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The seizure our dog experienced was certainly sobering for us, but knowing what caused them and treatment of the problem helped to alleviate our fears. This article explains what causes seizures, the various types of seizures, how they're treated and more...

What happens when a dog has a seizure is not totally understood but a brief review of how the brain works might provide a little insight. When our dog Lyric wants to walk, neurons or nerve cells in her brain controlling this action emit a small electrical charge. Simultaneously, these neurons produce neurotransmitters, a chemical messenger that when called upon either activates (excites) or stops (inhibits) still other surrounding cells. Under normal circumstances, neurotransmitters are excited and/or inhibited in just the right measure, and an orchestrated symphony of activity occurs in the brain, which in turn lets her walk.

But, when Lyric suffered her seizure, some of the cells in her brain (collectively called a seizure focus) started “short circuiting” and spread this discordant behavior to other cells. Normally, her brain would respond with enough inhibitory neurotransmitters to stop the spread. But, since her brain could not stop the random firing of these renegade cells, her seizure resulted. Seizures (also called epilepsy, convulsions or “a fit”) are usually self-limiting as the uncoordinated neurons eventually exhaust themselves and stop firing. Indeed, this was the case for our dog.

The literature reveals there are three distinct phases to a seizure: the aura, the ictus and the post- (after) ictus. In the aura phase, the beginning of the seizure occurs, with behaviors such as whining, restlessness, hiding or apprehension exhibited. In the brain, abnormal electrical discharges are beginning to take place among the neurons. The ictus is the actual seizure phase, characterized by signs usually associated with a seizure: a sudden impairment in the pet's state of mind, purposeless movements of the face and limbs, salivation, vomiting, and, frequently, loss of bowel or bladder control. This is the time when neurons are firing rapidly and are unresponsive to inhibitory requests from other brain cells. The postictal phase occurs immediately after the seizure and may last a few minutes to several days. It may be characterized by the animal having trouble walking or seeing or exhibiting changes in behavior, intellect, habits, and personality.

Types of Seizures

Normal brain circuitry that is disrupted by a seizure can be classified into two main categories-idiopathic or no known cause identified, also called inherited, congenital or primary epilepsy, and Secondary or acquired, caused by identifiable underlying factors

Whether idiopathic or secondary, types of generalized seizures include:

Seizure Causation

There are several reasons for seizures to occur in dogs. After the veterinarian is convinced that a seizure disorder is present, the most important question to be answered is whether the seizure is the result of primary brain disease (intracranial), the result of a disturbance outside the brain (extracranial), or is occurring idiopathically (without obvious cause).  Initially, the causes for seizures should be categorized into those secondary to an intracranial structural cause, an extracranial (metabolic or toxic) cause, or an unknown (idiopathic) cause.
 
Brain diseases that result in seizures include hydrocephalus, storage diseases, cancer (primary and secondary brain tumor), inflammatory diseases (infectious and non-infectious encephalitis), trauma (injury), and vascular diseases (stroke).  Primary brain tumors originate in the brain, while secondary cancers develop when cells from tumors outside the brain are either carried to the brain in the blood or invade the brain from adjacent structures.

Extracranial disease resulting in seizures can be separated into those causes arising within the patient itself (such as liver disease) or those arising external to the pet, such as from ingesting toxins. There are numerous metabolic diseases that can result in seizures. These include low blood sugar (hypoglycemia), high blood sugar (hyperglycemia), liver disease, thyroid disease, kidney disease, electrolyte disturbances, toxins (poisons), anemia, and heart and lung diseases. 

As indicated above, idiopathic epilepsy is a seizure disorder without an obvious detectable cause.  Idiopathic seizures (idiopathic epilepsy) typically begin between 8 months and 4 years of age, and almost always by 5 years of age.  Therefore, a dog that begins having seizures after the age of 5 is not likely to have idiopathic epilepsy; a secondary or acquired reason should therefore be considered.  Certain breeds of dogs are known or thought to be pre-disposed to seizures for their idiopathic epilepsy.  These include beagles, Belgian Tervurens, German Shepherds, Keeshonds, and Collies.  Other breeds with a high incidence include Saint Bernards, Golden Retrievers, Irish Ssetters, American Cocker Spaniels, Wire-Haired Fox Terriers, Bernese Mountain dogs, Alaskan Malamutes, Siberian Huskies, and Miniature Poodles.

Possible Veterinarian Responsibilities

Thorough and accurate client history and observation of characteristic signs that differentiate seizures from other episodic disorders are important in determining the presence of seizures in a dog. A general physical examination followed by routine blood tests is advised to determine if the seizures are caused by internal organ dysfunction. A complete neurological examination provides essential information about brain function, the results of which may lead to recommendation of more advanced diagnostic tests, including computed tomography (CT scan), MRI, electroencephalography (EEG), and analysis of cerebrospinal (CSF) fluid. The cost of these procedures may influence some dog owners from considering their use. Diagnosis of epilepsy is made in a pet of characteristic age and clinical signs in which other causes of seizures have been ruled out by results of diagnostic tests.

Seizure Treatment

Before any treatment can be prescribed, it is important to know any pattern of seizures in your dog so your veterinarian can best stabilize your pet.  This is because treatment of seizures is never considered curative unless an underlying triggering mechanism can be discovered and treated. The goal is to decrease the frequency, severity and duration of the seizures.

Phenobarbital is the most common drug used to treat canine seizures. The hope is that drug therapy will sedate the renegade neurons in the dog’s brain but won’t affect behavior so that the dog remains attentive and alert. Other drugs such as potassium bromide, clorazepate, clonazepam, dimethylglycine and felbamate can be used in conjunction or alone with Phenobarbital. In some rare cases, Phenobarbital had a negative affect on the liver. In any event, it is extremely important to know that a dog on seizure medication cannot skip or discontinue a prescribed dose as severe seizures can result.

What to do if your dog has a seizure

What can you do if your pet has a seizure

Today, Lyric is as happy, playful and alert as she ever was. However, as responsible pet owners, we recognize she is subject to seizures and we will both watch her carefully and be ready for her if and when she experiences another seizure.