Seizures in Dogs

What is a seizure?
Seizures are one of the most frequently seen neurological problems in dogs. A seizure is also known as a convulsion or fit. It may have all or any combination of the following:
1. Loss or derangement of consciousness
2. Contractions of all the muscles in the body
3. Changes in mental awareness from unresponsiveness to hallucinations
4. Involuntary urination, defecation, or salivation
5. Behavioral changes, including not recognizing the owner, viciousness, pacing, and running in circles

What are the three phases of a seizure?
Seizures consist of three components:
1. The pre-ictal phase, or aura, is a period of altered behavior in which the dog may hide, appear nervous, or seek out the owner. It may be restless, nervous, whining, shaking, or salivating. This may last a few seconds to a few hours.

2. The ictal phase is the seizure itself and lasts from a few seconds to about five minutes. During this period, all of the muscles of the body contract strongly. The dog usually falls on its side and seems paralyzed while shaking. The head will be drawn backward. Urination, defecation, and salivation often occur. If it is not over within five minutes, the dog is said to be in status epilepticus or prolonged seizure.

3. During the post-ictal phase, there is confusion, disorientation, salivation, pacing, restlessness, or temporary blindness. There is no direct correlation between the severity of the seizure and the duration of the post-ictal phase.

Is the dog in trouble during a seizure?
Despite the dramatic signs of a seizure, the dog feels no pain, only bewilderment. Dogs do not swallow their tongues. If you put your fingers into its mouth, you will not help your pet and you run a high risk of being bitten very badly. The important thing is to keep the dog from falling and hurting itself. As long as it is on the floor or ground, there is little chance of harm occurring. If seizures continue for longer than a few minutes, the body temperature begins to rise. If hyperthermia develops secondary to a seizure, another set of problems may have to be addressed.

What causes seizures?
There are many, many causes of seizures. Epilepsy is the most common cause of seizures in the dog. Other causes include liver disease, kidney failure, poisoning and brain tumors.

Now that the seizure is over, can anything be done to understand why it happened?

After a dog has a seizure episode, your veterinarian will begin by taking a thorough history, concentrating on possible exposure to poisonous or hallucinogenic substances or history of head trauma. The veterinarian will also perform a physical examination, blood and urine tests and an electrocardiogram (ECG). These tests rule out disorders of the liver, kidneys, heart, electrolytes, and blood sugar level. A heartworm test is performed if your dog is not taking heartworm preventative monthly.

If these tests are normal and there is no exposure to poison or recent trauma, further diagnostics may be performed depending on the severity and frequency of the seizures. Occasional seizures are of less concern than when the seizures are becoming more severe and frequent. In this instance, a spinal fluid analysis may be performed. Depending on availability specialized imaging of the head with a CT scan or MRI might be performed.

What is epilepsy?
Epilepsy is derived from the Greek word epilepsia which means seizure or falling sickness. It is a brain disorder characterized by recurrent seizures in the absence of any known cause or abnormal brain lesion. In other words, the brain appears to be normal but functions abnormally.

What causes epilepsy?
The cause of epilepsy is unknown. It may be related to a biochemical or neurochemical abnormality. It is thought to be genetic in many breeds although the exact mechanism of transmission is unknown. Breeds that have a higher incidence of epilepsy include beagles, shepherds, border collies, boxers, cocker spaniels, collies, dachshunds, golden retrievers, Irish setters, keeshonds, Labrador retrievers, French poodles, St. Bernards, Shetland sheepdogs, Siberian huskies, springer spaniels, Welsh corgis, and wire-haired fox terriers. Epilepsy is somewhat common in dogs and rare in cats.

What can be done to prevent future seizures?
Treatment is usually begun only after a pet has more than one seizure a month, clusters of seizures or grand mal seizures. Once anticonvulsant medication is started, it must be given for life. There is evidence that pets started on anticonvulsants which are then stopped may have a greater risk of developing more severe and dangerous seizures. Even normal dogs may be induced to seizure if placed on anticonvulsant medication and then abruptly withdrawn from it. Your veterinarian can outline a schedule for discontinuing the medication.

How is epilepsy diagnosed?
A diagnosis of epilepsy is made only after all other causes of seizures have been ruled out. A thorough medical history and physical examination are performed, followed by diagnostic testing which includes blood and urine tests and radiographs. Additional tests such as bile acids, cerebrospinal fluid (CSF) analysis, computed tomography (CT) or magnetic resonance imaging (MRI) may be recommended.

What is the treatment of epilepsy?
There are various anticonvulsants that may be recommended for your pet once it has been diagnosed with epilepsy.  Since anticonvulsants are very potent medications, and treatment must be continued for the remainder of the pet’s life, it is only started if one of the following criteria is met:

More Than One Seizure A Month - You will need to keep a detailed record of all episodes to determine the frequency of seizures 

Clusters of Seizures - If your pet has groups or 'clusters' of seizures, (one seizure following another within a very short period of time), the condition may progress to status epilepticus, a life-threatening condition characterized by a constant, unending seizure that may last for hours. Status epilepticus is a medical emergency! 

Grand mal or Severe Seizures - Prolonged or extremely violent seizure episodes. These may worsen over time, so should be avoided.

Phenobarbital is one of the more common anti-seizure medications used in dogs, and usually it must be administered twice daily.  Drug dependency will occur with this medication. Irregular dosing schedules (including starting and then stopping the medication, or forgetting to give pills so that blood levels fluctuate widely) may predispose your pet to more frequent or more violent seizures.  Dose ranges vary dramatically from patient to patient.

Blood samples to measure phenobarbital levels will be taken every two to four weeks until the most appropriate dosage is determined. Once the therapeutic dose for your pet is determined, phenobarbital blood levels and liver function tests will need to be monitored  every six months to ensure that your pet's blood levels stay within the therapeutic range (i.e. that they do not get dangerously high or low), and that the  no damage to the liver is occurring. In the event that phenobarbital blood levels get too high, liver failure can develop, which may lead to death. If the levels are too low, violent seizures may occur. Additional drugs such as potassium bromide may be used in difficult cases. Your veterinarian will determine the proper treatment plan for your pet's condition.

What is the prognosis for a pet with epilepsy?
Most dogs do well on anti-seizure medication and are able to resume a normal lifestyle. Some patients continue to experience periodic “break-through” seizures. Many dogs require periodic adjustment of their medication dosage, and some require the addition of other medications over time.

You mentioned status epilepticus. What does that mean?
Status epilepticus is a serious and life threatening situation. It is characterized by a seizure that lasts more than five minutes. When it occurs, the dog's life is endangered. Unless intravenous medication is given promptly, the patient may die. If this occurs, you should seek treatment by a veterinarian immediately.