What is the difference between a seizure disorder and epilepsy?

Seizure Disorder vs. Epilepsy: Key Distinctions

A seizure disorder and epilepsy are often used interchangeably, but technically "epilepsy" is the formal diagnosis requiring either two unprovoked seizures more than 24 hours apart, one unprovoked seizure with ≥60% recurrence risk, or diagnosis of an epilepsy syndrome, while "seizure disorder" is a broader, less specific term that may encompass any condition causing recurrent seizures. 1, 2

Core Definitions

Seizure:

• A single transient event of abnormal excessive or synchronous neuronal activity in the brain 1
• Approximately 10% of the population experiences at least one seizure during their lifetime 1, 3, 4
• A seizure is a symptom, not a diagnosis 3

Epilepsy (Formal Diagnostic Criteria): The International League Against Epilepsy (ILAE) defines epilepsy as meeting ANY of these three conditions: 1, 2

1. At least two unprovoked seizures occurring more than 24 hours apart 1, 2
2. One unprovoked seizure AND a probability of recurrence ≥60% over the next 10 years (similar to the risk after two unprovoked seizures) 2
3. Diagnosis of a specific epilepsy syndrome 1, 2

Epilepsy affects approximately 1.2% of the US population (3.4 million people) and represents a chronic disorder with enduring predisposition to generate seizures. 1, 3

Critical Distinction: Provoked vs. Unprovoked Seizures

This is the most clinically important distinction that determines whether someone has epilepsy:

Provoked (Acute Symptomatic) Seizures:

• Occur at the time of a systemic insult or in close temporal association with documented brain insult 5
• Common causes include: traumatic brain injury, cerebrovascular disease, drug withdrawal, metabolic derangements, infections 5, 4
• Incidence: 29-39 per 100,000 per year 5
• These patients do NOT have epilepsy and do NOT require long-term antiepileptic drugs 3
• Treatment focuses on correcting the underlying cause 3

Unprovoked Seizures:

• Occur in the absence of precipitating factors 5
• May result from static injury (remote symptomatic), progressive injury, or unknown cause 5
• Incidence of single unprovoked seizure: 23-61 per 100,000 person-years 5
• Only unprovoked seizures count toward an epilepsy diagnosis 2

When Does a Single Unprovoked Seizure Become "Epilepsy"?

High-risk features that indicate ≥60% recurrence risk (meeting epilepsy criteria after just ONE seizure): 4, 2

• History of prior brain insult 3
• EEG demonstrates epileptiform abnormalities 3, 4
• MRI demonstrates a structural lesion 3, 4
• Diagnosis of a specific epilepsy syndrome 2

Without these features, a single unprovoked seizure does NOT meet epilepsy criteria and typically does NOT require antiepileptic drug treatment. 3, 4

Practical Clinical Implications

For First-Time Seizure Patients:

1. Determine if provoked or unprovoked 5, 4

   • Check for acute metabolic derangements, drug/alcohol use, recent head trauma, stroke, infection
   • If provoked: treat underlying cause, no epilepsy diagnosis, no long-term AEDs needed 3

2. If unprovoked, assess recurrence risk 4

   • Obtain epilepsy-protocol MRI with thin-cut coronal slices 4
   • Obtain EEG (though normal EEG does not rule out epilepsy) 6, 4
   • Assess for prior brain injury history 3

3. Apply epilepsy diagnostic criteria 2

   • If high-risk features present (≥60% recurrence): diagnose epilepsy, consider AED treatment 2
   • If low-risk: single unprovoked seizure, observe without AEDs 3, 4

For Established Epilepsy:

• Only 2-3% of people who experience seizures develop epilepsy 4
• Epilepsy can be considered "resolved" if seizure-free for 10 years and off medications for 5 years 2

Common Pitfalls to Avoid

Do not diagnose epilepsy prematurely: When uncertain, it is better to postpone the diagnosis than to falsely diagnose epilepsy, as this has significant treatment and psychosocial implications 1

Do not treat provoked seizures with long-term AEDs: Acute symptomatic seizures require treatment of the underlying cause, not chronic antiepileptic medications 3

Do not assume all recurrent seizures equal epilepsy: Recurrent provoked seizures (e.g., repeated alcohol withdrawal seizures) are still provoked seizures, not epilepsy 5

Do not rely solely on EEG: A normal interictal EEG cannot rule out epilepsy and must be interpreted in clinical context 6

Terminology in Practice

"Seizure disorder" is often used colloquially but lacks precision: 3, 7

• It may refer to epilepsy (unprovoked recurrent seizures)
• It may refer to any condition causing seizures (including provoked)
• Use "epilepsy" when formal diagnostic criteria are met 2
• Use specific descriptors like "provoked seizure" or "single unprovoked seizure" when epilepsy criteria are not met 5