|
An 8 month-old boy underwent an evaluation for microcephaly and seizures. |
| Lissencephaly / Polymicrogyria / Pachygyria:
T2-weighted axial MRIs. This patient displays several abnormalities
on the spectrum of neuronal migration disorders. First, note the several areas
completely devoid of gyri and sulci (i.e., lissencephaly or "smooth brain").
However, if one looks closely at the posterior temporal/occipital area
on the right, one can see many abnormally small gyri (polymicrogyria).
Finally, note the abnormal shape of the deep white matter. The white matter
normally spreads like fingers as it
divides into different tracts going toward the cortical gyri. In this case,
the deep white matter simply surrounds the lateral ventricles. 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
11/04/06
Copyrighted 2006. David C Preston