Epilepsy is a disease of the brain that is characterized by recurrent, unprovoked, focal or generalized seizures. Two key points in that definition are important:

• Recurrent: A dog that has a single isolated seizure does not have epilepsy.
  
  
• Unprovoked: The seizures are not caused by something outside the brain. For example:
• A dog with hypoglycemia that seizes is experiencing provoked seizures, not epilepsy.
• A dog with metabolic or toxic causes of seizures is experiencing reactive seizures, not epilepsy.

Epilepsy itself is a primary brain disorder and it’s the most common neurologic condition seen in veterinary practice. While prevalence estimates hover around 0.75% to 1% of the canine population, that translates to hundreds of thousands of affected dogs in the U.S. alone.

Clinically, seizures fall into three main categories and distinguishing the type matters because treatment and prognoses differ significantly:

1. Structural epilepsy - due to identifiable brain disease (e.g., tumors, strokes, encephalitis, malformations)
2. Idiopathic epilepsy - believed or proven to be genetic, with no underlying structural cause. This is the most common type, accounting for ~60% of cases and up to 75% of true epilepsy diagnoses.
3. Reactive seizures
   Caused by systemic issues (e.g., liver disease, electrolyte imbalances, toxins)
   
   

The remainder of this article will focus on idiopathic epilepsy, which is considered a complex and heterogeneous disease or group of disorders. In fact, epilepsy stems from abnormalities occurring on a microscopic or cellular level and cannot be discerned even by advanced imaging (e.g., MRI, which shows macroscopic disease or abnormalities). Affected dogs may also exhibit other behavioral problems (ADHD-like including anxiety, aggression, poor trainability). There is also a great deal of individual variability with respect to manifestations of disease and response to therapy. In other words, two dogs of the same breed can have very different life experiences as epileptics. As such, treatment is not a “one-size-fits-all” proposition.

Antiepileptic drugs (AEDs) are the mainstay of therapy, but choosing the right treatment for a dog involves achieving balance between several factors: the effectiveness of the drug(s), cost for lifelong therapy, ease of administration, adverse effects, and drug interactions.

Based on ACVIM Consensus guidelines:¹

• Phenobarbital has the strongest evidence and highest recommendation for treating idiopathic epilepsy in dogs. This drug, alone, controls seizures in approximately 85% of treated dogs.²
• Potassium bromide has moderate support and, if used as a sole therapy, may control seizures in approximately 52% of patients.²
• Relatively newer drugs (levetiracetam, zonisamide) have gained popularity and are widely used but have limited high-quality evidence to support their efficacy.

Taking an evidence-based approach to prescribing treatment is always the goal, but there is a bit of a gap with respect to our knowledge about idiopathic epilepsy. This is largely due to the waxing and waning nature of the disease – seizures often improve temporarily regardless of intervention. Even placebo-controlled studies have demonstrated that up to 30% of dogs with epilepsy may seem to “improve” with placebo.

While many dogs can be successfully managed on medical therapy, roughly one third of patients can develop medically refractory seizures. Dogs with refractory epilepsy fail to achieve seizure control despite appropriate drug therapy and may require two or more medications to control their seizures. These patients are also at risk for shortened lifespans (median of ~2.3 years in some studies), death linked to their seizure disorder (50-75%), and euthanasia due to a poor quality of life. Risk factors for antiepileptic drug resistance include:

• Sex (males are at higher risk)
• Animals that are prone to cluster seizures
• Certain breeds have demonstrated a resistance or poorer response to AEDs including the Border Collie, German Shepherd Dog, Staffordshire Bull Terrier, and Labrador Retriever
• Concurrent allergic disease (skin or GI) may possibly contribute to AED resistance
  
  

The successful management of dogs with idiopathic epilepsy is often multimodal and, in addition to antiseizure drugs, a holistic treatment plan includes minimizing stress, addressing GI health, and possibly manipulating the diet. While ketogenic diets have been utilized in humans with epilepsy since the 1920s, there is limited evidence to support feeding high fat, low carbohydrate diets to dogs with epilepsy. However, diets enriched with medium chain triglycerides (MCTs) may be useful as an adjunct in treating these patients and, while MCTs have been shown to aid in improving seizure control, they should not be considered as a replacement for antiseizure drugs in dogs.

The intestinal micriobiome is known to play a role in a myriad of biological processes throughout the body including immune function, metabolism, and neurologic signaling and, in recent years, researchers have examined the influence of the intestinal microbiome on brain disease. While data is limited in veterinary medicine, there is enough evidence to suggest that gastrointestinal health likely plays a role in seizure control. Dogs with epilepsy that also have chronic diarrhea or vomiting, food allergies, or dysbiosis should have those other issues evaluated and managed to optimize control of their seizures. There are ongoing studies to evaluate the utility of probiotics, alterations of the microbiome, and other metabolic therapies for managing idiopathic epilepsy - research findings may reshape our approach to treating affected patients in the future.

One other important consideration is the impact of canine epilepsy on the quality of life of the caregiver (in addition to that of the patient). Upwards to 60% of caregivers have reported a negative influence of their pet’s disease on daily life due to emotional stress, sleep disruption, and lifestyle changes to accommodate a dog's treatment schedule. This can be further compounded by financial strain. Some patients could require medications that, alone, cost $200+ per month.

In conclusion, the implication of epilepsy in dogs expands beyond the brain and seizure disorder itself - it’s a complex, multifactorial disease that impacts patients, families, and veterinary teams alike. For now - pending findings of ongoing research into a cure for the disease - the best approach is to consider an evidence-based and individualized plan for every dog impacted by epilepsy. Learn more in The Canine Epilepsy Summit (available for viewing On Demand).

References:

[1] ACVIM Consensus Statement on the management of status epilepticus and cluster seizures in dogs and cats.  DOI: 10.1111/jvim.16928

[2] Comparison of phenobarbital with bromide as a first-choice antiepileptic drug for treatment of epilepsy in dogs.  DOI: 10.2460/javma.240.9.1073