective but serum levels of the drug need to be monitored every 4-6 months as they tend to drift downwards. Clorazepate is a benzodiazepine drug of the same group as Valium. It is available in regular and time-release form. In dogs, both forms work equally as well. It is given at 0.25 to 0.5mg/pound body weight every eight to twelve hours. 1mg/pound every twelve hours is sometimes satisfactory. Because dogs vary greatly in the blood levels of this drug which is attained, the pet’s blood serum should be checked at several points to be sure that 100-400 nanograms or a metabolite of chlorazepate (nordiazepam) is present in the blood. Side effects of clorazepate are sleepiness and a wobbly gait.

The primary advantage of felbamate is that it does not cause drowsiness. It is often given in conjunction with phenobarbital to lower the phenobarbital dose. The initial suggested dose of this drug is 7.5mg/pound-body weight given every eight hours. The toxicity of this drug is very low. If this initial dose of felbamate is does not eliminate seizures, the dose of the drug is increased in 7.5mg/lb increments every two weeks until the seizures cease. If serum levels of felbamate are monitored they should be within the 20-100 microgram/ml range. Blood samples should occasionally be taken to check for liver toxicity and bone marrow suppression, which are uncommon side effects.

This drug also causes little to no sedation. In humans, it is primarily used to control focal seizures rather than generalized epilepsy. It is often administered as a suplement to other anti-seizure medication such as phenobarbitol and bromide. The recommended dosage of this drug is 14.5-30mg/lb total daily dose divided into equal portions given every six to eight hours. Some neurologists begin this drug in dogs at 5mg/pound body weight three times a day. Therapeutic serum levels of this drug are thought to be 4-16mg/leter but as with felbamate, serum drug levels are rarely monitored because of the cost of the assay. My personal experience with this medication was in my daughter who suffered from frontal lobe epilepsy. In her case, the drug caused marked mental confusion. I do not know if the same effect occurs in pets. When using Neurontin, try to stay at the lowest possible dose.

This drug, sold as Keppra, is used in people to control both focal and generalized seizures. It has been used in dogs in combination with phenobarbital and bromide to lower the daily dose of phenobarbital received and in cases where phenobarbital was not able to control the seizures alone. The suggested initial dose of levetiracetam in dogs in 10mg/pound given three times a day. It takes twice the dose in dogs to achieve the same blood levels found in humans. In people the effective serum level of this drug is 5-45 micrograms/ml. It has a very high margin of safety. If the initial dose is not effective in ending seizures the dose can be doubled successively up to approximately 100mg/pound/day. The drug is quite safe. Rare side effects in dogs include stiff wobbly gait, vomiting and salivation.

We do not understand how this medication works. It is a different class of drug from other anti-seizure medications. It appears to cause little of no side effects.

Keppra is well-absorbed in its oral form. It is not significantly bound to blood proteins. It is excreted through the dog's urine without much metabolism in the liver. The drug's half-life in dogs is 3.3 hours - about half that in people. Tests in experimental dogs found minimal adverse effects even at high doses (UCB Pharma).

Several veterinary schools areconducting clinical trials in dogs with idiopathic epilepsy which could not be controlled with phenobarbital and bromide.

Of all the new anticonvulsant medications zonisamide shows the most promise in dogs. This drugs structure is based on the older sulfonamide antibiotics. It is effective in blocking both focal and generalized seizures and has minimal side effects. When used as an add-on therapy in dogs already receiving phenobarbital the initial dose is 5mg/lb given twice a day. Effective serum concentration in humans is 10-40 micrograms/ml. Dogs tolerate doses up to 37.5mg/lb/day quite well. When this drug is used in dogs, phenobarbital dosage can be drastically reduced or entirely eliminated.

With traditional anti-seizure medications an occasional pet will continue to have seizures or even appear to have them more frequently. But most go on to lead almost normal lives on their medications. It is quite common for the dosages and types of drugs given to need changes and adjustments during the pet’s life.a

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