Temporal Lobe & Focal Epilepsies
Temporal Lobe & Focal Epilepsies
What You'll Learn
- 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
HighYield Pearls
- MTLE-HS is THE most common localization-related epilepsy in adults: epigastric rising aura + déjà vu/jamais vu/fear → behavioral arrest with oroalimentary & ipsilateral hand automatisms + contralateral dystonic posturing; secondary GTC is uncommon
- Childhood febrile status epilepticus (NOT simple febrile seizures) is the key risk factor for HS — the FEBSTAT-style precipitating injury behind ILAE HS Type 1
- MRI hippocampal sclerosis triad: volume loss + increased T2/FLAIR signal + loss of internal architecture on coronal thin-cut sequences (3T epilepsy protocol through hippocampi, FLAIR, T1 IR) — Wieser-Engel/ILAE histopath Type 1a–c
- EEG: ipsilateral anterior temporal sharp waves (F7/F8), often best captured with a sphenoidal electrode; TIRDA has the same lateralizing value as IEDs
- Surgical pathway for drug-resistant MTLE-HS: anterior temporal lobectomy (Engel I in 60–70%) or selective amygdalohippocampectomy; LITT and RNS are MRI-conformal/palliative options — ERSET showed 73% seizure-free with early surgery vs 0% with continued meds
- Autosomal dominant lateral TLE = LGI1 → auditory aura (formed sounds, music, voices); ADNFLE/familial nocturnal frontal lobe epilepsy = nicotinic ACh receptor (CHRNA4 most common, also CHRNB2, CHRNA2) and is frequently misdiagnosed as parasomnia
- Frontal lobe semiology: brief (30–60 s) nocturnal clusters, bilateral asymmetric tonic posturing (fencer’s posture — SMA, awareness often preserved), hypermotor “bicycling,” rapid postictal recovery; orbitofrontal = autonomic + behavioral
- Gelastic seizures (mirthless laughter without emotion) = hypothalamic hamartoma pathognomonic — precocious puberty, refractory; treat with surgical/RFA/laser ablation
- Occipital seizures: colored circles/flashes, ictal blindness, eye blinking, ictal nystagmus, postictal blindness/headache (can mimic migraine); parietal = somatosensory Jacksonian march + distorted body image + vertigo
- FCD Type IIb (Taylor-type with balloon cells) = transmantle sign on MRI (radial sub-ependymal hyperintensity reaching cortex) and the most surgically curable cortical dysplasia; Type I is more diffuse and MRI-subtle
- ASMs for focal epilepsy: carbamazepine, oxcarbazepine, lacosamide, lamotrigine, levetiracetam, brivaracetam, perampanel are all reasonable; lamotrigine is not consistently superior to CBZ as focal monotherapy
🔍 Quick ReferenceSemiology · EEG / imaging · Localization / treatment
Semiology / clinical
- Epigastric rising + déjà vu + fear → mesial temporal lobe epilepsy (HS)
- Oroalimentary + ipsilateral hand automatisms + contralateral dystonic posturing → MTLE
- Formed auditory hallucinations (music, voices) → lateral temporal / LGI1 ADTLE
- Nocturnal hypermotor “bicycling” clusters, brief, rapid recovery → frontal lobe epilepsy (ADNFLE)
- Bilateral asymmetric tonic “fencer’s posture” with preserved awareness → SMA seizure
- Mirthless laughter without emotion → gelastic seizure / hypothalamic hamartoma
- Laryngeal/throat constriction + salivation + visceral aura → insular epilepsy
- Colored circles/flashes + ictal blindness + postictal headache → occipital lobe epilepsy
- Somatosensory Jacksonian march + distorted body image → parietal lobe epilepsy
EEG / imaging
- Anterior temporal sharp waves (F7/F8), sphenoidal-electrode positive → MTLE-HS
- Hippocampal volume loss + T2/FLAIR hyperintensity + loss of internal architecture → hippocampal sclerosis (ILAE Type 1)
- TIRDA (temporal intermittent rhythmic delta activity) → same lateralizing value as IEDs in MTLE
- Transmantle sign (radial sub-ependymal FLAIR hyperintensity reaching cortex) → FCD Type IIb (balloon cells, mTOR pathway)
- Posterior temporal spikes (T5/T6) with neocortical lesion → lateral/neocortical TLE
- MRI-negative focal epilepsy refractory to temporal resection → think insular — needs SEEG
- Sessile non-enhancing mass at the tuber cinereum → hypothalamic hamartoma
Localization / surgical / genetics
- LGI1 mutation → autosomal dominant lateral TLE (epilepsy with auditory features)
- CHRNA4 / CHRNB2 / CHRNA2 (nicotinic ACh receptor) → autosomal dominant nocturnal frontal lobe epilepsy
- Anterior temporal lobectomy or selective amygdalohippocampectomy → treatment of choice for drug-resistant MTLE-HS (Engel I 60–70%; ERSET 73%)
- LITT / RNS / VNS → options when open resection is not feasible or bitemporal
- Balloon cells on histopathology (FCD Type IIb) → best surgical outcome among FCDs (70–80% Engel I)
- Gelastic seizures + precocious puberty → hypothalamic hamartoma — RFA / laser ablation
- Auditory aura on boards → Heschl gyrus / lateral temporal — check for LGI1
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 | 60–70% Engel I at 1 year (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 (complex or prolonged febrile seizures — febrile status epilepticus per FEBSTAT cohort; simple febrile seizures are NOT associated; encephalitis) |
| Type 2 (CA1-predominant) | CA1-predominant loss with relative sparing of CA3/CA4 (distinguishes from Type 1) | 5–10% | Less favorable (~60% Engel I vs. ~70–80% for Type 1); less likely childhood precipitating event |
| Type 3 (CA4-predominant) | Predominantly CA4 + dentate granule cell loss | 4–7% | Less favorable (~60% Engel I vs. ~70–80% for Type 1); often dual pathology |
MRI Findings in HS
- ILAE-recommended HARNESS-MRI protocol (Bernasconi et al. 2019): 3T scanner, 3D T1 MPRAGE + 3D FLAIR + high-resolution coronal oblique T2 perpendicular to the long axis of the hippocampus
- 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 (note: epigastric aura also occurs in insular epilepsy), 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, ~80–90%)
Key Lateralizing Signs
- Contralateral dystonic posturing: ~90% lateralizing
- Ipsilateral hand automatisms + postictal nose wipe (ipsilateral hand, ~80–90%)
- 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. Complex or prolonged febrile seizures (febrile status epilepticus per FEBSTAT cohort) in childhood → latent period → drug-resistant mTLE = classic HS Type 1 board narrative; simple febrile seizures are NOT associated. CA1 (Sommer sector) is the most vulnerable hippocampal subfield; CA2 is the most resistant.
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