Overview

Idiopathic epilepsy is a neurological disorder characterized by recurrent seizures with no identifiable underlying cause. A seizure occurs when there is abnormal, excessive activity of brain cells (neurons), particularly within the brain hemispheres (the cerebral cortex). While some seizures are caused by a structural abnormality, like a tumor, or a metabolic disturbance such as an electrolyte imbalance, idiopathic epilepsy is diagnosed when no such cause is found. Some cases of idiopathic epilepsy may not require treatment initially (depending on the frequency and severity), but once treatment begins, they often necessitate lifelong management with oral anti-seizure medication and ongoing monitoring. 

Cause

The exact cause of idiopathic epilepsy is unknown, but a genetic component is known in some breeds and suspected in others. Specific genetic variants associated with epilepsy have been described in some breeds and are being studied in others. Dogs with idiopathic epilepsy typically begin having seizures between 6 months to 6 years of age, with a median age of onset of 2.5 years. The frequency of seizures varies widely–dogs may have either one or multiple seizures a day (named a cluster seizure), and may go weeks, months, or even years without any seizure activity. 

Epilepsy is more common in purebred dogs, including Beagles, Bernese Mountain Dogs, Border Collies, Boxers, Cocker Spaniels, Labrador Retrievers, and Golden Retrievers. Male dogs may be more predisposed to idiopathic epilepsy than females.

Clinical signs

Seizures can be described as either generalized or focal. A generalized seizure involves both sides of the brain, whereas a focal seizure involves a smaller region only on one side of the brain. Focal seizures may be more subtle and are sometimes harder to identify as they can mimic other diseases. For example, some dogs may display “fly biting” behavior, appearing to catch a nonexistent fly, which may be due to focal seizures or other causes. 

• Signs of a generalized seizure include
  • Loss of consciousness
  • Convulsions characterized by stiffening (tonic) and paddling (clonic) movements
  • Excessive drooling
  • Unusual vocalization
  • Involuntary urination or defecation 

• Signs of a focal seizure include
  • Abnormal repetitive, uncontrollable movements in one set of muscles or a group of muscles in the body
  • Increased salivation
  • Dilated pupils
  • May or may not lose consciousness

Seizures can last for a few seconds to a few minutes and are often characterized in dogs by three phases: 

• Pre-ictal phase -- Subtle behavioral changes, such as restlessness or anxiety, may or may not be noticeable preceding a seizure.
• Ictal phase -- The seizure itself, often lasting seconds to minutes.
• Post-ictal phase – A recovery period following the seizure, in which the brain is “resetting” after the abnormal activity, characterized by confusion, disorientation, and lethargy. Some dogs will show food craving during this period.

An active seizure lasting more than five minutes (status epilepticus) or multiple seizures in a 24-hour period (cluster seizures) is considered a medical emergency. All status epilepticus are life-threatening, and some of the cluster seizures can be as well. In both cases, your dog should be taken to the nearest emergency veterinarian immediately.  

Diagnosis

Idiopathic epilepsy is a diagnosis of exclusion–meaning all other causes of seizures should be ruled out. This often includes several diagnostic tests to rule out diseases outside the central nervous system that could affect the brain as well as advanced imaging (MRI) and cerebrospinal fluid (CSF) sampling.

Your primary veterinarian may perform some of these tests, or they may refer you to a veterinary neurologist. 

• Blood work (complete blood count, biochemistry panel) and urine test (urinalysis)—Used to assess overall health and rule out systemic illness.
• MRI -- A type of imaging best suited to rule out structural problems in the brain, like inflammation or a tumor, that could be causing seizures.
• CSF analysis- CSF is a fluid that surrounds the spinal cord and brain and may be analyzed for abnormalities such as pathogens and elevation in cells indicating inflammation or cancer. 

In some cases where referral for diagnostic imaging is limited, a presumptive diagnosis of idiopathic epilepsy can be made when blood work and neurologic exam (once past the post-ictal period) are normal without any other signs of illness. 

If no abnormalities are found in dogs that have had at least two seizures 24 hours apart, a tentative diagnosis of idiopathic epilepsy is made. 

Treatment

Anti-seizure drugs, or antiepileptic drugs (AEDs) are used to manage seizures. However, your veterinarian may not prescribe AEDs following the first seizure event because, once started, dogs often need to stay on these medications for life. Instead, they may recommend monitoring for additional episodes to confirm a pattern of seizure activity. Exceptions to this include more serious scenarios such as cluster seizures, seizures lasting longer than five minutes, or dogs having especially violent seizures or post-ictal signs such as blindness lasting for up to three days after the seizure event. Otherwise, AEDs are generally recommended if a dog has more than two seizures in six months. 

Multiple AED options are available with varying dosing regimens and side effects, though all are generally very safe and well-tolerated. Some dogs may require more than one medication to control their seizure. Your veterinarian will work with you to determine which is best for you and your dog. 

Common anti-epileptic drugs include:

• Phenobarbital
• Levetiracetam (Keppra)
• Zonisamide
• Potassium bromide (KBr)

Your veterinarian may also prescribe emergency medications that can be administered during a seizure, such as diazepam to be administered rectally or midazolam to be administered intranasally.

While not a substitute for anticonvulsant medications, these adjunctive therapies may make it possible to lower the dose of your dog’s seizure medication:

• Therapeutic Diets (e.g., Purina ProPlan NeuroCare) contain medium-chain triglycerides (MCTs), known to block one of the receptors in the brain responsible for seizures.
• Gabapentin
• Acupuncture 

Monitoring

It is important to monitor your dog for “breakthrough” seizures that occur after starting medication. Tracking when your dog’s seizures occur, recording what happened, how long the event lasted, and how they acted before and after will help your veterinarian manage their treatment. It is especially useful if you can take a video recording of these events.

Medication therapy will require regular veterinary appointments for blood work, as it is critical to ensure medications are being administered at levels that are helpful to your dog without causing harmful side effects.

Outcome

Many dogs achieve good seizure control with anti-epileptic drugs. However, complete disappearance of all seizure activity is rare, and lifelong medication is typically necessary once management is started. Some dogs may require adjustments in medications to control seizures, while others may not respond to any and may continue to have very frequent seizures. In refractory cases where seizures remain frequent, severe, and uncontrollable despite treatment, quality of life concerns may lead to the consideration of humane euthanasia.

Updated April 2025