Neuronal Migration and Organization Abnormalities

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Done

Parent item

Malformations of Cortical Development

Sub-item

Lissencephaly

Heterotopia

X-linked lissencephaly (double cortex syndrome)

Polymicrogyria

Schizencephaly

Microdysgenesis

Normal neuronal migration

Mechanistic classification

• See
• Malformation of cortical development classification
• Focal cortical dysplasia classification

1. Abnormal
• Proliferation (megancephaly) or
• Apoptosis (microcephaly).

2. Neurons do not migrate away from subventricular zone—
• subependymal/periventricular Heterotopia.

3. Neurons only migrate half way to cortex
• subcortical band Heterotopia.

4. Neurons reach cortex but abnormal cortical lamination—
• Lissencephaly type 1/pachygyria.

5. Neurons overshoot cortex and end up in subarachnoid space
• Marginal zone heterotopia (leptomeningeal glioneuronal heterotopia)
• Lissencephaly type 2 (cobblestone cortex).

6. Late stage migration defects with abnormal cortical organization or neuronal morphology
• Polymicrogyria
• Focal cortical dysplasia
• Microdysgenesis
• Schizencephaly