The Road Not Taken: Misclassifying an Anti-Seizure Medication as a Failure

To quantify how often anti-seizure medications (ASMs) appear ineffective yet provide benefit when considering seizure frequency (SF) variability.

We used the CHOCOLATES seizure diary simulator to generate 100,000 patient seizure diaries that reflect natural SF variation in a heterogeneous population. Medication effect was modeled as a 20% average SF reduction (standard deviation 10%). We identified how many patients with an observed ≥ 25% SF increase (apparent worsening) actually had a true ≥ 10% SF reduction (vs. no medication), and how many with an observed ≥ 50% SF reduction (apparent responders) would have shown < 0% reduction if not taking the ASM. We also quantified how many individuals who had apparent worsening were actual worsening (> 0% SF increase vs. no medication).

Simulations closely matched real-world ASM trials, showing a median SF reduction of 36% with ASM versus 17% with placebo; 35% of patients on ASM achieved ≥ 50% SF reduction versus 20% on placebo. Apparent worsening occurred in 12%; among these, 76% were true improvers. Of the apparent responders, 12% were true nonresponders. Only 4% of the individuals with apparent worsening truly worsened compared to no medication.

SF variability can lead to significant misclassification of ASM benefit. Many patients labeled as having "failed" an ASM trial were likely receiving meaningful benefit and may warrant reconsideration of the medication. Prospective clinical studies are needed to determine how best to account for SF variability and refine the interpretation of treatment response in epilepsy management.