Seizure Semiology & Localization
Seizure Definitions, Semiology & Localization
What Do You Need to Know?
- ILAE 2025 seizure classification (Beniczky et al., Epilepsia 2025) is a published ILAE position paper that builds on the 2017 framework: “awareness” → consciousness (defined by awareness + responsiveness); “motor/non-motor” → observable/non-observable manifestations; “onset” removed from class names. Know both: 2017 focal aware/impaired awareness and 2025 consciousness/observable-manifestation terminology.
- Focal seizures are classified by consciousness (preserved vs. impaired) and described by chronological semiologic sequence
- 21 seizure types across 4 classes (focal, generalized, unknown, unclassified) — down from 63 in 2017; classifiers (guide management) vs. descriptors (semiological features)
- Three-level framework: seizure type → epilepsy type → epilepsy syndrome; six etiologies (structural, genetic, infectious, metabolic, immune, unknown)
- Mesial temporal sequence: epigastric rising → behavioral arrest → oroalimentary automatisms → contralateral dystonic posturing
- Key lateralizing signs: figure-of-4 extended arm = contralateral; postictal nose wipe = ipsilateral hand; Todd paralysis = contralateral; dystonic posturing (~90% reliable)
- Epilepsy diagnosis: 2 unprovoked seizures >24h apart, OR 1 seizure + ≥60% recurrence risk, OR epilepsy syndrome
🚩 Don’t Miss — Test-Day Priorities
- ILAE 2017 framework (board standard): focal-onset (aware vs impaired awareness; motor vs non-motor) — generalized-onset (motor — tonic-clonic, clonic, tonic, myoclonic, MAS, atonic, epileptic spasms; non-motor — typical/atypical/myoclonic absence, eyelid myoclonia) — unknown-onset — unclassified. ILAE 2025 (consciousness, observable/non-observable) is supplementary.
- Mesial temporal (most common focal epilepsy): epigastric rising aura → déjà vu/fear → behavioral arrest → oroalimentary automatisms (lip-smacking/chewing) + ipsilateral hand automatisms + contralateral dystonic posturing → prolonged postictal confusion → ipsilateral nose wipe. MRI: hippocampal sclerosis.
- Lateral (neocortical) temporal: auditory aura (buzzing, voices, distorted sounds — Heschl gyrus); earlier speech arrest, less prominent automatisms.
- Frontal lobe: bilateral asymmetric tonic posturing / fencer’s posture (SMA), hypermotor “bicycling” / thrashing, nocturnal clusters, brief (<30 sec), rapid postictal recovery, interictal EEG often normal. SMA: preserved awareness despite bilateral motor activity.
- Parietal: somatosensory aura (tingling, Jacksonian march), body image distortion, ictal pain (rare — insular more often). Occipital: elementary visual hallucinations (flashes, colored circles — contrast with formed hallucinations of psychiatric disease / Charles Bonnet), eyelid fluttering, ictal nystagmus, postictal headache and visual deficit. Insular: laryngeal/throat constriction, visceral/painful, dysesthetic paresthesias — suspect after failed temporal surgery.
- Lateralizing signs (high yield): figure-of-4 at GTC onset → extended arm = contralateral to onset; unilateral dystonic posturing → contralateral (~90% reliable); early forced head version (sustained >10 sec pre-GTC) → contralateral; late head turning during GTC → often ipsilateral (FALSE lateralizing); Todd paralysis → contralateral; postictal nose wipe (hand) → ipsilateral hemisphere; postictal aphasia → dominant (usually left); ictal speech preservation → non-dominant; ictal vomiting/spitting → non-dominant (right) temporal.
- Epileptic seizure vs PNES: GTC features — eyes open, synchronous tonic-clonic, lateral tongue bite, urinary incontinence, postictal acidosis, postictal EEG slowing, brief duration, no recall. PNES — forced eye closure, pelvic thrusting, side-to-side head shake, asynchronous flailing, preserved awareness with bilateral motor activity, recall of details, normal post-ictal EEG, no acidosis, prolonged/waxing-waning course.
- Hyperkinetic frontal seizures (stereotyped + nocturnal + brief) are epileptic, NOT PNES — classic board trap. NREM parasomnias are non-epileptic and unrelated.
- Gelastic seizures (ictal laughter) → hypothalamic hamartoma + precocious puberty + cognitive/behavioral decline.
- Status epilepticus (Trinka 2015): GCSE — treat at 5 min (t1), injury at 30 min (t2); focal SE with impaired awareness — t1 10 min, t2 >60 min; absence SE — t1 10–15 min.
🔍 Buzzwords & Pathognomonic FindingsSemiology · Localization clues · Postictal / lateralizing
Semiology / aura
- Epigastric rising sensation + déjà vu + fear → mesial temporal (amygdala/hippocampus)
- Auditory aura (buzzing, voices, distorted sounds) → lateral temporal — Heschl gyrus
- Olfactory “uncinate fits” (burning/chemical smell) → uncus / mesial temporal (also orbitofrontal)
- Laryngeal constriction / throat tightening + visceral / dysesthetic pain → insular cortex
- Elementary visual hallucinations (multicolored flashes, circles in contralateral field) → occipital pole
- Somatosensory tingling with Jacksonian march + body-image distortion → parietal (primary sensory cortex)
- Cephalic / no aura + hypermotor “bicycling” or fencer’s posture, nocturnal → frontal lobe
- Gustatory (metallic/bitter) aura → insula / parietal operculum
- Ictal emesis + pallor (child, nocturnal) → Panayiotopoulos — occipital with autonomic features
Ictal localization signs
- Oroalimentary automatisms (lip-smacking, chewing) + ipsilateral hand automatisms + contralateral dystonic posturing → mesial temporal lobe epilepsy (classic MTLE sequence)
- Bilateral asymmetric tonic / fencer’s posture with preserved awareness, <30 sec, nocturnal → SMA (mesial frontal, area 6)
- Hypermotor “bicycling,” thrashing, rocking — brief, stereotyped, nocturnal clusters → frontal lobe (NOT PNES)
- Forced contralateral eye/head version (sustained >10 sec pre-GTC) → frontal eye fields (Brodmann area 8), contralateral to onset
- Figure-of-4 at GTC onset (one arm extended, one flexed) → extended arm contralateral to onset
- Unilateral clonic activity / Jacksonian march → contralateral primary motor cortex
- Eyelid fluttering + ictal nystagmus + contralateral eye deviation → occipital
- Ictal spitting → nondominant (right) temporal lobe
- Gelastic (ictal laughter, mirthless) → hypothalamic hamartoma (also anterior cingulate)
Postictal / lateralizing
- Postictal nose wiping with one hand → ipsilateral hemisphere (if dystonic posturing present, wipe is done by the non-dystonic — thus contralateral — hand, still ipsilateral to focus)
- Postictal aphasia → dominant hemisphere (usually left)
- Ictal speech preservation during bilateral motor activity → non-dominant hemisphere
- Todd paralysis (postictal focal weakness, resolves min–hours) → contralateral to focus
- Prolonged postictal confusion (30 sec — several min) → temporal lobe; rapid recovery / minimal confusion → frontal lobe
- Postictal headache + transient visual deficit/blindness → occipital
- Postictal psychosis after lucid interval (hours–days) → temporal lobe (often after seizure cluster)
- Lateral tongue bite + urinary incontinence + postictal lactic acidosis + EEG slowing → true GTC (helps distinguish from PNES)
- Forced eye closure + pelvic thrusting + side-to-side head shake + asynchronous flailing + recall preserved + normal post-event EEG → PNES
Seizure Classification (ILAE 2017 — Board Standard; ILAE 2025 supplementary)
Exam Note
ILAE 2017 remains the most familiar board framework (focal aware / focal impaired awareness / focal to bilateral tonic-clonic; motor vs non-motor), but the ILAE 2025 seizure classification is a published ILAE position paper. Know both: 2017 focal aware/impaired awareness and 2025 consciousness / observable-manifestation terminology.
Terminology Evolution
| Old Term | 2017 Term | 2025 Term |
|---|---|---|
| Simple partial seizure | Focal aware seizure | Focal preserved consciousness seizure (FPC) |
| Complex partial seizure | Focal impaired awareness seizure | Focal impaired consciousness seizure (FIC) |
| Secondarily generalized tonic-clonic | Focal to bilateral tonic-clonic | Focal-to-bilateral tonic-clonic seizure (FBTC) |
| Grand mal | Generalized-onset tonic-clonic | Generalized tonic-clonic seizure (GTC) |
| Petit mal | Absence (non-motor) | Absence seizure (“non-motor” removed) |
| Aura | Focal aware seizure | Focal preserved consciousness seizure |
Key Changes: ILAE 2017 → Proposed 2025 Update
| Feature | 2017 | 2025 |
|---|---|---|
| Class naming | “Focal-onset,” “Generalized-onset” | “Focal,” “Generalized” — “onset” removed (generalized seizures can have focal onset) |
| Classifier | Awareness (aware vs. impaired) | Consciousness (preserved vs. impaired) = awareness (recall) + responsiveness (react to verbal/motor tasks) |
| Descriptors | Motor vs. non-motor onset | Observable vs. non-observable manifestations (basic); chronological semiologic sequence (expanded) |
| Seizure description | First sign at onset determines subtype | Chronological sequence of all signs (e.g., aura → automatism → impaired responsiveness) |
| New seizure type | — | Generalized negative myoclonus (brief <500 ms interruption of tone) |
| Epileptic spasms | Seizure type in all classes | Seizure type only in generalized; descriptor in focal and unknown |
| Absence seizures | Classified as “non-motor” | “Non-motor” removed (absences often have observable motor features: automatisms, blinks, retropulsion) |
| Taxonomy | 63 seizure types; classifiers & descriptors not distinguished | 21 seizure types; classifiers (biological classes; guide management) vs. descriptors (semiological features) |
Complete Taxonomy: 4 Classes, 21 Seizure Types
| Class | Seizure Types | Abbreviation |
|---|---|---|
| 1. Focal (F) | Focal preserved consciousness | FPC |
| Focal impaired consciousness | FIC | |
| Focal-to-bilateral tonic-clonic | FBTC | |
| 2. Unknown (U) (whether focal or generalized) | Preserved consciousness | PC |
| Impaired consciousness | IC | |
| Bilateral tonic-clonic | BTC | |
| 3. Generalized (G) | 3.1 Absence seizures: | |
| Typical absence | TA | |
| Atypical absence | AA | |
| Myoclonic absence | MA | |
| Eyelid myoclonia ± absence | EMA | |
| 3.2 Generalized tonic-clonic (GTC): | ||
| Myoclonic-tonic-clonic | — | |
| Absence-to-tonic-clonic | — | |
| 3.3 Other generalized seizures: | ||
| Myoclonic / Clonic / Tonic / Atonic / Myoclonic-atonic | GM, GC, GT, GA, GMA | |
| Negative myoclonic (NEW) | GNM | |
| Generalized epileptic spasms | GES | |
| (Epileptic spasms in focal/unknown = descriptor, not seizure type) | ||
| 4. Unclassified | No meaningful seizure characteristics available | |
Consciousness as a Classifier
- Consciousness replaces “awareness” — operationally defined by:
- Awareness: ability to recall the event afterward
- Responsiveness: ability to respond to verbal and motor tasks during the seizure
- If either is impaired → classify as impaired consciousness
- Applies as classifier only to focal and unknown seizures; most generalized seizures impair consciousness — myoclonic seizures are a notable exception (consciousness usually preserved — patient drops object and remains aware)
- If consciousness undetermined → classify under the parent term (e.g., just “focal seizure”)
- Caution: isolated epileptic amnesia, ictal paresis, or ictal receptive aphasia can mimic impaired consciousness
Observable vs. Non-observable Manifestations
- Basic version (primary care, resource-limited): seizures described as with or without observable manifestations
- Expanded version (specialized centers): semiological features listed in chronological sequence using arrows (e.g., epigastric aura → right hand automatism → impaired responsiveness)
- Observable = motor, aphasic, autonomic, or other features readily identified by eyewitnesses; non-volitional
- Non-observable = sensory, cognitive, affective phenomena; indescribable auras
- Impaired consciousness itself counts as an observable manifestation
- “Non-motor” removed from absence seizure classification because absences often show observable motor features (automatisms, eyelid blinking, head retropulsion)
Generalized Seizure Subtypes
Absence Seizures
- Typical absence: abrupt stare, ≥2.5 Hz (classically 3 Hz) generalized spike-wave; rapid recovery; no postictal confusion; median few seconds to 30 s
- Atypical absence: slower onset/offset, <2.5 Hz slow spike-wave; pronounced tone changes; Lennox-Gastaut
- Myoclonic absence: rhythmic 3 Hz bilateral upper-limb jerks with arm abduction; median 7–12 s
- Eyelid myoclonia: brief 3–6 Hz eyelid jerks ± absence; median 1.5 s; Jeavons syndrome
Generalized Tonic-Clonic & Subtypes
- Generalized tonic-clonic (GTC): sustained tonic phase → progressive slowing clonic phase; median 80 s; bilateral but may be asymmetric
- Myoclonic-tonic-clonic: myoclonic jerks preceding GTC (classic JME)
- Absence-to-tonic-clonic: absence seizure evolving into GTC
Other Generalized Seizures
- Myoclonic: brief (<100 ms) bilateral jerks; JME (morning predominance)
- Clonic: regular, repetitive myoclonic jerks at low frequency; median 4 s; neonates/young children
- Tonic: sustained bilateral muscular contraction; median 8 s; Lennox-Gastaut
- Atonic: sudden loss/decrease in muscle tone; drop attacks; median 1 s; LGS
- Myoclonic-atonic: brief myoclonic jerk followed by atonic component; median 1.25 s; Doose syndrome
- Negative myoclonic (NEW in 2025): brief (<500 ms) interruption of muscle tone; requires voluntary activation to document; distinct from asterixis in toxic-metabolic encephalopathies. Can also be focal (cortical), classically centroparietal, seen in atypical benign partial epilepsy / ESES spectrum
- Generalized epileptic spasms: brief (≤2 s) axial muscle contractions; clusters upon awakening; infantile epileptic spasm syndrome (IESS)
Epileptic Spasms: Updated Classification
- Generalized (bilateral symmetric) = seizure type (“generalized epileptic spasms”)
- Focal (unilateral or asymmetric) = descriptor within focal seizure semiology (“focal epileptic spasm”)
- Unknown = descriptor when focal vs. generalized cannot be determined
- Classification requires multimodal approach (semiology + EEG + MRI + genetics)
- Focal spasms → consider early surgical evaluation, especially if spasms-specific therapy fails
- Terminology: “infantile spasms” → “epileptic spasms” (can occur at any age)
Unknown Onset Seizures
- Valid category when origin cannot be determined — can be reclassified when more data available
- Three types: preserved consciousness, impaired consciousness, bilateral tonic-clonic
- Epileptic spasms in this class are a descriptor, not a seizure type
💎 Board Pearl
- Consciousness = awareness (recall) + responsiveness (react) — if either is impaired, classify as impaired
- An aura IS a seizure — classified as focal preserved consciousness seizure with non-observable manifestations
- If a question says “patient has impaired awareness but intact responsiveness” or vice versa → classify as impaired consciousness (either component suffices)
- The 2025 classification is backward-compatible: “impaired awareness” converts directly to “impaired consciousness”; “motor seizure” = “observable manifestation”
- Epileptic spasms: generalized = seizure type; focal = descriptor — focal spasms warrant surgical evaluation
Three-Level Framework & Epilepsy Definition
Three-Level Classification
| Level | Classification | Basis |
|---|---|---|
| Level 1 | Seizure type | History, witness description, ±EEG/video |
| Level 2 | Epilepsy type | Focal, generalized, combined, or unknown |
| Level 3 | Epilepsy syndrome | Characteristic clinical + EEG cluster, age of onset, prognosis |
Six Etiologic Categories
- Structural: stroke, tumor, MTS, cortical malformation — concordant with semiology/EEG
- Genetic: known genetic variant with seizures as core symptom (e.g., SCN1A in Dravet); may be de novo
- Infectious: viral encephalitis, neurocysticercosis, malaria
- Metabolic: POLG, MELAS, amino acid/mitochondrial/lysosomal disorders
- Immune: NMDAR, LGI1, GAD antibody encephalitis — early immunotherapy critical
- Unknown: ~1/3 of all epilepsy; may have multiple etiologic categories simultaneously
Practical Epilepsy Definition (ILAE 2014)
- Criterion 1: ≥2 unprovoked (or reflex) seizures occurring >24 hours apart
- Criterion 2: 1 unprovoked seizure + ≥60% probability of recurrence over next 10 years
- Criterion 3: Diagnosis of an epilepsy syndrome
💎 Board Pearl
- A single seizure + remote cortical lesion + epileptiform EEG = can diagnose epilepsy (≥60% recurrence risk)
- Epilepsy can be "resolved" if seizure-free for 10 years with ≥5 years off medications, or past the applicable age of an age-dependent epilepsy syndrome
- A patient can have more than one etiologic category (e.g., structural + genetic in TSC)
Status Epilepticus — ILAE 2015 Operational Definitions (Trinka 2015)
Two Time-Points: t1 (treat) and t2 (long-term consequences)
| SE Type | t1 (treatment threshold — abnormally prolonged seizure) | t2 (long-term consequences begin) |
|---|---|---|
| Generalized convulsive SE | 5 min | 30 min |
| Focal SE with impaired awareness | 10 min | >60 min |
| Absence SE | 10–15 min | Unknown |
4-Axis Classification (Trinka 2015)
- Axis 1 — Semiology: with prominent motor features vs. without (NCSE); with/without coma
- Axis 2 — Etiology: known (symptomatic: acute, remote, progressive) vs. unknown (cryptogenic)
- Axis 3 — EEG correlates: location, pattern, morphology, time-related features
- Axis 4 — Age: neonatal, infancy, childhood, adolescence/adult, elderly
💎 Board Pearl
- t1 = when to treat (5 min for GCSE); t2 = when neuronal injury begins (30 min for GCSE) — both shortened from the older 30-min definition based on outcome data
- Focal SE with impaired awareness has a longer t1 (10 min) but a much longer t2 (>60 min)
- Absence SE: treatment threshold 10–15 min; long-term consequences unknown
ILAE 2022 Epilepsy Syndromes (by Age of Onset)
Neonatal / Infant Onset
- KCNQ2-DEE / BFNE: KCNQ2 variants; spectrum from self-limited benign familial neonatal epilepsy (BFNE) to developmental and epileptic encephalopathy
- Ohtahara / EME → EIDEE: early-infantile developmental and epileptic encephalopathy (unified term); burst-suppression EEG; structural or genetic etiology
- West / IESS: infantile epileptic spasms syndrome; epileptic spasms + hypsarrhythmia + developmental regression; first-line ACTH/vigabatrin
- Dravet: SCN1A; fever-triggered prolonged hemiclonic seizures in year 1 → multiple types + developmental slowing; avoid sodium channel blockers
Childhood Onset
- SeLECTS (formerly BECTS / Rolandic): self-limited epilepsy with centrotemporal spikes; nocturnal hemifacial sensorimotor seizures; resolves by adolescence
- Panayiotopoulos: early-onset childhood occipital epilepsy with autonomic features (ictal emesis, pallor); often nocturnal; self-limited
- Gastaut occipital: late-onset childhood occipital epilepsy; elementary visual hallucinations; postictal headache
- CAE: childhood absence epilepsy; brief 3 Hz absences provoked by hyperventilation; ethosuximide/valproate
- LGS: Lennox-Gastaut syndrome; multiple seizure types (tonic, atonic, atypical absence) + slow spike-wave + cognitive impairment
- Doose (EMAtS): epilepsy with myoclonic-atonic seizures; drop attacks; normal development at onset
- Landau-Kleffner: acquired epileptic aphasia; verbal auditory agnosia + CSWS on EEG
- CSWS / DEE-SWAS: developmental/epileptic encephalopathy with spike-and-wave activation in sleep (>85% of NREM sleep)
Variable Age of Onset
- JME: juvenile myoclonic epilepsy; morning myoclonic jerks + GTC ± absence; lifelong; valproate/levetiracetam
- JAE: juvenile absence epilepsy; less frequent absences than CAE; high GTC rate
- GTCA: epilepsy with generalized tonic-clonic seizures alone
- Jeavons: eyelid myoclonia with absences; photosensitive; lifelong; valproate/levetiracetam
- Reflex / reading / photosensitive epilepsies: seizures triggered by specific stimuli (reading, photic, hot water, music)
Progressive Myoclonic Epilepsies (PME)
- ULD (Unverricht-Lundborg): CSTB gene; teen onset; stimulus-sensitive myoclonus + GTC; relatively preserved cognition; longest survival of PMEs
- Lafora: EPM2A/EPM2B (laforin/malin); teen onset; rapidly progressive dementia + myoclonus + occipital seizures; periodic acid-Schiff (PAS)-positive inclusions on skin/axillary biopsy
- MERRF: myoclonic epilepsy with ragged red fibers; mtDNA tRNA-Lys (m.8344A>G); myoclonus + ataxia + myopathy
- NCL (Batten): neuronal ceroid lipofuscinoses (CLN1–14); progressive vision loss + dementia + seizures; age of onset by subtype
- Sialidosis: NEU1; cherry-red macular spot; action myoclonus + ataxia
💎 Board Pearl
- Renamed terminology to remember: BECTS → SeLECTS; Ohtahara/EME → EIDEE; West → IESS; Doose → EMAtS; CSWS → DEE-SWAS
- PME triad: action/stimulus myoclonus + GTC + progressive neurologic decline (ataxia, dementia)
- Lafora body on axillary skin biopsy (PAS-positive inclusions in eccrine sweat duct cells) = pathognomonic for Lafora disease
- Dravet: SCN1A loss-of-function — avoid sodium channel blockers (carbamazepine, lamotrigine, phenytoin) which worsen seizures
Semiology by Lobe
| Lobe / Region | Typical Aura | Motor Features | Duration | Postictal State |
|---|---|---|---|---|
| Temporal (mesial) | Epigastric rising, déjà vu, fear, olfactory | Behavioral arrest → oroalimentary automatisms → ipsilateral hand automatisms → contralateral dystonic posturing | 1–2 min | Prolonged confusion; aphasia (dominant); ipsilateral nose wipe |
| Temporal (lateral) | Auditory (buzzing), complex visual, vertigo | Less prominent automatisms; early speech arrest; early head version | Variable | Aphasia (dominant hemisphere) |
| Frontal (SMA) | None or cephalic | Fencing posture (bilateral asymmetric tonic); abrupt onset/offset; awareness often preserved | <30 sec | Minimal/absent |
| Frontal (dorsolateral) | Nonspecific or none | Forced head/eye version (contraversive); tonic posturing; rapid generalization. Frontal eye fields (Brodmann area 8) → forced contralateral eye/head version | Brief | Minimal |
| Frontal (orbitofrontal) | Olfactory (overlaps uncal) | Complex gestural automatisms; autonomic features; mimics temporal seizures | Brief | Minimal |
| Frontal (cingulate) | Emotional (fear, anxiety) | Complex behavioral automatisms; affective features; gelastic features | Brief | Minimal |
| Frontal (primary motor) | None | Contralateral clonic activity; Jacksonian march along homunculus | Variable | Todd paralysis (contralateral) |
| Frontal (hyperkinetic) | None or vague | Thrashing, bicycling, body rocking; violent-appearing; nocturnal clusters | <30 sec | Minimal; mimics PNES |
| Parietal | Somatosensory (tingling, numbness); body image distortion; ictal pain (rare) | Sensory Jacksonian march; rapid propagation obscures onset | Brief | Residual sensory symptoms |
| Occipital | Brief multicolored flashes, circles in contralateral field | Contralateral eye deviation; eyelid fluttering; propagates to temporal lobe | Brief | Postictal headache; visual deficit |
| Insular | Laryngeal constriction, visceral, bilateral somatosensory; painful/dysesthetic paresthesias (often large or bilateral cutaneous territory); ictal pain most often insular (not parietal) | Mimics temporal and frontal seizures; prominent autonomic features | Variable | Suspect after failed temporal surgery |
Temporal vs. Frontal Lobe Seizures — Key Differences
| Feature | Temporal Lobe | Frontal Lobe |
|---|---|---|
| Duration | 1–2 minutes | <30 seconds (often <15 sec) |
| Aura | Common (epigastric, déjà vu, fear) | Rare or absent |
| Automatisms | Oroalimentary (lip smacking, chewing) | Hyperkinetic (thrashing, bicycling, rocking) |
| Motor features | Contralateral dystonic posturing; ipsilateral hand automatisms | Bilateral asymmetric tonic; prominent proximal limb/trunk |
| Nocturnal | Not typical | Frequently nocturnal |
| Secondary generalization | Common but not rapid | Rapid bilateral spread |
| Postictal confusion | Prolonged (30 sec – several min) | Minimal or absent; rapid recovery |
| Interictal EEG | Anterior temporal spikes (F7/F8, T3/T4) | Often normal or non-localizing |
Focal to Bilateral Tonic-Clonic vs. Primary Generalized Tonic-Clonic
| Feature | Focal to Bilateral TC | Generalized TC |
|---|---|---|
| Preceding aura | Often present (focal onset features) | None |
| Asymmetry at onset | Common (version, figure-of-4, asymmetric tonic) | Symmetric from start |
| Head version pre-GTC | Forced version = contralateral lateralizing | Absent |
| Postictal Todd paralysis | May be present (contralateral) | Absent |
| Postictal aphasia | Present if dominant hemisphere onset | Absent |
| Interictal EEG | Focal spikes or sharp waves | Generalized spike-wave (2.5–5.5 Hz) |
Clinical Pearl
Occipital seizure vs. migraine aura: Epileptic visual aura = brief (seconds), multicolored flashes, circular/spherical. Migraine visual aura = gradual (20–30 min), zigzag/fortification spectra, followed by headache. Duration is the most reliable distinguishing feature.
Clinical Pearl
Insular epilepsy: Suspect when a patient with presumed temporal lobe epilepsy fails surgical resection. Insular seizures produce laryngeal constriction, visceral aura, and bilateral somatosensory phenomena that mimic mesial temporal seizures but originate deep to the sylvian fissure.
Lateralizing Signs
| Sign | Lateralization | Reliability | Mechanism / Notes |
|---|---|---|---|
| Figure-of-4 sign | Extended arm = contralateral to onset | High | One arm extended, one flexed forming "4" at onset of the bilateral tonic-clonic phase (lateralizing — extended arm contralateral to onset) |
| M2e sign (asymmetric tonic limb posturing) | Extended limb = contralateral to onset | High | Asymmetric tonic posturing with one limb extended; SMA / frontal onset |
| Fencing posture | Extended arm = contralateral to seizure onset zone | High | Asymmetric tonic posturing; head deviates toward extended arm; extended arm = contralateral to onset; localizes to SMA (area 6) |
| Forced head version (early) | Contralateral | High (pre-GTC) | Sustained forced tonic turning; must be early and forced to reliably lateralize |
| Forced head version (late) | Ipsilateral (FALSE lateralizing) | Low | Late turning during GTC phase is often toward side of onset — do not use for lateralization |
| Postictal nose wiping | Ipsilateral hand | Moderate-High | Patient wipes with ipsilateral (non-paretic) hand; temporal > frontal |
| Todd paralysis | Contralateral | High | Postictal focal weakness; resolves minutes to hours; confirms hemisphere of origin |
| Postictal aphasia | Dominant hemisphere | High | Transient language difficulty = dominant (usually left) hemisphere involvement |
| Ictal speech preservation | Nondominant hemisphere | Moderate | Ability to speak during seizure = onset in nondominant hemisphere |
| Unilateral automatisms | Ipsilateral hemisphere | Moderate-High | Hand performing automatisms is ipsilateral; contralateral hand often dystonic |
| Contralateral dystonic posturing | Contralateral | Very high (~90%) | Sustained arm/hand posturing; contralateral basal ganglia activation; most reliable lateralizing sign |
| Ictal spitting | Nondominant (usually R) temporal | Moderate-High | Repetitive spitting automatism lateralizes to nondominant temporal lobe |
| Unilateral clonic activity | Contralateral | Very high | Jacksonian march; contralateral primary motor cortex |
💎 Board Pearl
- Early forced head version (tonic, pre-GTC) = contralateral; late head turning during GTC = often ipsilateral (false lateralizing) — timing is everything
- Figure-of-4: look at which arm is EXTENDED — seizure started in the opposite hemisphere
- Contralateral dystonic posturing + ipsilateral automatisms in the same seizure = powerful lateralizing combination for TLE
Aura Types & Localizing Value
💎 High-Yield Aura Localization Summary (Board Quick Reference)
| Aura | Localization |
|---|---|
| Epigastric rising | Mesial temporal |
| Auditory hallucination | Lateral temporal (Heschl gyrus) |
| Laryngeal constriction / throat tightening | Insular |
| Multicolored / formed visual phenomena | Occipital |
| Somatosensory tingling | Parietal (primary sensory cortex) |
| Fear / anxiety | Mesial temporal (amygdala) or cingulate |
| Olfactory / gustatory | Uncus / insula |
| Déjà vu / jamais vu | Mesial temporal |
| Aura Type | Description | Localization |
|---|---|---|
| Epigastric rising | "Butterflies" or wave rising from abdomen to throat | Mesial temporal; less commonly insula |
| Déjà vu / jamais vu | Intense familiarity or unfamiliarity; dreamy state | Mesial temporal (hippocampus/parahippocampus) |
| Fear / anxiety | Sudden overwhelming dread without trigger | Mesial temporal (amygdala) or cingulate |
| Laryngeal constriction / throat tightening | Sudden "throat closing," dyspnea, or breath-holding sensation | Insular cortex (anterior/visceral insula); operculum |
| Olfactory | Unpleasant odors (burning, chemical) | Uncus; mesial temporal; orbitofrontal |
| Gustatory | Abnormal taste (metallic, bitter) | Insula; parietal operculum |
| Auditory | Ringing, buzzing, distorted sounds | Lateral temporal / Heschl gyrus |
| Visual (elementary) | Flashing lights, colored circles in contralateral field | Primary visual cortex (occipital pole) |
| Somatosensory | Tingling, numbness, "electric" sensation; contralateral | Primary somatosensory cortex (parietal) |
| Vertiginous | Spinning or sense of movement | Parieto-temporal junction; posterior insula |
💎 Board Pearl
- Epigastric rising = most common aura in MTLE — always evaluate for hippocampal sclerosis on MRI
- Olfactory aura (uncinate fits) = uncus/mesial temporal; can also arise from orbitofrontal cortex
- Auditory aura = lateral temporal (Heschl gyrus); gustatory = insula/parietal operculum — board favorite
Postictal Features & Localizing Value
| Postictal Feature | Localizing / Lateralizing Significance |
|---|---|
| Postictal confusion duration | Temporal: prolonged (30 sec – several min); Frontal: minimal/absent — rapid recovery |
| Todd paralysis | Contralateral weakness to seizure focus; resolves minutes to hours |
| Postictal aphasia | Dominant hemisphere temporal or perisylvian involvement |
| Postictal nose wiping | Ipsilateral hand to focus (non-paretic hand); temporal > frontal |
| Postictal cough | Temporal lobe onset; reflects autonomic activation |
| Postictal psychosis | Hours to days after seizure clusters; temporal lobe; follows a lucid interval |
Clinical Pearl
Postictal confusion duration differentiates temporal from frontal seizures. Temporal lobe = prolonged confusion (30 sec to several minutes); frontal lobe = minimal or no confusion with rapid return to baseline. Useful when ictal phase is unwitnessed.
Board Pearls & Clinical Pearls
💎 Board Pearl
- Contralateral dystonic posturing (~90% lateralizing) — dystonic limb is contralateral to seizure onset zone; one of the most reliable lateralizing signs
- Hyperkinetic seizures (thrashing, bicycling, rocking) are brief, nocturnal, stereotyped, frontal lobe — do NOT confuse with PNES. Stereotypy + nocturnal = epileptic until proven otherwise
- Frontal lobe seizures can have a normal interictal EEG — deep/mesial focus; scalp EEG may show minimal ictal changes
- Ictal vomiting in adults = nondominant (right) temporal
- Panayiotopoulos syndrome = childhood occipital epilepsy with autonomic features including ictal emesis
- First observable feature determines classification — tingling then clonic = focal sensory, not focal clonic
- Gelastic seizures (ictal laughter) — classically hypothalamic hamartoma (often with precocious puberty and behavioral/cognitive decline); also anterior cingulate, mesial temporal
- Propagation mimics different onset zones: occipital → temporal propagation produces TLE-like automatisms; only aura or video-EEG reveals true onset
Clinical Pearl
Classic MTLE semiologic sequence: epigastric aura → behavioral arrest (stare) → oroalimentary automatisms (lip smacking) → ipsilateral hand automatisms → contralateral dystonic posturing → postictal confusion with ipsilateral nose wiping. This is the most commonly tested seizure sequence on neurology boards.
Clinical Pearl
SMA seizures: bilateral asymmetric tonic posturing (fencing), preserved awareness, <30 seconds, often nocturnal, abrupt onset/offset, no postictal confusion. Frequently misdiagnosed as nonepileptic events. A normal interictal EEG does not exclude the diagnosis.
References
- Beniczky S, Trinka E, Wirrell E, et al. Updated classification of epileptic seizures: Position paper of the ILAE. Epilepsia 2025;66:1804–1823.
- Fisher RS, Cross JH, French JA, et al. Operational classification of seizure types by the ILAE. Epilepsia 2017;58(4):522–530.
- Scheffer IE, Berkovic S, Capovilla G, et al. ILAE classification of the epilepsies. Epilepsia 2017;58(4):512–521.
- Fisher RS, Acevedo C, Arzimanoglou A, et al. A practical clinical definition of epilepsy. Epilepsia 2014;55:475–482.
- Fisher RS, Cross JH, D'Souza C, et al. Instruction manual for the ILAE 2017 classification. Epilepsia 2017;58(4):531–542.
- Beniczky S, Tatum WO, Blumenfeld H, et al. Seizure semiology: ILAE glossary of terms. Epileptic Disord 2022;24(3):447–495.
- Noachtar S, Arnold S. Simple motor seizures: localizing and lateralizing value. In: Textbook of Epilepsy Surgery. Informa Healthcare; 2008:450–461.
- Bianchin MM, Sakamoto AC. Complex motor seizures: localizing and lateralizing value. In: Textbook of Epilepsy Surgery. Informa Healthcare; 2008:462–478.
- Marashly A, Ewida A, Agarwal R, et al. Ictal motor sequences: lateralization and localization. Epilepsia 2016;57(3):369–375.
- Fayerstein J, McGonigal A, Pizzo F, et al. Hyperkinetic seizures and seizure onset zone. Epilepsia 2020;61(5):1019–1026.
- Nascimento FA, Friedman D, Peters JM, et al. Focal epilepsies: update on diagnosis and classification. Epileptic Disord 2023;25(1):1–17.
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