Demonstration of different histological layers of the pachygyria/agyria cortex using diffusion tensor MR imaging.

Purpose: Pachygyria/agyria are congenital brain malformations characterized by presence of a few broad, flat gyri with thickened cortex, resulting from arrest of neuronal migration in early gestation. We are hereby describing diffusion tensor imaging findings in different histological layers of lissencephaly cortex in two children.

Method: DTI in addition to conventional MR imaging was performed in two children on a 3 T MRI and post-processed with vendor supplied software to generate the fractional anisotropy, mean diffusivity and trace maps. Tractography was also performed to identify presence of tracts in the thickened cortex.

Results: DTI demonstrated the dysplastic multilayered cortex in cases of pachygyria/agyria; the thickened fourth layer and superficial layer demonstrated high anisotropy on diffusion tensor imaging.

Conclusion: DTI is a useful tool for identifying gross histological features of pachygyria-agyria complex. Superficial layer and thickened fourth layer demonstrate high anisotropy. Identification of anisotropy in the superficial layer has not been described in previous reports.