Magnetic resonance images of neuronal migration anomalies.

Neuronal migration anomalies are a spectrum of brain malformations caused by insults to migrating neuroblasts during the sixth week to fifth month of gestation. To study the characteristics of MRI findings in migration anomalies, MR images of 36 patients (28 children and 8 adults) with migration anomalies were evaluated. Five patients had lissencephaly, eight had pachygyria, twelve had schizencephaly, six had heterotopias of gray matter, three had hemimegalencephaly, and two had polymicrogyria. The frequency of migration anomalies was 0.51% of all cranial MRI studies and 1.21% of pediatric cranial MRI studies at our hospital. The major clinical presentations of these patients were seizure (64%), development delay (42%), motor deficits (42%) and mental retardation (25%). Twenty-five patients (69%) associated with other brain anomalies, including: other migration anomalies in 12 cases (33%), absence of the septum pellucidum in 10 cases (28%), Dandy-Walker malformation/variant in 5 cases, arachnoid cyst in 4 cases, agenesis of the corpus callosum in 3 cases, holoprosencephaly in 2 cases, mega cisterna magna in 1 case and cephalocele in 1 case. Some of them presented with multiple complicated anomalies. As MR imaging provides superb gray-white matter distinction, details of cortical anatomy and multiplanar capability, it can clearly delineate the detail morphologic changes of the brain caused by neuronal migration disorders as well as the associated anomalies.