What is the difference between epilepsy and seizures, and how are they diagnosed and treated in patients presenting with seizure symptoms?

Epilepsy vs Seizures: Key Distinctions

A seizure is a single event of abnormal electrical brain activity, while epilepsy is defined as recurrent unprovoked seizures—specifically, at least two unprovoked seizures occurring more than 24 hours apart, or one unprovoked seizure with a high probability of recurrence. 1

Fundamental Definitions

Seizures

• Seizures are symptoms, not diseases—they represent excessive synchronous cortical electrical activity causing generalized movements with unresponsiveness 1
• Approximately 8-10% of the population will experience at least one seizure during their lifetime 1, 2
• Only 2-3% of people who experience a seizure will go on to develop epilepsy 2

Epilepsy

• Epilepsy is a chronic disorder characterized by recurrent unprovoked seizures 1, 3
• Affects approximately 1-3% of the U.S. population (about 3.4 million people) 1, 3
• Requires meeting one of three criteria: 1) at least two unprovoked seizures >24 hours apart, 2) one unprovoked seizure with recurrence risk similar to two seizures over 10 years, or 3) diagnosis of an epilepsy syndrome 1

Critical Classification: Provoked vs Unprovoked Seizures

Provoked (Acute Symptomatic) Seizures

Provoked seizures occur at the time of or within 7 days of an acute neurologic, systemic, metabolic, or toxic insult 1, 4, 5

Common causes include:

• Electrolyte abnormalities: hyponatremia (most common), hypocalcemia, hypomagnesemia 6, 4, 5
• Metabolic derangements: hypoglycemia, hyperglycemia, uremia 6, 4
• Toxic ingestions: cocaine, tricyclic antidepressants, tramadol 6, 4
• Alcohol withdrawal 1, 4
• Acute CNS infections: meningitis, encephalitis 4
• Acute structural lesions: intracranial hemorrhage, stroke 4

Unprovoked Seizures

Unprovoked seizures occur without acute precipitating factors 1, 4

Categories include:

• Remote symptomatic seizures: resulting from CNS insult >7 days prior (prior stroke, traumatic brain injury, anoxia) 1, 4
• Idiopathic seizures: no identifiable cause 1, 4
• Genetic epilepsy syndromes 4

Diagnostic Approach

Initial Emergency Evaluation

All patients with first-time seizures require immediate assessment for life-threatening causes 1

Immediate Actions:

• Check blood glucose immediately—hypoglycemia is rapidly correctable and common 5
• Obtain vital signs and perform focused neurologic examination 1
• Focal neurologic deficits correlate with symptomatic seizures in 97% of cases 4

Laboratory Testing:

The American College of Emergency Physicians recommends comprehensive metabolic evaluation for all first seizures, as approximately 8% have correctable metabolic abnormalities 4, 5

Essential labs include:

• Complete blood count 4
• Comprehensive metabolic panel (sodium, calcium, magnesium, glucose, renal function) 6, 4, 5
• Toxicology screen when appropriate 4

Critical caveat: History and physical examination predict most metabolic abnormalities except occasional hypoglycemia cases and subdural hematomas 4

Neuroimaging

Emergency Setting:

Non-contrast CT head is the initial imaging modality for acute seizure presentations—it rapidly identifies hemorrhage, stroke, mass lesions, and hydrocephalus requiring urgent intervention 1

Indications for emergent CT:

• Persistent focal neurologic deficits 4
• Failure to return to baseline within several hours 4
• Note: 17% of patients with normal neurologic exams still have focal CT abnormalities 5

Outpatient/Elective Setting:

MRI with epilepsy protocol is the preferred imaging modality for unprovoked seizures, including thin-cut coronal slices to evaluate for structural abnormalities 5, 2

Electroencephalography (EEG)

EEG is required for all patients with unprovoked seizures to determine recurrence risk and guide treatment decisions 2

• Epileptiform abnormalities on EEG indicate high risk for seizure recurrence 3

Treatment Principles

Provoked Seizures

The American College of Emergency Physicians recommends treating the underlying cause rather than initiating long-term antiseizure medications for provoked seizures 6

Management approach:

• Correct metabolic abnormalities (electrolytes, glucose) 6
• Remove offending agents (toxins, medications) 6
• Treat infections 4
• Short-acting benzodiazepines may be used for temporary seizure control if needed 6

Critical principle: Single provoked seizures do NOT constitute epilepsy and do NOT require chronic antiepileptic therapy 6, 3

Unprovoked Seizures and Epilepsy

Antiepileptic drug (AED) therapy is indicated for:

• Recurrent unprovoked seizures (epilepsy diagnosis) 3
• Single unprovoked seizure with high recurrence risk (history of brain insult, epileptiform EEG, structural lesion on MRI) 3, 2

Medication selection depends on seizure type, epilepsy syndrome, comorbidities, and drug characteristics 3, 2

Status Epilepticus

Status epilepticus is defined as seizures lasting >5 minutes or recurrent seizures without return to baseline consciousness 1

Treatment algorithm:

• First-line: Benzodiazepines (lorazepam IV or midazolam IM) 1, 6
• Second-line: Fosphenytoin, levetiracetam, or valproic acid (all with 45-47% efficacy for seizure cessation within 60 minutes) 6
• Mortality ranges from 5-22%, up to 65% in refractory cases 1

Common Pitfalls to Avoid

Diagnostic Errors:

• Do not assume alcohol withdrawal seizures without excluding other causes—this should be a diagnosis of exclusion 1, 4
• Do not miss fever in seizure patients—strongly consider CNS infection 4
• Do not rely solely on normal neurologic exam—17% with normal exams have CT abnormalities 5

Treatment Errors:

• Do not start chronic AEDs for provoked seizures—treat the underlying cause 6
• Do not use prophylactic anticonvulsants in stroke patients—may negatively affect neurological recovery 6
• Do not treat single self-limiting seizures within 24 hours of ischemic stroke with long-term anticonvulsants 6

Medication Compliance:

Non-compliance with antiseizure medications is a significant risk factor for seizure recurrence in patients with established epilepsy 6

Risk Stratification for Recurrence

High-risk features for seizure recurrence after first unprovoked seizure:

• History of prior brain insult 3
• Epileptiform abnormalities on EEG 3
• Structural lesion on neuroimaging 3

Patients meeting these criteria warrant consideration for AED initiation even after a single unprovoked seizure 3, 2