Epilepsy in Dogs: Causes and Diagnosis

Finding the cause of epilepsy in dogs is not as simple as performing a single test. Different dogs have different causes of epilepsy, and sometimes a specific cause cannot be determined.

To make a diagnosis of epilepsy, veterinarians start by confirming that a dog is having seizures and not experiencing some other kind of problem. The full process can require several different kinds of tests to gather the information needed to make the best decisions for treatment.

How Many Seizures Are Considered Epilepsy?

A single seizure does not mean a dog has epilepsy. The diagnosis of epilepsy in dogs is usually made after two or more unprovoked seizures that happen at least 24 hours apart. These seizures must not be caused by a toxin, infection or another treatable medical issue to be considered epilepsy.¹

Causes of Epilepsy in Dogs¹

So what causes epilepsy in dogs? Epilepsy is not just one condition. It can have different causes depending on the dog. Veterinarians group epilepsy in dogs into several categories based on what they believe to be the underlying cause.

Idiopathic Epilepsy in Dogs

This is the most common type of epilepsy in dogs, yet the exact cause is unknown. Idiopathic epilepsy means that a dog has had two or more unprovoked seizures, but no underlying problem can be found on exams or testing.

When do dogs start experiencing idiopathic epilepsy? This form of epilepsy is believed to be due to a genetic tendency, and it usually starts between 6 months and 6 years of age.

Idiopathic epilepsy accounts for more than half of all dog epilepsy cases. It has been reported in many breeds.

In some breeds, specific genetic forms have been identified. However, in most cases, the genetic cause is complex and still being studied.

Male dogs may be slightly more likely to develop idiopathic epilepsy than females.

Structural Epilepsy in Dogs

Structural epilepsy occurs when seizures are caused by a physical problem in the brain, such as a tumor, stroke, inflammation or a birth defect. This type is more common in older dogs, although it can occur at any age.

In one study of dogs that began having seizures at age 7 or older, nearly 80% had a structural problem in the brain.¹ As dogs get older, the chances of seizures being caused by a tumor or other brain disease increases.

Signs of structural epilepsy in dogs often include unusual behavior between seizures or other neurologic symptoms, like trouble walking, vision loss or circling. Advanced imaging like magnetic resonance imaging (MRI) and spinal fluid testing is usually needed for a veterinarian to make this diagnosis.

Epilepsy of Unknown Cause

Sometimes, a dog has repeated seizures that do not clearly fit into any of the categories above. If no structural cause is found and a genetic cause seems unlikely, the condition may be called “epilepsy of unknown cause.”

This term may also be used if a full workup has not been done yet. In these cases, additional testing may help clarify whether the seizures are caused by idiopathic epilepsy or a structural issue.

Reactive Seizures in Dogs¹

Reactive seizures are not actually a form of epilepsy, but they are important to note because they can look the same. These seizures are caused by something outside the brain that temporarily disrupts its function. Examples include low blood sugar, liver disease, electrolyte imbalances or poisoning.

Toxins like rat bait, antifreeze, lead or certain insecticides can all cause seizures. In fact, poisoning is the most common cause of reactive seizures in dogs. Hypoglycemia (low blood sugar) is another common cause.

Dogs with reactive seizures may be very sick at the time of the episode. They are also more likely to develop status epilepticus, a dangerous condition where seizures do not stop without emergency care.

How to Confirm Dog Epilepsy: Veterinary Diagnosis¹

When it comes to diagnosis, there is no single test to confirm epilepsy in dogs. Instead, veterinarians carefully rule out other possible causes of seizures and look at the overall pattern of your dog’s health, behavior and test results. This kind of process is called a diagnosis of exclusion.

The first step is confirming that your dog is truly having epileptic seizures. Many other conditions can cause sudden, unusual episodes that may look like seizures, including fainting (syncope), muscle disorders and balance problems. That’s why a detailed history is so important. Your veterinarian will ask questions about what your dog was doing before, during and after the event. If possible, recording a video of the episode can be incredibly helpful.

Once seizures are confirmed, the veterinarian will consider your dog’s age and overall health. Idiopathic epilepsy in dogs is more likely if seizures began between 6 months and 6 years of age and if the dog appears healthy between seizures. A family history of epilepsy may also support the diagnosis.

To rule out other causes of seizures, your veterinarian may recommend a number of tests, including the following.

Blood and Urine Testing

Your veterinarian may recommend blood work and urine testing to check for problems such as low blood sugar, liver disease, kidney problems and electrolyte imbalances. Tests often include:

• Complete blood count (CBC)
• Blood chemistry panel
  • Blood glucose
  • Liver and kidney enzymes  
  • Electrolytes (like sodium, potassium, and calcium)
• Urinalysis

Additional Lab Tests

Depending on the symptoms of epilepsy in dogs, additional tests may be done to check for conditions like thyroid disease, insulin-secreting tumors, or muscle disorders. These might include:

• Thyroid hormone testing (T₄, free T₄, thyroid-stimulating hormone [TSH])
• Fructosamine and glucose tests
• Creatine kinase (CK) for muscle damage
• Blood ammonia
• Infectious disease testing (such as polymerase chain reaction [PCR] or antibody tests)
• Vitamin B-12 levels
• Ionized calcium

Genetic Testing

In some breeds, inherited forms of epilepsy are known. Your veterinarian may recommend a genetic test if your dog is a breed with a known genetic condition, such as juvenile epilepsy in a Lagotto Romagnolo or progressive myoclonic epilepsy in a Wirehaired Dachshund.

Other Tools

If a structural problem in the brain, like a tumor, inflammation or birth defect, is suspected, advanced testing will be needed. This may include MRI of the brain and cerebrospinal fluid (CSF) analysis.

In addition, your veterinarian may recommend:  

• Electroencephalography (EEG) to look at brain wave patterns
• Blood pressure measurement if high blood pressure is suspected
• Eye exam (ocular fundic exam)
• Chest and abdominal imaging if cancer is a concern

By combining information from your dog’s medical history, physical and neurologic exams, lab work and any additional tests, your veterinarian can determine whether your dog has epilepsy. While it may take time and a few steps to reach a diagnosis, each test helps guide the best care for your dog.

Treatment for Epilepsy in Dogs

Epilepsy is a long-term condition, which means managing it is an ongoing process. Your veterinarian will need to evaluate your dog’s response to treatment regularly and make adjustments as needed over time. Your input throughout this journey is essential in choosing the best management strategy for your dog. This article describes specific options you and your veterinarian might consider.

For more expert tips on epilepsy in dogs, explore the treatment options.

Reference

1. Risio LD, Bhatti S, Muñana K, et al. International veterinary epilepsy task force consensus proposal: diagnostic approach to epilepsy in dogs. BMC Vet Res. 2015;11(1):148.