[Agyria-pachygyria and pachygyria in children. Contribution of imaging]

BACKGROUND--Lissencephaly (agyria-pachygyria) is a defect in migration of cerebral neurons resulting in failure of cortical gyri to develop. Progress in imaging techniques improves its diagnosis. POPULATION AND METHODS--The files of 17 patients (ten boys and seven girls), aged 7 months to 16 years, were retrospectively studied. The clinical picture consisted of mental retardation (17 patients), seizures (eight patients), facial dysmorphia (seven patients), axial hypotonia (four patients). CT scan was performed in 16 cases and MRI with T1 and T2 weighted images in all 17. RESULTS--The CT scan identified pachygyria in 12 cases. Cerebral calcifications were seen in four cases. MRI detected typical changes in all 17 cases: thickened cortex and gyri, loss of cortical white matter interdigitations, lack of operculisation of the sylvian fissure. Pachygyria was generalized (six patients) or localized (11 patients). Associated abnormalities were dysgenesis of corpus callosum in three patients, cerebellar hypoplasia in one, deep grey matter heterotopia in one; hypersignal of the white matter was identified on T2 weighted images in five patients. CONCLUSION--MR imaging permits precise analysis of abnormalities secondary to a defect in neuronal migration.