HEMIMEGALENCEPHALY

Overview
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Seizure Classification
Generalized onset seizure
- Motor Onset
- Non-Motor Onset
Focal Onset Seizure
- By Onset Feature
- Focal to Bilateral Tonic-Clonic
- Hemispheric lateralization
- Lobar localization
  - Frontal
  - Temporal
  - Parietal
  - Occipital
Unknown Onset Seizure
Neonatal Seizure
Epilepsy Classification
Generalized Epilepsy
Focal Epilepsy
Generalized and Focal Epilepsy
Unknown Epilepsy
Epilepsy Syndromes
Neonate/Infant
- Self-limited
- With developmental and epileptic encephalopathy
Childhood
- Self-limited focal epilepsy syndromes
  - Remission expected in all cases by adolescence
    - Self-limited epilepsy with centrotemporal spikes
    - Self-limited epilepsy with autonomic seizures
  - Remission expected in most cases by adolescence
    - Childhood occipital visual epilepsy
    - Photosensitive occipital lobe epilepsy
- Genetic generalised epilepsy syndromes
  - Epilepsy with eyelid myoclonia
  - Epilepsy with myoclonic absence
- Idiopathic generalised epilepsy syndrome
  - Childhood absence epilepsy
- With developmental and/or epileptic encephalopathy
Variable Age
- Idiopathic generalised epilepsy syndromes
- Focal epilepsy syndromes
- Combined generalised and focal epilepsy syndrome
  - Epilepsy with reading-induced seizures
- With developmental and/or epileptic encephalopathy or progressive neurological deterioration
  - Progressive myoclonus epilepsies
  - Rasmussen syndrome
Epilepsy Etiologies
Genetic Etiologies
- Chromosomal abnormalities
- Gene abnormalities
Structural Etiologies
- Malformations of cortical development
- Vascular malformations
- Hippocampal sclerosis
- Hypoxic-Ischemic
- Traumatic brain injury
- Tumors
- Porencephalic Cyst
Metabolic Etiologies
Immune Etiologies
Infectious Etiologies
Unknown Etiologies
Encephalopathy
Epilepsy imitators

HEMIMEGALENCEPHALY

GENETICS

PATTERN OF INHERITANCE

De novo acquired somatic gene abnormality.

KNOWN GENES

Hemimegalencephaly has been linked with acquired somatic gene abnormalities in genes involved in the PI3K/AKT/mTOR pathway, including PIK3CA, AKT3, TSC1, TSC2. These gene abnormalities have been found directly in a small percentage of brain cells from the abnormal hemisphere.

FAMILY HISTORY

May be present (see above).

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