|
A 2 year-old boy underwent an evaluation for developmental delay and a mild left hemiparesis. |
| Lissencephaly / Polymicrogyria / Pachygyria:
MP-RAGE axial MRI scans. First, note the asymmetry between the right
and left hemispheres. If one looks closely, one sees that there are many
abnormally small gyri (polymicrogyria)
over the right hemisphere. In addition, the gray and white
matter are reduced on the right side, resulting in brain atrophy. Also note
the larger CSF space over the right hemisphere. This is an example of a neuronal migration disorder; in
this case, polymicrogyria.
Neuronal migration disorders are a group of congenital disorders caused by impaired migration of neurons in the developing brain. Neuronal migration normally occurs during the second month of gestation. If the signals that guide neurons are impaired, a variety of structural defects may occur, including:
• Lissencephaly In lissencephaly, there is a complete absence of gyri and sucli, with the surface of the brain appearing perfectly smooth. These children typically have severe mental retardation with microcephaly and seizures. Pachygyria is a milder variant of lissencephaly, characterized by a thickened cortex and large, broad gyri. |
Revised
11/30/06
Copyrighted 2006. David C Preston