Why did my pet have a seizure?

A seizuring pet can be a very scary experience for both the pet and the pet owner. So we asked Dr. Yung to explain more about seizures and what to do if you think your pet is having one.


Seizures are any involuntary activity that occurs abnormally. Most often in our patients, we encounter descriptions of a grand mal seizure where the seizure activity encompasses the whole body – resulting in collapse, stiffened limbs, convulsions that range in severity but are usually mild to moderate, loss of consciousness and loss of urinary or bowel continence.

In humans, people with seizures describe a “pre-ictal” period when they describe an aura or particular feeling that precludes a seizure. Our pets are unable to describe these abstract feelings to us, but a pet who has a seizure does typically exhibit a describable “post-ictal” period where they may be briefly disoriented, may stumble, act confused, or even appear as if they have lost vision.
A description of a post-ictal activity also helps differentiate neurological-based seizure activity from a “fainting” episode that would suggest a cardiovascular abnormality. A patient who has a “fainting” spell is generally quite normal quickly after the incident.


Seizures often occur abruptly without any prior signs of illness. Unless the seizure activity is caused by a toxin or traumatic event, they usually only last for a minute or few minutes and resolve. At this point, it is important to have the pet checked out to start evaluating the underlying cause of the seizure.

**If your DOG has seizure-like symptoms, it is important to approach the situation with safety in mind- do not put your hands around your dog’s mouth, etc. If appropriate, wait a minute or so for the seizure to pass, and then call your veterinarian.

***CATS should be seen immediately.


When we try and classify the “why” of a seizure, we think about intracranial or extracranial causes. Intracranial causes include those things that happen inside the brain – brain tumors, brain or meningeal infections, structural congenital brain abnormalities, or, at the microscopic level, a misfiring of neurons. Extracranial causes are those diseases that occur outside of the brain – liver disease or liver shunts that allow toxins into the brain, toxin ingestion, trauma, or electrolyte abnormalities.


Age and time of seizure presentation can give us a clue on whether we are dealing with intracranial or extracranial causes:

  • Dogs less than one years old – Congenital abnormalities like a liver shunt, hydrocephalus, or atlanto-axial subluxation are more suspect.
  • Dogs 3-6 years old – Epilepsy (a misfiring of neurons on the molecular level) is most common. This is the most common cause of seizures in our canine patients.
  • Dogs older than six years – Epilepsy is still possible, but older age raises the suspicion and concern of brain tumors or other extracranial causes like liver disease or other endocrine abnormalities.
  • Cats – Our feline friends are NOT typically affected with seizures. Any cat with a description of seizure activity should be treated immediately as an emergency.


A full Chemistry Panel and CBC should be evaluated on every pet that has a seizure. If there are indications of any of the extracranial causes (liver enzyme elevations, electrolyte abnormalities, low blood sugar), then we address those concerns and treatment options.

If all normal and the age of the pet fits, then we can consider that Epilepsy is most likely. If other circumstances occur – such as a cat with seizures, an older dog with sudden seizures, then further diagnostics like a CSF tap, MRI or CT scan is appropriate.

For epilepsy, we say that we can manage the illness, though we are unable to cure it. Seizures will likely occur lifelong if not on medication, so these patients will need lifetime medication. Medication choice is base on the patient and situation. First, we don’t start all pets on anti-seizure medications after a single seizure incident. We often request that the owner keeps a written log of the seizures – when, how long, what happened. We start medical treatment if and when:

  • The seizures are frequent or increase in frequency. A seizure more than once a month or every two months is concerning.
  • The seizure time is lengthening – from a minute to minutes.
  • The seizures have a profound pre or post ictal period. Some patients have been reported to be excessively agitated or uncomfortable for days following a seizure.
  • The seizures are occurring in clusters – meaning that the seizures are occurring back-to-back. **This is an emergency situation and the pet should be brought into a veterinary hospital immediately. Prolonged seizure activity will cause permanent brain damage.**

Phenobarbital and Potassium Bromide are the two most commonly used first line medications for seizure control. The decision on which medication to use – or to use both – is a medical decision based on the patient’s seizure activity severity and frequency.

  • Phenobarbital is a controlled drug that works quickly but can have significant side effects such as lethargy, increased appetite and weight gain, and liver damage. It is a medication that can be abused.
  • Potassium Bromide is a drug that needs to be compounded into either a liquid or a capsule. It works very well and is considered safer than Phenobarbital but takes 3 weeks to buildup in the patient’s system and up to 3 months to reach a consistent therapeutic level.

Both medications are evaluated with blood levels at an appropriate time after starting medication to ensure a therapeutic dose and, especially in the case of Phenobarbital, that there is no liver damage. Minimal yearly blood checks are required thereafter.


Good for seizure control in most patients if epilepsy. Some patients have severe or refractory seizures and other medications need to be added on to effect control, or a neurologist consult is appropriate.

What's Next

  • 1

    Call us or schedule an appointment online.

  • 2

    Meet with a doctor for an initial exam.

  • 3

    Put a plan together for your pet.