2  What is Epilepsy?

2.1 ILAE Definition

According to the International League Against Epilepsy (ILAE)[@fisher2014], epilepsy is a disease of the brain defined by any of the following conditions:

  1. At least two unprovoked (or reflex) seizures occurring more than 24 hours apart

  2. One unprovoked (or reflex) seizure and a probability of further seizures similar to the general recurrence risk (at least 60%) after two unprovoked seizures, occurring over the next 10 years

  3. Diagnosis of an epilepsy syndrome

Let’s break down what this means in practical terms.

2.2 Understanding “Unprovoked” Seizures

The key word here is unprovoked. This means the seizure happened without an immediate, reversible cause.

Unprovoked seizures occur due to an enduring change in the brain that makes it prone to seizures. Examples include:

  • Seizures due to a brain malformation
  • Seizures from an old brain injury (stroke, trauma)
  • Seizures from genetic factors
  • Seizures with no identifiable cause (idiopathic epilepsy)

Provoked (acute symptomatic) seizures happen because of a temporary, reversible condition. Examples include:

  • Seizures during a high fever (febrile seizures)
  • Seizures from low blood sugar
  • Seizures from acute alcohol withdrawal
  • Seizures within a week of a head injury or stroke
  • Seizures from an active brain infection

2.3 When is Epilepsy Diagnosed?

2.3.1 Scenario 1: Two or More Unprovoked Seizures

If someone has two or more unprovoked seizures that occur more than 24 hours apart, they meet the definition of epilepsy.

2.3.2 Scenario 2: One Seizure Plus High Risk of Recurrence

Sometimes epilepsy can be diagnosed after just one seizure if there’s strong evidence the person has a high risk (60% or more) of having another seizure. This might be the case when:

  • Brain imaging shows a structural problem that’s known to cause epilepsy (like a malformation, old stroke, or brain tumor)
  • EEG shows epileptiform activity (specific abnormal patterns that indicate an increased seizure risk)
  • The person has a specific epilepsy syndrome where one seizure type predicts more will follow

2.3.3 Scenario 3: Epilepsy Syndrome

Some people are diagnosed with a specific epilepsy syndrome: a recognizable pattern that includes specific seizure types, EEG findings, age of onset, and sometimes other features. When an epilepsy syndrome is identified, the diagnosis of epilepsy is made even if only one seizure has occurred.

We’ll discuss specific epilepsy syndromes in more detail in a later chapter.

2.4 How Common is Epilepsy?

Epilepsy is one of the most common neurological conditions:

  • About 1 in 26 people will develop epilepsy at some point in their lifetime
  • Approximately 3.4 million people in the United States have epilepsy
  • Worldwide, about 50 million people live with epilepsy
  • It can start at any age, though it’s most commonly diagnosed in childhood and after age 60

2.5 What Causes Epilepsy?

Epilepsy has many possible causes. In some cases, the cause is clear; in others, it remains unknown despite thorough testing.

Structural causes:

  • Brain malformations present from birth
  • Brain injury from trauma, stroke, or infection
  • Brain tumors

Genetic causes:

  • Inherited epilepsy syndromes
  • Genetic mutations affecting brain development or function
  • Chromosomal abnormalities

Infectious causes:

  • Previous brain infections (meningitis, encephalitis)
  • Parasitic infections in certain parts of the world

Metabolic causes:

  • Inborn errors of metabolism
  • Mitochondrial disorders

Immune causes:

  • Autoimmune encephalitis
  • Other immune-mediated conditions affecting the brain

Unknown causes:

  • Despite thorough evaluation, the cause remains unidentified in about 40-50% of people with epilepsy
  • This is sometimes called “idiopathic” or “cryptogenic” epilepsy

2.6 Can Epilepsy Be Cured?

Epilepsy is not always a lifelong condition. The outlook depends on the underlying cause and type of epilepsy:

Some people outgrow their epilepsy:

  • Many childhood epilepsy syndromes resolve with age
  • Some people with well-controlled epilepsy can eventually stop medication and remain seizure-free

Epilepsy is considered “resolved” when:

  • Someone has been seizure-free for at least 10 years, with no seizure medications for at least the last 5 years, OR
  • Someone has passed the age range of their age-dependent epilepsy syndrome

However, for many people, epilepsy is a chronic condition that requires ongoing management.

2.7 Living with Epilepsy

While epilepsy is a serious condition that requires medical attention, most people with epilepsy lead full, active lives. With appropriate treatment:

  • About 2/3 of people with epilepsy can become seizure-free with medication
  • For those who don’t respond to medication, other options like surgery, devices, or dietary therapy may help
  • Many people with well-controlled epilepsy can drive, work, have families, and participate fully in their communities

The key is working with your healthcare team to find the right treatment approach and understanding how to live safely with epilepsy.

2.8 What’s Next?

Now that you understand what epilepsy is, the next steps typically involve:

  1. Determining what type of epilepsy you have (we’ll cover epilepsy classification in the next chapter)
  2. Understanding your specific seizures and how to recognize them
  3. Finding the right treatment to control your seizures
  4. Learning to live safely with epilepsy

In the following chapters, we’ll explore these topics in detail, helping you navigate your epilepsy diagnosis with confidence and clarity.