I. Introduction and Classification (ILAE 2017)
Focal epilepsies are characterized by seizures originating within networks limited to one hemisphere. They may be discrete (localized) or more widely distributed. Classification by Etiology/Prognosis:
- Self-Limiting (Benign) Focal Epilepsies of Childhood: Age-dependent, genetic predisposition, normal MRI, excellent prognosis.
- Symptomatic (Structural/Metabolic) Focal Epilepsies: Associated with lesions (MTS, tumors, cortical dysplasia), variable prognosis.
- Genetic/Familial Focal Epilepsies: Autosomal dominant inheritance (e.g., ADNFLE).
- Epileptic Encephalopathies with Focal Features: e.g., Rasmussen’s, CSWS.
II. Self-Limiting (Benign) Focal Epilepsies
These are the most common childhood epilepsy syndromes (15–25% of pediatric epilepsy).
1. Benign Epilepsy with Centrotemporal Spikes (BECTS) / Rolandic Epilepsy
- Age of Onset: 3–13 years (Peak: 7–9 years).
- Clinical Features:
- Timing: 75% occur during NREM sleep (shortly after falling asleep or before waking).
- Semiology: Unilateral sensorimotor symptoms involving the face, tongue, and pharynx.
- Symptoms: Oropharyngeal paresthesia (“numbness inside cheek”), guttural sounds, drooling (sialorrhea), speech arrest (anarthria). May evolve into hemifacial motor clonic jerks or focal-to-bilateral tonic-clonic seizures (GTCS).
- Neurology: Normal exam; normal development.
- EEG Features (Hallmark):
- Interictal: High-voltage, blunt, biphasic spikes in the centrotemporal (Rolandic) region (C3/C4, T3/T4).
- Dipole: Horizontal dipole (negativity centrotemporal, positivity frontal).
- Activation: Prominent activation with sleep.
- Management:
- Many do not require medication if seizures are infrequent/nocturnal only.
- First-line (if needed): Carbamazepine, Oxcarbazepine, or Levetiracetam.
- Prognosis: Excellent. Remission by puberty (age 15–16) is the rule.
2. Panayiotopoulos Syndrome (Early Onset Benign Occipital Epilepsy)
- Age of Onset: 3–6 years (Early childhood).
- Clinical Features:
- Autonomic Status: Prominent autonomic features: Emesis (vomiting is cardinal), pallor, sweating, pupil dilation.
- Duration: Seizures are often prolonged (>30 mins), mimicking status epilepticus, but non-convulsive.
- Eye Deviation: Lateral deviation of eyes (open) is common. Visual hallucinations are rare (unlike late-onset).
- EEG: High-amplitude sharp-and-slow wave complexes, often occipital, but can shift locations (multifocal) on serial EEGs (“Fixation-off sensitivity”).
- Management: Rescue benzodiazepines for prolonged events. Daily AEDs often not needed due to infrequency.
- Prognosis: Excellent. Remission usually within 1–2 years of onset.
3. Gastaut Type (Late Onset Childhood Occipital Epilepsy)
- Age of Onset: 8–11 years.
- Clinical Features:
- Visual Aura: Elementary visual hallucinations (multicolored circles, flashes), blindness, or hemianopia.
- Post-ictal: Severe migraine-like headache.
- EEG: Occipital spikes (O1/O2) that attenuate with eye-opening (Fixation sensitivity).
- Prognosis: Variable; less likely to remit spontaneously compared to Panayiotopoulos.
III. Symptomatic / Structural Focal Epilepsies
1. Temporal Lobe Epilepsy (TLE)
The most common form of focal epilepsy in adolescents and adults.
- Etiology:
- Mesial Temporal Sclerosis (MTS): Hippocampal atrophy and gliosis. Often history of prolonged febrile seizures in infancy.
- Tumors (Ganglioglioma, DNET), Cortical Dysplasia.
- Semiology:
- Aura: Epigastric rising sensation (most common), Déjà vu (familiarity), Jamais vu, fear, olfactory hallucinations (uncinate fits).
- Ictal: Behavioral arrest (staring), Oro-alimentary automatisms (lip-smacking, chewing), Manual automatisms (picking, fumbling).
- Post-ictal: Confusion, nose-wiping (ipsilateral to focus), transient aphasia (if dominant hemisphere).
- Investigation:
- MRI: Hyperintensity on T2/FLAIR in hippocampus; atrophy.
- EEG: Anterior temporal spikes/sharp waves.
- Management: Often drug-resistant. Surgical resection (Anterior Temporal Lobectomy) is highly effective (70–80% cure).
2. Frontal Lobe Epilepsy (FLE)
- Etiology: Cortical dysplasia (FCD), post-traumatic, tumors.
- Semiology:
- Hyperkinetic: Bizarre, thrashing movements, pelvic thrusting, cycling leg movements, vocalization (screaming/grunting).
- Timing: Clusters during sleep (often misdiagnosed as night terrors/parasomnias).
- Duration: Very brief (<30 seconds) with rapid recovery (minimal post-ictal confusion).
- EEG: Often normal or obscured by muscle artifact.
- Genetics: ADNFLE (Autosomal Dominant Nocturnal Frontal Lobe Epilepsy) – Mutation in nicotinic acetylcholine receptor (CHRNA4).
IV. Specific Etiology-Linked Syndromes
1. Rasmussen’s Encephalitis
- Pathology: Chronic, progressive T-cell mediated autoimmune encephalitis affecting one hemisphere.
- Age: Peak 6–7 years.
- Clinical:
- EPC: Epilepsia Partialis Continua (continuous focal jerking of a limb/face).
- Progression: Intractable seizures Hemiparesis Cognitive decline (dementia).
- MRI: Progressive hemi-atrophy of the affected hemisphere.
- Management: Medical therapy fails. Functional Hemispherectomy is the only curative option.
2. Hypothalamic Hamartoma (Gelastic Epilepsy)
- Lesion: Non-neoplastic heterotopia in the tuber cinereum/hypothalamus.
- Clinical:
- Gelastic Seizures: Mirthless, mechanical laughter (often starts in infancy).
- Dacrystic Seizures: Crying seizures.
- Comorbidity: Central Precocious Puberty.
- Management: Surgical disconnection or Stereotactic Radiosurgery (Gamma Knife).
3. Sturge-Weber Syndrome
- Pathology: Leptomeningeal angiomatosis.
- Clinical: Focal motor seizures contralateral to Port-Wine Stain.
- Course: Seizures often start in infancy, leading to hemiparesis and calcification (tram-track sign).
V. Acquired Epileptic Aphasia (Landau-Kleffner Syndrome)
- Nature: An epileptic encephalopathy with focal EEG features but global cognitive impact.
- Clinical: Normal early development Subacute onset of Verbal Auditory Agnosia (“Word deafness”) Loss of speech.
- Seizures: Infrequent focal motor seizures (25% have no clinical seizures).
- EEG: CSWS (Continuous Spike and Waves during Sleep). >85% of slow-wave sleep occupied by discharges, usually temporal/parietal.
- Treatment: Steroids (high dose), IVIG, Benzodiazepines.
VI. Management Summary
| Modality | Indication | Agents/Procedure |
|---|---|---|
| Pharmacotherapy | First line for all focal epilepsies (except self-limiting with rare events). | 1st Line: Carbamazepine, Oxcarbazepine, Levetiracetam. 2nd Line: Lacosamide, Lamotrigine, Topiramate, Zonisamide. Avoid: Ethosuximide (ineffective), Phenobarbital (cognitive side effects). |
| Dietary | Drug-resistant cases (esp. young children). | Ketogenic Diet, Modified Atkins Diet. |
| Surgery | Drug-resistant focal epilepsy (failure of 2 drugs) with identifiable focus. | Resective: Lobectomy, Lesionectomy. Disconnective: Hemispherectomy (Rasmussen, Hemimegalencephaly), Corpus Callosotomy. Palliative: VNS, RNS. |