ILAE Definition of Epilepsy
According to the International League Against Epilepsy (ILAE) definition, epilepsy is defined as having at least two unprovoked seizures occurring more than 24 hours apart, one unprovoked seizure and a probability of further seizures similar to the general recurrence risk after two unprovoked seizures occurring over the next 10 years, or diagnosis of an epilepsy syndrome. 1
Correct Answer: Option B - 2 unprovoked seizures
The ILAE definition of epilepsy includes multiple criteria, but the traditional and most commonly recognized definition is the occurrence of at least two unprovoked seizures more than 24 hours apart. This corresponds directly to option B in the question.
Understanding the Complete ILAE Definition
The complete ILAE definition of epilepsy has three possible criteria, any one of which is sufficient for diagnosis:
- At least two unprovoked seizures occurring more than 24 hours apart
- One unprovoked seizure and a probability of further seizures similar to the general recurrence risk after two unprovoked seizures (at least 60%), occurring over the next 10 years 2
- Diagnosis of an epilepsy syndrome 1, 2
Why Option A is Incorrect
Option A states "A single episode of unprovoked seizures with a higher – 60% tendency of repeat seizure." While this partially aligns with the second criterion of the ILAE definition, it is not precisely correct. The ILAE definition specifies that the probability of further seizures should be similar to the general recurrence risk after two unprovoked seizures, which is at least 60% over the next 10 years 2. The wording in option A lacks the specific timeframe (10 years) and the comparison to the recurrence risk after two seizures.
Why Option C is Incorrect
Option C states "2 provoked seizures." This is clearly incorrect because the ILAE definition specifically refers to unprovoked seizures. Provoked seizures occur at the time of or within 7 days of an acute neurologic, systemic, metabolic, or toxic insult 1. Examples include seizures due to hyponatremia, alcohol withdrawal, toxic ingestions, or acute CNS infections. These are classified as acute symptomatic or provoked seizures, not epilepsy 1.
Clinical Implications
Understanding the correct definition of epilepsy is crucial for:
- Accurate diagnosis and classification
- Appropriate treatment decisions
- Prognostication
- Research and communication among healthcare providers
The 2014 update to the ILAE definition expanded the traditional definition to include patients with a single seizure who have a high risk of recurrence, allowing earlier diagnosis and treatment in high-risk patients 3, 2.
Common Pitfalls
- Confusing provoked and unprovoked seizures
- Failing to recognize that a single unprovoked seizure with high recurrence risk can now meet criteria for epilepsy
- Not considering epilepsy syndromes as part of the definition
- Overlooking the time criterion (seizures must be >24 hours apart)
The ILAE definition has evolved over time, with the most recent significant update in 2014, which expanded the definition beyond the traditional requirement of two unprovoked seizures 2.