Temporal Lobe & Focal Epilepsies
Temporal Lobe & Focal Epilepsies
What Do You Need to Know?
- Mesial TLE is the most common focal epilepsy in adults; hippocampal sclerosis (HS) is the defining substrate — selective loss in CA1, CA3, CA4 with CA2 sparing
- Classic mTLE sequence: epigastric rising → behavioral arrest → oroalimentary automatisms → contralateral dystonic posturing
- EEG: anterior temporal sharp waves (F7/F8); ictal 5–9 Hz temporal theta; TIRDA has similar lateralizing value to interictal epileptiform discharges
- MRI: hippocampal atrophy + T2/FLAIR hyperintensity on coronal thin-cut sequences
- Frontal lobe epilepsy: brief (<60s), nocturnal, hyperkinetic, stereotyped, minimal postictal confusion — SMA = fencer posture with preserved awareness
- FCD Type IIb (balloon cells + transmantle sign) has the BEST surgical outcome among FCDs (70–80% Engel I); linked to mTOR pathway
- ERSET trial: early surgery for mTLE = 73% seizure-free vs. 0% continued medical therapy
- Insular epilepsy: suspect after failed temporal surgery; laryngeal + bilateral somatosensory + visceral aura; requires SEEG
Mesial TLE vs. Lateral TLE
| Feature | Mesial TLE (mTLE) | Lateral (Neocortical) TLE |
|---|---|---|
| Frequency | ~80% of TLE | ~20% of TLE |
| Onset zone | Hippocampus, amygdala, entorhinal cortex | Superior/middle temporal gyrus, fusiform gyrus |
| Typical aura | Epigastric rising, déjà vu, fear, olfactory | Auditory hallucinations (Heschl gyrus), auditory illusions, vertigo |
| Semiology | Behavioral arrest → oroalimentary automatisms → contralateral dystonic posturing | Early speech arrest, less prominent automatisms, early contralateral version |
| Interictal EEG | Anterior temporal sharp waves (F7/F8) | Posterior temporal spikes (T5/T6) |
| Common etiology | Hippocampal sclerosis (65–70% of surgical specimens) | Tumors (ganglioglioma, DNET), cortical dysplasia, cavernomas |
| MRI | Hippocampal atrophy + T2/FLAIR hyperintensity | Neocortical lesion or MRI-negative |
| Surgical outcome | 60–80% Engel I (with HS) | 50–60% Engel I (lesional); lower if MRI-negative |
💎 Board Pearl
Auditory aura = lateral temporal (Heschl gyrus). Epigastric rising = mesial temporal. On boards, auditory hallucinations in a focal seizure + LGI1 mutation = epilepsy with auditory features (autosomal dominant lateral TLE).
Hippocampal Sclerosis
ILAE Hippocampal Sclerosis Types
| ILAE HS Type | Pattern of Neuronal Loss | Frequency | Surgical Outcome |
|---|---|---|---|
| Type 1 (classical) | Severe CA1 + CA3 + CA4 loss; CA2 spared | 60–80% | Best outcome — associated with IPI (febrile seizures, encephalitis) |
| Type 2 (CA1-predominant) | Predominantly CA1 loss; other subfields preserved | 5–10% | Less favorable; less likely childhood precipitating event |
| Type 3 (CA4-predominant) | Predominantly CA4 + dentate granule cell loss | 4–7% | Less favorable; often dual pathology |
MRI Findings in HS
- Hippocampal atrophy on coronal T1 thin-cut + T2/FLAIR hyperintensity (gliosis)
- Loss of internal architecture (hippocampal digitations) on high-resolution sequences
- Secondary signs: ipsilateral temporal horn enlargement, mammillary body/fornix atrophy
- Quantitative volumetry increases sensitivity by 10–15% over visual inspection
Classic mTLE Seizure Sequence
- Aura: epigastric rising, déjà vu, or fear
- Behavioral arrest (motionless stare, loss of awareness)
- Oroalimentary automatisms (lip smacking, chewing) + ipsilateral manual automatisms
- Contralateral dystonic posturing (~90% lateralizing)
- Focal to bilateral tonic-clonic (30–50% of untreated patients)
- Postictal: prolonged confusion; aphasia (dominant); nose wipe (ipsilateral hand)
Key Lateralizing Signs
- Contralateral dystonic posturing: ~90% lateralizing
- Ipsilateral hand automatisms + postictal nose wipe (ipsilateral hand, ~90%)
- Ictal speech preservation: nondominant hemisphere; postictal aphasia: dominant hemisphere
- Figure-of-4 sign: extended arm = contralateral to seizure onset
💎 Board Pearl
HS Type 1 (CA1 + CA3 + CA4 loss, CA2 sparing) = most common (60–80%) AND best surgical outcome. Prolonged febrile seizures in childhood → latent period → drug-resistant mTLE = classic HS Type 1 board narrative.
EEG in Temporal Lobe Epilepsy
Interictal EEG
- Anterior temporal sharp waves: phase reversal at F7/F8 — hallmark of mTLE
- TIRDA: 1–3 Hz rhythmic delta over temporal region — same lateralizing value as IEDs
- IED frequency increases 2–3x during NREM sleep; bilateral independent IEDs in 30–40%
Ictal EEG
- Rhythmic 5–9 Hz theta over ipsilateral temporal region; evolves with increasing amplitude
- Postictal regional slowing: ipsilateral temporal polymorphic delta lateralizes to onset zone
- 10–20% of mTLE seizures have no clear scalp EEG correlate at onset
EEG Pitfalls
- Wicket spikes = NORMAL VARIANT — arciform, no aftergoing slow wave; do NOT treat as epileptiform
- Frontal/insular seizures propagate to temporal structures → “pseudo-temporal” pattern
💎 Board Pearl
TIRDA = same lateralizing value as temporal IEDs. Wicket spikes are a normal variant (no aftergoing slow wave, arciform morphology) — boards love asking you to distinguish these from true temporal sharp waves.
Frontal Lobe Epilepsy
- Second most common focal epilepsy (20–30%); brief (<60s), nocturnal, rapid recovery
- Prominent motor features; minimal postictal confusion; EEG normal in 30–50%
Semiology by Frontal Subregion
| Subregion | Semiology | Key Features |
|---|---|---|
| SMA | Fencer posture; forced version; vocalization | Brief (10–30s); preserved awareness; nocturnal; EEG often non-localizing |
| Dorsolateral | Contralateral version/clonic activity | Forced head version = contralateral; rapid generalization |
| Orbitofrontal | Complex automatisms, autonomic signs | Mimics TLE; impaired awareness; rapid generalization |
| Cingulate | Gelastic/dacrystic; complex motor | Misdiagnosed as psychiatric; bilateral spread |
| Primary motor | Contralateral clonic; jacksonian march | Highly localizing; Todd paralysis common |
Hyperkinetic Seizures
- Thrashing, kicking, bicycling, pelvic thrusting; brief (<60s), nocturnal, stereotyped
- Multiple episodes per night; preserved/rapid recovery; often misdiagnosed as PNES or parasomnia
FLE vs. PNES
| Feature | Frontal Lobe Epilepsy | PNES |
|---|---|---|
| Semiology | Stereotyped (same pattern every time) | Variable between events |
| Duration | <60 seconds | >2 minutes |
| Occurrence from sleep | Yes (common, nocturnal clusters) | Rare (can occur from pseudo-sleep) |
| Eyes during event | Open | Closed |
| Recovery | Rapid, minimal postictal confusion | Gradual; emotional component common |
| Scalp EEG | May be normal (deep mesial focus) | Normal (no epileptiform correlate) |
💎 Board Pearl
SMA seizures: fencer posture + brief + preserved awareness + nocturnal + rapid recovery = classic board vignette. Key: normal scalp EEG does NOT exclude frontal lobe seizures (deep mesial focus). FLE from sleep with eyes open and stereotyped <60s events = NOT PNES.
Parietal Lobe Epilepsy
- ~5–10% of focal epilepsies; often misdiagnosed
- Somatosensory aura (60–70%): contralateral tingling, numbness, electric-like sensation, or pain
- Body image distortion: limb feels distorted, absent, or foreign (nondominant parietal)
- Ictal pain: rare but leads to extensive pain workup before epilepsy is considered
- Rapid propagation to frontal, temporal, or occipital lobes — masks parietal origin
- Misdiagnosed as TIA (positive tingling = seizure; negative numbness/weakness = TIA)
💎 Board Pearl
Parietal epilepsy = somatosensory aura. Positive symptoms (tingling, paresthesias) favor seizure; negative symptoms (numbness, weakness) favor TIA. Parietal seizures propagate rapidly and can mimic temporal or frontal epilepsy — often requires invasive monitoring for localization.
Occipital Lobe Epilepsy
| Feature | Occipital Epilepsy | Migraine with Aura |
|---|---|---|
| Visual symptoms | Multicolored flashing lights, phosphenes | Zigzag, fortification spectra, scotoma |
| Duration / Onset | Brief (sec–3 min); abrupt | Gradual (20–30 min); spreading |
| Color | Often multicolored | Often black-and-white |
| Associated | Contralateral eye deviation, ictal blindness | Headache follows aura |
| EEG | Occipital spikes; ictal fast activity | Normal |
- Anterior propagation to temporal lobe masks occipital origin (automatisms appear)
- Etiologies: cortical dysplasia, calcified lesions, posterior infarcts, mitochondrial (MELAS, POLG)
💎 Board Pearl
Brief + abrupt + multicolored visual flashes = occipital epilepsy. Gradual + 20–30 min + zigzag/fortification spectra = migraine aura. This distinction is one of the highest-yield board differentiators in epilepsy localization.
Insular Epilepsy
- Laryngeal symptoms: throat tightness, choking, dysarthria — highly suggestive of insular onset
- Bilateral somatosensory symptoms: perioral tingling, widespread bilateral distribution (unlike unilateral parietal)
- Visceral aura: epigastric, thoracic, throat sensations mimicking mTLE
- Gustatory hallucinations: metallic taste; ictal pain (bilateral/diffuse)
- Scalp EEG rarely detects insular discharges — may falsely localize to temporal or frontal
- Suspect after failed temporal or frontal surgery
- SEEG with insular electrode placement = required for diagnosis
- Insular surgery risks MCA branches; LITT and SEEG-guided thermocoagulation are alternatives
💎 Board Pearl
Insular epilepsy = the great mimicker. Think insular when: (1) laryngeal symptoms + bilateral somatosensory + visceral aura, (2) mTLE semiology but failed temporal surgery, (3) scalp EEG falsely localizing to temporal or frontal. SEEG is required for diagnosis.
Focal Cortical Dysplasia
ILAE FCD Classification
| FCD Type | Histopathology | MRI Features | Surgical Outcome |
|---|---|---|---|
| Type I | Abnormal cortical layering (Ia: radial; Ib: tangential; Ic: both) | Often MRI-negative or subtle cortical thinning; may involve temporal pole | Less favorable (50–60% Engel I) — poorly defined margins |
| Type IIa | Dysmorphic neurons without balloon cells | Cortical thickening, T2/FLAIR hyperintensity, blurred gray-white junction | Favorable when completely resected |
| Type IIb | Dysmorphic neurons + balloon cells; mTOR pathway dysregulation | Cortical thickening + transmantle sign (funnel-shaped T2/FLAIR hyperintensity from cortex to ventricle) | BEST outcome: 70–80% Engel I — well-defined lesion margins |
| Type III | FCD associated with another principal lesion | Features of both FCD and associated lesion | Depends on resection of both lesions |
FCD Type III Subtypes
- IIIa: FCD + HS; IIIb: FCD + tumor; IIIc: FCD + vascular; IIId: FCD + other acquired pathology
Genetics of FCD
- FCD Type II = mTOR pathway — somatic mutations (MTOR, PIK3CA, AKT3, DEPDC5, NPRL2, NPRL3); detectable only in resected tissue, NOT blood
- GATOR1 complex (DEPDC5, NPRL2, NPRL3): germline mutations = most common familial focal epilepsy genes
- Familial focal epilepsy with variable foci: different family members, different FCD locations
💎 Board Pearl
FCD IIb = balloon cells + transmantle sign + mTOR pathway + BEST surgical outcome (70–80% Engel I). FCD I = often MRI-negative = worst surgical localization. GATOR1 complex (DEPDC5, NPRL2, NPRL3) = most common familial focal epilepsy genes — expect this on boards.
Key Surgical Trials & Outcomes
ERSET Trial (2012)
- Design: RCT of early surgery (within 2 years of drug resistance) vs. continued medical therapy for mTLE
- Result: 73% seizure-free at 2 years (surgery) vs. 0% (medical therapy)
- Despite Level 1 evidence, average time from epilepsy onset to surgery remains >20 years
- ILAE recommends referral to epilepsy surgery center after failure of 2 appropriate ASMs
ATL Outcomes for Hippocampal Sclerosis
- 60–70% Engel I (seizure-free) at 1 year for unilateral HS
- 70% maintain seizure freedom at 10 years
- ASM withdrawal possible in 25–50% of seizure-free patients after 2–5 years
Predictors of Favorable Outcome
- Unilateral HS on MRI with concordant ictal EEG and semiology
- Complete lesion resection (strongest predictor); FCD Type IIb histology
- Absence of contralateral abnormalities or dual pathology
Surgical Options
- ATL + amygdalohippocampectomy: standard for mTLE-HS; 60–80% Engel I
- SAH: spares neocortex; potentially better neuropsychological outcomes
- LITT: MRI-guided laser ablation; 50–60% seizure-free; minimally invasive
- RNS: closed-loop stimulation; 50–70% seizure reduction; option for bilateral TLE
💎 Board Pearl
- mTLE seizure sequence: epigastric rising → behavioral arrest → oroalimentary automatisms → contralateral dystonic posturing — memorize this progression
- Wicket spikes are a normal variant (arciform, no aftergoing slow wave) — do NOT treat as epileptiform
- TIRDA has the same lateralizing value as interictal epileptiform discharges
- FLE vs. PNES: stereotyped + <60s + from sleep + eyes open = FLE; variable + >2 min + eyes closed = PNES
- FCD IIb = balloon cells + transmantle sign = best FCD surgical outcome (70–80% Engel I)
- GATOR1 complex (DEPDC5, NPRL2, NPRL3) = most common familial focal epilepsy gene group
- Failed temporal surgery → think insular epilepsy → needs SEEG with insular electrodes
Clinical Pearls
- SMA seizure mimicking PNES: brief, bizarre motor events from sleep with preserved awareness and normal scalp EEG — the normal EEG does NOT exclude epilepsy with deep mesial frontal focus
- Occipital epilepsy vs. migraine: brief (<3 min) + abrupt + multicolored = epilepsy; gradual (20–30 min) + zigzag/fortification = migraine — wrong diagnosis leads to wrong treatment for years
- ERSET supports early surgery referral after failure of 2 ASMs — do not wait 20 years; delay worsens cognitive outcomes and quality of life
References
- Engel J Jr, McDermott MP, Wiebe S, et al. Early surgical therapy for drug-resistant temporal lobe epilepsy: a randomized trial (ERSET). JAMA. 2012;307(9):922–930.
- Blümcke I, Thom M, Aronica E, et al. International consensus classification of hippocampal sclerosis in temporal lobe epilepsy. Epilepsia. 2013;54(7):1315–1329.
- Blümcke I, Thöm M, Aronica E, et al. The clinicopathologic spectrum of focal cortical dysplasias: a consensus classification (ILAE). Brain Pathol. 2011;21(1):1–11.
- Nascimento FA, Friedman D, Peters JM, et al. Focal epilepsies: update on diagnosis and classification. Epileptic Disord. 2023;25(1):1–17.
- Isnard J, Guenot M, Sindou M, Mauguiere F. Clinical manifestations of insular lobe seizures: a stereo-electroencephalographic study. Epilepsia. 2004;45(9):1079–1090.
- Jobst BC, Cascino GD. Resective epilepsy surgery for drug-resistant focal epilepsy: a review. JAMA. 2015;313(3):285–293.
- Wiebe S, Blume WT, Girvin JP, Eliasziw M. A randomized, controlled trial of surgery for temporal-lobe epilepsy. N Engl J Med. 2001;345(5):311–318.
- Gooley S, Crompton DE, Berkovic SF. ILAE genetic literacy series: familial focal epilepsy syndromes. Epileptic Disord. 2022;24(2):221–228.
- Riney K, Bogacz A, Somerville E, et al. ILAE classification and definition of epilepsy syndromes with onset at a variable age. Epilepsia. 2022;63(6):1443–1474.
- Beniczky S, Tatum WO, Blumenfeld H, et al. Seizure semiology: ILAE glossary of terms and their significance. Epileptic Disord. 2022;24(3):447–495.