Unfortunately, the short answer is. . . yes. This can occur for multiple reasons. Check out the list below that highlights some of the reasons your pet’s seizures may get worse over time.

 1. Kindling Phenomenon

The kindling model is one of the primary mechanisms believed to explain why seizures can become more severe or more frequent over time. Kindling refers to the process by which repeated seizure events can continue to simulate additional seizure activity by increasing sensitivity and decreasing seizure threshold over time. This process is thought to result from changes in the brain's excitability, with neurons becoming more easily triggered. Over time, this heightened sensitivity can lead to more severe and frequent seizures. Ensuring your pet’s seizures are well-controlled is the best thing you can do to help prevent or limit this phenomenon. Some medications have proposed/possible “anti-kindling” effects.

2. Structural Brain Changes

Repeated seizures can lead to physical and structural changes in the brain. Some scientists consider this a physical manifestation of kindling, while others associate this more with cluster event seizures or prolonged seizures (status epilepticus). No matter the underlying cause, when these structural changes occur, it leads to an increased risk of seizure activity. Any structural abnormality in the brain has the potential to increase seizure frequency, especially when it leads to changes in the normal brain tissue around it.

3. Systemic/ Environmental Effects

The body can be very sensitive to systemic conditions, and just because your pet has epilepsy doesn’t mean they won’t develop other conditions. Some medical conditions include normal body changes such as hormone variation (such as those that occur in intact females) or other conditions such as food allergies or endocrine disorders. Additionally, changes in the environment can have effects on stress and seizure threshold.

4. Drug Resistance

This is, perhaps, in this author’s experience, one of the most common causes of short-term worsening of seizures. Often, when dogs or cats have an increased frequency of seizures, one of the first things veterinarians and pet parents should consider is that the pet’s body is getting used to the medications. Some meds, such as phenobarbital, increase liver metabolism, so over time, the drug makes the body metabolize itself quicker! This can lead to lower drug levels in the blood and, thus, decreased drug effectiveness. MANY factors play into drug resistance.  

5. Underlying Progressive Conditions

Lastly, some seizures worsen over time because they are symptoms of underlying conditions that themselves progress. Neurodegenerative diseases, brain tumors, and progressive metabolic disorders can all lead to a gradual increase in seizure severity and frequency. In these cases, managing the primary condition is crucial to controlling the seizures.

Ensuring that you are keeping a seizure log for your pet, scheduling routine check-ins with your veterinarian, and being vigilant about any changes in your pet’s condition are the first steps to limiting the progression of seizures.

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Want to deep dive into the science? (Copy and paste the paper DOI into your browser). All articles should be open-access.

 Kindling Model In Humans: DOI: 10.1111/j.1528-1167.2007.01068.x

Pathophysiology of Drug Resistance: DOI: 10.1016/j.tvjl.2023.105990