Epilepsy: The Road to a Diagnosis

Potential causes must be ruled out independently

Epilepsy is a neurological disorder that causes recurring seizures in cats. The Feline Health Center sees an average of four to five cats each week with a neurological disorder, says Curtis Dewey, DVM, Associate Professor, Section of Neurology/Neurosurgery at Cornell University.

Depending on severity, recurring seizures may occur from once every few months to multiple times a day. Seizures can range from a localized twitch or repetitive movement to full-body convulsions.

Since your cat cannot tell you if he had a seizure while you were at work, though, determining how many seizures may have occurred can be difficult. These variations add to the complexity of determining the cause of a seizure, whether it was an isolated event, and how to prevent further episodes.

Although this condition can be secondary to head injuries, metabolic irregularities, or tumors, a relatively common form is termed idiopathic epilepsy—so named because there is no discernible cause for the seizures that an affected cat experiences.

“Cats with idiopathic epilepsy are typically normal in every other respect,” says Dr. Dewey. Fortunately, epilepsy is usually manageable with the daily administration of various medicines. For your veterinarian to make this diagnosis, all known causes for seizures in cats need to be ruled out.

Physical Exam

Your veterinarian will do a thorough physical exam to check for any abnormalities, including an irregular heartbeat, severe ear infection, fever, or neurologic deficits such as a head tilt or poor reflexes. Results of the physical exam can help to narrow down your vet’s primary concerns, ranging from toxic shock to an infection.

It’s extremely important that you provide as much history as possible (see “What You Should Do” below). Some neurologic issues can develop subtly over time but indicate an underlying problem within the brain, ranging from strokes to a tumor.

What You Should Do

Bring your veterinarian a thorough history. Write down everything that you can think of, and bring the notes with you to your veterinarian so that you can be sure you do not miss anything. The more information you provide, the better the chances that your vet can pick up on a potential cause. Useful details include:

  •    When the seizure(s) occurred
  •    Length of the seizure
  •    What the cat was doing just before the seizure
  •    New medications (including flea/tick preventives)
  •    New houseplants
  •    Changes to routine
  •    A history of access to toxins such as plants, cleaning supplies, or medications
  •    Traumatic events
  •    How your cat acts after the seizure

Traumatic events, such as being hit by a car or attacked by a dog, can cause trauma to the brain. The effects of such damage may be seen immediately or can be delayed as swelling and/or slow bleeding progresses in the brain. A poorly healed skull fracture could potentially impact the brain long after the initial incident.

If your cat got into something toxic, contact a pet poison control center immediately, but remember that bit of history for your veterinarian.

Bloodwork and a urinalysis are generally the first line of diagnostic tools and can be used to rule out possible causes and to detect signs of disease. Tests may include:

Complete blood count (CBC). This checks for anemia and signs of infection.

Chemistry panel. Most panels evaluate liver and kidney function, electrolyte and blood-glucose levels, the amount of protein in the blood, and levels of indicators of pancreas and other organ function.

Thyroid test. This checks for hyperthyroidism, which is an overactive thyroid gland.

Feline immunodeficiency virus (FIV) and feline leukemia (FeLV) tests. These infectious diseases are most common in cats that go outside and may encounter other infected cats.

Urinalysis. This checks for urinary tract infections, diabetes, signs of advanced kidney disease, and, rarely, certain parasites.

Radiographs and Ultrasound. Radiographs, or x-rays, and ultrasound allow your vet to look at your cat’s organ systems for any problems. An enlarged heart, abnormal lungs, tumors, or signs of internal bleeding can all impact oxygen flow to your cat’s brain or suggest metastatic tumors that may have spread to the brain and caused the seizure.

Blood Pressure. High blood pressure can cause capillaries in the brain to burst, and low blood pressure can result in poor blood flow to the brain. Low blood pressure is usually accompanied by shock, either toxic or after a traumatic event. High blood pressure can be more insidious and go undetected for long periods of time. Two of the most common causes of high blood pressure in cats include kidney disease and hyperthyroidism, but cats can have primary high blood pressure. It may be necessary to track your cat’s blood pressure over time to determine if it is a chronic issue.

CT and MRI. Computed tomography (CT) and magnetic resonance imaging (MRI) allow the veterinarian to see the structure of the brain. These scans are excellent for finding tumors, structural abnormalities, or signs of bleeding in the brain, and are highly recommended for cats who are having seizures. The downside to these two technologies is that they are only available at specialty clinics, are expensive, and require anesthesia or heavy sedation.

CSF analysis. Cerebrospinal fluid (CSF) exists within membranes that enclose the brain and spinal cord. It is possible to take a sample of this fluid via a spinal tap and analyze it for signs of infection or other abnormalities that may not show up in the main bloodstream. This is considered an invasive procedure and may require a visit to a specialty clinic. Your cat will be anesthetized and the area around where the spinal needle is going to be inserted will be shaved and scrubbed to keep it sterile.

Electroencephalography. Electroencephalography measures the electrical activity of the brain. This is a diagnostic tool used in humans with seizure disorders. Unfortunately, more research needs to be done in cats before it can be used effectively.

Catch-All Diagnosis

Diagnosing a seizure disorder can be frustrating. The ideal course of action is to keep testing until all possible causes have been ruled out, at which point your veterinarian will arrive at a diagnosis of idiopathic epilepsy.

Unfortunately, this is not always possible. Discuss any financial or travel limitations with your veterinarian so that he or she can combine this information with the history you provide and the findings of the physical exam to determine which tests are most likely to yield useful results for your cat’s case.