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Why Do Dogs Have Seizures? 10 Common Causes (Vet Answer)

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By Dr. Karyn Kanowski

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Written by

Dr. Karyn Kanowski

BVSc MRCVS (Veterinarian)

The information is current and up-to-date in accordance with the latest veterinarian research.

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Seizures are a scary yet relatively common occurrence in dogs. Witnessing a seizure can be terrifying. You may feel helpless, and although most seizures do not last more than a few minutes, it can feel like a lifetime. If your dog has a seizure, one of the first things you will want to know is why.

Sometimes a seizure will be an isolated event—a one-off, never to be repeated, and the cause may never be known. More often, however, if a dog has a seizure, it is likely that more will follow hours, days, or even months later. Understanding the cause of the seizures can help predict, treat, and even prevent more from happening.

In the following article, we will take a brief look at the different types of seizures before exploring the 10 most common reasons they occur.

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What Is a Seizure: The 3 Main Types

A seizure, or fit, is the result of an abnormal burst of energy in the brain, often leading to uncontrolled movements and behavior. There are three main types of seizures:

1. Generalized or Grand Mal Seizures

The most common type of seizure in dogs. This type of seizure affects the whole body, and commonly includes:

  • Trembling/twitching of muscles
  • Collapse
  • Loss of consciousness or responsiveness
  • Loss of control over bladder/bowels
  • Paddling of the limbs

Following a seizure, dogs may be disoriented, agitated, and even aggressive, so you should always be careful, as even the most placid dog may bite following a seizure.


2. Focal or Localized Seizure

Seizure activity (trembling or twitching) occurs in a single limb or part of the body.


3. Absence or Petit Mal Seizures

Characterized by “spaced out” behavior, gazing at nothing.

The last two types are relatively uncommon in dogs and can sometimes occur without the owner noticing. The following is a list of the most common causes of generalized seizures.

sick chihuahua dog lying on a rug
Image Credit: Zozz_, Pixabay

Divider 5The 10 Common Causes of Dog Seizures

The following list covers the most common factors that cause, or may cause, seizures in dogs.

1. Epilepsy

Also known as Idiopathic Epilepsy, this is by far the most common cause of seizures in dogs. We refer to epilepsy as a “diagnosis of exclusion,” which means there is no specific test for it, so it is diagnosed when the other reasons for seizures have been ruled out.

Epilepsy usually starts in dogs from 6 months to 6 years old, and once they begin to have seizures, they will generally be affected by them for life. It can affect any breed, but Border Collies, Labradors, and Golden Retrievers are among the breeds affected more commonly.

The treatment of epilepsy with anti-seizure medication is generally quite successful but is only started if the seizures are frequent (more than one or two a month) or quite severe.


2. Low Blood Sugar

If blood glucose levels drop too low (known as hypoglycemia), this can trigger a seizure. This can happen in very young or malnourished dogs, but the most common reason for hypoglycemia in dogs is due to a tumor on the pancreas called an insulinoma.

a border collie dog looking sick covered with blanket on couch
Image Credit: Lindsay Helms, Shutterstock

3. Tumors

A mass growing in the brain can cause a range of neurological signs, including seizures, depending on where the mass is located.


4. Toxins

The ingestion of a substance that disrupts brain chemistry directly, or by damaging other organs, can cause seizures in dogs. Some examples include:

  • Poisonous substances, such as antifreeze or rat bait
  • Natural substances, such as venom/poisons from plants or animals
  • Foods, such as xylitol, chocolate, or salt
  • Heavy metals, such as lead and zinc
  • Illicit drugs, such as cocaine, methamphetamines, or cannabis
  • Medications
  • Pesticides
sick australian shepherd dog lying on the floor
Image Credit: Stéphanie Briand, Pixabay

5. Metabolic Disorders

Diseases of the liver or kidneys can lead to the accumulation of toxins in the bloodstream which, at certain levels, can cross into the brain and cause seizures.


6. Heart Disease

Cardiac insufficiency can trigger a seizure by temporarily starving the brain of oxygen due to reduced blood flow or result in blood clots that can travel to the brain.

a sick dog with tick-borne disease
Image Credit: Pamela Lico, Shutterstock

7. Inflammatory Conditions

Inflammatory conditions can also trigger seizures. Common conditions include:

  • Granulomatous Meningoencephalitis (GME): A disease affecting particular cells in the brain, seen most commonly in smaller breeds such as chihuahuas, miniature poodles, or small terriers.
  • Meningitis: Inflammation or infection of the cerebrospinal fluid (CSF). Bacterial and viral meningitis are rare in dogs, but idiopathic or steroid-responsive meningitis are relatively common.

8. Infection

Certain infections could also cause seizures, such as:

  • Protozoa: Neospora and Toxoplasma are protozoal organisms that can invade various tissues and cause neurological signs, including seizures. Fortunately, most infections are mild and quickly fought off by a healthy immune system.
  • Bacterial or Viral: These types of infections can produce neurological signs such as seizures directly (e.g., canine distemper) or indirectly by causing high fever.
  • Fungal: Cryptococcus is a fungal infection spread in bird feces that can cause seizures in immunocompromised dogs.
Vet specialist examination sick dog
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9. Fever

Dogs fighting infection will often develop a fever, but if that temperature exceeds 106oF (41.1oC) it can lead to brain damage and seizures. The heat produced by the muscles during a seizure can cause body temperature to rise even further, compounding the problem.


10. Heat Stroke

Dogs don’t sweat, which means their primary method of cooling down is through panting. In warm, humid conditions, this cooling mechanism does not work very efficiently. The danger on a hot day is less about how hot the dog gets and more about how quickly it can cool down. This is why more dogs are likely to suffer from heat stroke at warm temperatures with high humidity than those in hot but dry conditions.

Sick dog on pillow
Image By: PickPik

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Final Thoughts

Seizures are frightening episodes for dogs and their humans, and they occur relatively commonly. This is likely due to the wide range of things that can disrupt normal brain function by directly damaging neurological tissue, by damaging other organ systems which have a knock-on effect on the brain, or by creating an inflammatory response that leads to a dangerously high body temperature.

Epilepsy is the most common cause of seizures in dogs, but fortunately, this is a condition that can usually be well managed with medication. Dogs can have single, isolated seizures with no further episodes, so treatment is not always necessary, but you should always contact your vet immediately if your dog has had or is having a seizure.

Remember that dogs can have an altered mental state or behavior after a seizure, so keep yourself safe when tending to your post-seizure patient.

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