My Dog Had a Seizure (Part 4): How Veterinarians Diagnose the Cause of Seizures

How Veterinarians Diagnose the Cause of Seizures

One of the biggest misconceptions about seizures is that there's a single test that tells us why they happened.

Unfortunately, it isn't that simple.

Diagnosing the cause of a seizure is often like putting together a puzzle. Every piece of information—from your dog's age to the results of bloodwork to what we see during a neurological exam—helps narrow the list of possibilities.

Our goal isn't simply to say, "Your dog had a seizure."

You already know that.

Our goal is to answer the much more important question:

"Why did your dog have a seizure?"

The answer to that question determines what treatment, if any, your dog needs.

Step 1: Your Dog's History

Believe it or not, one of the most important diagnostic tools isn't a machine.

It's you.

The story you tell us often provides our first—and sometimes biggest—clues.

We'll ask questions like:

• How old is your dog?
• Was this the first seizure?
• How long did it last?
• What was your dog doing beforehand?
• Did your dog recover completely?
• Has your dog had any recent illnesses?
• Has your dog gotten into medications, recreational drugs, or other toxins?
• Has anything changed at home recently?
• Is your dog taking any prescription medications?
• Does your dog have any chronic medical conditions?
• Have you noticed personality or behavior changes over the past few weeks or months?

Every answer helps us narrow our list of possible causes.

Step 2: The Physical Examination

After gathering your dog's history, we'll perform a complete physical examination.

Although seizures originate in the brain, many diseases affecting the rest of the body can trigger seizures.

We'll evaluate things such as:

• Heart rate and rhythm
• Lung sounds
• Body temperature
• Hydration
• Blood pressure
• Signs of pain
• Signs of toxin exposure
• Abdominal abnormalities
• Evidence of trauma

Sometimes the physical examination immediately points us toward the underlying problem.

Step 3: The Neurological Examination

A neurological exam is different from a routine physical exam.

Its purpose is to determine whether your dog's brain and nervous system appear to be functioning normally between seizures.

During this exam, your veterinarian may evaluate:

• Mental awareness
• Ability to walk normally
• Balance and coordination
• Cranial nerve function
• Vision
• Reflexes
• Muscle strength
• Limb placement
• Response to stimulation

If your dog has a completely normal neurological examination after recovering from a seizure, certain diagnoses become more likely.

If abnormalities are present, they may suggest disease affecting a specific part of the brain or nervous system.

Step 4: Bloodwork

Bloodwork is one of the first diagnostic tests recommended after many first-time seizures.

Why? Because many treatable diseases outside the brain can cause seizures.

Routine blood tests can help identify problems such as:

• Low blood sugar
• Liver disease
• Kidney disease
• Electrolyte abnormalities
• Severe infection
• Inflammation
• Certain metabolic disorders

Many of these conditions require very different treatment than epilepsy.

Finding one of these abnormalities early can completely change your dog's treatment plan—and in some cases, be lifesaving.

Step 5: Urinalysis

Although owners are sometimes surprised when we recommend a urine sample, it provides valuable information that bloodwork alone cannot.

A urinalysis helps us evaluate:

• Kidney function
• Hydration
• Evidence of infection
• Sugar in the urine
• Protein loss
• Crystal formation

When combined with bloodwork, it gives us a much more complete picture of your dog's overall health.

Step 6: Additional Testing

Depending on your dog's age, medical history, and examination findings, your veterinarian may recommend additional laboratory tests.

These might include:

• Bile acid testing to evaluate liver function
• Infectious disease testing
• Tick-borne disease testing when appropriate
• Hormone testing
• Toxicology testing in select situations

Not every dog needs these tests.

They are recommended when your dog's history or examination suggests a particular underlying condition.

Step 7: Blood Pressure Measurement

High blood pressure doesn't always cause seizures, but it can contribute to neurological problems in some dogs.

Because measuring blood pressure is quick, painless, and non-invasive, it may be included as part of your dog's evaluation—especially in senior pets or those with certain medical conditions.

Step 8: Advanced Imaging (MRI)

An MRI allows us to look directly at the structure of the brain.

Unlike X-rays, which primarily show bones, MRI provides incredibly detailed images of the brain's soft tissues.

This helps us identify problems such as:

• Brain tumors
• Inflammation
• Congenital abnormalities
• Previous strokes
• Bleeding
• Structural changes

MRI is often recommended when:

• An older dog experiences its first seizure
• The neurological examination is abnormal
• Seizures become progressively worse
• We suspect structural brain disease
• Initial testing doesn't explain what's happening

Because MRI requires general anesthesia and specialized equipment, it is usually performed by a specialty hospital or veterinary neurologist.

Step 9: Cerebrospinal Fluid (CSF) Analysis

In some cases, your veterinarian or neurologist may recommend collecting a sample of cerebrospinal fluid.

This clear fluid surrounds the brain and spinal cord.

Analyzing it can help diagnose:

• Meningitis
• Encephalitis
• Immune-mediated brain disease
• Certain infections
• Inflammatory disorders

CSF collection is generally performed while your dog is under anesthesia, often immediately following an MRI.

When Is a Neurologist Recommended?

Many dogs with seizures can be managed successfully by their primary care veterinarian.

However, referral to a veterinary neurologist may be recommended if:

Your dog is experiencing difficult-to-control seizures.

Seizures continue despite medication.

Your dog's neurological examination is abnormal.

Advanced imaging is recommended.

The diagnosis remains uncertain.

Specialized treatment options are needed.

Neurologists receive advanced training in diseases of the brain, spinal cord, nerves, and muscles, making them an invaluable part of the team for more complex seizure cases.

Will My Dog Need Every Test?

No.

One of the most important things to understand is that seizure diagnostics are not one-size-fits-all.

The evaluation for a healthy two-year-old Labrador with a single, brief seizure is often very different from the evaluation for a twelve-year-old dog having its first seizure and showing personality changes.

Your veterinarian develops a diagnostic plan based on your dog's:

• Age
• Breed
• Medical history
• Physical examination
• Neurological examination
• Frequency and severity of seizures
• Overall health

Our goal is to recommend the tests most likely to provide meaningful answers for your dog.

What If All the Tests Are Normal?

Owners sometimes worry that normal test results mean they've "wasted money."

I look at it very differently.

Every normal result rules out another potentially serious disease.

If bloodwork, physical examination, neurological examination, and additional testing are all normal, that information is incredibly valuable.

It allows us to become more confident that we're dealing with conditions like idiopathic epilepsy rather than toxins, organ disease, or structural brain abnormalities.

Sometimes the most important diagnosis comes from what we don't find.

From My Exam Room

One of the most difficult conversations I have is with owners who want one test to provide one simple answer.

I wish medicine worked that way.

Instead, every test gives us another piece of the story.

Sometimes the diagnosis becomes obvious after routine bloodwork.

Other times, we need advanced imaging or a neurology consultation.

And occasionally, after carefully ruling out other possibilities, we diagnose idiopathic epilepsy—not because we found a specific abnormality, but because we've confidently excluded other causes.

That's why I encourage owners to think of diagnostics as a process rather than a destination.

Each step brings us closer to understanding what's happening inside your dog's brain and, most importantly, how we can help them live the healthiest life possible.