Clinical Approach to Seizures
Comprehensive Practical Framework1. Symptom Overview
Understanding the clinical significance and classification of seizures
Seizures represent one of the most common neurological emergencies, affecting approximately 10% of the population at some point in their lifetime. Each year, approximately 150,000 adults present to emergency departments with a first-time seizure, and seizures account for roughly 1-2% of all emergency department visits. Epilepsy, defined as recurrent unprovoked seizures, has a prevalence of 0.5-1% worldwide, making it one of the most common chronic neurological disorders. The lifetime risk of developing epilepsy is approximately 3%, with incidence highest in the first year of life and after age 60.
Definition
A seizure is a transient occurrence of signs and symptoms due to abnormal, excessive, or synchronous neuronal activity in the brain. This paroxysmal electrical discharge results in alterations in consciousness, motor activity, sensory phenomena, or behavior. A seizure is a symptom, not a diagnosis — the underlying cause must always be sought.
Essential Terminology
| Term | Definition | Clinical Importance |
|---|---|---|
| Seizure | Single episode of abnormal neuronal discharge | A symptom requiring etiological investigation |
| Epilepsy | Condition characterized by ≥2 unprovoked seizures more than 24 hours apart, OR one unprovoked seizure with high recurrence risk (≥60%) | A diagnosis with implications for long-term management |
| Provoked (Acute Symptomatic) Seizure | Seizure occurring in close temporal relationship to an acute central nervous system insult | Lower recurrence risk; treat underlying cause |
| Unprovoked Seizure | Seizure occurring without identifiable acute precipitant | Higher recurrence risk; consider antiseizure medication |
| Status Epilepticus | Seizure lasting >5 minutes OR ≥2 seizures without return to baseline | Medical emergency requiring immediate intervention |
Classification by Onset (2017 International League Against Epilepsy Classification)
| Onset Type | Definition | Subtypes | Clinical Features |
|---|---|---|---|
| Focal Onset | Originates in networks limited to one hemisphere | Aware or impaired awareness; motor or non-motor onset | Symptoms reflect area of cortex involved; may evolve to bilateral tonic-clonic |
| Generalized Onset | Originates simultaneously in bilateral networks | Motor (tonic-clonic, tonic, clonic, myoclonic, atonic) or non-motor (absence) | Consciousness typically impaired from onset; bilateral motor manifestations |
| Unknown Onset | Onset not witnessed or cannot be determined | Motor or non-motor; may be reclassified later | Requires further investigation to characterize |
Classification by Motor Manifestation
Tonic-Clonic (Grand Mal)
Description: Initial tonic stiffening (10-20 seconds) followed by rhythmic clonic jerking (30-60 seconds). Often associated with tongue biting, urinary incontinence, and prolonged postictal confusion.
Clinical significance: Most dramatic presentation; high risk of injury; always warrants urgent evaluation.
Absence (Petit Mal)
Description: Brief episodes (5-30 seconds) of staring and unresponsiveness with abrupt onset and offset. No postictal confusion. May have subtle automatisms.
Clinical significance: Often mistaken for daydreaming; typically begins in childhood; may occur hundreds of times daily.
Myoclonic
Description: Brief, shock-like jerks of a muscle or group of muscles. Typically occurs in clusters, often shortly after awakening.
Clinical significance: May herald progression to tonic-clonic seizure; common in juvenile myoclonic epilepsy.
Atonic (Drop Attacks)
Description: Sudden loss of muscle tone causing falls. Very brief duration (1-2 seconds). No postictal confusion.
Clinical significance: High injury risk from falls; often seen in severe epilepsy syndromes.
Classification by Clinical Context
| Category | Definition | Common Causes | Recurrence Risk |
|---|---|---|---|
| First Unprovoked Seizure | Initial seizure without acute precipitant | Idiopathic, remote structural lesion, genetic predisposition | 21-45% at 2 years; higher with abnormal electroencephalogram or imaging |
| Acute Symptomatic Seizure | Seizure within 7 days of acute brain insult | Stroke, traumatic brain injury, central nervous system infection, metabolic derangement | 3-10% develop epilepsy; depends on underlying cause |
| Remote Symptomatic Seizure | Seizure due to prior brain injury (>7 days after insult) | Prior stroke, traumatic brain injury, encephalitis | High recurrence risk (>60%); generally warrants treatment |
| Progressive Symptomatic Seizure | Seizure due to progressive neurological disease | Brain tumor, neurodegenerative disease, autoimmune encephalitis | Very high; requires treatment of underlying condition |
Classification by Temporal Pattern
| Pattern | Description | Suggests |
|---|---|---|
| Upon awakening | Seizures occurring within 1-2 hours of waking | Juvenile myoclonic epilepsy, idiopathic generalized epilepsy |
| Sleep-related | Seizures predominantly during sleep | Frontal lobe epilepsy, benign epilepsy with centrotemporal spikes |
| Catamenial | Seizures clustering around menstruation | Hormone-sensitive epilepsy; consider hormonal therapy |
| Reflex/Triggered | Seizures provoked by specific stimuli | Photosensitive epilepsy (flashing lights), reading epilepsy, startle epilepsy |
| Clustering | Multiple seizures in 24-hour period | May indicate medication non-compliance, intercurrent illness, or progressive disease |
Key Concept: The “Big Five” Provoked Seizure Causes
When evaluating any seizure, systematically exclude these common provoked causes:
- Metabolic: Hypoglycemia, hyponatremia, hypocalcemia, uremia, hepatic encephalopathy
- Toxic: Alcohol withdrawal, drug intoxication or withdrawal, medication toxicity
- Infectious: Central nervous system infection, febrile illness (in predisposed individuals)
- Structural: Acute stroke, traumatic brain injury, intracranial hemorrhage
- Sleep deprivation: Often overlooked but significant trigger, especially in idiopathic generalized epilepsy
Impact on Quality of Life
Beyond the Seizure
Seizures significantly impact quality of life through driving restrictions (typically 3-12 months seizure-free required), employment limitations, social stigma, medication side effects, and psychological comorbidities (depression and anxiety affect 30-50% of patients with epilepsy). The unpredictable nature of seizures creates substantial anxiety for patients and families.
2. Pathophysiology and Mechanisms
Understanding the underlying mechanisms of seizures
Seizures result from an imbalance between excitatory and inhibitory neurotransmission, leading to hypersynchronous neuronal firing. Understanding these mechanisms is essential for appreciating why certain conditions cause seizures and how antiseizure medications work. The brain normally maintains a careful balance between excitation (primarily glutamate-mediated) and inhibition (primarily gamma-aminobutyric acid-mediated), and disruption of this balance in either direction can precipitate seizure activity.
Normal Excitation-Inhibition Balance
| Component | Excitatory System | Inhibitory System |
|---|---|---|
| Primary Neurotransmitter | Glutamate | Gamma-aminobutyric acid (GABA) |
| Key Receptors | NMDA, AMPA, kainate receptors | GABA-A (fast, ionotropic), GABA-B (slow, metabotropic) |
| Ion Movement | Sodium and calcium influx → depolarization | Chloride influx → hyperpolarization |
| Net Effect | Increases neuronal firing | Decreases neuronal firing |
Mechanisms of Seizure Generation
Increased Excitation
Mechanism: Enhanced glutamatergic transmission
Causes: Hypoglycemia, hypoxia, stroke, fever
Medication examples: Tramadol, fluoroquinolones, bupropion
Decreased Inhibition
Mechanism: Reduced GABAergic transmission
Causes: Alcohol withdrawal, benzodiazepine withdrawal, isoniazid toxicity
Medication examples: GABA antagonists, vitamin B6 deficiency
Ion Channel Dysfunction
Mechanism: Altered sodium, potassium, or calcium channel function
Causes: Genetic channelopathies, electrolyte disturbances
Examples: Hyponatremia, hypocalcemia, SCN1A mutations
Focal versus Generalized Seizure Mechanisms
| Aspect | Focal Seizures | Generalized Seizures |
|---|---|---|
| Origin | Discrete cortical focus (epileptogenic zone) | Bilateral thalamocortical networks simultaneously |
| Spread Pattern | Local → regional → may become bilateral | Immediate bilateral involvement |
| Underlying Pathology | Often structural: scar, tumor, vascular malformation, cortical dysplasia | Often genetic: channelopathy, neurotransmitter dysfunction |
| Electroencephalogram Pattern | Focal spikes, focal slowing | Generalized spike-wave, polyspike-wave |
| Treatment Implication | May be surgical candidate if medication-refractory | Generally not surgical candidate; medication-dependent |
The Seizure Threshold Concept
Understanding Seizure Threshold: Every brain has a theoretical “seizure threshold” — the level of excitation required to trigger a seizure. This threshold varies between individuals and can be lowered by various factors:
- Genetic factors: Family history, inherited channelopathies
- Structural lesions: Tumors, scars, vascular malformations
- Metabolic derangements: Electrolyte abnormalities, hypoglycemia
- Sleep deprivation: Significantly lowers threshold
- Alcohol/drug withdrawal: Dramatically lowers threshold
- Fever/infection: Lowers threshold, particularly with central nervous system involvement
- Medications: Many drugs lower seizure threshold
How Specific Conditions Cause Seizures
| Condition | Mechanism | Treatment Implication |
|---|---|---|
| Hypoglycemia | Glucose is primary neuronal fuel; hypoglycemia causes energy failure, membrane depolarization, and glutamate release | Correct glucose immediately; antiseizure medications ineffective without glucose correction |
| Hyponatremia | Low extracellular sodium reduces action potential threshold, causing neuronal hyperexcitability and cerebral edema | Careful sodium correction (risk of osmotic demyelination if too rapid) |
| Alcohol Withdrawal | Chronic alcohol enhances GABA and suppresses glutamate; withdrawal causes GABA downregulation and glutamate upregulation → excitotoxicity | Benzodiazepines (enhance GABA); seizures typically 6-48 hours after last drink |
| Acute Stroke | Ischemia causes ionic pump failure, glutamate release, calcium influx; hemorrhage causes direct cortical irritation | Early seizures (within 7 days) are acute symptomatic; late seizures indicate post-stroke epilepsy |
| Traumatic Brain Injury | Mechanical disruption, hemorrhage, edema, inflammation; gliosis creates epileptogenic focus over time | Early seizures may warrant prophylaxis; late seizures indicate post-traumatic epilepsy |
| Central Nervous System Infection | Direct neuronal injury, inflammation, edema, blood-brain barrier disruption | Treat infection; may need antiseizure medication during acute phase |
| Brain Tumor | Mass effect, cortical irritation, disruption of normal circuitry, altered neurotransmitter levels | Seizures often presenting symptom; may improve with tumor treatment |
| Autoimmune Encephalitis | Antibodies target neuronal surface antigens (NMDA receptor, LGI1, GABA-B receptor) or intracellular antigens | Immunotherapy essential; may be refractory to standard antiseizure medications |
Status Epilepticus: A Pathophysiological Emergency
Time-Dependent Changes in Status Epilepticus
Early Phase (0-30 minutes):
- GABA-A receptors functional
- Benzodiazepines effective
- Compensatory mechanisms active
Late Phase (>30 minutes):
- GABA-A receptor internalization
- Benzodiazepine resistance develops
- NMDA receptor upregulation
- Neuronal injury begins
Clinical Implication: Early aggressive treatment is critical. Benzodiazepine efficacy decreases from ~80% to ~40% after 30 minutes of continuous seizure activity.
The Postictal State: Understanding Recovery
| Phenomenon | Mechanism | Duration | Clinical Relevance |
|---|---|---|---|
| Postictal Confusion | Neuronal exhaustion, neurotransmitter depletion, transient cortical dysfunction | Minutes to hours | Duration correlates with seizure severity; prolonged confusion suggests status or structural lesion |
| Todd’s Paralysis | Focal neuronal exhaustion in motor cortex following focal motor seizure | Minutes to 48 hours | Localizes seizure focus; must distinguish from stroke |
| Postictal Psychosis | Complex; involves dopaminergic and serotonergic dysfunction | Hours to days (lucid interval typical) | May be misdiagnosed as primary psychiatric disorder |
| Postictal Headache | Vascular changes, cortical spreading depression, muscle tension | Hours to days | Common; may mimic migraine; responds to analgesics |
Often Overlooked: The Role of Sleep
Sleep deprivation is one of the most potent seizure triggers, yet it is frequently underappreciated. Sleep deprivation reduces GABAergic inhibition and increases cortical excitability. This is why electroencephalograms are often performed after sleep deprivation — it increases the yield for detecting epileptiform abnormalities. When evaluating any patient with new or breakthrough seizures, always ask about sleep patterns. In patients with idiopathic generalized epilepsy, a single night of significant sleep deprivation can be sufficient to provoke a seizure, even in well-controlled patients.
Epileptogenesis: From Insult to Epilepsy
The Latent Period
Following a brain insult (trauma, stroke, infection), there is often a “latent period” of months to years before epilepsy develops. During this time, complex neuroplastic changes occur:
- Gliosis: Scar formation disrupts normal circuits
- Synaptic reorganization: Aberrant excitatory connections form
- Ion channel changes: Altered expression of sodium and potassium channels
- Neuroinflammation: Chronic inflammation promotes hyperexcitability
- Blood-brain barrier dysfunction: Allows entry of seizure-promoting substances
Understanding epileptogenesis is crucial: it explains why late seizures after brain injury indicate epilepsy (high recurrence risk), whereas early seizures may be provoked events with lower long-term risk.
3. History Taking
A comprehensive approach to eliciting the seizure history
Red Flags — Require Urgent Evaluation
- Prolonged seizure (>5 minutes) — Status epilepticus
- Multiple seizures without recovery — Status epilepticus
- New focal neurological deficit — Stroke, mass lesion, Todd’s paralysis
- Fever with seizure in adult — Central nervous system infection
- Severe headache before or after — Subarachnoid hemorrhage, meningitis
- Seizure during pregnancy — Eclampsia until proven otherwise
- Anticoagulation use — Intracranial hemorrhage risk
- Recent head trauma — Intracranial hemorrhage, contusion
- Immunocompromised patient — Opportunistic central nervous system infection
- Known malignancy — Brain metastases, paraneoplastic syndrome
The Most Important Question: Was this actually a seizure?
Up to 20-30% of patients referred for “seizures” have alternative diagnoses. The differential includes syncope, psychogenic nonepileptic seizures, transient ischemic attack, migraine with aura, movement disorders, and sleep disorders. A detailed history from both the patient AND a witness is essential.
Systematic History: The “SEIZURE” Approach
Use the mnemonic “SEIZURE” to ensure comprehensive history taking:
- S — Setting and Start: What was the patient doing? Any warning (aura)? How did it begin?
- E — Event Description: What did witnesses observe? Motor activity? Eye deviation? Duration?
- I — Ictal Features: Responsiveness during event? Incontinence? Tongue biting? Cyanosis?
- Z — Zero-in on Recovery: How long to return to baseline? Confusion? Weakness? Headache?
- U — Underlying Causes: Recent illness, sleep deprivation, alcohol, medications, missed doses?
- R — Risk Factors and Recurrence: Prior seizures? Family history? Head injury? Stroke? Brain surgery?
- E — Epilepsy History: If known epilepsy: seizure type, frequency, current medications, compliance?
The Witness History: What to Ask
Witness Information is Critical
The patient often has amnesia for the event. A witness account is frequently the most valuable diagnostic information. Ask witnesses to demonstrate what they saw — this is often more accurate than verbal description.
| Phase | Key Questions for Witness | What It Helps Distinguish |
|---|---|---|
| Before (Pre-ictal) | “What was the patient doing just before? Did they complain of anything? Did they look pale or sweaty? Did they cry out?” | Syncope (pallor, diaphoresis) versus seizure (cry, no prodrome) |
| During (Ictal) | “Did the eyes deviate? Which direction? Was shaking on both sides or one side? Did it spread? How long did it last?” | Focal versus generalized; psychogenic (eyes closed, side-to-side movement) |
| After (Post-ictal) | “How long until they could talk normally? Were they confused? Did they sleep? Any weakness on one side?” | Postictal confusion suggests seizure; immediate recovery suggests syncope |
Targeted Questions by Suspected Cause
| Suspected Cause | Key Features | Ask This Question |
|---|---|---|
| Alcohol Withdrawal | Seizure 6-48 hours after last drink, tremor, autonomic symptoms | “When was your last alcoholic drink? How much do you typically drink daily? Have you had withdrawal seizures before?” |
| Drug Intoxication or Withdrawal | Stimulant use, benzodiazepine/barbiturate withdrawal | “Do you use any recreational drugs? Have you recently stopped any medications, including sleeping pills or anxiety medications?” |
| Hypoglycemia | Diabetic patient, missed meal, excessive insulin | “Do you have diabetes? When did you last eat? Did you take your insulin or diabetes medication?” |
| Central Nervous System Infection | Fever, headache, neck stiffness, altered mental status | “Have you had fever, headache, or neck pain? Any recent infections or sick contacts? Any travel history?” |
| Stroke or Intracranial Hemorrhage | Sudden onset, focal deficits, headache, vascular risk factors | “Did you have sudden severe headache? Any weakness, numbness, or difficulty speaking before or after the event?” |
| Brain Tumor | Progressive headaches, focal symptoms, personality change | “Have you had progressive headaches, especially worse in the morning? Any vision changes or personality changes noticed by family?” |
| Eclampsia | Pregnant or postpartum, hypertension, edema, proteinuria | “Are you pregnant or have you recently given birth? Have you had high blood pressure, headaches, or swelling?” |
| Medication Non-compliance | Known epilepsy, missed doses, ran out of medication | “Have you missed any doses of your seizure medication? Have you run out? Any recent changes to your medications?” |
| Sleep Deprivation | Known epilepsy or first seizure after poor sleep | “How much sleep have you been getting? Any recent travel across time zones? Working night shifts?” |
| Autoimmune Encephalitis | Subacute onset, psychiatric symptoms, movement disorders, memory problems | “Over the past weeks, have you had memory problems, confusion, psychiatric symptoms, or unusual movements?” |
The Aura: Localizing Value
An aura is a focal seizure with awareness — the patient remains conscious and can describe the experience. Auras provide important localizing information:
| Aura Type | Description | Suggests Localization |
|---|---|---|
| Epigastric rising sensation | “A feeling rising up from my stomach” | Mesial temporal lobe (most common aura) |
| Déjà vu or jamais vu | Inappropriate familiarity or unfamiliarity | Temporal lobe |
| Fear or anxiety | Sudden intense fear without cause | Amygdala (mesial temporal) |
| Olfactory hallucination | Usually unpleasant smell (burning, feces) | Mesial temporal or orbitofrontal |
| Visual hallucination (simple) | Flashing lights, colors, geometric shapes | Occipital lobe |
| Visual hallucination (complex) | Formed images, people, scenes | Temporal-occipital junction |
| Sensory (tingling, numbness) | Spreading paresthesias | Parietal lobe (sensory cortex) |
| Motor (focal twitching) | Rhythmic jerking starting in one area | Frontal lobe (motor cortex) |
Medication and Substance History
Medications That LOWER Seizure Threshold
- Antibiotics: Fluoroquinolones (especially with renal impairment), carbapenems (imipenem > meropenem), isoniazid, metronidazole (high dose)
- Psychiatric medications: Bupropion, clozapine, olanzapine (less common), tricyclic antidepressants (overdose)
- Analgesics: Tramadol, meperidine
- Anesthetics: Enflurane, ketamine (high dose)
- Immunosuppressants: Cyclosporine, tacrolimus
- Others: Theophylline, lithium (toxicity), baclofen withdrawal
Substances and Withdrawal
- Alcohol withdrawal: Seizures typically 6-48 hours after cessation; peak risk 24-48 hours
- Benzodiazepine withdrawal: Can occur 2-7 days after stopping; may be life-threatening
- Barbiturate withdrawal: Similar to alcohol; can be severe
- Stimulants (intoxication): Cocaine, amphetamines, synthetic cathinones
- Opioid withdrawal: Rare in adults but possible
- GHB withdrawal: Can cause severe seizures
Social and Occupational History
Lifestyle Factors
- Sleep: Hours per night, shift work, recent travel across time zones
- Alcohol: Amount, frequency, last drink, history of withdrawal
- Recreational drugs: Stimulants, synthetics, “party drugs”
- Stress: Major life stressors can lower seizure threshold
- Screen time: Video games, flashing lights (photosensitive epilepsy)
Safety and Functional Impact
- Driving: Essential for management discussion and legal reporting requirements
- Occupation: Heights, machinery, commercial driving, military, pilot
- Living situation: Alone versus with others; supervision available?
- Swimming/bathing: Drowning risk assessment
- Pregnancy: Current or planned (affects medication choice)
Distinguishing Seizure from Common Mimics
| Feature | Seizure | Syncope | Psychogenic Nonepileptic Seizure |
|---|---|---|---|
| Trigger | Often none; may have sleep deprivation | Standing, pain, emotional stress, heat | Often emotional stress; may occur with audience |
| Warning | Aura (seconds); or none | Lightheadedness, tunnel vision, warmth (longer) | Variable; may describe prolonged warning |
| Eyes during event | Open, deviated | Open or closed; may roll upward | Often tightly closed (forced closure) |
| Motor activity | Tonic-clonic: rhythmic, synchronous | Brief myoclonic jerks possible (convulsive syncope) | Asynchronous, waxing/waning, side-to-side head movement |
| Duration | Usually 1-2 minutes | Seconds to <1 minute | Often prolonged (>2 minutes); variable |
| Tongue biting | Lateral tongue (highly specific) | Tip of tongue possible | Rare; if present, often tip |
| Incontinence | Common | Possible | Rare |
| Postictal confusion | Yes, often prolonged (minutes to hours) | Brief or none; rapid recovery | Variable; may cry or have emotional response |
| Recall of event | Amnesia for ictal period | May recall prodrome and falling | May recall event or parts of it |
Clinical Pearl: Lateral Tongue Biting
Lateral tongue biting (on the side of the tongue) is highly specific for generalized tonic-clonic seizures. It occurs because the tongue is forcefully clenched between the teeth during the tonic phase. Tip-of-tongue biting can occur in syncope when the patient falls. Always examine the tongue and ask specifically about tongue soreness.
4. Physical Examination
A systematic head-to-toe approach for seizures
Examination Goals: The physical examination in a patient with seizures serves three purposes: (1) identify signs of the underlying etiology, (2) detect complications of the seizure itself, and (3) assess for ongoing seizure activity or postictal state. The examination findings depend heavily on timing — during the event, immediately after, or remote from the event.
General Inspection
- Level of consciousness: Alert, confused, drowsy, obtunded, comatose — is the patient in postictal state?
- Ongoing seizure activity: Subtle signs such as eye deviation, facial twitching, or rhythmic movements may indicate ongoing nonconvulsive seizure
- Signs of trauma: Lacerations, contusions, shoulder dislocation (from tonic phase)
- Evidence of incontinence: Urinary or fecal incontinence suggests seizure rather than syncope
- Nutritional status: Cachexia may suggest malignancy or chronic illness
- Medic alert bracelet: Check for epilepsy, diabetes, or other relevant conditions
Vital Signs
| Vital Sign | What to Look For | Clinical Significance |
|---|---|---|
| Temperature | Fever (>38°C) | Central nervous system infection, sepsis, or postictal hyperthermia (can occur after prolonged seizure) |
| Heart Rate | Tachycardia, bradycardia, irregularity | Postictal tachycardia is common; arrhythmia may suggest cardiac cause of syncope misdiagnosed as seizure |
| Blood Pressure | Hypertension, hypotension | Severe hypertension: hypertensive encephalopathy, eclampsia, posterior reversible encephalopathy syndrome; hypotension: postictal or sepsis |
| Respiratory Rate | Tachypnea, irregular breathing | Postictal tachypnea common; Cheyne-Stokes or irregular breathing suggests brainstem involvement |
| Oxygen Saturation | Hypoxia | May be transiently low during or immediately after seizure; persistent hypoxia suggests aspiration or ongoing seizure |
| Glucose | Hypoglycemia (<70 mg/dL) or hyperglycemia | Point-of-care glucose is essential in ALL seizure patients; treat hypoglycemia immediately |
Never Skip the Glucose
Point-of-care glucose measurement is mandatory in every patient presenting with seizure or altered mental status. Hypoglycemia is a rapidly reversible cause of seizures, and failure to identify and treat it can result in permanent neurological injury. Antiseizure medications will not stop hypoglycemic seizures — glucose is the treatment.
Head and Neck Examination
Head
- Scalp: Lacerations, hematomas (from fall during seizure or from trauma causing seizure)
- Battle sign: Mastoid ecchymosis — basilar skull fracture
- Raccoon eyes: Periorbital ecchymosis — basilar skull fracture
- Hemotympanum: Blood behind tympanic membrane — basilar skull fracture
- Cerebrospinal fluid otorrhea/rhinorrhea: Clear fluid from ear or nose — skull fracture
Neck
- Meningismus: Neck stiffness — meningitis, subarachnoid hemorrhage (may be absent in comatose patients)
- Thyroid: Goiter, nodules — thyroid storm can cause seizures
- Lymphadenopathy: May suggest infection or malignancy
- Carotid bruits: Cerebrovascular disease
- Jugular venous distension: Heart failure, superior vena cava syndrome
Eye Examination
| Finding | Description | Clinical Significance |
|---|---|---|
| Pupil size and reactivity | Dilated, constricted, asymmetric, fixed | Asymmetry suggests structural lesion; fixed dilated pupils after seizure are concerning for herniation |
| Fundoscopy | Papilledema, hemorrhages | Papilledema suggests raised intracranial pressure (tumor, hydrocephalus); subhyaloid hemorrhages suggest subarachnoid hemorrhage |
| Eye deviation | Conjugate deviation to one side | During seizure: eyes deviate TOWARD the seizing hemisphere; postictal: eyes deviate AWAY from lesion (toward weak side) |
| Nystagmus | Rhythmic eye movements | May indicate ongoing seizure activity, drug toxicity, or cerebellar lesion |
| Kayser-Fleischer rings | Golden-brown rings at corneal limbus | Wilson disease (rare but treatable cause of seizures in young adults) |
Oral Examination
- Tongue: Lateral tongue lacerations are highly specific for generalized tonic-clonic seizures
- Buccal mucosa: Bite marks on inner cheek
- Gingival hyperplasia: Phenytoin use
- Oral thrush: Immunocompromise (opportunistic central nervous system infection risk)
- Alcohol on breath: Intoxication or withdrawal
Neurological Examination
Mental Status
- Level of consciousness: Glasgow Coma Scale or descriptive terms
- Orientation: Person, place, time, situation
- Attention: Months backward, serial 7s — impaired in postictal state
- Language: Aphasia may localize to dominant hemisphere
- Memory: Amnesia for the event is expected; persistent memory impairment may suggest temporal lobe pathology
Cranial Nerves
| Cranial Nerve | Test | Abnormality Suggests |
|---|---|---|
| II (Optic) | Visual fields, fundoscopy | Field cut: occipital lesion; papilledema: raised intracranial pressure |
| III, IV, VI (Ocular motor) | Eye movements, pupil response | Third nerve palsy with dilated pupil: uncal herniation |
| VII (Facial) | Facial symmetry, strength | Unilateral weakness: stroke, postictal Todd’s paralysis |
| IX, X (Glossopharyngeal, Vagus) | Gag reflex, palate elevation | Brainstem lesion; important for airway protection |
| XII (Hypoglossal) | Tongue protrusion | Deviation toward weak side; assess for tongue lacerations |
Motor Examination
- Tone: Increased (spasticity from prior stroke), decreased (postictal flaccidity)
- Power: Test all major muscle groups; focal weakness suggests structural lesion or Todd’s paralysis
- Drift: Pronator drift is sensitive for upper motor neuron weakness
- Coordination: Finger-nose-finger, heel-shin — cerebellar signs
Todd’s Paralysis
Todd’s (postictal) paralysis is focal weakness following a focal or focal-to-bilateral tonic-clonic seizure. It typically resolves within 48 hours (usually much sooner) and localizes the seizure focus. The presence of Todd’s paralysis is helpful diagnostically but must be distinguished from stroke — if there is any doubt, neuroimaging is required.
Sensory Examination
- Light touch and pinprick: Hemisensory loss suggests contralateral parietal lesion
- Proprioception and vibration: Posterior column dysfunction
- Sensory inattention (extinction): Parietal lobe lesion
Reflexes
- Deep tendon reflexes: Asymmetry suggests upper motor neuron lesion
- Plantar response: Upgoing (Babinski sign) indicates upper motor neuron lesion; may be transiently present postictally
- Frontal release signs: Grasp, snout — frontal lobe pathology
Cardiovascular Examination
Important to identify cardiac causes of syncope that may be misdiagnosed as seizure:
- Heart rhythm: Irregular rhythm (atrial fibrillation — embolic stroke risk)
- Heart sounds: Murmurs (aortic stenosis, hypertrophic cardiomyopathy — causes of syncope)
- Carotid bruits: Cerebrovascular disease
- Peripheral edema: Heart failure
- Signs of endocarditis: Splinter hemorrhages, Janeway lesions (septic emboli to brain)
Skin Examination
| Finding | Description | Associated Condition |
|---|---|---|
| Ash-leaf spots | Hypopigmented macules (best seen with Wood lamp) | Tuberous sclerosis (cortical tubers cause seizures) |
| Facial angiofibromas | Red papules on face (adenoma sebaceum) | Tuberous sclerosis |
| Port-wine stain (facial) | Unilateral facial capillary malformation in V1 distribution | Sturge-Weber syndrome (leptomeningeal angioma causes seizures) |
| Café-au-lait spots | Light brown macules; >6 suggests diagnosis | Neurofibromatosis type 1 (increased brain tumor risk) |
| Track marks | Injection sites on arms | Intravenous drug use (infection risk, drug-induced seizure) |
| Petechiae, purpura | Non-blanching spots | Meningococcemia, thrombotic thrombocytopenic purpura, disseminated intravascular coagulation |
| Jaundice | Yellow skin and sclerae | Hepatic encephalopathy |
Musculoskeletal Examination
- Shoulder: Posterior shoulder dislocation is classic complication of seizure (tonic contraction); check range of motion
- Spine: Vertebral compression fractures can occur during severe seizures
- Long bones: Fractures from falls
- Joints: Hemarthrosis in hemophilia patients who seize
Expected Examination Findings by Etiology
| Condition | General | Neurological | Other Key Findings |
|---|---|---|---|
| Central Nervous System Infection | Fever, ill-appearing | Meningismus, altered mental status, focal signs possible | Petechiae (meningococcal), Kernig/Brudzinski signs |
| Acute Stroke | May be normal | Focal deficits (hemiparesis, aphasia, visual field cut) | Atrial fibrillation, carotid bruits, cardiac murmurs |
| Brain Tumor | May show cachexia | Focal signs, papilledema, cognitive changes | Signs of primary malignancy elsewhere |
| Alcohol Withdrawal | Tremor, diaphoresis, tachycardia | Often normal neurologically or mild confusion | Signs of chronic liver disease, malnutrition |
| Metabolic (Hypoglycemia) | Diaphoresis, pallor, tachycardia | Altered consciousness, may have focal signs | Point-of-care glucose low; rapid improvement with glucose |
| Eclampsia | Hypertension, edema | May have hyperreflexia, clonus | Proteinuria, gravid uterus or recent delivery |
| Idiopathic Epilepsy | Often normal | Often completely normal between seizures | May have gingival hyperplasia (phenytoin) |
Important Teaching Point
Normal examination is common! Many patients with epilepsy have entirely normal physical and neurological examinations between seizures. In idiopathic generalized epilepsy, the examination is typically normal. A normal examination does not exclude significant underlying pathology — it simply means the examination is non-localizing. The history, electroencephalogram, and neuroimaging provide the diagnostic information.
5. Differential Diagnosis
Systematic approach organized by probability, etiology, and clinical context
The approach to seizure differential diagnosis involves two parallel considerations: (1) Is this actually a seizure, or is it a seizure mimic? and (2) If it is a seizure, what is the underlying cause? The differential varies significantly based on whether this is a first seizure, a seizure in a patient with known epilepsy, or a presentation concerning for status epilepticus.
First Unprovoked Seizure in Adults
| Probability | Etiology | Approximate Frequency | Key Features |
|---|---|---|---|
| COMMON | Idiopathic/Cryptogenic (no identifiable cause) | 40-50% | Normal neuroimaging and electroencephalogram; may have family history; often young adults |
| COMMON | Remote symptomatic (prior brain injury) | 15-25% | History of stroke, traumatic brain injury, or central nervous system infection months to years prior |
| LESS COMMON | Acute symptomatic (provoked) | 15-20% | Metabolic derangement, alcohol withdrawal, acute stroke, acute infection within 7 days |
| LESS COMMON | Brain tumor | 5-10% | Primary or metastatic; progressive symptoms; focal features; older patients |
| UNCOMMON BUT SERIOUS | Central nervous system infection | 2-5% | Fever, headache, meningismus, altered mental status |
| UNCOMMON BUT SERIOUS | Autoimmune encephalitis | 1-3% | Subacute onset, psychiatric symptoms, movement disorders, refractory seizures |
Provoked (Acute Symptomatic) Seizure Causes
Step-by-Step Approach to Provoked Seizures:
- Step 1: Check glucose immediately — hypoglycemia is rapidly reversible
- Step 2: Review medications and substances — withdrawal syndromes and pro-convulsant drugs
- Step 3: Check basic metabolic panel — sodium, calcium, magnesium, renal function
- Step 4: Consider acute structural cause — stroke, hemorrhage, trauma
- Step 5: Evaluate for infection — especially if fever or immunocompromised
| Category | Specific Causes | Key Features | Time Course |
|---|---|---|---|
| METABOLIC | Hypoglycemia | Diabetic patient, missed meal, insulin overdose; diaphoresis, confusion | Immediate; resolves with glucose |
| METABOLIC | Hyponatremia | Usually sodium <120 mEq/L; often rapid drop more important than absolute value | Hours to days; correlates with rate of change |
| METABOLIC | Hypocalcemia | Post-thyroidectomy, renal failure, vitamin D deficiency; tetany, Chvostek sign | Variable |
| METABOLIC | Uremia | End-stage renal disease; encephalopathy, asterixis | Gradual; often with other uremic symptoms |
| METABOLIC | Hepatic encephalopathy | Liver failure; asterixis, confusion, fetor hepaticus | Variable; often precipitated by infection or bleeding |
| TOXIC/WITHDRAWAL | Alcohol withdrawal | 6-48 hours after last drink; tremor, autonomic instability | Peak risk 24-48 hours |
| TOXIC/WITHDRAWAL | Benzodiazepine/barbiturate withdrawal | 2-7 days after stopping; similar to alcohol withdrawal | Later onset than alcohol |
| TOXIC/WITHDRAWAL | Drug intoxication | Cocaine, amphetamines, synthetic cannabinoids, tramadol | During intoxication |
| TOXIC/WITHDRAWAL | Medication toxicity | Theophylline, lithium, isoniazid, fluoroquinolones, bupropion | Variable; check levels if available |
| STRUCTURAL | Acute ischemic stroke | Focal deficits; cortical involvement increases seizure risk | Within 7 days of stroke |
| STRUCTURAL | Intracranial hemorrhage | Severe headache, focal deficits, altered consciousness | Acute presentation |
| STRUCTURAL | Traumatic brain injury | History of trauma; early seizures within 7 days | Early (within 7 days) versus late (>7 days) |
| INFECTIOUS | Bacterial meningitis | Fever, headache, meningismus, altered mental status | Acute; hours to days |
| INFECTIOUS | Viral encephalitis (especially herpes simplex virus) | Fever, behavioral changes, temporal lobe focus | Subacute; days to weeks |
| OTHER | Eclampsia | Pregnancy or postpartum, hypertension, proteinuria, edema | Third trimester through 6 weeks postpartum |
| OTHER | Hypertensive encephalopathy | Severe hypertension, headache, visual changes, altered mental status | Acute |
Anatomical Approach to Seizure Etiology
Cortical (Most Common)
Stroke (ischemic or hemorrhagic)
Brain tumor (primary or metastatic)
Cortical dysplasia
Mesial temporal sclerosis
Post-traumatic gliosis
Arteriovenous malformation
Meningeal/Infectious
Bacterial meningitis
Viral encephalitis
Brain abscess
Neurocysticercosis
Tuberculous meningitis
Fungal infection (immunocompromised)
Systemic/Metabolic
Hypoglycemia
Electrolyte disturbances
Uremia
Hepatic encephalopathy
Thyroid storm
Porphyria
Toxic/Pharmacologic
Alcohol withdrawal
Benzodiazepine withdrawal
Drug intoxication
Medication-induced
Carbon monoxide poisoning
Heavy metal toxicity
Seizure Mimics: The Differential of “Not a Seizure”
| Condition | Key Distinguishing Features | Diagnostic Approach |
|---|---|---|
| Syncope (including convulsive syncope) | Prodrome (lightheadedness, warmth, tunnel vision), trigger (standing, pain), brief duration, rapid recovery, pallor during event | Electrocardiogram, orthostatic vitals, echocardiogram if cardiac cause suspected |
| Psychogenic nonepileptic seizures | Eyes closed, asynchronous movements, waxing/waning, prolonged duration, emotional triggers, preserved awareness during “generalized” movements | Video electroencephalogram monitoring is gold standard |
| Transient ischemic attack | Negative symptoms (weakness, numbness, vision loss) rather than positive symptoms; no altered consciousness unless posterior circulation | MRI with diffusion-weighted imaging, vascular imaging |
| Migraine with aura | Visual aura spreads slowly (over 20-30 minutes), followed by headache; positive visual phenomena | Clinical diagnosis; consider electroencephalogram if atypical |
| Transient global amnesia | Sudden anterograde amnesia, repetitive questioning, no other neurological deficits, resolves within 24 hours | Clinical diagnosis; MRI may show hippocampal diffusion restriction |
| Movement disorders | Tremor, dystonia, myoclonus — but no alteration of consciousness, stereotyped pattern | Neurological examination, electroencephalogram during events |
| Sleep disorders (parasomnias) | Events only during sleep, complex behaviors, often no memory of events | Polysomnography, video electroencephalogram |
| Panic attacks | Intense fear, palpitations, dyspnea, paresthesias; preserved awareness; longer duration | Clinical diagnosis; consider electroencephalogram if atypical |
Drug-Induced Seizures
| Drug or Drug Class | Mechanism | Risk Factors | Management Notes |
|---|---|---|---|
| Bupropion | Lowers seizure threshold; dose-dependent | Doses >450 mg/day, eating disorders, alcohol use | Dose reduction; avoid in high-risk patients |
| Tramadol | Lowers seizure threshold; serotonergic effects | High doses, concurrent serotonergic drugs, epilepsy history | Avoid in epilepsy; use alternative analgesics |
| Fluoroquinolones | GABA-A receptor antagonism | Renal impairment, concurrent nonsteroidal anti-inflammatory drugs, epilepsy history | Use alternative antibiotics when possible |
| Carbapenems (especially imipenem) | GABA-A receptor antagonism | Renal impairment, central nervous system pathology | Meropenem has lower seizure risk than imipenem |
| Isoniazid | Depletes pyridoxine (vitamin B6), reducing GABA synthesis | Overdose, chronic use without B6 supplementation | Treat with pyridoxine; standard antiseizure medications less effective |
| Theophylline | Adenosine receptor antagonism | Toxicity (level >20 μg/mL), drug interactions | Check levels; seizures may be refractory |
| Lithium | Multiple mechanisms; usually in toxicity | Toxicity, dehydration, drug interactions | Check levels; may need hemodialysis |
| Tricyclic antidepressants | Sodium channel blockade, anticholinergic effects | Overdose | Sodium bicarbonate for QRS widening |
| Cocaine/Amphetamines | Increased catecholamines, hyperthermia | High doses, concurrent alcohol use | Benzodiazepines first-line; avoid beta-blockers for cocaine |
| Synthetic cannabinoids | Variable; often contaminated with other substances | Unpredictable composition | Supportive care; seizures may be prolonged |
Breakthrough Seizures in Known Epilepsy
When a patient with known epilepsy presents with a seizure, consider these causes of breakthrough:
- Medication non-compliance — most common cause; ask directly and check drug levels
- Subtherapeutic drug levels — drug interactions, malabsorption, weight change, pregnancy
- Sleep deprivation — frequently underappreciated trigger
- Intercurrent illness — fever, infection lower seizure threshold
- Alcohol or drug use — intoxication or withdrawal
- Medication change — new interacting drug, generic substitution
- Disease progression — worsening underlying condition (tumor, progressive disease)
- Menstrual cycle — catamenial epilepsy
Quick Reference: “If You See This, Think This”
| Clinical Clue | Think This First | Next Step |
|---|---|---|
| Seizure 24-48 hours after last alcohol drink | Alcohol withdrawal seizure | CIWA protocol, benzodiazepines, thiamine |
| Diabetic patient with seizure | Hypoglycemia | Check glucose immediately; treat if low |
| Fever + seizure + headache + stiff neck | Bacterial meningitis | Blood cultures, lumbar puncture, empiric antibiotics |
| Pregnant or postpartum with seizure + hypertension | Eclampsia | Magnesium sulfate, delivery planning |
| Focal seizure + progressive headaches + weight loss | Brain tumor | Urgent MRI brain with contrast |
| Seizure + psychiatric symptoms + memory problems (subacute) | Autoimmune encephalitis | MRI, lumbar puncture, autoimmune antibody panel |
| Seizure + lateral tongue bite + postictal confusion | True epileptic seizure (not syncope) | Electroencephalogram, neuroimaging, epilepsy workup |
| Prolonged event + eyes tightly closed + asynchronous movements | Psychogenic nonepileptic seizure | Video electroencephalogram monitoring; psychiatric evaluation |
| Patient on isoniazid with refractory seizures | Isoniazid-induced (pyridoxine depletion) | Give pyridoxine (vitamin B6) — specific antidote |
| Seizure + port-wine stain on face | Sturge-Weber syndrome | MRI brain with contrast (leptomeningeal enhancement) |
Age-Based Differential Considerations
| Age Group | More Common Etiologies | Key Considerations |
|---|---|---|
| Young Adults (18-35) | Idiopathic generalized epilepsy, traumatic brain injury, drug/alcohol-related, genetic epilepsies | Ask about sleep, substances, family history; juvenile myoclonic epilepsy often presents in this age range |
| Middle-Aged Adults (35-60) | Brain tumor, alcohol-related, medication-induced, remote symptomatic | Higher index of suspicion for structural lesions; comprehensive drug review |
| Older Adults (>60) | Cerebrovascular disease (stroke), brain tumor, metabolic, neurodegenerative disease | Stroke is most common cause of new-onset epilepsy in elderly; consider subdural hematoma |
6. Diagnostic Investigations
A stepwise, evidence-based approach guided by clinical suspicion
The investigation of seizures aims to: (1) identify treatable underlying causes, (2) assess recurrence risk, and (3) guide treatment decisions. The extent of workup depends on clinical context — a first unprovoked seizure requires comprehensive evaluation, while a breakthrough seizure in known epilepsy may need only targeted testing.
Immediate Bedside Tests (All Patients)
Do Not Delay These Tests
- Point-of-care glucose: Hypoglycemia is immediately treatable; delays cause harm
- Oxygen saturation: Assess for hypoxia during or after seizure
- Electrocardiogram: Arrhythmia may cause syncope mimicking seizure; post-seizure changes common
- Temperature: Fever raises concern for central nervous system infection
Baseline Laboratory Investigations
| Investigation | Purpose | What to Look For | Practical Points |
|---|---|---|---|
| Serum Glucose | Exclude hypoglycemia | Glucose <70 mg/dL (3.9 mmol/L) | Point-of-care first; laboratory confirmation |
| Serum Sodium | Exclude hyponatremia | Sodium <135 mEq/L; seizures more common <120 mEq/L or with rapid drops | Rate of change often more important than absolute value |
| Serum Calcium | Exclude hypocalcemia | Corrected calcium <8.5 mg/dL (2.1 mmol/L) | Correct for albumin; check ionized calcium if borderline |
| Serum Magnesium | Exclude hypomagnesemia | Magnesium <1.5 mg/dL (0.6 mmol/L) | Often coexists with hypocalcemia and hypokalemia |
| Renal Function (Creatinine, Blood Urea Nitrogen) | Assess for uremia; guide drug dosing | Elevated creatinine, blood urea nitrogen | Uremia can cause seizures; affects antiseizure medication dosing |
| Liver Function Tests | Assess for hepatic encephalopathy; guide drug selection | Elevated bilirubin, transaminases, low albumin | Affects antiseizure medication metabolism and protein binding |
| Complete Blood Count | Screen for infection, hematologic abnormality | Leukocytosis (infection); anemia; thrombocytopenia | Mild leukocytosis can occur postictally (stress response) |
| Toxicology Screen | Identify drug intoxication or recent use | Cocaine, amphetamines, opioids, benzodiazepines | Urine drug screen; serum levels for specific drugs if indicated |
Additional Laboratory Tests (Based on Clinical Suspicion)
If Suspecting Infection
- Blood cultures: Before antibiotics if possible
- Lumbar puncture: If meningitis/encephalitis suspected (after neuroimaging if focal signs or papilledema)
- Cerebrospinal fluid analysis: Cell count, protein, glucose, Gram stain, culture, herpes simplex virus polymerase chain reaction
If Suspecting Toxicity
- Antiseizure medication levels: Phenytoin, valproate, carbamazepine, phenobarbital (if applicable)
- Specific drug levels: Lithium, theophylline, digoxin
- Ethanol level: If alcohol involvement suspected
- Ammonia: If hepatic encephalopathy suspected
If Suspecting Autoimmune Encephalitis
- Serum autoimmune antibody panel: Anti-NMDA receptor, anti-LGI1, anti-CASPR2, anti-GABA-B, anti-AMPA
- Cerebrospinal fluid antibody panel: Often more sensitive than serum
- Paraneoplastic panel: If malignancy suspected
If Suspecting Eclampsia
- Urinalysis: Proteinuria
- Platelet count: Thrombocytopenia (HELLP syndrome)
- Liver enzymes: Elevated (HELLP syndrome)
- Uric acid: Often elevated in preeclampsia
Electroencephalogram (EEG)
The Role of Electroencephalogram
Electroencephalogram is the most important diagnostic test for epilepsy. It can: (1) support the diagnosis of epilepsy, (2) classify seizure type, (3) identify epilepsy syndrome, and (4) assess recurrence risk. However, a normal electroencephalogram does NOT exclude epilepsy — up to 50% of patients with epilepsy have a normal initial routine electroencephalogram.
| Electroencephalogram Type | Timing | Yield | When to Use |
|---|---|---|---|
| Routine Electroencephalogram (20-40 minutes) | Within 24-48 hours of seizure increases yield | Epileptiform abnormalities in 30-50% of patients with epilepsy | First-line for all first seizures; follow-up in known epilepsy |
| Sleep-Deprived Electroencephalogram | After night of sleep deprivation | Increases yield by 20-30% | If routine electroencephalogram normal but clinical suspicion high |
| Prolonged Ambulatory Electroencephalogram (24-72 hours) | Outpatient monitoring | Captures sleep, increases interictal detection | Frequent events or if routine electroencephalogram non-diagnostic |
| Video Electroencephalogram Monitoring (inpatient) | Continuous monitoring for days | Gold standard for capturing events | Distinguish epileptic versus psychogenic seizures; presurgical evaluation |
| Continuous Electroencephalogram (Intensive Care Unit) | Real-time monitoring | Detects nonconvulsive seizures and status epilepticus | Unexplained altered mental status, after convulsive status epilepticus |
Key Electroencephalogram Findings
| Finding | Description | Clinical Significance |
|---|---|---|
| Focal spikes or sharp waves | Epileptiform discharges localized to one region | Supports focal epilepsy; localizes seizure focus |
| Generalized spike-and-wave (3 Hz) | Bilateral synchronous discharges at approximately 3 Hz | Classic for absence epilepsy |
| Generalized polyspike-and-wave | Multiple spikes followed by slow wave | Suggests idiopathic generalized epilepsy (juvenile myoclonic epilepsy) |
| Temporal intermittent rhythmic delta activity | Rhythmic slowing over temporal region | Suggests temporal lobe pathology; associated with temporal lobe epilepsy |
| Periodic lateralized epileptiform discharges | Periodic sharp waves over one hemisphere | Suggests acute structural lesion (stroke, encephalitis, tumor); high seizure risk |
| Generalized periodic discharges | Bilateral periodic sharp waves | Seen in anoxic injury, Creutzfeldt-Jakob disease, severe encephalopathy |
Neuroimaging
When to Image Emergently
Urgent Computed Tomography Indications
- New focal neurological deficit
- Persistent altered mental status
- Fever (before lumbar puncture if focal signs)
- Recent head trauma
- Anticoagulation use
- Known malignancy
- Immunocompromised patient
- Status epilepticus
- No return to baseline within expected timeframe
| Modality | Advantages | Limitations | When to Use |
|---|---|---|---|
| Computed Tomography (CT) Head without Contrast | Rapid, widely available, excellent for hemorrhage and large lesions | Poor for subtle lesions, temporal lobes, posterior fossa; radiation | Emergency setting; rule out hemorrhage, large mass, hydrocephalus |
| MRI Brain (Epilepsy Protocol) | Superior soft tissue detail; detects mesial temporal sclerosis, cortical dysplasia, small tumors | Longer acquisition, less available, contraindications | All first unprovoked seizures (if not done emergently); epilepsy workup |
| MRI with Contrast | Enhances tumor, infection, inflammation | Gadolinium contraindicated in severe renal impairment | Suspected tumor, infection, inflammatory condition |
| CT or MR Angiography | Vascular imaging | CT requires contrast; MR limited availability | Suspected vascular malformation, venous thrombosis, vasculitis |
Epilepsy Protocol MRI
What Makes an “Epilepsy Protocol” MRI Different:
- Thin coronal slices through hippocampi (3 mm or less)
- T2 and FLAIR sequences optimized for temporal lobes
- Volumetric T1-weighted sequence for cortical analysis
- Specific attention to common epileptogenic lesions: mesial temporal sclerosis, cortical dysplasia, tumors, vascular malformations
A standard brain MRI may miss subtle epileptogenic lesions — always request epilepsy protocol for seizure workup.
Lumbar Puncture
Indications
- Fever with seizure (suspected central nervous system infection)
- Immunocompromised patient
- Persistent altered mental status
- Suspected autoimmune encephalitis
- Suspected subarachnoid hemorrhage (if CT negative)
Cerebrospinal Fluid Studies to Order
- Basic: Cell count, protein, glucose, Gram stain, culture
- Viral: Herpes simplex virus polymerase chain reaction (always include if encephalitis suspected)
- Autoimmune: Autoimmune encephalitis antibody panel
- Other: Cytology (if malignancy suspected), fungal/tuberculosis studies (if immunocompromised)
Practical Pearl: Postictal Cerebrospinal Fluid Pleocytosis
Seizures themselves can cause a mild cerebrospinal fluid pleocytosis (typically <20 white blood cells per microliter) and mildly elevated protein. This “postictal pleocytosis” can confuse the picture when infection is being considered. Key distinctions: postictal changes are typically mild, glucose is normal, and there should be a clear seizure history. When in doubt, treat empirically for infection while awaiting cultures.
Investigation Algorithm by Clinical Scenario
First Unprovoked Seizure
| Step | Investigation | Rationale |
|---|---|---|
| 1 | Glucose, basic metabolic panel, complete blood count | Exclude common metabolic causes |
| 2 | Electrocardiogram | Exclude cardiac arrhythmia as cause of syncope mimic |
| 3 | Toxicology screen | Identify drug-related cause |
| 4 | CT head (emergent) OR MRI brain (preferred if stable) | Exclude structural lesion |
| 5 | Electroencephalogram within 24-48 hours | Assess for epileptiform activity; risk stratification |
| 6 | MRI brain with epilepsy protocol (if not done emergently) | Detect subtle structural abnormalities |
Breakthrough Seizure in Known Epilepsy
| Step | Investigation | Rationale |
|---|---|---|
| 1 | Antiseizure medication levels | Assess compliance and therapeutic levels |
| 2 | Basic metabolic panel | Exclude metabolic precipitant |
| 3 | Review recent medication changes | Identify drug interactions or generic substitution issues |
| 4 | Neuroimaging only if: new focal features, prolonged postictal state, or significantly changed seizure pattern | Evaluate for new structural lesion or disease progression |
Recurrence Risk After First Unprovoked Seizure
Factors That Increase Recurrence Risk
Overall recurrence risk after a first unprovoked seizure is approximately 40-50% within 2 years. The following factors increase risk to ≥60%, meeting criteria for epilepsy diagnosis after a single seizure:
- Abnormal electroencephalogram: Epileptiform abnormalities double recurrence risk
- Abnormal neuroimaging: Remote structural lesion (prior stroke, traumatic brain injury)
- Nocturnal seizure: Higher recurrence than daytime seizure
- Prior acute symptomatic seizure: Previous seizure at time of brain insult
- Focal seizure: Suggests underlying structural abnormality
- Todd’s paralysis: Indicates focal onset, structural substrate
7. Pattern Recognition and Clinical Decision-Making
Practical algorithms and decision pathways
Step 1: Is This Urgent?
| Clinical Scenario | Urgency Level | Immediate Action |
|---|---|---|
| Ongoing seizure activity (>5 minutes) | EMERGENT | Activate status epilepticus protocol; benzodiazepines immediately; airway management |
| Multiple seizures without return to baseline | EMERGENT | Treat as status epilepticus; intravenous access; continuous monitoring |
| Seizure with fever and meningismus | EMERGENT | Empiric antibiotics and acyclovir; blood cultures; urgent lumbar puncture after imaging |
| Seizure in pregnancy or postpartum with hypertension | EMERGENT | Magnesium sulfate; obstetric and anesthesia consultation; prepare for delivery |
| New focal neurological deficit after seizure (not resolving) | URGENT | Urgent neuroimaging (CT then MRI); differentiate Todd’s paralysis from stroke |
| First seizure with return to baseline, no red flags | URGENT | Emergency department evaluation; laboratory tests, imaging, electroencephalogram within 24-48 hours |
| Breakthrough seizure in known epilepsy, back to baseline | ROUTINE | Check medication levels and compliance; outpatient follow-up unless concerning features |
Status Epilepticus: Time-Based Treatment Algorithm
Status Epilepticus is a Medical Emergency
Defined as seizure lasting >5 minutes OR ≥2 seizures without return to baseline. Mortality increases with duration. Treatment must be rapid and aggressive.
| Time | Phase | Treatment | Key Actions |
|---|---|---|---|
| 0-5 minutes | Stabilization | Supportive care | Airway, breathing, circulation; oxygen; intravenous access; glucose check; monitor vitals |
| 5-20 minutes | Initial Therapy | Benzodiazepines (first-line) | Lorazepam 4 mg intravenous (may repeat once) OR Midazolam 10 mg intramuscular OR Diazepam 10 mg intravenous |
| 20-40 minutes | Second-Line Therapy | Antiseizure medication loading | Fosphenytoin 20 mg phenytoin equivalents/kg intravenous OR Levetiracetam 60 mg/kg intravenous (max 4500 mg) OR Valproate 40 mg/kg intravenous |
| >40 minutes | Refractory Status | Anesthetic agents | Intensive care unit admission; continuous electroencephalogram; Propofol OR Midazolam infusion OR Pentobarbital; intubation required |
Step 2: First Seizure Decision Pathway
Key Question: Does this patient need to be started on antiseizure medication after a first unprovoked seizure?
| Clinical Scenario | Recurrence Risk | Decision | Rationale |
|---|---|---|---|
| Provoked seizure (metabolic, toxic, acute structural) | Low (if cause corrected) | Treat underlying cause; antiseizure medication usually NOT needed long-term | Remove the provocation and seizure risk resolves |
| First unprovoked seizure, normal electroencephalogram and MRI | ~35% at 2 years | Treatment optional; shared decision-making with patient | Medication reduces recurrence by ~35% but does not alter long-term prognosis |
| First unprovoked seizure WITH abnormal electroencephalogram OR MRI | >60% at 2 years | Treatment recommended; meets criteria for epilepsy diagnosis | High recurrence risk justifies treatment; functionally equivalent to having had two seizures |
| Two or more unprovoked seizures (>24 hours apart) | >60% | Treatment recommended; this IS epilepsy by definition | Established epilepsy; ongoing seizure risk without treatment |
Factors Influencing the Treatment Decision
Factors Favoring Treatment
- Abnormal electroencephalogram (epileptiform activity)
- Abnormal MRI (structural lesion)
- Nocturnal seizure
- Focal onset seizure
- Todd’s paralysis
- High-risk occupation (driver, pilot, operates machinery)
- Patient preference for seizure prevention
- Prior acute symptomatic seizure at time of brain injury
Factors Favoring Observation
- Normal electroencephalogram and MRI
- Clear provocation identified and corrected
- Patient preference to avoid medication
- Concerns about medication side effects
- Medication interactions (polypharmacy)
- Pregnancy planning (some medications teratogenic)
- Low-risk lifestyle (can accommodate driving restriction)
Step 3: Antiseizure Medication Selection
| Seizure Type | First-Line Options | Alternatives | Avoid |
|---|---|---|---|
| Focal seizures (with or without bilateral tonic-clonic) | Levetiracetam, Lamotrigine, Oxcarbazepine | Lacosamide, Carbamazepine, Valproate, Zonisamide | Ethosuximide (ineffective) |
| Generalized tonic-clonic (primary generalized) | Valproate, Levetiracetam, Lamotrigine | Topiramate, Zonisamide, Perampanel | Carbamazepine, Oxcarbazepine, Phenytoin (may worsen) |
| Absence seizures | Ethosuximide (first-line), Valproate | Lamotrigine | Carbamazepine, Phenytoin, Gabapentin (may worsen) |
| Juvenile myoclonic epilepsy | Valproate, Levetiracetam | Lamotrigine (may worsen myoclonus), Topiramate | Carbamazepine, Oxcarbazepine, Phenytoin, Gabapentin |
| Unknown seizure type | Levetiracetam, Valproate, Lamotrigine | Topiramate, Zonisamide | Avoid narrow-spectrum agents until type clarified |
Medication Selection in Special Populations
| Population | Preferred Options | Avoid or Use Caution | Key Considerations |
|---|---|---|---|
| Women of childbearing potential | Levetiracetam, Lamotrigine, Oxcarbazepine | Valproate (teratogenic — neural tube defects, cognitive effects) | Folic acid supplementation; preconception counseling essential |
| Elderly | Levetiracetam, Lamotrigine, Lacosamide | Phenytoin (drug interactions, osteoporosis), Carbamazepine (hyponatremia) | Start low, go slow; watch for drug interactions; renal dosing |
| Renal impairment | Phenytoin, Valproate, Lamotrigine (no renal adjustment) | Levetiracetam, Gabapentin, Pregabalin (require dose reduction) | Adjust doses based on creatinine clearance |
| Hepatic impairment | Levetiracetam, Gabapentin, Lacosamide | Valproate (hepatotoxic), Phenytoin, Carbamazepine | Avoid hepatically metabolized drugs; monitor liver function |
| Psychiatric comorbidity | Lamotrigine (mood stabilizer), Valproate (if not childbearing) | Levetiracetam (may worsen depression/anxiety in some), Topiramate | Consider psychiatric effects; coordinate with psychiatry |
“What Do I Do If…” Decision Reference
| Clinical Situation | Immediate Action | Next Step |
|---|---|---|
| Patient is actively seizing in front of me | Protect from injury; position on side; time the seizure; call for help | If >5 minutes: benzodiazepine; prepare for status epilepticus protocol |
| Patient has stopped seizing but is confused | Maintain safe environment; check glucose; monitor vitals | Allow postictal recovery; reassess frequently; escalate if not improving |
| Seizure resolved but focal weakness persists | Document timing and distribution of weakness | If not improving within 30-60 minutes OR any doubt: urgent CT to rule out stroke |
| Known epilepsy patient, missed medication doses | Resume medications; give loading dose if significantly subtherapeutic | Check drug level; address barriers to compliance; outpatient follow-up |
| Suspected alcohol withdrawal seizure | Benzodiazepines for seizure and withdrawal; thiamine before glucose | CIWA protocol; monitor for delirium tremens; address alcohol use disorder |
| Seizure in patient on anticoagulation | Urgent CT head to rule out intracranial hemorrhage | Consider reversal agents if hemorrhage present; neurosurgical consultation |
| Seizure with fever in adult | Blood cultures; empiric antibiotics; consider acyclovir | Lumbar puncture after imaging; treat presumptively for central nervous system infection until ruled out |
| Events suspicious for psychogenic nonepileptic seizures | Ensure safety; do not give unnecessary medications | Video electroencephalogram monitoring for definitive diagnosis; psychiatric evaluation |
| Patient wants to drive after first seizure | Counsel on legal requirements and safety | Document discussion; most jurisdictions require seizure-free period (typically 3-12 months); know local laws |
Troubleshooting Refractory Seizures
When Seizures Continue Despite Treatment, Ask These Questions
- Is the diagnosis correct? Up to 20-30% of “refractory epilepsy” is actually psychogenic nonepileptic seizures
- Is the medication appropriate for the seizure type? Sodium channel blockers can worsen generalized epilepsies
- Are drug levels therapeutic? Check levels; consider pharmacokinetic issues
- Is there a compliance issue? Ask directly; consider simplified regimen
- Are there ongoing triggers? Sleep deprivation, alcohol, stress, medication interactions
- Has the underlying condition changed? Tumor progression, new lesion, autoimmune process
- Is surgical evaluation indicated? Drug-resistant focal epilepsy may be curable with surgery
When to Refer to Epilepsy Specialist
Urgent Referral
- Diagnostic uncertainty (epilepsy versus non-epileptic events)
- Seizures despite two appropriate antiseizure medications
- Suspected epilepsy syndrome requiring specialized management
- Consideration of epilepsy surgery
- Pregnancy in woman with epilepsy
Routine Referral
- First seizure workup for further risk stratification
- Medication intolerance requiring alternative options
- Patient preference for specialist involvement
- Complex comorbidities affecting treatment
- Consideration of medication withdrawal after seizure freedom
8. Clinical Pearls and Pitfalls
Practical wisdom — learn from successes and avoid common mistakes
Must-Know Clinical Pearls
Always check glucose: Hypoglycemia is the most rapidly reversible cause of seizures. Point-of-care glucose should be checked within minutes of any seizure presentation. Antiseizure medications will not stop hypoglycemic seizures.
Lateral tongue biting is highly specific: Biting on the side of the tongue strongly supports a diagnosis of generalized tonic-clonic seizure over syncope or psychogenic events. Always examine the tongue and ask about tongue soreness.
The witness is your best diagnostic tool: Patients typically have amnesia for the seizure. A detailed witness account (or video) is often more valuable than any test. Ask witnesses to demonstrate what they saw.
Eyes open suggests seizure, eyes closed suggests psychogenic: During epileptic seizures, the eyes are typically open (often with deviation). Tightly closed eyes, especially with resistance to opening, strongly suggest psychogenic nonepileptic seizures.
Sleep deprivation is a potent trigger: Always ask about sleep. In patients with idiopathic generalized epilepsy, a single night of significant sleep deprivation can provoke a seizure. This is also why sleep-deprived electroencephalograms increase diagnostic yield.
Alcohol withdrawal seizures have a specific time window: Seizures typically occur 6-48 hours after the last drink, with peak risk at 24-48 hours. Seizures occurring outside this window or recurring despite treatment should prompt evaluation for other causes.
Isoniazid-induced seizures need pyridoxine: Isoniazid depletes pyridoxine (vitamin B6), which is essential for GABA synthesis. Standard antiseizure medications may be ineffective. Give pyridoxine — it is the specific antidote.
An abnormal electroencephalogram or MRI after first seizure changes management: These findings increase recurrence risk to greater than 60%, meeting criteria for epilepsy diagnosis after a single seizure and supporting initiation of antiseizure medication.
Critical Pitfalls to Avoid
Assuming all “seizures” are epileptic: Up to 20-30% of patients referred for refractory epilepsy actually have psychogenic nonepileptic seizures. Video electroencephalogram monitoring is the gold standard when there is diagnostic uncertainty.
Treating provoked seizures with long-term antiseizure medications: Seizures due to hypoglycemia, hyponatremia, or alcohol withdrawal do not require chronic antiseizure medication. Treat the underlying cause; the seizure risk resolves when the provocation is corrected.
Using carbamazepine or phenytoin for generalized epilepsy: Sodium channel blockers can worsen absence seizures, myoclonic seizures, and some generalized epilepsy syndromes. Always determine seizure type before selecting medication.
Prescribing valproate to women of childbearing potential without counseling: Valproate is highly teratogenic (neural tube defects, cognitive impairment in offspring). Use alternatives when possible, and always provide preconception counseling and contraception.
Confusing Todd’s paralysis with stroke: Todd’s paralysis is postictal weakness that resolves within 48 hours (usually much faster). However, when in doubt, always image urgently — stroke can also cause seizures, and the two conditions can coexist.
Delaying benzodiazepines in status epilepticus: Benzodiazepine efficacy decreases from approximately 80% to 40% as status epilepticus duration increases. Early, adequate-dose benzodiazepines are critical. Do not underdose.
Relying on a normal routine electroencephalogram to exclude epilepsy: Up to 50% of patients with epilepsy have a normal initial electroencephalogram. If clinical suspicion is high, repeat with sleep deprivation or pursue prolonged monitoring.
Forgetting to ask about driving: Driving restrictions after seizures are a legal requirement in most jurisdictions. Failing to counsel patients and document the discussion has medicolegal implications and safety consequences.
Key Takeaways
- A seizure is a symptom, not a diagnosis — always seek the underlying cause through systematic evaluation.
- Distinguish provoked seizures (treat the cause) from unprovoked seizures (consider antiseizure medication based on recurrence risk).
- Check glucose immediately in every patient presenting with seizure — hypoglycemia is rapidly reversible and delays cause harm.
- The detailed witness history is often the most valuable diagnostic information; ask witnesses to demonstrate what they observed.
- Lateral tongue biting, postictal confusion, and urinary incontinence support epileptic seizure over syncope or psychogenic events.
- Eyes tightly closed during an event, asynchronous movements, and prolonged duration suggest psychogenic nonepileptic seizures.
- Status epilepticus (>5 minutes) is a medical emergency requiring immediate benzodiazepines — efficacy decreases with duration.
- Electroencephalogram and MRI are the core investigations; abnormal findings increase recurrence risk and support treatment after a first seizure.
- Match antiseizure medication to seizure type — sodium channel blockers can worsen generalized epilepsies.
- Avoid valproate in women of childbearing potential due to teratogenicity; prefer levetiracetam or lamotrigine.
- When seizures persist despite treatment, question the diagnosis — consider video electroencephalogram to rule out psychogenic nonepileptic seizures.
- Always address driving restrictions, safety counseling, and quality-of-life issues — seizures impact far more than just the ictal event.
Quick Reference Algorithm
Systematic Approach to Seizures:
- Stabilize: Ensure safety, airway, breathing, circulation. If actively seizing >5 minutes, initiate status epilepticus protocol.
- Check glucose: Immediately. Treat hypoglycemia if present.
- Determine if seizure or mimic: Use detailed history (witness account), examination findings (tongue, incontinence), and clinical context.
- Classify the seizure: Provoked versus unprovoked? First versus recurrent? Focal versus generalized?
- Investigate: Metabolic panel, toxicology, electroencephalogram, neuroimaging (CT emergently if indicated, MRI for comprehensive workup).
- Identify and treat underlying cause: Correct metabolic abnormalities, treat infection, address withdrawal, manage structural lesions.
- Risk stratify: Use electroencephalogram and MRI findings to determine recurrence risk and need for antiseizure medication.
- Select appropriate medication: Match to seizure type, consider patient factors (age, sex, comorbidities, pregnancy potential).
- Counsel and educate: Driving restrictions, safety precautions, medication adherence, trigger avoidance, when to seek emergency care.
- Arrange follow-up: Epilepsy specialist referral if diagnostic uncertainty, treatment failure, or complex management required.