Polymicrogyria Overview

Summary

The following are the goals of this overview.

Diagnosis

Clinical Characteristics

Differential Diagnosis

Other malformations of cortical development that need to be distinguished from PMG:

• Pachygyria/lissencephaly, a distinct brain malformation in which reduced or absent cortical folding is combined with a thick cortex. Pachygyria and PMG may look similar on low-resolution neuroimaging (e.g., CT) because in both conditions the cortical thickness can appear to be increased and the gyri can appear to be broad and smooth. The cortex in PMG is overfolded but not thickened. The microgyri and microsulci of PMG and stippling of the gray-white junction that can be appreciated with high-quality MRI can distinguish PMG from pachygyria [Leventer et al 2010].
• Cobblestone lissencephaly, a brain surface that has a bumpy contour resulting from migration of neurons and glial cells through the basement membrane into the leptomeninges. Sometimes regions populated by these misplaced cells are incorrectly initially diagnosed as PMG based on the MRI appearance and are only distinguished from PMG by the presence of other brain abnormalities (e.g., white matter and cerebellar abnormalities) in combination with ocular anomalies and congenital muscular dystrophy. The cobblestone lissencephalies comprise brain malformations associated with congenital muscular dystrophy, including Walker-Warburg syndrome, muscle-eye-brain disease, and Fukuyama congenital muscular dystrophy.
• Schizencephaly, a specific pattern of PMG that describes a full-thickness cleft in the brain lined by PMG. While either CT or MRI is usually sufficient to diagnose schizencephaly, MRI is preferred when determining if the schizencephaly is open- or closed-lipped.

Management