Diffuse Neuronal Migration Disorders
Lissencephalies Overview
- Human fetal brain initially has a smooth (agyric) surface.
- Failure of gyral development leads to neuronal migration disorders: lissencephaly continuum.
- Two major types:
- Type 1: Under-migration of neurons.
- Type 2: Over-migration of neurons.
Type 1 Lissencephaly
- Lissencephaly with cerebellar hypoplasia (LCH)
- X-linked lissencephaly (XLIS)
- X-linked lissencephaly with ambiguous genitalia (XLAG)
- Micro-lissencephaly
Pachygyria Phenotype
- Neuronal migration arrested prematurely.
- Cerebral cortex resembles a 12–13-week gestation brain.
- Mutations: LIS1 (chromosome 17), DCX (X chromosome), ARX, TUBA1A, RELN.
- Dysregulation of microtubular function disrupts neuronal migration.
- Classic findings:
- Thickened cortex with a 4-layered structure.
- Small brain, shallow sylvian fissures, axial figure-of-eight shape on fetal MRI.
Subcortical Band Heterotopia
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